ALXN


Line plots across dimensions of each concept
Tables

Table of contents



us-gaap:CommonStockValue

us-gaap:CommonStockSharesIssued
us-gaap:StatementEquityComponents
us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStockSharesAuthorized

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
us-gaap:DerivativeInstrumentRisk, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents
us-gaap:ProductOrService
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents
us-gaap:StatementBusinessSegments
us-gaap:StatementGeographical, us-gaap:StatementBusinessSegments

us-gaap:Revenues

us-gaap:CostOfRevenue

us-gaap:CostOfGoodsAndServicesSold

us-gaap:CostsAndExpenses

us-gaap:ResearchAndDevelopmentExpense

us-gaap:SellingGeneralAndAdministrativeExpense

us-gaap:OperatingIncomeLoss

us-gaap:InterestExpense
us-gaap:DerivativeInstrumentRisk, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:IncomeTaxExpenseBenefit
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:NetIncomeLoss
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:Assets

us-gaap:Liabilities

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents

us-gaap:AssetsCurrent

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:AccountsReceivableNetCurrent

us-gaap:InventoryNet
us-gaap:PublicUtilitiesInventory

us-gaap:InventoryFinishedGoods

us-gaap:OtherAssetsCurrent

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:Goodwill
us-gaap:BusinessAcquisition

us-gaap:IntangibleAssetsNetExcludingGoodwill
us-gaap:BusinessAcquisition, us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FiniteLivedIntangibleAssetsNet
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:OtherAssetsNoncurrent

us-gaap:LiabilitiesCurrent

us-gaap:LongTermDebtCurrent

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent

us-gaap:OtherLiabilitiesCurrent
us-gaap:CreditFacility, us-gaap:DebtInstrument, us-gaap:LongtermDebtType
us-gaap:LongTermDebt

us-gaap:LongTermDebtNoncurrent

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents

us-gaap:CommonStockValue

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:TreasuryStockValue

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:DepreciationDepletionAndAmortization

us-gaap:IncreaseDecreaseInInventories

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:RepaymentsOfLongTermDebt

us-gaap:PaymentsForRepurchaseOfCommonStock

us-gaap:RepaymentsOfLongTermDebt

us-gaap:EffectiveIncomeTaxRateContinuingOperations

us-gaap:ShareBasedCompensation

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

alxn:AmortizationofIntangibleAssetsAcquired

alxn:AssetAcquisitionContingentConsiderationMilestonePayments
us-gaap:BusinessAcquisition
alxn:BusinessCombinationConsiderationTransferredPerShare
us-gaap:StatementScenario, us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition
alxn:BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresTransactionCosts
us-gaap:CounterpartyName, us-gaap:TypeOfArrangement
alxn:CollaborationAgreementPotentialFuturePaymentsMilestoneAchievement
us-gaap:TypeOfArrangement
us-gaap:CounterpartyName, us-gaap:TypeOfArrangement
alxn:DerivativeFairValueDiscountedCostOfDebt
us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass
alxn:FairValueInputsCostOfDebt

alxn:FairValueInputsWeightedAverageCostOfCapital
us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass

alxn:NoncashOrPartNoncashAcquisitionContingentConsiderationIssued

alxn:OperatingRightOfUseAssetsExchangedForOperatingLeaseLiability

alxn:RestructuringChargesAndAccrualAdjustment

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementEquityComponents

us-gaap:AmortizationOfFinancingCosts

us-gaap:AmortizationOfIntangibleAssets

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisitionsProFormaRevenue

us-gaap:BusinessCombinationAcquisitionRelatedCosts
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationConsiderationTransferred1
us-gaap:StatementScenario, us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationIntegrationRelatedCosts
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed

us-gaap:CapitalExpendituresIncurredButNotYetPaid

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:DeferredIncomeTaxesAndTaxCredits
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation, us-gaap:IncomeStatementLocation

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:GainLossOnDerivativeInstrumentsNetPretax
us-gaap:HedgingDesignation
us-gaap:GainLossOnFairValueHedgesRecognizedInEarnings

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities

us-gaap:IncreaseDecreaseInAccountsReceivable

us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InvestmentIncomeNet

us-gaap:OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax
us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation
us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
us-gaap:StatementEquityComponents
us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax

us-gaap:OtherNoncashIncomeExpense

us-gaap:OtherSignificantNoncashTransactionValueOfConsiderationGiven1

us-gaap:PaymentsForProceedsFromOtherInvestingActivities

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:PaymentsToAcquireEquityMethodInvestments

us-gaap:PaymentsToAcquireIntangibleAssets

us-gaap:PaymentsToAcquireOtherInvestments

us-gaap:PaymentsToAcquireTradingSecuritiesHeldforinvestment

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities

us-gaap:ProceedsFromSaleAndMaturityOfMarketableSecurities

us-gaap:ProceedsFromStockOptionsExercised

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
us-gaap:StatementEquityComponents

us-gaap:RepaymentsOfLinesOfCredit
us-gaap:BusinessAcquisition
us-gaap:RestructuringCosts
us-gaap:BusinessAcquisition
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesRestrictedStockAwardGross
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised

us-gaap:StockIssuedDuringPeriodValueRestrictedStockAwardGross

us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised
us-gaap:StatementEquityComponents

us-gaap:TreasuryStockSharesAcquired
us-gaap:StatementEquityComponents
us-gaap:SubsequentEventType

us-gaap:TreasuryStockValueAcquiredCostMethod
us-gaap:StatementEquityComponents
us-gaap:SubsequentEventType

us-gaap:UnrealizedGainLossOnInvestments
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:BusinessAcquisition
alxn:BusinessCombinationContingentConsiderationLiabilityPostCombinationServicePeriodCompensation
us-gaap:Range, us-gaap:BusinessAcquisition
alxn:BusinessCombinationEstimatedMilestonePayments
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
alxn:DerivativeNotionalAmount1

alxn:GoodwillAccumulatedAmortization

alxn:IntangibleAssetsAccumulatedAmortization

alxn:IntangibleAssetsCost
us-gaap:CounterpartyName, us-gaap:TypeOfArrangement
alxn:ResearchandDevelopmentArrangementPotentialPaymentMaximum

us-gaap:AdditionalPaidInCapitalCommonStock
us-gaap:FinancialInstrument
us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:FinancialInstrument
us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis

us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:BalanceSheetLocation
us-gaap:FinancialInstrument
us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass
us-gaap:BusinessCombinationContingentConsiderationLiability
us-gaap:BalanceSheetLocation, us-gaap:FairValueByLiabilityClass
us-gaap:FairValueByLiabilityClass

us-gaap:BusinessCombinationContingentConsiderationLiabilityNoncurrent
us-gaap:BusinessAcquisition
us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities
us-gaap:BusinessAcquisition, us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass
us-gaap:BusinessAcquisition, us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass
us-gaap:CashAndCashEquivalentsFairValueDisclosure
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:ContractWithCustomerAssetNetCurrent

us-gaap:ContractWithCustomerLiabilityCurrent

us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months

us-gaap:DeferredFinanceCostsNet

us-gaap:DeferredIncomeTaxAssetsNet

us-gaap:DeferredIncomeTaxLiabilitiesNet
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeCollateralObligationToReturnSecurities
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeCollateralRightToReclaimSecurities
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeFairValueOfDerivativeAsset
us-gaap:BalanceSheetLocation, us-gaap:HedgingDesignation, us-gaap:InvestmentType
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeFairValueOfDerivativeLiability
us-gaap:BalanceSheetLocation, us-gaap:HedgingDesignation, us-gaap:InvestmentType
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral
us-gaap:Range, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeFixedInterestRate
us-gaap:CounterpartyName, us-gaap:TypeOfArrangement
us-gaap:DerivativeLiabilities
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:EquitySecuritiesFvNi
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FiniteLivedIntangibleAssetsGross
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass
us-gaap:ForeignCurrencyContractAssetFairValueDisclosure
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass
us-gaap:ForeignCurrencyContractsLiabilityFairValueDisclosure
us-gaap:BalanceSheetLocation, us-gaap:FairValueByLiabilityClass

us-gaap:GoodwillGross
us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass
us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass
us-gaap:InterestRateDerivativeAssetsAtFairValue
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass
us-gaap:InterestRateDerivativeLiabilitiesAtFairValue
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:InventoryRawMaterials

us-gaap:InventoryWorkInProcess
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass
us-gaap:InvestmentsFairValueDisclosure
us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:MarketableSecuritiesCurrent

us-gaap:OperatingLeaseLiabilityNoncurrent

us-gaap:RestrictedCashAndCashEquivalentsAtCarryingValue

us-gaap:RestrictedCashAndCashEquivalentsNoncurrent

us-gaap:TradingSecurities

us-gaap:TreasuryStockShares
us-gaap:StatementEquityComponents
us-gaap:CounterpartyName
us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount

