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2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

dei: Entity Common Stock Shares Outstanding NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Weighted Average Number Of Diluted Shares Outstanding 109.13 92.86 NA 61.75 61.73 61.71 NA 63.86 64.08 64.94 NA 65.04 64.71 60.60 NA 58.64 56.70 56.65 NA 56.53 48.07

Weighted Average Number Of Shares Outstanding Basic 109.11 92.86 NA 61.67 61.66 61.59 NA 63.76 64.00 64.79 NA 64.83 64.50 60.31 NA 58.25 56.34 56.24 NA 56.09 47.61

Earnings Per Share Basic 0.59 -0.36 0.83 0.76 0.69 0.83 0.75 0.76 0.57 0.45 0.81 0.76 0.59 0.69 0.67 0.71 0.74 0.65 0.61 0.49 0.46

Earnings Per Share Diluted 0.59 -0.36 0.83 0.76 0.69 0.83 0.75 0.76 0.57 0.45 0.80 0.76 0.59 0.69 0.66 0.71 0.74 0.65 0.60 0.48 0.45

Tier One Risk Based Capital To Risk Weighted Assets 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Capital To Risk Weighted Assets 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Interest And Fee Income Loans And Leases 191.70 151.70 105.10 111.90 105.40 107.80 117.00 112.30 112.10 112.00 118.60 120.00 120.90 111.40 112.20 103.90 96.50 91.70 93.13 94.02 73.89

Interest Expense 7.40 6.00 4.00 4.20 4.50 4.60 5.30 5.90 6.30 9.10 11.80 15.80 16.80 14.60 12.70 11.20 9.20 7.80 7.85 7.97 6.55

Interest Income Expense Net 237.90 178.00 121.80 126.90 118.80 120.70 128.40 123.00 122.50 123.10 128.20 125.50 125.30 116.00 118.90 110.00 103.80 99.80 100.84 100.79 79.32

Interest Paid Net 7.50 6.00 6.80 2.70 6.30 3.50 7.50 6.70 7.80 10.90 12.00 15.90 14.40 12.40 11.60 10.70 NA NA NA NA NA

Gains Losses On Extinguishment Of Debt 0.00 1.40 NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Income Tax Expense Benefit 16.20 -7.90 15.40 13.60 12.60 14.10 14.80 14.70 10.40 8.20 16.50 15.30 10.90 11.40 11.80 12.10 11.90 10.30 15.16 13.71 11.88

Income Taxes Paid 13.70 0.10 15.50 5.60 14.70 21.00 18.40 11.50 13.00 11.50 16.40 10.30 24.50 0.00 9.50 6.10 5.10 4.60 4.48 9.90 -14.37

Other Comprehensive Income Loss Net Of Tax -127.80 -191.00 -25.30 -9.80 17.40 -49.90 -5.30 -3.30 25.40 28.80 -2.40 2.90 14.90 20.20 14.80 -4.40 -2.60 -17.20 NA -0.97 4.59

Net Income Loss 64.10 -33.40 51.10 47.10 42.50 51.40 46.90 48.30 36.70 29.30 52.40 49.10 37.90 41.60 40.40 41.40 41.70 36.70 34.27 27.26 21.87

Comprehensive Income Net Of Tax -63.70 -224.40 25.80 37.30 59.90 1.50 41.60 45.00 62.10 58.10 50.00 52.00 52.80 61.80 55.20 37.00 39.10 19.50 21.28 26.29 26.46

Interest Income Expense After Provision For Loan Loss 239.60 116.70 131.30 126.90 118.80 125.80 125.20 117.80 103.00 94.10 124.40 122.90 121.50 112.30 117.30 108.00 100.90 97.70 97.31 97.35 76.97

Noninterest Expense 210.30 207.20 102.20 105.90 99.00 98.40 97.40 99.50 95.60 100.30 90.70 99.30 112.10 93.80 99.40 90.70 84.90 85.90 85.07 94.66 80.40

Noninterest Income 51.00 49.20 37.40 39.70 35.30 38.10 33.90 44.70 39.70 43.70 35.20 40.80 39.40 34.50 34.30 36.20 37.60 35.20 37.19 38.27 37.18

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Assets 32061.80 33162.20 19671.90 19372.20 18940.50 18443.40 17648.70 17069.50 16471.40 14411.40 14644.20 14701.60 14414.60 13498.20 13300.20 13355.80 12235.70 12273.40 12213.25 12206.47 12236.34

Liabilities 28789.90 29721.10 17685.30 17387.40 16969.60 16510.00 15688.90 15091.90 14472.50 12455.30 12630.30 12719.00 12466.00 11761.30 11606.30 11701.40 10777.40 10841.00 10785.64 10787.06 10830.96

Liabilities And Stockholders Equity 32061.80 33162.20 19671.90 19372.20 18940.50 18443.40 17648.70 17069.50 16471.40 14411.40 14644.20 14701.60 14414.60 13498.20 13300.20 13355.80 12235.70 12273.40 12213.25 12206.47 12236.34

Stockholders Equity 3271.90 3441.10 1986.60 1984.80 1970.90 1933.40 1959.80 1977.60 1998.90 1956.10 2013.90 1982.60 1948.60 1736.90 1693.90 1654.40 1458.30 1432.40 1427.62 1419.41 1405.38

Tier One Risk Based Capital 2451.40 2446.70 1469.00 1442.60 1415.60 1396.40 1369.00 1378.30 1393.10 1367.70 1422.30 1385.20 1346.30 1237.90 1212.00 1181.20 1086.80 1058.00 1040.30 1026.02 1011.14

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents 1059.30 3811.30 2344.80 2233.50 1948.40 2196.00 2276.80 1860.60 1425.00 869.20 1076.80 1269.60 1128.90 955.20 822.00 965.00 712.00 NA 758.90 NA NA

Available For Sale Securities Debt Securities 7741.10 6283.80 4820.50 4403.60 3957.80 4020.10 4008.70 3453.50 3317.60 3000.30 2960.00 2732.20 2609.70 2572.00 2270.70 2158.80 2178.00 2280.70 2208.70 2111.70 2080.19

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Property Plant And Equipment Gross NA NA 495.80 NA NA NA 491.30 NA NA NA 475.10 NA NA NA 422.00 NA NA NA 404.20 NA NA

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment NA NA 196.20 NA NA NA 179.00 NA NA NA 169.10 NA NA NA 176.80 NA NA NA 162.30 NA NA

Amortization Of Intangible Assets 4.10 3.60 2.50 2.40 2.50 2.50 2.60 2.70 2.70 2.90 2.90 3.00 3.00 2.30 2.40 2.00 1.70 1.80 1.86 1.89 1.06

Property Plant And Equipment Net 442.70 444.40 299.60 297.30 299.10 305.50 312.30 307.80 309.50 308.50 306.00 302.80 321.10 298.20 245.20 244.20 233.70 240.20 241.90 242.94 243.15

Goodwill 1099.80 1137.60 621.60 621.60 621.60 621.60 621.60 621.60 621.60 621.60 621.60 622.60 623.50 546.30 546.70 546.40 445.60 445.60 444.70 445.03 444.33

Indefinite Lived Intangible Assets Excluding Goodwill 105.10 109.60 41.30 43.70 46.10 48.60 51.20 53.80 56.50 59.20 62.10 65.00 67.90 54.60 56.90 NA NA NA 49.10 NA NA

Finite Lived Intangible Assets Net 105.10 109.60 41.30 NA NA NA NA NA NA NA NA NA NA 54.60 NA 59.30 45.60 47.30 49.10 50.97 52.84

Held To Maturity Securities Accumulated Unrecognized Holding Loss 270.00 208.80 35.70 8.90 9.10 13.70 NA NA 0.00 0.00 0.00 0.00 0.10 0.50 8.30 19.40 17.50 16.40 12.70 10.35 9.54

Held To Maturity Securities Fair Value 2860.50 3029.10 1667.50 1632.50 1701.90 855.60 55.00 58.40 71.10 72.60 94.50 97.20 100.80 118.00 400.70 407.40 432.80 455.50 483.35 510.40 535.14

Held To Maturity Securities 3131.60 3220.30 1687.60 1618.10 1685.50 866.30 51.60 55.00 67.90 70.20 92.30 94.90 98.80 117.00 406.80 417.80 440.90 462.30 484.50 505.99 529.44

Available For Sale Debt Securities Amortized Cost Basis 8193.80 6575.10 4859.30 4408.80 3949.40 4011.00 3932.70 3369.20 3229.00 2946.70 2945.50 2714.70 2596.50 2579.00 2305.20 2213.20 2226.20 2325.00 2229.30 2110.20 2076.11

Held To Maturity Securities Accumulated Unrecognized Holding Gain 0.50 19.20 15.60 23.30 25.50 3.00 3.40 3.40 3.20 2.40 2.20 2.30 2.10 1.50 2.20 9.00 9.40 9.60 11.50 14.77 15.25