Tables

  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:CommonStockValue ▁▁▁▁▁▁▁▁▁▁▁▁▁▁██████▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▆▃▃0.00.00.00.00.00.00.00.00.00.00.00.00.00.023000.023000.023000.023000.023000.023000.020000.020000.020000.020000.020000.020000.020000.020000.020000.020000.019000.019000.019000.019000.019000.018000.06000.06000.0NANANA
us-gaap:CommonStockSharesIssued ████████████████████▆▆▆▆▆▆▆▆▆▆▆▆▆▅▅▅▁▁2382372372372372362352352352342342342332322312312312302292292022012012001991971971961951941941921861851841849291NANANA
 us-gaap:CommonStockSharesOutstanding us-gaap:StatementEquityComponents us-gaap:CommonStock█▆▆▆▆▄▃▃▃▁238237237237237236235235235234NANANA232NANANA230NANANA201NANANA197NANANA194NANANA185NANANA91NANANA
us-gaap:CommonStockSharesAuthorized ████████████████████████████████████▁▁290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290145145NANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding 222NA224225225NA224222223NA225225226NA226225226NA226204202NA201201201NA199199199NA201197194NA19219195NA18618592
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic 221NA223224223NA222222222NA223224224NA224224225NA226202199NA198197197NA195195194NA193188185NA18318290NA17817888
us-gaap:EarningsPerShareBasic ▆█▆▆▆▃▅▁▅▄▄▄▄▄▄▄▄▄▂▄▄▄▄▄▄▃▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄2.524.022.092.052.63-0.21.48-2.051.120.130.350.740.760.410.420.510.410.3-0.810.840.460.770.90.840.81-0.10.480.490.420.420.480.190.240.260.360.190.30.150.160.120.24
us-gaap:EarningsPerShareDiluted ▆█▆▆▆▃▅▁▅▄▄▄▄▄▄▄▄▄▂▄▄▄▄▄▄▃▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄2.54.02.082.042.61-0.21.47-2.051.110.130.350.730.750.410.420.510.410.29-0.810.830.450.760.880.830.79-0.10.470.480.410.40.460.180.230.250.340.180.280.140.150.120.23
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax ██▇▇▆▆▆▆▅▅▅▅▅▅▅▄▄▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁14441384126312031140112810261045930909859912869831799753701701666636600599555512566441400370338320294274244227204185166155141125117
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ProductOrService alxn:NetProductSales1444NA126312021140NA10261044930NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ProductOrService alxn:OtherRevenue200000.0NA0.0800000.0200000.0NA0.0300000.0500000.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ProductOrService us-gaap:Product█▇▆▅▄▄▂▃▁14441384126312021140112810261044930NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments alxn:Soliris1022NA990980962NA888898800NA755813783NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments alxn:StrensiqProductLine172NA154141130NA113125110NA878373NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments alxn:Ultomiris222NA895424NA000NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementGeographical,us-gaap:StatementBusinessSegments alxn:OtherNonUsExcludingEuropeAndAsiaPacific,alxn:Ultomiris400000.0NA0.00.00.0NA0.00.00.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementGeographical,us-gaap:StatementBusinessSegments country:US,alxn:Soliris556NA496496463NA404395336NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementGeographical,us-gaap:StatementBusinessSegments srt:Europe,alxn:Soliris263NA255280264NA262253250NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:Revenues ██▇▇▆▆▆▆▅▅▅▅▅▅▅▄▄▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁14441384126312031140112810261045930909859912869831799753701701666636600599555512566441400370338320294274244227204185166155141125117
us-gaap:CostOfRevenue ▄▅▃▃▂▃▃▃▃▇█▂▁111114959985969095911441578369NANANANANANANANA4951NANANA51NANANA-20NANANA23NANANANANANA
us-gaap:CostOfGoodsAndServicesSold ▄▅▃▃▂▃▃▃▃▇█▂▁111114959985969095911441578369NANANANANANANANA4951NANANA51NANANA-20NANANA23NANANANANANA
us-gaap:CostsAndExpenses 749NANANA623NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:ResearchAndDevelopmentExpense ▅█▇▅▅▅▄▄▄█▅▅▆▅▅▄▄▅▄▃▆▂▁▁▅20026923218719520517417317626519519921920519517917619116513122112910092191NA886874NA545945NA363530NA252322
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us-gaap:Liabilities ██▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▂▂▂▂▂▂▂▂▁▂▂▂▂▁▁▁▁▁64006272444744044293476646734723471746904699461445794559478948304740487449004614898899767672678935695603595642633707804260249226253152NANANA
us-gaap:LiabilitiesAndStockholdersEquity ██▇▇▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▆▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁1814817544148151456713999139311384313490138301358313643134891343513253132931302912802131331315313167441442013890355333793317304928152685261325052457201713941305117911541012NANANA
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us-gaap:CashAndCashEquivalentsAtCarryingValue ▇█▇▆▅▄▄▃▂▂▂▂▂▃▃▂▂▃▄▄▃▃▃▂▂▂▃▃▃▃▃▃▁▂▂▁▁▁▁▁▁23152685217119841544136512287275115845505427139667615977101010116313229169437526125285299109361022989905806359540438347289267209212186
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us-gaap:OtherAssetsCurrent █▆▆▇▇▆▅▅▅▄▃▄▃▄▄▄▃▃▄▄▄▃▃▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁5754564324604974263703423272922072252152602412422192172722682731891471118787787181758473735052232426NANANA
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us-gaap:PropertyPlantAndEquipmentNet ▆▆▆▆▆████▇▇▇▆▆▅▅▄▄▃▃▂▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁11591163114811231095147114431422137913251354123311381036931825749697618555440392328273218201178173164165165164165165164163160162NANANA
us-gaap:Goodwill ████████████████████▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁507250375037503750375037503750375037503750375037503750375037503750495047501550072542542542542542542542542542532532552647980807919NANANA
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us-gaap:NetCashProvidedByUsedInInvestingActivities ▆▇▇▇▇▇▇█▆▇▇▆▆▇▇▆▇▇▇▁▇▇▇▇▇-76656-8-41252104568-2540-171-253-495114-65-330-5-161-195-3179-48-57-750-90NANANA-5NANANA-609NANANA-72NANANA-2
us-gaap:NetCashProvidedByUsedInFinancingActivities ▂▂▁▂▁▂▂▂▂▁▂▁▂▁▂▂▁▂▂█▂▂▂▂▂-138-59-365-61-2523117-123-225-95-207-69-283-62-24-466-181-18533465-30-59-22119NANANA-4NANANA364NANANA69NANANA10
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities █▇██▇▄▆▁▆▅▆▆▆▆▆▅▅▅▅▅▄▆▆▄▃54951759953842983387-34329925727028030838229124316719022323823283281106-31NANANA46NANANA62NANANA24NANANA21
us-gaap:NetIncomeLoss ▆█▆▆▆▃▅▁▅▄▄▄▄▄▄▄▄▄▂▄▄▄▄▄▄▃▄▄▄▄▄▄▄▄▄▄▄▄▄▃▃557889467459587-45330-457249307816517093941149266-18317091153177166159-18939582809236454865342626272120
 us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings▆█▆▆▆▃▅▁▅557889467459587-45330-457249NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:DepreciationDepletionAndAmortization ▄▄▄▄▄▅▅▅▅█▅▅▅▅▅▄▄▄▃▁▁▁▁▁▁8990929697981041001011851101029910010097969349121018999NANANA6NANANA5NANANA4NANANA3
us-gaap:IncreaseDecreaseInInventories ▁▆█▄▄▆▁▄▃▄▅▄▄▄▅▅▃█▄▃▃▆▃▄▄-375181121141-308-31936141911333538112-2-240-81420NANANA5NANANA9NANANA10NANANA12
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities ▆▇▇▇▇▇▇█▆▇▇▆▆▇▇▆▇▇▇▁▇▇▇▇▇-76656-8-41252104568-2540-171-253-495114-65-330-5-161-195-3179-48-57-750-90NANANA-5NANANA-609NANANA-72NANANA-2
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▁▂▃▄▃▃▃▅▅▇▇▇▆█▇▅▅▆▆▅▄▄▂▃▁1230414636424162668894100751079466648076735752224317NANANA5NANANA3NANANA2NANANA2
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities ▂▂▁▂▁▂▂▂▂▁▂▁▂▁▂▂▁▂▂█▂▂▂▂▂-138-59-365-61-2523117-123-225-95-207-69-283-62-24-466-181-18533465-30-59-22119NANANA-4NANANA364NANANA69NANANA10
us-gaap:RepaymentsOfLongTermDebt ▂▂▂▂▁▁▁█▂▂▂▂▂▇▁▁▆▂▁▂▁▁▁▁▂32323232000250434444434420000175430451212121219NANANA0NANANANANANANANANANANANA
us-gaap:PaymentsForRepurchaseOfCommonStock ▃▂█▂▁▁▁▁▃▄▂▅▂▂▂▂▇▄▃▁▂▁▃▄▁1073233437110008516460171683069342961529123601910415622NANANA35NANANA0NANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:RepaymentsOfLongTermDebt ▂▂▂▂▁▁▁█▂▂▂▂▂▇▁▁▆▂▁▂▁▁▁▁▂32323232000250434444434420000175430451212121219NANANA0NANANANANANANANANANANANA

Adjustments To Additional Paid In Capital Stock Split

Common Stock Value

us-gaap:CommonStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value0.00.00.00.00.00.00.00.00.00.00.00.00.00.023000.023000.023000.023000.023000.023000.020000.020000.020000.020000.020000.020000.020000.020000.020000.020000.019000.019000.019000.019000.019000.018000.06000.06000.05000.0
Percentage of CommonStockValue0.00.00.00.00.00.00.00.00.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Par Or Stated Value Per Share

Common Stock Shares Issued

us-gaap:CommonStockSharesIssued



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value238237237237237236235235235234234234233232231231231230229229202201201200199197197196195194194192186185184184929189
Percentage of CommonStockSharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Outstanding

us-gaap:StatementEquityComponents

us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value23823723723723723623523523523423223020119719418591898175
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Authorized

us-gaap:CommonStockSharesAuthorized



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290290145145145
Percentage of CommonStockSharesAuthorized100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value2222242252252242222232252252262262252262262042022012012011991991992011971941921919518618592
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value2212232242232222222222232242242242242252262021991981971971951951941931881851831829017817888
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value2.524.022.092.052.63-0.21.48-2.051.120.130.350.740.760.410.420.510.410.3-0.810.840.460.770.90.840.81-0.10.480.490.420.420.480.190.240.260.360.190.30.150.160.120.24
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value2.54.02.082.042.61-0.21.47-2.051.110.130.350.730.750.410.420.510.410.29-0.810.830.450.760.880.830.79-0.10.470.480.410.40.460.180.230.250.340.180.280.140.150.120.23
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Revenue From Contract With Customer Excluding Assessed Tax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value14441384126312031140112810261045930909859912869831799753701701666636600599555512566441400370338320294274244227204185166155141125117
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ForeignExchangeForward, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value119119793-1-13
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.80.70.90.80.60.90.3-0.2-1.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.80.70.90.80.60.90.3-0.2-1.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ForeignExchangeForward us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProductOrService

alxn:NetProductSales



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value144412631202114010261044930
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.099.9100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.099.9100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:NetProductSales100.0100.0100.0100.0100.0100.0100.0

alxn:OtherRevenue



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value200000.00.0800000.0200000.00.0300000.0500000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.10.00.00.00.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.10.00.00.00.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:OtherRevenue100.00.0100.0100.00.0100.0100.0

us-gaap:Product



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value14441384126312021140112810261044930
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.099.9100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.099.9100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:Product100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value1111973-1-13
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.80.90.80.60.3-0.2-1.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.80.90.80.60.3-0.2-1.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementBusinessSegments

alxn:KanumaProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value26282623252119161512
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.82.22.22.12.52.02.11.91.71.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.82.22.22.12.52.02.11.91.71.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:KanumaProductLine100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:Soliris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value1022990980962888898800755813783
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax70.878.481.584.486.586.086.087.989.190.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax70.878.481.584.486.586.086.087.989.190.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:Soliris100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:StrensiqProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value172154141130113125110878373
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax11.912.211.711.411.012.011.910.19.28.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax11.912.211.711.411.012.011.910.19.28.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:StrensiqProductLine100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:Ultomiris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value222895424000
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax15.47.14.52.20.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax15.47.14.52.20.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:Ultomiris100.0100.0100.0100.00.00.00.0

us-gaap:StatementGeographical, us-gaap:StatementBusinessSegments

alxn:OtherNonUsExcludingEuropeAndAsiaPacific, alxn:KanumaProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value1422610
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.40.20.20.60.10.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.40.20.20.60.10.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:OtherNonUsExcludingEuropeAndAsiaPacific alxn:KanumaProductLine100.0100.0100.0100.0100.0100.0100.0

alxn:OtherNonUsExcludingEuropeAndAsiaPacific, alxn:Soliris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value11612094132123155127
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax8.09.57.811.712.014.913.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax8.09.57.811.712.014.913.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:OtherNonUsExcludingEuropeAndAsiaPacific alxn:Soliris100.0100.0100.0100.0100.0100.0100.0

alxn:OtherNonUsExcludingEuropeAndAsiaPacific, alxn:StrensiqProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value6333221
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.30.30.30.30.20.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.30.30.30.30.20.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:OtherNonUsExcludingEuropeAndAsiaPacific alxn:StrensiqProductLine100.0100.0100.0100.0100.0100.0100.0

alxn:OtherNonUsExcludingEuropeAndAsiaPacific, alxn:Ultomiris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value400000.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax alxn:OtherNonUsExcludingEuropeAndAsiaPacific alxn:Ultomiris100.00.00.00.00.00.00.0

country:US, alxn:KanumaProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value16161513131311
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.11.31.31.21.31.21.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.11.31.31.21.31.21.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax country:US alxn:KanumaProductLine100.0100.0100.0100.0100.0100.0100.0

country:US, alxn:Soliris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value556496496463404395336
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax38.539.341.240.739.437.936.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax38.539.341.240.739.437.936.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax country:US alxn:Soliris100.0100.0100.0100.0100.0100.0100.0

country:US, alxn:StrensiqProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value12811810699869989
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax8.99.38.88.78.49.69.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax8.99.38.88.78.49.69.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax country:US alxn:StrensiqProductLine100.0100.0100.0100.0100.0100.0100.0

country:US, alxn:Ultomiris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value131655424000
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.15.24.52.20.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.15.24.52.20.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax country:US alxn:Ultomiris100.0100.0100.0100.00.00.00.0

srt:AsiaPacific, alxn:KanumaProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value0110011
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.10.10.10.10.10.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.10.10.10.10.10.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:AsiaPacific alxn:KanumaProductLine100.0100.0100.0100.0100.0100.0100.0

srt:AsiaPacific, alxn:Soliris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value87118110100989385
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax6.09.39.28.89.69.09.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax6.09.39.28.89.69.09.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:AsiaPacific alxn:Soliris100.0100.0100.0100.0100.0100.0100.0

srt:AsiaPacific, alxn:StrensiqProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value1314129765
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.91.11.00.90.70.60.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.91.11.00.90.70.60.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:AsiaPacific alxn:StrensiqProductLine100.0100.0100.0100.0100.0100.0100.0

srt:AsiaPacific, alxn:Ultomiris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value57300000
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.00.30.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.00.30.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:AsiaPacific alxn:Ultomiris100.0100.00.00.00.00.00.0

srt:Europe, alxn:KanumaProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value7666455
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.50.50.60.60.50.60.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.50.50.60.60.50.60.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:Europe alxn:KanumaProductLine100.0100.0100.0100.0100.0100.0100.0

srt:Europe, alxn:Soliris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value263255280264262253250
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax18.220.223.323.225.524.227.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax18.220.223.323.225.524.227.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:Europe alxn:Soliris100.0100.0100.0100.0100.0100.0100.0

srt:Europe, alxn:StrensiqProductLine



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value24191917161614
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.71.51.61.51.61.61.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.71.51.61.51.61.61.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:Europe alxn:StrensiqProductLine100.0100.0100.0100.0100.0100.0100.0

srt:Europe, alxn:Ultomiris



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value332100000
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.31.70.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.31.70.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:Europe alxn:Ultomiris100.0100.00.00.00.00.00.0