Held To Maturity Securities Accumulated Unrecognized Holding Loss 270.00 208.80 35.70 8.90 9.10 13.70 NA NA 0.00 0.00 0.00 0.00 0.10 0.50 8.30 19.40 17.50 16.40 12.70 10.35 9.54

Held To Maturity Securities Continuous Unrealized Loss Position Fair Value NA NA 1067.70 801.30 771.30 851.50 NA NA NA NA NA 0.00 19.70 NA 307.30 274.90 271.40 287.70 268.30 105.93 107.15

Held To Maturity Securities Debt Maturities Next Rolling Twelve Months Fair Value 10.10 355.30 687.20 667.40 688.10 335.70 8.40 8.90 NA NA NA NA NA NA NA NA NA NA NA NA NA

Held To Maturity Securities Debt Maturities Rolling After Ten Years Fair Value 1764.10 443.80 340.50 328.60 339.60 179.00 1.40 1.50 NA NA NA NA NA NA NA NA NA NA NA NA NA

Held To Maturity Securities Debt Maturities Rolling Year Six Through Ten Fair Value 718.40 956.00 276.20 266.80 276.00 146.90 16.20 16.10 NA NA NA NA NA NA NA NA NA NA NA NA NA

Held To Maturity Securities Debt Maturities Rolling Year Two Through Five Fair Value 367.90 1274.00 363.60 369.70 398.20 194.00 29.00 31.90 NA NA NA NA NA NA NA NA NA NA NA NA NA

Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value NA NA NA NA NA NA NA NA NA NA NA NA 0.00 NA 216.90 88.80 76.80 73.70 87.70 28.07 18.65

Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value NA NA 1067.70 801.30 771.30 851.50 NA NA NA NA NA NA 19.70 NA 90.40 186.10 194.60 214.00 180.60 77.86 88.50

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Deposits 26863.80 28088.30 16269.60 16007.30 15565.70 15094.00 14217.00 13882.40 13340.40 11565.10 11663.50 11799.60 11489.90 10814.70 10680.70 10845.60 9945.50 10025.90 9934.90 9933.47 10020.00

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Long Term Debt NA NA 98.70 NA NA NA 98.60 NA NA NA NA NA NA NA NA NA NA NA NA NA NA

Long Term Debt And Capital Lease Obligations NA NA 112.40 NA NA NA 112.40 NA NA NA 13.90 NA NA NA 15.80 NA NA NA 13.10 NA NA

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Stockholders Equity 3271.90 3441.10 1986.60 1984.80 1970.90 1933.40 1959.80 1977.60 1998.90 1956.10 2013.90 1982.60 1948.60 1736.90 1693.90 1654.40 1458.30 1432.40 1427.62 1419.41 1405.38

Common Stocks Including Additional Paid In Capital 2607.90 2668.60 945.00 943.60 941.60 938.50 941.10 976.80 1021.20 1018.70 1049.30 1047.80 1045.60 866.60 866.70 865.50 690.70 688.00 686.99 686.51 685.29

Retained Earnings Accumulated Deficit 993.80 974.50 1052.60 1026.90 1005.20 988.20 962.10 938.90 912.50 897.60 953.60 921.40 892.50 874.70 851.80 828.30 802.60 776.70 752.59 731.88 718.09

Accumulated Other Comprehensive Income Loss Net Of Tax -329.80 -202.00 -11.00 14.30 24.10 6.70 56.60 61.90 65.20 39.80 11.00 13.40 10.50 -4.40 -24.60 -39.40 -35.00 -32.30 -11.96 1.02 2.00

Stock Issued During Period Value New Issues 0.00 1722.50 NA NA NA NA NA NA 0.00 NA 0.00 0.00 176.10 NA 0.00 173.30 0.00 NA 0.03 0.00 385.97

Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value 3.80 2.40 NA 2.00 3.10 2.40 NA 1.80 2.40 1.40 NA 2.00 2.70 1.90 1.30 1.30 1.80 1.10 0.45 0.95 1.59

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Net Cash Provided By Used In Operating Activities 204.30 64.90 76.90 99.30 35.60 70.50 105.50 153.60 -32.10 41.30 70.60 8.60 0.50 47.60 48.30 74.20 34.30 63.40 59.99 6.14 15.52

Net Cash Provided By Used In Investing Activities -1685.90 1522.50 -246.10 -199.20 -715.50 -959.20 -233.70 -256.20 -1406.10 26.20 -167.90 -106.00 245.00 12.10 -77.70 1.30 20.80 -126.70 -174.61 5.49 49.22