Revenues

us-gaap:Revenues



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value14441384126312031140112810261045930909859912869831799753701701666636600599555512566441400370338320294274244227204185166155141125117
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Sales Revenue Net

Sales Revenue Goods Net

Cost Of Revenue

us-gaap:CostOfRevenue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312014-12-312014-09-302013-09-302012-09-302011-09-30
Value111114959985969095911441578369495151-2023
Percentage of CostOfRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.78.37.58.27.58.68.89.19.815.918.39.27.98.29.312.8-6.911.5

Cost Of Goods And Services Sold

us-gaap:CostOfGoodsAndServicesSold



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312014-12-312014-09-302013-09-302012-09-302011-09-30
Value111114959985969095911441578369495151-2023
Percentage of CostOfGoodsAndServicesSold100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.78.37.58.27.58.68.89.19.815.918.39.27.98.29.312.8-6.911.5

Cost Of Goods Sold

Gross Profit

Operating Expenses

Costs And Expenses

us-gaap:CostsAndExpenses



Period End2020-03-312019-03-31
Value749623
Percentage of CostsAndExpenses100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax51.954.7

Research And Development Expense

us-gaap:ResearchAndDevelopmentExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value20026923218719520517417317626519519921920519517917619116513122112910092191886874545945363530252322
Percentage of ResearchAndDevelopmentExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.919.518.415.617.218.217.016.619.029.222.721.825.224.824.523.825.127.324.920.736.821.518.118.133.822.018.522.018.521.718.617.919.218.517.818.819.0

Selling General And Administrative Expense

us-gaap:SellingGeneralAndAdministrativeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value319381299299281318258277257296271265262259230231232241212221187183157159129122123108899487777865575650
Percentage of SellingGeneralAndAdministrativeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax22.127.523.724.924.728.225.226.527.632.631.529.030.131.228.830.833.234.531.934.831.230.728.431.122.830.733.332.130.634.535.638.042.139.640.444.643.1

Operating Income Loss

us-gaap:OperatingIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value69554153053251643358-400267108802262121271791941659715418110320323621820913813513711610714283707566494045423230
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax48.139.142.044.345.33.934.9-38.328.711.99.324.824.415.322.425.923.713.923.228.517.334.042.642.737.031.233.837.234.533.748.530.528.633.132.426.424.228.930.225.726.0

Interest Expense

us-gaap:InterestExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value25211718192424252425252424242423232319300001111122000000
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.81.61.41.51.72.22.42.42.62.82.92.62.82.93.13.23.43.33.00.60.10.10.10.10.20.30.30.30.60.80.90.10.10.10.10.10.2

us-gaap:DerivativeInstrumentRisk, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:InterestRateContract, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value40-3-4-4-5-4-3-1
Percentage of InterestExpense17.8-3.7-19.0-24.6-23.1-20.8-16.3-12.4-5.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.3-0.1-0.3-0.4-0.4-0.5-0.4-0.3-0.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:InterestRateContract us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest0.00.00.00.00.00.00.00.00.0

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value03300222-120-202-1-1-30
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.12.40.00.00.20.20.2-0.10.30.0-0.20.00.2-0.1-0.1-0.40.0

Income Loss From Continuing Operations Before Income Taxes Domestic

Income Loss From Continuing Operations Before Income Taxes Foreign

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value106-2876739-4612113810259-204124116355517323715525852524041344845220141314109
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.3-20.75.43.3-4.01.11.13.711.06.5-2.34.52.81.48.07.37.31.148.51.12.68.710.510.29.310.111.210.216.516.59.20.17.78.410.48.27.8

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value133210-2
Percentage of IncomeTaxExpenseBenefit1.54.78.1-5.615.20.5-2.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.30.30.20.20.0-0.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest14.029.135.237.151.5-11.820.6

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
Value522870477422577-61340-4142373255115146169771113374-19111315416125816015562841067745
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax36.262.937.835.150.6-5.533.2-39.725.63.66.412.616.820.49.614.84.810.6-28.817.825.727.046.631.327.515.522.831.426.516.5

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

Net Income Loss

us-gaap:NetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value557889467459587-45330-457249307816517093941149266-18317091153177166159-18939582809236454865342626272120
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax38.664.237.038.251.6-4.032.2-43.826.83.39.118.119.611.211.815.313.19.5-27.626.815.225.632.032.528.1-4.323.425.924.325.331.313.218.621.232.118.716.217.019.717.317.8

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value51110951-9
Percentage of NetIncomeLoss0.92.42.31.51.7-0.3-3.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.90.90.80.50.1-1.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest45.6101.8114.3128.6169.7-70.668.7

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value557889467459587-45330-457249
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax38.664.237.038.251.6-4.032.2-43.826.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.0

Net Income Loss Available To Common Stockholders Diluted

Assets

us-gaap:Assets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1814817544148151456713999139311384313490138301358313643134891343513253132931302912802131331315313167441442013890355333793317304928152685261325052457201713941305117911541012786
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value6400627244474404429347664673472347174690469946144579455947894830474048744900461489889976767267893569560359564263370780426024922625315298
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets35.335.830.030.230.734.233.835.034.134.534.434.234.134.436.037.137.037.137.335.020.321.419.718.920.128.222.821.422.224.625.328.839.918.719.119.221.915.012.5

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1814817544148151456713999139311384313490138301358313643134891343513253132931302912802131331315313167441442013890355333793317304928152685261325052457201713941305117911541012786
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-312007-12-31
Value117471127110367101639706916591698767911288938944887588568694850481998062825882528552351633023123288127002382235422112090197018721749121311341055953901859688247101
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets64.764.270.069.869.365.866.265.065.965.565.665.865.965.664.062.963.062.962.765.079.778.680.381.179.971.877.278.677.875.474.771.260.181.380.980.878.185.087.50.00.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312010-12-312009-12-312008-12-312007-12-31
Value-101-66-48-57-20-96-2-45-34606256-24-7-12-1
Percentage of StockholdersEquity-0.9-0.6-0.5-0.6-0.2-0.10.1-0.0-0.5-0.40.70.81.7-1.0-0.8-0.31.2-1.4
Percentage of Assets-0.6-0.4-0.3-0.4-0.1-0.10.0-0.0-0.3-0.30.50.51.3-0.7-0.7-0.20.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value886488048738867786048539848184208350829079577726259221061852126111731093941833
Percentage of StockholdersEquity75.578.184.385.488.693.292.596.091.693.291.593.678.588.494.0111.2136.5158.9381.1820.9
Percentage of Assets48.850.259.059.661.561.361.362.460.461.060.058.861.763.570.990.5116.0139.10.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value0.00.00.00.00.00.00.00.00.00.00.023000.020000.020000.020000.019000.06000.05000.05000.04000.0
Percentage of StockholdersEquity0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value5197463937503283282323252370204024972242181811801036379126-128-303-400-696-729
Percentage of StockholdersEquity44.241.236.232.329.125.425.923.327.425.220.914.331.415.96.4-11.3-35.4-58.2-281.8-718.2
Percentage of Assets28.626.425.322.520.216.717.115.118.116.513.79.024.711.44.8-9.2-30.0-51.00.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-2213-2105-2073-1738-1701-1689-1689-1689-1689-1604-1141-710-382-80-14-2-2-2-1-1
Percentage of StockholdersEquity-18.8-18.7-20.0-17.1-17.5-18.4-18.4-19.3-18.5-18.0-13.1-8.6-11.6-3.4-0.7-0.2-0.3-0.4-0.5-1.2
Percentage of Assets-12.2-12.0-14.0-11.9-12.2-12.1-12.2-12.5-12.2-11.8-8.6-5.4-9.1-2.4-0.5-0.2-0.3-0.30.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Assets Current

us-gaap:AssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value48705076434141683650338532482836315229532882278927332578259423612127242524802533285227962559234122452186191516781550149514101276811941817700669646373
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets26.828.929.328.626.124.323.521.022.821.721.120.720.319.519.518.116.618.518.919.264.666.565.865.966.565.962.859.657.757.256.351.940.267.562.659.458.063.947.5

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value2315268521711984154413651228727511584550542713966761597710101011631322916943752612528529910936102298990580635954043834728926720921218615713895
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets12.815.314.713.611.09.88.95.43.74.34.04.05.37.35.74.65.57.78.810.020.822.519.317.215.616.029.933.338.137.936.132.817.838.833.629.525.126.40.00.00.020.00.00.0

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value13451243111611231016922910853776726705710660650676609586532512535479432436440429421404355323295311282267244221212200168113
Percentage of AccountsReceivableNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets7.47.17.57.77.36.66.66.35.65.35.25.34.94.95.14.74.64.13.94.110.910.311.212.412.712.713.312.612.111.312.411.513.317.517.018.017.416.714.5

Inventory Net

us-gaap:InventoryNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value58662757649448247243246345646044141039637536332929328923623417417614014412610210511210194909492817875746240
Percentage of InventoryNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.23.63.93.43.43.43.13.43.33.43.23.02.92.82.72.52.32.21.81.84.04.23.64.13.73.13.44.03.83.63.63.84.65.86.06.46.46.15.2

us-gaap:PublicUtilitiesInventory

alxn:PreApprovalInventory



Period End2020-03-312019-12-31
Value6760
Percentage of InventoryNet11.59.6
Percentage of Assets0.40.3
Percentage of Assets alxn:PreApprovalInventory0.00.0

Inventory Finished Goods

us-gaap:InventoryFinishedGoods



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value428405360339342350314292289307279260203215153152114911121138254607145283045404450554034502020
Percentage of InventoryFinishedGoods100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.42.32.42.32.42.52.32.22.12.32.01.91.51.61.21.20.90.70.90.91.91.31.62.01.30.91.01.61.51.72.02.32.02.53.91.72.0

Other Assets Current

us-gaap:OtherAssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value575456432460497426370342327292207225215260241242219217272268273189147111878778718175847373505223242620
Percentage of OtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.22.62.93.23.63.12.72.52.42.21.51.71.62.01.81.91.71.72.12.06.24.53.83.12.62.62.62.53.02.93.43.03.63.64.02.02.22.72.6

Land

Machinery And Equipment Gross

Noncurrent Assets

Property Plant And Equipment Gross

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value11591163114811231095147114431422137913251354123311381036931825749697618555440392328273218201178173164165165164165165164163160162164
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.46.67.77.77.810.610.410.510.09.89.99.18.57.87.06.35.95.34.74.210.09.38.47.76.56.15.96.26.16.36.66.78.211.912.613.913.916.020.9

Goodwill

us-gaap:Goodwill



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value50725037503750375037503750375037503750375037503750375037503750375049504750155007254254254254254254254254254253253255264798080791919
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets27.928.734.034.636.036.236.437.336.437.136.937.337.538.037.938.739.438.438.138.05.86.06.57.17.57.78.39.09.59.710.110.413.15.76.16.86.92.02.5

us-gaap:BusinessAcquisition

alxn:Achillion



Period End2020-01-28
Value34
Percentage of Goodwill0.0
Percentage of Assets0.0
Percentage of Assets alxn:Achillion0.0

Intangible Assets Net Excluding Goodwill

us-gaap:IntangibleAssetsNetExcludingGoodwill



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value41873344341034873560364137133793387439544032411242234303446745474627470747874824587587597599603609646643644646648675677919294952428
Percentage of IntangibleAssetsNetExcludingGoodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets23.119.123.023.925.426.126.828.128.029.129.630.531.432.533.634.936.135.836.436.613.314.015.416.917.818.421.222.824.024.725.927.533.66.67.18.08.32.43.6

Finite Lived Intangible Assets Net

us-gaap:BusinessAcquisition, us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsNet

alxn:SynagevaBioPharmaCorp., alxn:PurchasedTechnology



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value29272992305731223187
Percentage of FiniteLivedIntangibleAssetsNet100.0100.0100.0100.0100.0
Percentage of Assets16.117.120.621.422.8
Percentage of Assets alxn:SynagevaBioPharmaCorp. alxn:PurchasedTechnology0.00.00.00.00.0

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

alxn:PurchasedTechnology



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value324833213395347135513631371137913871395140324112419242724351443145114591467100440
Percentage of FiniteLivedIntangibleAssetsNet111.0111.0111.1111.2111.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets17.918.922.923.825.426.126.828.128.029.129.630.531.232.232.734.035.235.035.50.00.00.20.30.0
Percentage of Assets alxn:PurchasedTechnology0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:LicensingAgreements



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-31
Value2122141699122200000000009102021221417
Percentage of FiniteLivedIntangibleAssetsNet0.70.70.50.50.30.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets0.10.10.10.10.10.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.30.40.80.91.11.01.7
Percentage of Assets us-gaap:LicensingAgreements0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value100000.0200000.0200000.0200000.0200000.0200000.0200000.0200000.0300000.0300000.0400000.0
Percentage of FiniteLivedIntangibleAssetsNet0.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:OtherIntangibleAssets0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Patents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value000000000000000000001356
Percentage of FiniteLivedIntangibleAssetsNet0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.40.7
Percentage of Assets us-gaap:Patents0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Deferred Tax Assets Liabilities Net

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value4324296715414623964004003873123383183042992622572482552502472801371017755624555593813191712115545
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.42.44.53.73.32.82.93.02.82.32.52.42.32.32.02.01.91.91.91.96.33.32.62.21.61.91.52.02.21.50.50.80.90.90.90.50.50.50.7

Liabilities Current

us-gaap:LiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1119119410911031943117410271044942952972856837823103465860371876676958060650241739658239530229536036137535323021118721713885
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.26.87.47.16.78.47.47.76.87.07.16.36.26.27.85.14.75.55.85.813.114.412.911.811.717.613.010.811.013.814.415.317.516.516.215.918.813.710.8

Long Term Debt Current

us-gaap:LongTermDebtCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value12612612612612693612816716716716716716732279351751751314548484848484848484848481080
Percentage of LongTermDebtCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets0.70.70.90.90.90.70.40.21.21.21.21.21.21.32.40.60.31.31.31.01.01.11.21.41.41.41.61.71.81.81.92.05.40.0

Accounts Payable Current

Accounts Payable And Accrued Liabilities Current

us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value862966868728669698710
Percentage of AccountsPayableAndAccruedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.85.55.95.04.85.05.2

Other Accrued Liabilities Current

Taxes Payable Current

Other Liabilities Current

us-gaap:OtherLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1301009676493428316559493722233689876245367605456585612759953791715114
Percentage of OtherLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.70.60.70.50.40.20.20.20.50.40.40.30.20.20.30.70.70.50.00.41.51.41.41.61.71.70.40.30.20.40.40.20.20.60.71.51.31.20.6

Long Term Debt

us-gaap:CreditFacility, us-gaap:DebtInstrument, us-gaap:LongtermDebtType

us-gaap:LongTermDebt

alxn:SeniorSecuredTermLoan, alxn:CreditAgreement, us-gaap:LineOfCredit



Period End2020-03-312019-12-312018-12-312018-09-302018-06-30
Value24812514261226122612
Percentage of LongTermDebt100.0100.0100.0100.0100.0
Percentage of Assets13.714.318.818.919.4
Percentage of Assets alxn:SeniorSecuredTermLoan alxn:CreditAgreement us-gaap:LineOfCredit0.00.00.00.00.0

Long Term Debt Noncurrent

us-gaap:LongTermDebtNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value23432375240624382470250125332564267827202763280428462888292931713212328133253368092133456577891011011131802470
Percentage of LongTermDebtNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0
Percentage of Assets12.913.516.216.717.618.018.319.019.420.020.320.821.221.822.024.325.125.025.325.60.00.20.60.91.32.02.53.23.83.94.57.312.20.0

Deferred Tax Liabilities Noncurrent

Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value302265280269267155129132151140118134110901311241077382217755344534547524236221812911910992
Percentage of OtherLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.71.51.91.81.91.10.91.01.11.00.91.00.80.71.01.00.80.60.61.71.71.31.11.51.41.41.71.51.40.90.70.50.50.80.80.90.80.90.3

Stockholders Equity

us-gaap:StockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-312007-12-31
Value117471127110367101639706916591698767911288938944887588568694850481998062825882528552351633023123288127002382235422112090197018721749121311341055953901859688247101
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets64.764.270.069.869.365.866.265.065.965.565.665.865.965.664.062.963.062.962.765.079.778.680.381.179.971.877.278.677.875.474.771.260.181.380.980.878.185.087.50.00.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312010-12-312009-12-312008-12-312007-12-31
Value-101-66-48-57-20-96-2-45-34606256-24-7-12-1
Percentage of StockholdersEquity-0.9-0.6-0.5-0.6-0.2-0.10.1-0.0-0.5-0.40.70.81.7-1.0-0.8-0.31.2-1.4
Percentage of Assets-0.6-0.4-0.3-0.4-0.1-0.10.0-0.0-0.3-0.30.50.51.3-0.7-0.7-0.20.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value886488048738867786048539848184208350829079577726259221061852126111731093941833
Percentage of StockholdersEquity75.578.184.385.488.693.292.596.091.693.291.593.678.588.494.0111.2136.5158.9381.1820.9
Percentage of Assets48.850.259.059.661.561.361.362.460.461.060.058.861.763.570.990.5116.0139.10.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value0.00.00.00.00.00.00.00.00.00.00.023000.020000.020000.020000.019000.06000.05000.05000.04000.0
Percentage of StockholdersEquity0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value5197463937503283282323252370204024972242181811801036379126-128-303-400-696-729
Percentage of StockholdersEquity44.241.236.232.329.125.425.923.327.425.220.914.331.415.96.4-11.3-35.4-58.2-281.8-718.2
Percentage of Assets28.626.425.322.520.216.717.115.118.116.513.79.024.711.44.8-9.2-30.0-51.00.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-2213-2105-2073-1738-1701-1689-1689-1689-1689-1604-1141-710-382-80-14-2-2-2-1-1
Percentage of StockholdersEquity-18.8-18.7-20.0-17.1-17.5-18.4-18.4-19.3-18.5-18.0-13.1-8.6-11.6-3.4-0.7-0.2-0.3-0.4-0.5-1.2
Percentage of Assets-12.2-12.0-14.0-11.9-12.2-12.1-12.2-12.5-12.2-11.8-8.6-5.4-9.1-2.4-0.5-0.2-0.3-0.30.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Value

us-gaap:CommonStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value0.00.00.00.00.00.00.00.00.00.00.00.00.00.023000.023000.023000.023000.023000.023000.020000.020000.020000.020000.020000.020000.020000.020000.020000.020000.019000.019000.019000.019000.019000.018000.06000.06000.05000.0
Percentage of CommonStockValue0.00.00.00.00.00.00.00.00.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value519746393750328328232325237020402497224222122134196918181724138712721180111312971127103688270453837939830420812645-46-83-128-176-242-277-303-400
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets28.626.425.322.520.216.717.115.118.116.516.215.814.713.713.010.69.99.08.59.925.524.722.719.815.911.413.110.87.84.81.8-1.9-4.1-9.2-13.5-20.5-24.0-30.0-51.0

Treasury Stock Value

us-gaap:TreasuryStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value221321052073173817011689168916891689160414401380120911411110104110077105584664423823632581028080804914222222222
Percentage of TreasuryStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets12.212.014.011.912.212.112.212.512.211.810.610.29.08.68.48.07.95.44.23.510.09.19.37.33.02.42.62.91.80.50.10.10.10.20.20.20.20.30.3

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value-101-66-48-57-20-96-2-45-34-37-143660-16036254621195648-32-26-22-121930621674-3-19-14-7-1
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-0.6-0.4-0.3-0.4-0.1-0.10.0-0.0-0.3-0.3-0.3-0.10.30.5-0.10.00.00.50.40.52.71.41.2-0.9-0.8-0.7-0.40.71.20.30.10.70.40.3-0.2-1.7-1.2-0.7-0.2

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-312009-12-31
Value-9-9-2-2-2-2-4-4-4-4-7-7-7-7-8-8-7-9-15-24-16-16-14-14-11-11-8-8-5-5-4-4-4-4-3-1
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax9.113.85.44.512.726.8-59.4141.49.014.018.950.0-19.4-11.750.3-1207.3-195.8-15.4-27.7-38.4-14.1-29.2-30.443.743.550.368.7-43.0-18.5-86.1-212.5-30.1-55.4-100.142.357.7
Percentage of Assets-0.1-0.1-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.2-0.4-0.4-0.4-0.4-0.3-0.3-0.3-0.3-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.1
Percentage of Assets us-gaap:AccumulatedDefinedBenefitPlansAdjustment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value-66-40-26-38093321-29-13
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax65.660.054.166.1-2.9-99.0478.3-744.864.140.4
Percentage of Assets-0.4-0.2-0.2-0.30.00.10.20.2-0.2-0.1
Percentage of Assets us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest0.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-312011-12-312010-12-312009-12-31
Value0000000000000-1020000000000000000
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax0.30.10.20.20.53.1-1.46.90.4-0.6-0.0-0.00.0-1.7-4.6385.918.7-1.30.30.00.7-0.40.4-3.0-2.50.60.1-1.20.00.0-0.1-1.1
Percentage of Assets-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.00.00.00.00.0-0.00.00.00.0-0.00.00.00.0-0.00.00.00.0-0.0-0.0-0.00.00.00.00.0
Percentage of Assets us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedTranslationAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-312009-12-31
Value-25-17-19-16-18-16-21-20-12-15-15-17-21-24-17-17-17-19-19-17-19-13-9-6-6-7-3-4-4-2-2-3-2-2-1-1
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax25.026.040.229.289.8169.1-317.4696.626.546.240.5121.4-58.3-40.0104.6-2575.5-471.8-32.1-36.3-28.7-16.0-24.2-20.321.026.032.327.4-22.2-13.8-42.3-115.9-22.4-34.1-70.822.856.8
Percentage of Assets-0.1-0.1-0.1-0.1-0.1-0.1-0.2-0.1-0.1-0.1-0.1-0.1-0.2-0.2-0.1-0.1-0.1-0.2-0.2-0.1-0.4-0.3-0.3-0.2-0.2-0.2-0.1-0.2-0.2-0.1-0.1-0.2-0.1-0.2-0.2-0.1
Percentage of Assets us-gaap:AccumulatedTranslationAdjustment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value54951759953842983387-34329925727028030838229124316719022323823283281106-3146622421
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax38.037.447.544.737.77.437.7-32.932.228.331.430.735.446.136.532.424.027.233.537.43.847.350.720.7-5.513.725.714.718.3

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-76656-8-41252104568-2540-171-253-495114-65-330-5-161-195-3179-48-57-750-90-5-609-72-2
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-53.04.1-0.7-3.40.34.610.254.4-27.40.1-19.9-27.7-57.013.8-8.2-43.9-0.8-23.1-29.3-499.8-8.1-9.5-13.60.0-15.9-1.6-248.9-43.9-1.9

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-138-59-365-61-2523117-123-225-95-207-69-283-62-24-466-181-18533465-30-59-22119-43646910
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-9.6-4.3-29.0-5.1-22.10.31.10.7-13.3-24.8-11.1-22.7-7.9-34.1-7.8-3.2-66.5-25.9-27.8526.00.8-5.0-10.7-4.421.0-1.3149.042.19.1

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value54951759953842983387-34329925727028030838229124316719022323823283281106-3146622421
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax38.037.447.544.737.77.437.7-32.932.228.331.430.735.446.136.532.424.027.233.537.43.847.350.720.7-5.513.725.714.718.3

Net Income Loss

us-gaap:NetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value557889467459587-45330-457249307816517093941149266-18317091153177166159-18939582809236454865342626272120
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax38.664.237.038.251.6-4.032.2-43.826.83.39.118.119.611.211.815.313.19.5-27.626.815.225.632.032.528.1-4.323.425.924.325.331.313.218.621.232.118.716.217.019.717.317.8