Net Cash Provided By Used In Financing Activities -1270.40 -120.90 280.50 385.00 432.30 807.90 544.40 538.20 1994.00 -275.10 -95.50 238.10 -71.80 73.50 -113.60 177.50 -87.30 48.60 -9.23 -48.58 47.08

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Net Cash Provided By Used In Operating Activities 204.30 64.90 76.90 99.30 35.60 70.50 105.50 153.60 -32.10 41.30 70.60 8.60 0.50 47.60 48.30 74.20 34.30 63.40 59.99 6.14 15.52

Net Income Loss 64.10 -33.40 51.10 47.10 42.50 51.40 46.90 48.30 36.70 29.30 52.40 49.10 37.90 41.60 40.40 41.40 41.70 36.70 34.27 27.26 21.87

Depreciation Depletion And Amortization 14.20 13.30 11.00 11.10 10.90 11.40 12.10 11.80 11.50 9.70 9.70 9.70 11.80 7.50 7.70 6.80 6.50 6.60 0.51 8.26 5.05

Deferred Income Tax Expense Benefit -2.30 -6.50 0.40 -4.40 -0.60 9.60 0.50 -1.30 -1.40 -4.40 4.90 -2.20 0.00 2.70 2.60 3.90 -0.80 10.10 1.15 35.60 -17.85

Share Based Compensation 3.80 2.40 1.40 2.00 3.10 2.40 1.90 1.80 2.40 1.40 1.40 2.00 2.70 1.90 1.30 1.40 1.80 1.10 0.45 0.95 1.59

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Net Cash Provided By Used In Investing Activities -1685.90 1522.50 -246.10 -199.20 -715.50 -959.20 -233.70 -256.20 -1406.10 26.20 -167.90 -106.00 245.00 12.10 -77.70 1.30 20.80 -126.70 -174.61 5.49 49.22

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Net Cash Provided By Used In Financing Activities -1270.40 -120.90 280.50 385.00 432.30 807.90 544.40 538.20 1994.00 -275.10 -95.50 238.10 -71.80 73.50 -113.60 177.50 -87.30 48.60 -9.23 -48.58 47.08

Payments Of Dividends Common Stock 44.80 44.70 25.40 25.40 25.50 25.30 23.70 21.90 21.80 61.20 20.20 20.20 20.10 18.70 16.90 15.70 15.80 15.70 13.56 13.47 10.79

Payments For Repurchase Of Common Stock 64.50 1.40 0.00 0.00 0.00 5.40 37.90 46.30 0.00 32.60 0.00 0.00 0.10 2.40 0.00 0.10 0.00 0.90 0.41 0.05 0.03

2022-06-30 2022-03-31 2021-12-31 2021-09-30 2021-06-30 2021-03-31 2020-12-31 2020-09-30 2020-06-30 2020-03-31 2019-12-31 2019-09-30 2019-06-30 2019-03-31 2018-12-31 2018-09-30 2018-06-30 2018-03-31 2017-12-31 2017-09-30 2017-06-30

Credit And Debit Card 19.50 14.80 11.30 12.20 11.40 10.20 11.10 10.50 9.30 10.20 10.80 10.80 10.50 9.40 9.80 10.10 12.90 10.50 12.30 12.40 10.20

Deposit Account 6.30 7.70 4.40 4.40 3.90 3.80 4.30 4.30 3.60 5.40 5.40 5.30 5.40 5.00 5.20 5.70 5.30 5.60 6.00 5.90 5.10

Financial Service Other 3.60 4.30 2.80 1.40 1.60 2.10 2.10 5.00 2.90 4.70 4.40 4.20 4.20 4.30 4.00 3.40 3.80 3.90 3.70 3.60 3.40

Plots across concepts

IncomeStatement

Expenses

Balance Sheet

Assets

NonCurrent Assets

PropertyPlantAndEquipmentNet

Liabilities

Noncurrent Liabilities

Stockholders Equity

CashFlow

NetCashProvidedByUsedInOperatingActivities

NetCashProvidedByUsedInFinancingActivities

DividendsAndRepurchase

FiniteLivedIntangibleAssets

BanksAndOrInsurance

AssetsBanks

LiabilitiesBanks

Line plots across dimensions of each concept

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
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us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:FinancialInstrument
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us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:FairValueByMeasurementBasis, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
('us-gaap:EstimateOfFairValueFairValueDisclosure', 'us-gaap:FairValueMeasurementsRecurring', None)

us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
('us-gaap:FairValueInputsLevel2', 'us-gaap:FairValueMeasurementsRecurring', None)

us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:FairValueByMeasurementBasis
(None,)

us-gaap:AvailableForSaleSecuritiesDebtSecurities
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(None, 'us-gaap:EstimateOfFairValueFairValueDisclosure')

us-gaap:PropertyPlantAndEquipmentGross
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(None,)

us-gaap:FiniteLivedIntangibleAssetsNet
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
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us-gaap:HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
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us-gaap:HeldToMaturitySecuritiesFairValue
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(None, 'us-gaap:EstimateOfFairValueFairValueDisclosure')