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value51110951-9
Percentage of NetIncomeLoss0.92.42.31.51.7-0.3-3.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.90.90.80.50.1-1.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest45.6101.8114.3128.6169.7-70.668.7

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value557889467459587-45330-457249
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax38.664.237.038.251.6-4.032.2-43.826.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.0

Depreciation Depletion And Amortization

us-gaap:DepreciationDepletionAndAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value89909296979810410010118511010299100100979693491210189996543
Percentage of DepreciationDepletionAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Increase Decrease In Inventories

us-gaap:IncreaseDecreaseInInventories



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-375181121141-308-31936141911333538112-2-240-81420591012
Percentage of IncreaseDecreaseInInventories100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-76656-8-41252104568-2540-171-253-495114-65-330-5-161-195-3179-48-57-750-90-5-609-72-2
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-53.04.1-0.7-3.40.34.610.254.4-27.40.1-19.9-27.7-57.013.8-8.2-43.9-0.8-23.1-29.3-499.8-8.1-9.5-13.60.0-15.9-1.6-248.9-43.9-1.9

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value12304146364241626688941007510794666480767357522243175322
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-138-59-365-61-2523117-123-225-95-207-69-283-62-24-466-181-18533465-30-59-22119-43646910
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-9.6-4.3-29.0-5.1-22.10.31.10.7-13.3-24.8-11.1-22.7-7.9-34.1-7.8-3.2-66.5-25.9-27.8526.00.8-5.0-10.7-4.421.0-1.3149.042.19.1

Proceeds From Issuance Of Long Term Debt

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value323232320002504344444344200200001754304512121212190
Percentage of RepaymentsOfLongTermDebt100.0100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.00.0100.0100.0100.0100.0100.0100.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Payments For Repurchase Of Common Stock

us-gaap:PaymentsForRepurchaseOfCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value1073233437110008516460171683069342961529123601910415622350
Percentage of PaymentsForRepurchaseOfCommonStock100.0100.0100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value323232320002504344444344200200001754304512121212190
Percentage of RepaymentsOfLongTermDebt100.0100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.00.0100.0100.0100.0100.0100.0100.00.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Debt Instrument Interest Rate Stated Percentage

Effective Income Tax Rate Continuing Operations

us-gaap:EffectiveIncomeTaxRateContinuingOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value0.16-0.1420.1270.079-0.0850.1260.033-0.0930.2920.093-0.3450.1990.124-0.042999999999999980.4030.3240.358-0.105999999999999982.3190.040.1460.00200000000000000180.2480.2390.2480.3020.3010.2960.3450.5560.330.0020.2920.3430.3460.321
Percentage of EffectiveIncomeTaxRateContinuingOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price

Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period

Share Based Compensation

us-gaap:ShareBasedCompensation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value576059605652455351715761544046475666516742332828231613118
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Deferred Tax Liabilities

Deferred Tax Assets Net

Unrecognized Tax Benefits

Deferred Tax Assets Valuation Allowance

Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value2032042062091920
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.00.0

Cash And Cash Equivalents Period Increase Decrease

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value23552723220319841546136712317325135865505417159681010
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:AmortizationofIntangibleAssetsAcquired



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-03-312013-03-31
Value73737580808080808080808080798280807936000000
Percentage of AmortizationofIntangibleAssetsAcquired100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.00.0100.0

alxn:AssetAcquisitionContingentConsiderationMilestonePayments



Period End2020-03-312019-09-30
Value160100
Percentage of AssetAcquisitionContingentConsiderationMilestonePayments100.0100.0

us-gaap:BusinessAcquisition

alxn:BusinessCombinationConsiderationTransferredPerShare

alxn:Achillion



Period End2020-01-28
Value6.3
Percentage of BusinessCombinationConsiderationTransferredPerShare100.0

us-gaap:StatementScenario, us-gaap:BusinessAcquisition

srt:ScenarioForecast, alxn:PortolaPharmaceuticals



Period End2020-09-30
Value18.0
Percentage of BusinessCombinationConsiderationTransferredPerShare0.0

us-gaap:BusinessAcquisition

alxn:BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresTransactionCosts

alxn:Achillion



Period End2020-03-312019-03-31
Value10
Percentage of BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresTransactionCosts100.00.0

us-gaap:CounterpartyName, us-gaap:TypeOfArrangement

alxn:CollaborationAgreementPotentialFuturePaymentsMilestoneAchievement

alxn:EidosMember, alxn:AffibodyABDomain



Period End2020-03-31
Value30
Percentage of CollaborationAgreementPotentialFuturePaymentsMilestoneAchievement100.0

alxn:Zealand, alxn:ZealandPharma



Period End2020-03-312019-09-302019-06-302019-03-31
Value61000610
Percentage of CollaborationAgreementPotentialFuturePaymentsMilestoneAchievement2033.30.00.00.0

us-gaap:TypeOfArrangement

alxn:CollaborationandLicenseAgreement



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value42-780-30838
Percentage of CollaborationAgreementPotentialFuturePaymentsMilestoneAchievement141.70.00.00.00.0

us-gaap:CounterpartyName, us-gaap:TypeOfArrangement

alxn:DerivativeFairValueDiscountedCostOfDebt

alxn:CaelumBiosciences, us-gaap:CollaborativeArrangement



Period End2020-03-31
Value0.021
Percentage of DerivativeFairValueDiscountedCostOfDebt100.0

us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass

alxn:FairValueInputsCostOfDebt

srt:Maximum, us-gaap:FairValueInputsLevel3, alxn:AcquisitionRelatedContingentConsideration



Period End2020-01-282020-03-31
Value0.0230.018
Percentage of FairValueInputsCostOfDebt100.0100.0

srt:Minimum, us-gaap:FairValueInputsLevel3, alxn:AcquisitionRelatedContingentConsideration



Period End2020-01-282020-03-31
Value0.0210.016
Percentage of FairValueInputsCostOfDebt88.991.3

alxn:FairValueInputsWeightedAverageCostOfCapital



Period End2020-03-31
Value0.115
Percentage of FairValueInputsWeightedAverageCostOfCapital100.0

us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass

srt:Minimum, us-gaap:FairValueInputsLevel3, alxn:AcquisitionRelatedContingentConsideration



Period End2020-03-31
Value0.09
Percentage of FairValueInputsWeightedAverageCostOfCapital78.3

alxn:NoncashOrPartNoncashAcquisitionContingentConsiderationIssued



Period End2020-03-312019-03-31
Value1550
Percentage of NoncashOrPartNoncashAcquisitionContingentConsiderationIssued100.00.0

alxn:OperatingRightOfUseAssetsExchangedForOperatingLeaseLiability



Period End2020-03-312019-09-302019-06-302019-03-312018-09-30
Value332000
Percentage of OperatingRightOfUseAssetsExchangedForOperatingLeaseLiability100.0100.0100.00.00.0

alxn:RestructuringChargesAndAccrualAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value00029010105572324100011716715000
Percentage of RestructuringChargesAndAccrualAdjustment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value576059605551445351
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value576059605551445351
Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AmortizationOfFinancingCosts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-30
Value1111111322222222322
Percentage of AmortizationOfFinancingCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AmortizationOfIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-03-312014-12-312014-09-302014-06-302013-12-312013-09-302013-06-30
Value7475778180808080808080808079828080793601100700
Percentage of AmortizationOfIntangibleAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0

us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value3312233664432211122301112123
Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessAcquisitionsProFormaNetIncomeLoss

alxn:Achillion



Period End2020-03-312019-03-31
Value574515
Percentage of BusinessAcquisitionsProFormaNetIncomeLoss100.0100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessAcquisitionsProFormaRevenue

alxn:Achillion



Period End2020-03-312019-03-31
Value14441140
Percentage of BusinessAcquisitionsProFormaRevenue100.0100.0

us-gaap:BusinessCombinationAcquisitionRelatedCosts



Period End2020-03-312019-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-31
Value3800000002611108102130413019
Percentage of BusinessCombinationAcquisitionRelatedCosts100.00.0100.00.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationConsiderationTransferred1

alxn:Achillion



Period End2020-01-28
Value926
Percentage of BusinessCombinationConsiderationTransferred1100.0

us-gaap:StatementScenario, us-gaap:BusinessAcquisition

srt:ScenarioForecast, alxn:PortolaPharmaceuticals



Period End2020-09-30
Value1380
Percentage of BusinessCombinationConsiderationTransferred10.0

us-gaap:BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value54296-28553452942445405-14182941110810-1212
Percentage of BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

alxn:Achillion



Period End2020-03-31
Value1
Percentage of BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability129.3

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationIntegrationRelatedCosts

alxn:Achillion



Period End2020-03-312019-03-31
Value100000.00.0
Percentage of BusinessCombinationIntegrationRelatedCosts100.00.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed

alxn:Achillion



Period End2020-03-312019-03-31
Value380
Percentage of BusinessCombinationSeparatelyRecognizedTransactionsAdditionalDisclosuresAcquisitionCostExpensed100.00.0

us-gaap:CapitalExpendituresIncurredButNotYetPaid



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value1310-1131011-5-16321-25300-312443911214000
Percentage of CapitalExpendituresIncurredButNotYetPaid100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-367520218438179138498219-72348-171-252
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredIncomeTaxesAndTaxCredits



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value49-319-9540-81-46-32228811-7923-18194629938921-246-48-54-582523106
Percentage of DeferredIncomeTaxesAndTaxCredits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

us-gaap:DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred

us-gaap:InterestRateContract, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value42-5-8-1510-313-6156102
Percentage of DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation, us-gaap:IncomeStatementLocation

us-gaap:ForeignExchangeForward, us-gaap:DesignatedAsHedgingInstrument, us-gaap:Sales



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302017-09-302016-09-30
Value2724-12176-25-13
Percentage of DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred66.0-276.179.9163.649.6-2500.00.0

us-gaap:EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents



Period End2020-03-312019-03-312018-03-312017-03-31
Value-13-163
Percentage of EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0

us-gaap:ForeignCurrencyTransactionGainLossBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value-7-106-134-152-5-381-1-1-20-12-210-2-11000000000000
Percentage of ForeignCurrencyTransactionGainLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value-4344431
Percentage of ForeignCurrencyTransactionGainLossBeforeTax64.8-425.075.0-242.197.6-20.456.0

us-gaap:GainLossOnDerivativeInstrumentsNetPretax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value15126-5-5513-63-3-1618-10
Percentage of GainLossOnDerivativeInstrumentsNetPretax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:HedgingDesignation

us-gaap:GainLossOnFairValueHedgesRecognizedInEarnings

us-gaap:Nondesignated



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-03-31
Value161-53618-8-30-9-2-5-122-6612-12-2160
Percentage of GainLossOnFairValueHedgesRecognizedInEarnings100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value663602535499541-32342-4183518958206194104158169143741391771062052362182111341371161408167654940423230
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:StatementEquityComponents

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value614131171-11
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments1.02.72.72.12.1-0.3-3.3

us-gaap:IncreaseDecreaseInAccountsPayableAndAccruedLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-682318331-8112-36-56-7329412239579935-4231-1362-139888138-60-62-25-4
Percentage of IncreaseDecreaseInAccountsPayableAndAccruedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInAccountsReceivable



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value1201202101951160944220-11433-764273724-1850585139026202617
Percentage of IncreaseDecreaseInAccountsReceivable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value72-11-846858702923324347713-22312265-223193812-1151-33-13-51-9
Percentage of IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value101110101021201110022033444478888866
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements100.00.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentIncomeNet



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value-523-144257
Percentage of InvestmentIncomeNet100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
Value0000000000001-1-1110001000000000
Percentage of OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent100.00.00.00.0100.0100.0100.00.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
Value-82-21-25-1-830243-60010-11-5-3-20000-10-1
Percentage of OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value-29-1020-27-1-61545-200-24-40-1589-87-442418-29882185-6-2-9-27-429
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value0-6000001000000002-39-70-20-30-30-20
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax-0.062.30.0-0.0-0.0-4.9-0.72.6-0.5-100.0-0.0-0.0-0.01.10.7-13.6-4.6-12.352.926.0-0.5-9.2-0.744.42.734.20.362.3-0.2

us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value-2123-2801752-24
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax72.2112.0105.6-0.0111.1114.0116.7

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value0000000000000-1-1210001000000
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax0.7-0.00.0-0.0-11.11.60.71.11.940.0-0.0-0.0-0.0-2.116.728.7-3.0-3.80.82.71.2-1.9-0.9-4.4-30.11.3-0.5

us-gaap:AccumulatedTranslationAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value-82-21-25-1-830270-60010-11-5-3-200-400-1
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax27.1-18.9-12.0-5.6111.1-90.2-11.1-17.7-18.2120.0-8.3-17.5-0.0-7.4-5.41.7-4.5-0.9-10.2-4.0-6.1-17.8-3.5-0.7-18.843.0-3.61.8-4.9

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax



Period End2020-03-312019-03-31
Value-26-9
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax100.0100.0

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value-83-12-2215-4
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax

us-gaap:ForeignExchangeForward, us-gaap:CashFlowHedging, us-gaap:Sales



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value88752-1-10
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestRateContract, us-gaap:CashFlowHedging, us-gaap:InterestExpense



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value-3233321
Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax-40.930.248.666.7124.0-192.3-10.9

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-34-189-37-10-16942-112-23-50-2476-17-3-587-8-5662880-6-3-31-11-24-148-3
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value0-600010001000100258-70-10-2000
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent-0.035.50.0-0.0-0.0-9.00.00.0-6.290.5-0.0-0.0-0.02.3-0.129.2-3.669.8-110.412.6-0.4-21.9-0.744.6-0.0-0.0-0.0

us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value-2612-38-91150-15
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent76.4125.8104.083.3116.3118.9136.3

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value0000000000001-1-11100010000
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent0.6-0.00.0-0.0-1.91.21.00.03.5-19.0-0.0-0.0-4.2-2.011.0-63.0-2.6-11.9-1.71.41.7-5.1-1.0-5.0-22.7

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-349-37-10-16-38-48-11
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0-392.9-112.6100.0

us-gaap:AccumulatedTranslationAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value-82-21-25-1-830243-60010-11-5-3-20010
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent23.1-10.8-25.8-4.018.5-33.1-17.3-18.9-33.6-28.6-8.7-8.0-12.5-8.6-2.8-4.0-3.4-2.722.8-2.1-8.6-47.0-3.7-0.8-14.1-6.011.3

us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax

us-gaap:ForeignExchangeForward, us-gaap:CashFlowHedging



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value2630-314949-32
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestRateContract, us-gaap:CashFlowHedging



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value-476-7-24-14-23738
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax-181.90.0-23.3630.8-100.00.073.56.3-24.9

us-gaap:OtherNoncashIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value-130010-116-6-6-8-1215-2-1010-805-12-3-2100000
Percentage of OtherNoncashIncomeExpense100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherSignificantNoncashTransactionValueOfConsiderationGiven1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value04700270000
Percentage of OtherSignificantNoncashTransactionValueOfConsiderationGiven10.0100.0100.0100.0100.00.00.00.00.0

us-gaap:PaymentsForProceedsFromOtherInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value000000-10-25-4-2001000-40000009000
Percentage of PaymentsForProceedsFromOtherInvestingActivities0.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value19291041011158270342
Percentage of PaymentsToAcquireAvailableForSaleSecuritiesDebt100.0100.0100.0100.00.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired



Period End2020-03-312019-03-312016-12-312016-09-302015-12-312015-09-302014-12-312014-09-302013-03-312012-03-312011-03-31
Value83700000000605105
Percentage of PaymentsToAcquireBusinessesNetOfCashAcquired100.00.00.00.00.0100.00.00.00.0100.0100.0

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:PaymentsToAcquireEquityMethodInvestments

alxn:CommonStockInBiotechnologyCompany



Period End2020-03-31
Value14
Percentage of PaymentsToAcquireEquityMethodInvestments100.0

us-gaap:PaymentsToAcquireIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value008080000
Percentage of PaymentsToAcquireIntangibleAssets0.00.0100.00.0100.00.00.00.00.0

us-gaap:PaymentsToAcquireOtherInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value349190431000000001200250000
Percentage of PaymentsToAcquireOtherInvestments100.0100.0100.00.0100.0100.00.00.00.00.00.00.00.0100.00.00.0100.00.00.00.00.0

us-gaap:PaymentsToAcquireTradingSecuritiesHeldforinvestment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value642553125132311132812100100
Percentage of PaymentsToAcquireTradingSecuritiesHeldforinvestment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value-1-1-1-1-1-10-50-40-93-4-200-4-3-100000000
Percentage of ProceedsFromPaymentsForOtherFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value14111714692117301899155157374276282232191242696662854176221122176990
Percentage of ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:ProceedsFromSaleAndMaturityOfMarketableSecurities



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312012-03-312011-03-312010-03-31
Value32533323110355
Percentage of ProceedsFromSaleAndMaturityOfMarketableSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

us-gaap:ProceedsFromStockOptionsExercised



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value2621010516159916134798163311962436252130915
Percentage of ProceedsFromStockOptionsExercised100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value58111091052-9-2-1109128101416262726134001465
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value00000-1010-10000000-800000000000
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax0.00.00.00.00.0-11.4-1.841.46.253.8-0.00.00.0-6.0-0.9-0.6-0.6-51.12.4-1.7-0.9-1.5-1.342.6-8.2-7.9-2.3-1.7-1.4

us-gaap:AccumulatedGainLossCashFlowHedgeIncludingNoncontrollingInterest



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value51110951-9
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0101.841.493.8

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value0.00.00.00.00.0100000.00.0500000.00.0200000.00.00.0-1000000.0-340000.0410000.095000.0-165000.012000.01000.014000.08000.015000.09000.00.01000.08000.0-60000.0
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax0.00.00.00.00.01.00.017.2-0.0-7.7-0.00.0-11.1-2.64.90.9-1.10.10.00.10.00.10.2-0.00.10.6-1.4

us-gaap:AccumulatedTranslationAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value000000000003-30000000000000000
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax0.00.00.00.00.00.00.00.0-0.0-0.0-0.030.0-33.30.00.00.00.00.00.00.00.00.00.0-0.00.00.00.00.00.0

us-gaap:RepaymentsOfLinesOfCredit



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312016-12-312016-09-302015-12-312015-09-302014-12-312014-09-30
Value000250000000000
Percentage of RepaymentsOfLinesOfCredit0.00.00.0100.00.00.00.00.00.00.00.00.00.0

us-gaap:BusinessAcquisition

us-gaap:RestructuringCosts

alxn:Achillion



Period End2020-03-312019-03-31
Value100
Percentage of RestructuringCosts100.00.0

us-gaap:BusinessAcquisition

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost

alxn:Achillion



Period End2020-01-282020-03-312019-03-31
Value20250
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedCompensationCost100.0100.00.0

us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesRestrictedStockAwardGross

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1000000.0200000.0100000.0200000.0700000.0300000.0100000.0100000.0800000.0
Percentage of StockIssuedDuringPeriodSharesRestrictedStockAwardGross100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesStockOptionsExercised

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value100000.0100000.0100000.0100000.0100000.0100000.0200000.0200000.0100000.0
Percentage of StockIssuedDuringPeriodSharesStockOptionsExercised100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueRestrictedStockAwardGross



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value0.00.00.00.00.00.0300000.0-300000.0
Percentage of StockIssuedDuringPeriodValueRestrictedStockAwardGross0.00.00.00.00.00.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueStockOptionsExercised



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2611110616159
Percentage of StockIssuedDuringPeriodValueStockOptionsExercised100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2611110616159
Percentage of StockIssuedDuringPeriodValueStockOptionsExercised100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TreasuryStockSharesAcquired



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-12-31
Value13000000110020000100000
Percentage of TreasuryStockSharesAcquired100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value103000000
Percentage of TreasuryStockSharesAcquired100.00.0100.0100.0100.00.00.00.0100.0

us-gaap:SubsequentEventType

us-gaap:SubsequentEvent



Period End2020-05-062019-10-212019-04-252018-02-082017-07-272016-12-222016-04-292016-02-082015-11-022015-04-242014-10-242014-07-252014-04-25
Value400000.0100000.0100000.0700000.01000000.0250000.0245000.0648000.0776000.0126000.0100000.0180000.0480000.0
Percentage of TreasuryStockSharesAcquired0.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStockValueAcquiredCostMethod



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value107323343711000851646017168306934296152912360191041562200313511
Percentage of TreasuryStockValueAcquiredCostMethod100.0100.0100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value10732334371100085
Percentage of TreasuryStockValueAcquiredCostMethod100.0100.0100.0100.0100.00.00.00.0100.0

us-gaap:SubsequentEventType

us-gaap:SubsequentEvent



Period End2020-05-062020-01-312019-10-212019-04-252018-02-082017-07-272017-04-272016-12-222016-04-292016-02-082015-11-022015-04-242014-10-242014-07-252014-04-25
Value3517985543230349812322162871
Percentage of TreasuryStockValueAcquiredCostMethod0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:UnrealizedGainLossOnInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-03-312015-03-31
Value-9612-2533-60001000011-11-170
Percentage of UnrealizedGainLossOnInvestments100.0100.0100.0100.0100.0100.00.00.0100.00.00.0100.0100.0100.0100.0

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

alxn:CommonStockInBiotechnologyCompany



Period End2020-03-31
Value600000.0
Percentage of UnrealizedGainLossOnInvestments-6.5

alxn:Dicerna



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value-36-1031
Percentage of UnrealizedGainLossOnInvestments33.7101.6-9.2-3.69.8-2.3

alxn:EidosMember



Period End2020-03-312019-12-312019-09-30
Value-352
Percentage of UnrealizedGainLossOnInvestments40.279.424.2

alxn:Stealth



Period End2020-03-312019-12-31
Value-2-5
Percentage of UnrealizedGainLossOnInvestments30.4-82.5

alxn:Zealand



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value00320
Percentage of UnrealizedGainLossOnInvestments2.2-11.130.8-11.52.1

us-gaap:BusinessAcquisition

alxn:BusinessCombinationContingentConsiderationLiabilityPostCombinationServicePeriodCompensation

alxn:Achillion



Period End2020-01-28
Value5
Percentage of BusinessCombinationContingentConsiderationLiabilityPostCombinationServicePeriodCompensation100.0

us-gaap:Range, us-gaap:BusinessAcquisition

alxn:BusinessCombinationEstimatedMilestonePayments

srt:Maximum, alxn:Achillion



Period End2020-01-28
Value306
Percentage of BusinessCombinationEstimatedMilestonePayments100.0

srt:Minimum, alxn:Achillion



Period End2020-01-28
Value0.0
Percentage of BusinessCombinationEstimatedMilestonePayments0.0

us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

alxn:DerivativeNotionalAmount1

alxn:ForeignExchangeForwardOpenExpense, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-09-30
Value1215
Percentage of DerivativeNotionalAmount1100.0100.0

us-gaap:ForeignExchangeForward, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-09-30
Value10961211
Percentage of DerivativeNotionalAmount18634.67768.6

us-gaap:ForeignExchangeForward, us-gaap:Nondesignated



Period End2020-03-312019-09-30
Value10661103
Percentage of DerivativeNotionalAmount18399.27071.8

alxn:GoodwillAccumulatedAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value222222222233332222222222
Percentage of GoodwillAccumulatedAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:IntangibleAssetsAccumulatedAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value1508143413581280119911191038958878798719639559479397315235155753827201511
Percentage of IntangibleAssetsAccumulatedAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:IntangibleAssetsCost



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value569647784768476847604760475247524752475247514751478247824865486348634863486362663766710636
Percentage of IntangibleAssetsCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CounterpartyName, us-gaap:TypeOfArrangement

alxn:ResearchandDevelopmentArrangementPotentialPaymentMaximum

alxn:Dicerna, alxn:DicernaPharmaceuticalCollaborationAgreement



Period End2020-03-312019-12-31
Value614629
Percentage of ResearchandDevelopmentArrangementPotentialPaymentMaximum100.0100.0

us-gaap:AdditionalPaidInCapitalCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value886488048738867786048539848184208350829082098135806079577906785277937726764276592713259225552467229121062049196818991852182717821291126112381218119511731093
Percentage of AdditionalPaidInCapitalCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinancialInstrument