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us-gaap:HeldToMaturitySecurities
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us-gaap:HeldToMaturitySecurities
fibk:CreditRating, us-gaap:FinancialInstrument
('fibk:AAARating', None)

us-gaap:HeldToMaturitySecurities
fibk:CreditRating, us-gaap:FinancialInstrument
(None, 'us-gaap:USStatesAndPoliticalSubdivisions')

us-gaap:HeldToMaturitySecurities
fibk:CreditRating, us-gaap:FinancialInstrument
(None, 'us-gaap:CorporateDebtSecurities')

us-gaap:HeldToMaturitySecurities
fibk:CreditRating
(None,)

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis
us-gaap:FinancialInstrument
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us-gaap:HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
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us-gaap:HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
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us-gaap:HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
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us-gaap:HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
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us-gaap:HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
us-gaap:FinancialInstrument
(None,)

us-gaap:LongTermDebt
us-gaap:ConsolidatedEntities, us-gaap:DebtInstrument, us-gaap:LongtermDebtType
('Subsidiaries', None, 'us-gaap:NotesPayableOtherPayables')

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents
(None,)

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
us-gaap:ProductOrService
(None,)

	2022-06-30	2022-03-31	2021-12-31	2021-09-30	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
dei: Entity Common Stock Shares Outstanding	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Weighted Average Number Of Diluted Shares Outstanding	109.13	92.86	NA	61.75	61.73	61.71	NA	63.86	64.08	64.94	NA	65.04	64.71	60.60	NA	58.64	56.70	56.65	NA	56.53	48.07
Weighted Average Number Of Shares Outstanding Basic	109.11	92.86	NA	61.67	61.66	61.59	NA	63.76	64.00	64.79	NA	64.83	64.50	60.31	NA	58.25	56.34	56.24	NA	56.09	47.61
Earnings Per Share Basic	0.59	-0.36	0.83	0.76	0.69	0.83	0.75	0.76	0.57	0.45	0.81	0.76	0.59	0.69	0.67	0.71	0.74	0.65	0.61	0.49	0.46
Earnings Per Share Diluted	0.59	-0.36	0.83	0.76	0.69	0.83	0.75	0.76	0.57	0.45	0.80	0.76	0.59	0.69	0.66	0.71	0.74	0.65	0.60	0.48	0.45
Tier One Risk Based Capital To Risk Weighted Assets	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Capital To Risk Weighted Assets	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00

	2022-06-30	2022-03-31	2021-12-31	2021-09-30	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Interest And Fee Income Loans And Leases	191.70	151.70	105.10	111.90	105.40	107.80	117.00	112.30	112.10	112.00	118.60	120.00	120.90	111.40	112.20	103.90	96.50	91.70	93.13	94.02	73.89
Interest Expense	7.40	6.00	4.00	4.20	4.50	4.60	5.30	5.90	6.30	9.10	11.80	15.80	16.80	14.60	12.70	11.20	9.20	7.80	7.85	7.97	6.55
Interest Income Expense Net	237.90	178.00	121.80	126.90	118.80	120.70	128.40	123.00	122.50	123.10	128.20	125.50	125.30	116.00	118.90	110.00	103.80	99.80	100.84	100.79	79.32
Interest Paid Net	7.50	6.00	6.80	2.70	6.30	3.50	7.50	6.70	7.80	10.90	12.00	15.90	14.40	12.40	11.60	10.70	NA	NA	NA	NA	NA
Gains Losses On Extinguishment Of Debt	0.00	1.40	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Income Tax Expense Benefit	16.20	-7.90	15.40	13.60	12.60	14.10	14.80	14.70	10.40	8.20	16.50	15.30	10.90	11.40	11.80	12.10	11.90	10.30	15.16	13.71	11.88
Income Taxes Paid	13.70	0.10	15.50	5.60	14.70	21.00	18.40	11.50	13.00	11.50	16.40	10.30	24.50	0.00	9.50	6.10	5.10	4.60	4.48	9.90	-14.37