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax

us-gaap:CorporateBondSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value100000.00.00.00.00.0100000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax100.00.00.00.00.0100.0

us-gaap:DebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value100000.00.00.00.00.0100000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax100.00.00.00.00.0100.0

us-gaap:FinancialInstrument

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis

us-gaap:CertificatesOfDeposit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value62715241833
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis100.0100.0100.0100.0100.0100.0

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value13424628727428952
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis2064.6901.11841.71127.61538.3156.9

us-gaap:CorporateBondSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value32442873122
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis55.488.729.5115.2388.3370.2

us-gaap:DebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value204369446444438225
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis3143.11346.72864.11827.62334.6679.8

us-gaap:USGovernmentAgenciesDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value60701301174317
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis923.1256.9836.5484.8231.452.7

us-gaap:AvailableForSaleSecuritiesDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-03-312016-12-312016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-30
Value204369446444438225387545114291378843334668977928213631181103197910301027412187
Percentage of AvailableForSaleSecuritiesDebtSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation

alxn:MarketableSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-03-312017-12-312017-03-312016-12-312016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-30
Value254023849018110588717323143053662871641001101310269791026983391182
Percentage of AvailableForSaleSecuritiesDebtSecurities12.311.15.319.120.580.692.695.492.972.588.253.136.958.273.585.899.4100.099.695.795.097.3

us-gaap:CashAndCashEquivalents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-03-312017-12-312017-03-312016-12-312016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-30
Value179328423359348438442571204032349211836116750443205
Percentage of AvailableForSaleSecuritiesDebtSecurities87.788.994.780.979.519.47.44.77.227.711.846.963.141.826.514.20.60.00.44.35.02.7

us-gaap:FinancialInstrument

us-gaap:CertificatesOfDeposit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value62715241833
Percentage of AvailableForSaleSecuritiesDebtSecurities3.27.43.55.54.314.7

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value13424628727428952
Percentage of AvailableForSaleSecuritiesDebtSecurities65.766.964.361.765.923.1

us-gaap:CorporateBondSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value32442873122
Percentage of AvailableForSaleSecuritiesDebtSecurities1.76.61.06.316.654.4

us-gaap:DebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value204369446444438225
Percentage of AvailableForSaleSecuritiesDebtSecurities100.0100.0100.0100.0100.0100.0

us-gaap:USGovernmentAgenciesDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value60701301174317
Percentage of AvailableForSaleSecuritiesDebtSecurities29.419.129.226.59.97.8

us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass

us-gaap:BusinessCombinationContingentConsiderationLiability

alxn:ContingentConsideration, us-gaap:FairValueInputsLevel3, alxn:AcquisitionRelatedContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value358192188158154183179156152168160156132129126109107121158129126116107108106106139
Percentage of BusinessCombinationContingentConsiderationLiability100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherCurrentLiabilities, us-gaap:FairValueInputsLevel3, alxn:OtherContingentPayments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value2624141313
Percentage of BusinessCombinationContingentConsiderationLiability7.312.57.48.88.9

us-gaap:BalanceSheetLocation, us-gaap:FairValueByLiabilityClass

alxn:ContingentConsideration, alxn:AcquisitionRelatedContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value358192188158154183179156152168160156132129126109107121158129126116107108106106139
Percentage of BusinessCombinationContingentConsiderationLiability100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherCurrentLiabilities, alxn:OtherContingentPayments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value2624141313
Percentage of BusinessCombinationContingentConsiderationLiability7.312.57.48.88.9

us-gaap:FairValueByLiabilityClass

alxn:AcquisitionRelatedContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value358192188258252280275226221168160181157153207167162177158178174162152144142142
Percentage of BusinessCombinationContingentConsiderationLiability100.0100.0100.0163.2163.2153.3153.4145.1145.0100.0100.0116.0118.9118.6164.9153.0151.7146.0100.0138.2137.9140.0142.8133.6134.3133.7

us-gaap:BusinessCombinationContingentConsiderationLiabilityNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302016-12-312016-09-302016-06-302015-12-312015-09-302015-06-302014-12-31
Value358192188158154183179156342160156129126109121158129116
Percentage of BusinessCombinationContingentConsiderationLiabilityNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BusinessAcquisition

alxn:Achillion



Period End2020-03-312020-01-28
Value162160
Percentage of BusinessCombinationContingentConsiderationLiabilityNoncurrent45.20.0

us-gaap:BusinessAcquisition

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities

alxn:Achillion



Period End2020-01-28
Value59
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities100.0

us-gaap:BusinessAcquisition, us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass

alxn:Achillion, alxn:AcquiredIprd



Period End2020-01-28
Value205
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities343.3

us-gaap:BusinessAcquisition, us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass

us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets

alxn:Achillion, alxn:AcquiredIprd



Period End2020-01-28
Value918
Percentage of BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass

us-gaap:CashAndCashEquivalentsFairValueDisclosure

us-gaap:CashEquivalents, alxn:OtherGovernmentObligations



Period End2020-03-312019-12-312016-09-302015-12-312015-09-302015-06-302015-03-312014-12-312013-09-302013-06-30
Value60602631778612303
Percentage of CashAndCashEquivalentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CashEquivalents, us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-03-312013-12-312013-09-30
Value119227287240289359655459151770963031922794415111721619
Percentage of CashAndCashEquivalentsFairValueDisclosure198.5377.30.00.00.00.00.00.00.00.00.00.00.0372.10.00.0609.9360.3534.8245.1489.70.00.00.03333.2

us-gaap:CashEquivalents, us-gaap:MoneyMarketFunds



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value6796355294985455695035432266832782179133605192176217256236234717813853803
Percentage of CashAndCashEquivalentsFairValueDisclosure1132.31052.80.00.00.00.00.00.00.00.00.0322.50.00.0570.2172.67209.5310.3734.80.00.00.00.0119663.327129.80.00.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:CashEquivalents, alxn:OtherGovernmentObligations, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312016-09-302015-12-312015-09-302015-06-302015-03-312014-12-312013-09-302013-06-30
Value60602631778612303
Percentage of CashAndCashEquivalentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CashEquivalents, us-gaap:CommercialPaper, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-03-312013-12-312013-09-30
Value119227287240289359655459151770963031922794415111721619
Percentage of CashAndCashEquivalentsFairValueDisclosure198.5377.30.00.00.00.00.00.00.00.00.00.00.0372.10.00.0609.9360.3534.8245.1489.70.00.00.03333.2

us-gaap:CashEquivalents, us-gaap:MoneyMarketFunds, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value6796355294985455695035432266832782179133605192176217256236234717813853803
Percentage of CashAndCashEquivalentsFairValueDisclosure1132.31052.80.00.00.00.00.00.00.00.00.0322.50.00.0570.2172.67209.5310.3734.80.00.00.00.0119663.327129.80.00.0

us-gaap:ContractWithCustomerAssetNetCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value13451243111611231016922910853776726
Percentage of ContractWithCustomerAssetNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ContractWithCustomerLiabilityCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value2262633333115
Percentage of ContractWithCustomerLiabilityCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value202102556128
Percentage of DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months100.0100.0100.0100.0100.0100.0

us-gaap:DeferredFinanceCostsNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value141517181920222321
Percentage of DeferredFinanceCostsNet100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredIncomeTaxAssetsNet



Period End2020-03-312019-12-312018-12-31
Value22232290101
Percentage of DeferredIncomeTaxAssetsNet100.0100.0100.0

us-gaap:DeferredIncomeTaxLiabilitiesNet



Period End2020-03-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value21132081391365396529
Percentage of DeferredIncomeTaxLiabilitiesNet100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeCollateralObligationToReturnSecurities

us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value1421112418301613102627372316494227109800215212710
Percentage of DerivativeCollateralObligationToReturnSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeCollateralRightToReclaimSecurities

us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value1421112418301613102627372316494227109800215212710
Percentage of DerivativeCollateralRightToReclaimSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

us-gaap:DerivativeFairValueOfDerivativeAsset

us-gaap:OtherNoncurrentAssets, us-gaap:ForeignExchangeForward, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value104110011471543593144356669821255838469
Percentage of DerivativeFairValueOfDerivativeAsset100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PrepaidExpensesAndOtherCurrentAssets, us-gaap:ForeignExchangeForward, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value291232121916161612172861804885
Percentage of DerivativeFairValueOfDerivativeAsset2645.52116.7792.71127.31158.85633.32414.3842.1314.6242.9186.7141.9135.6154.3128.3

us-gaap:BalanceSheetLocation, us-gaap:HedgingDesignation, us-gaap:InvestmentType

us-gaap:PrepaidExpensesAndOtherCurrentAssets, us-gaap:Nondesignated, us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value241710161123100104841726
Percentage of DerivativeFairValueOfDerivativeAsset2190.92866.7251.21463.6694.17866.71442.921.1243.957.153.39.328.87.410.1

us-gaap:DerivativeInstrumentRisk

us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value5430493546606449414842641201668110793158148171241136871724312642492719322025
Percentage of DerivativeFairValueOfDerivativeAsset4936.45083.31202.43200.02752.920300.09200.02615.83425.01190.2600.0426.7279.1281.4262.4243.3267.3238.4214.0208.5192.6231.8229.4416.4389.3321.70.00.00.00.00.00.00.00.0

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral

us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value543049354660644941484264120166811079315814817124113687172431264227
Percentage of DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral

us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value39937102830473630221527971503264651471391632411358513473617
Percentage of DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

us-gaap:DerivativeFairValueOfDerivativeLiability

us-gaap:OtherCurrentLiabilities, us-gaap:ForeignExchangeForward, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value16372710154934321872252115132002192120
Percentage of DerivativeFairValueOfDerivativeLiability100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherCurrentLiabilities, us-gaap:InterestRateContract, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value42191610200000110001
Percentage of DerivativeFairValueOfDerivativeLiability2476.5314.5455.6142.1120.811.00.00.00.00.03.15.60.00.03.74.7

us-gaap:OtherNoncurrentLiabilities, us-gaap:ForeignExchangeForward, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value010103593026281994383630455000111314
Percentage of DerivativeFairValueOfDerivativeLiability47.117.722.223.737.542.558.063.962.974.787.5105.6128.6200.0148.6170.1193.7320.1182.3187.019.610.830.457.262.473.5

us-gaap:OtherNoncurrentLiabilities, us-gaap:InterestRateContract, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value7541555231170000120004
Percentage of DerivativeFairValueOfDerivativeLiability4458.8675.81547.2686.81295.8237.00.00.00.00.03.111.10.00.03.122.5

us-gaap:BalanceSheetLocation, us-gaap:HedgingDesignation, us-gaap:InvestmentType

us-gaap:OtherCurrentLiabilities, us-gaap:Nondesignated, us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312013-12-312012-12-31
Value1220131551131313597109816402
Percentage of DerivativeFairValueOfDerivativeLiability729.4329.0375.0202.6220.8157.539.06.58.039.415.650.0100.0500.035.340.8102.0278.80.00.0

us-gaap:DerivativeInstrumentRisk

us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value132899087424019268374674923167572621098002313435245210126310
Percentage of DerivativeFairValueOfDerivativeLiability7811.81437.12500.01155.31775.0547.9197.0170.3170.8214.1209.4272.2328.6800.0290.7338.0395.7698.9298.3287.0119.6110.8130.4157.2164.0173.50.00.00.00.00.00.00.00.0

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral

us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value13289908742401926837467492316757262109800231343524510
Percentage of DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral

us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value117677863249313734840120025293400000015127400
Percentage of DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.00.00.00.00.00.00.0100.0100.0100.0100.00.00.0

us-gaap:Range, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation

us-gaap:DerivativeFixedInterestRate

srt:Minimum, alxn:InterestRateSwapFour, us-gaap:DesignatedAsHedgingInstrument



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.02370.02370.02370.02790.0279
Percentage of DerivativeFixedInterestRate100.0100.0100.0100.0100.0

us-gaap:CounterpartyName, us-gaap:TypeOfArrangement

us-gaap:DerivativeLiabilities

alxn:CaelumBiosciences, us-gaap:CollaborativeArrangement



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value2624272727
Percentage of DerivativeLiabilities100.0100.0100.0100.0100.0

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:EquitySecuritiesFvNi

alxn:CommonStockInBiotechnologyCompany



Period End2020-03-31
Value15
Percentage of EquitySecuritiesFvNi100.0

alxn:Dicerna



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value15181213128
Percentage of EquitySecuritiesFvNi101.30.00.00.00.00.0

alxn:EidosMember



Period End2020-03-312019-12-312019-09-30
Value242717
Percentage of EquitySecuritiesFvNi159.60.00.0

alxn:Stealth



Period End2020-03-312019-12-31
Value14
Percentage of EquitySecuritiesFvNi10.60.0

alxn:Zealand



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value2728201714
Percentage of EquitySecuritiesFvNi183.40.00.00.00.0

us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue

us-gaap:FairValueInputsLevel3, alxn:AcquisitionRelatedContingentConsideration



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value-358-192-188-258-252-280-275-226221168160181157153207167162177158178174162152144142-142144141
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization

alxn:PurchasedTechnology



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value1462138813141239115910799999198397586795995194393582761961163600000
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.00.0

us-gaap:LicensingAgreements



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value3534323029292928282829292929282828282828181398
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization2.42.52.52.52.62.72.93.13.43.84.34.85.66.67.910.314.524.477.80.00.01648.12523.30.0

us-gaap:OtherIntangibleAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value300000.0200000.0200000.0200000.0200000.0200000.0200000.0200000.0100000.0100000.00.0
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Patents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value10101010101010101010111111111010101010109653
Percentage of FiniteLivedIntangibleAssetsAccumulatedAmortization0.70.80.80.80.91.01.11.11.31.41.61.82.12.52.93.85.39.028.70.00.0855.51332.50.0

us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsGross

alxn:PurchasedTechnology



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value471047104710471047104710471047104710471047114711471147114710470847084708470800550
Percentage of FiniteLivedIntangibleAssetsGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.00.0

us-gaap:LicensingAgreements



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value575747473939313131312929292928282828282828232325
Percentage of FiniteLivedIntangibleAssetsGross1.21.21.01.00.80.80.70.70.70.70.60.60.60.60.60.60.60.60.60.00.0473.8473.00.0

us-gaap:Patents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value101010101010101010101111111110101010101010101010
Percentage of FiniteLivedIntangibleAssetsGross0.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.20.00.0210.3210.30.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass

us-gaap:ForeignCurrencyContractAssetFairValueDisclosure

us-gaap:OtherNoncurrentAssets, us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value1041100114715435931443566698212558384699
Percentage of ForeignCurrencyContractAssetFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PrepaidExpensesAndOtherCurrentAssets, us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302016-12-312016-09-302015-12-31
Value5329422831402716222136975091
Percentage of ForeignCurrencyContractAssetFairValueDisclosure4836.44983.31043.92590.91852.913500.03857.1863.2558.5300.0240.0164.4161.7138.4

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:OtherNoncurrentAssets, us-gaap:ForeignExchangeForward, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value104110014715435931443566698212558384699
Percentage of ForeignCurrencyContractAssetFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PrepaidExpensesAndOtherCurrentAssets, us-gaap:ForeignExchangeForward, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302016-12-312016-09-302015-12-31
Value5329422831402716222136975091
Percentage of ForeignCurrencyContractAssetFairValueDisclosure4836.44983.31043.92590.91852.913500.03857.1863.2558.5300.0240.0164.4161.7138.4

us-gaap:BalanceSheetLocation, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByLiabilityClass

us-gaap:ForeignCurrencyContractsLiabilityFairValueDisclosure

us-gaap:OtherCurrentLiabilities, us-gaap:FairValueInputsLevel2, us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value1426172371813165248372714123430325320021921205
Percentage of ForeignCurrencyContractsLiabilityFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherNoncurrentLiabilities, us-gaap:FairValueInputsLevel2, us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value0101035930262819943836304550001113144
Percentage of ForeignCurrencyContractsLiabilityFairValueDisclosure5.74.14.77.811.716.541.760.058.253.675.770.464.333.3109.9120.895.984.5157.3187.019.610.830.457.261.573.581.6

us-gaap:BalanceSheetLocation, us-gaap:FairValueByLiabilityClass

us-gaap:OtherCurrentLiabilities, us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value1426172371813165248372714123430325320021921205
Percentage of ForeignCurrencyContractsLiabilityFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherNoncurrentLiabilities, us-gaap:ForeignExchangeForward



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-31
Value0101035930262819943836304550001113144
Percentage of ForeignCurrencyContractsLiabilityFairValueDisclosure5.74.14.77.811.716.541.760.058.253.675.770.464.333.3109.9120.895.984.5157.3187.019.610.830.457.261.573.581.6

us-gaap:GoodwillGross



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312011-12-312010-12-31
Value50755040504050405040504050405040504050405040504050405040504050405052505050182562562568222
Percentage of GoodwillGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IndefiniteLivedIntangibleAssetsByMajorClass

us-gaap:IndefiniteLivedIntangibleAssetsExcludingGoodwill

alxn:AcquiredIprd



Period End2020-03-312019-12-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-31
Value91800003131116116116116116587598628628654654670
Percentage of IndefiniteLivedIntangibleAssetsExcludingGoodwill100.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass

us-gaap:InterestRateDerivativeAssetsAtFairValue

us-gaap:OtherLiabilities, us-gaap:InterestRateContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value754155523117
Percentage of InterestRateDerivativeAssetsAtFairValue100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:OtherLiabilities, us-gaap:InterestRateContract, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312018-12-31
Value75410
Percentage of InterestRateDerivativeAssetsAtFairValue100.0100.04.6

us-gaap:OtherNoncurrentAssets, us-gaap:InterestRateContract, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value000001422151210101010
Percentage of InterestRateDerivativeAssetsAtFairValue0.00.00.00.04.60.00.00.00.00.00.00.00.0

us-gaap:PrepaidExpensesAndOtherCurrentAssets, us-gaap:InterestRateContract, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value02513202291594320
Percentage of InterestRateDerivativeAssetsAtFairValue0.04.310.743.7116.20.00.00.00.00.00.00.00.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass

us-gaap:InterestRateDerivativeLiabilitiesAtFairValue

us-gaap:OtherCurrentLiabilities, us-gaap:InterestRateContract



Period End2020-03-312019-12-31
Value4219
Percentage of InterestRateDerivativeLiabilitiesAtFairValue100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:OtherCurrentLiabilities, us-gaap:InterestRateContract, us-gaap:FairValueInputsLevel1



Period End2020-03-31
Value0.0
Percentage of InterestRateDerivativeLiabilitiesAtFairValue0.0

us-gaap:OtherCurrentLiabilities, us-gaap:InterestRateContract, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-31
Value4219
Percentage of InterestRateDerivativeLiabilitiesAtFairValue100.0100.0

us-gaap:OtherCurrentLiabilities, us-gaap:InterestRateContract, us-gaap:FairValueInputsLevel3



Period End2020-03-31
Value0.0
Percentage of InterestRateDerivativeLiabilitiesAtFairValue0.0

us-gaap:InventoryRawMaterials



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value49413638393110554121922171719161717211414131612121214468789744
Percentage of InventoryRawMaterials100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InventoryWorkInProcess



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value108180180116100901071641611481501311711431921571621801069977107655668626152574330314337205037
Percentage of InventoryWorkInProcess100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass

us-gaap:InvestmentsFairValueDisclosure

alxn:MarketableSecurities, alxn:MutualFunds



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value22232020201618202018181817131312118776432210
Percentage of InvestmentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:MarketableSecurities, us-gaap:CertificatesOfDeposit



Period End2020-03-312019-12-312018-12-312018-03-312017-12-312017-09-302017-03-312016-12-312016-09-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value683338112411513272211818133
Percentage of InvestmentsFairValueDisclosure28.635.5201.2185.663.8133.364.738.596.930.51683.4617.5630.3795.91278.4625.0

alxn:MarketableSecurities, us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-12-312015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value151903316100834961821214414111661292439667710631
Percentage of InvestmentsFairValueDisclosure66.582.30.0163.3101.2529.1411.4237.035.1100.0116.7123.5338.51053.0964.8702.9456.5583.71160.62325.83442.610460.36649.0

alxn:MarketableSecurities, us-gaap:CorporateBondSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value334287312213621555543146443137511318120812112012788501484524485510461180
Percentage of InvestmentsFairValueDisclosure15.416.022.1135.3361.4743.0719.61065.32672.62331.42577.82394.42205.9869.21354.61725.31029.61366.71607.71154.67653.911329.215419.316989.322550.745339.537569.8

us-gaap:OtherAssets, us-gaap:EquitySecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value837914411313890
Percentage of InvestmentsFairValueDisclosure369.2342.0694.2547.3685.1550.3

us-gaap:BalanceSheetLocation, us-gaap:FairValueByAssetClass, us-gaap:FairValueByFairValueHierarchyLevel

alxn:MarketableSecurities, alxn:MutualFunds, us-gaap:FairValueInputsLevel1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value22232020201618202018181817131312118776432210
Percentage of InvestmentsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:MarketableSecurities, us-gaap:CertificatesOfDeposit, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312018-12-312018-03-312017-12-312017-09-302017-03-312016-12-312016-09-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value683338112411513272211818133
Percentage of InvestmentsFairValueDisclosure28.635.5201.2185.663.8133.364.738.596.930.51683.4617.5630.3795.91278.4625.0

alxn:MarketableSecurities, us-gaap:CommercialPaper, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302015-12-312015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value151903316100834961821214414111661292439667710631
Percentage of InvestmentsFairValueDisclosure66.582.30.0163.3101.2529.1411.4237.035.1100.0116.7123.5338.51053.0964.8702.9456.5583.71160.62325.83442.610460.36649.0

alxn:MarketableSecurities, us-gaap:CorporateBondSecurities, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value334287312213621555543146443137511318120812112012788501484524485510461180
Percentage of InvestmentsFairValueDisclosure15.416.022.1135.3361.4743.0719.61065.32672.62331.42577.82394.42205.9869.21354.61725.31029.61366.71607.71154.67653.911329.215419.316989.322550.745339.537569.8

us-gaap:OtherAssets, us-gaap:EquitySecurities, us-gaap:FairValueInputsLevel1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value59513230268
Percentage of InvestmentsFairValueDisclosure263.0221.6155.8147.8132.253.9

us-gaap:OtherAssets, us-gaap:EquitySecurities, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value24271128211181
Percentage of InvestmentsFairValueDisclosure106.2120.3538.5399.5553.0496.4

us-gaap:MarketableSecuritiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value4764441051101983064491079889979902749327550582317374295172100810171029982102998439200720599419
Percentage of MarketableSecuritiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0

us-gaap:OperatingLeaseLiabilityNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value1621641661651500
Percentage of OperatingLeaseLiabilityNoncurrent100.0100.0100.0100.0100.00.0

us-gaap:RestrictedCashAndCashEquivalentsAtCarryingValue



Period End2020-03-312019-12-312019-09-302019-03-312018-12-312018-09-302017-12-31
Value4037310000
Percentage of RestrictedCashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.00.0

us-gaap:RestrictedCashAndCashEquivalentsNoncurrent



Period End2020-03-312019-12-312019-09-302019-03-312018-12-312018-09-302017-12-31
Value0001120
Percentage of RestrictedCashAndCashEquivalentsNoncurrent100.0100.0100.0100.0100.0100.00.0

us-gaap:TradingSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value2223202020161820201818181713131211877643221
Percentage of TradingSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TreasuryStockShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-312009-12-31
Value171616131212121212121110987764333222100000000
Percentage of TreasuryStockShares100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-31
Value17161613121212121212842000000
Percentage of TreasuryStockShares100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:CounterpartyName

us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount

alxn:LonzaGroupAG



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302017-09-302017-06-302016-09-302016-06-302015-09-302015-06-30
Value105310621044105411741086118811531122114312041226
Percentage of UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

alxn:OtherThirdPartyManufacturers



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302017-09-302017-06-302016-09-302016-06-302015-09-302015-06-30
Value646365576328202333333940
Percentage of UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount6.15.96.25.45.42.61.72.02.92.93.23.3

Line plots across dimensions of each concept

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments


us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:ProductOrService


us-gaap:StockholdersEquity us-gaap:StatementEquityComponents


us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass


us-gaap:StockholdersEquity us-gaap:StatementEquityComponents


us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents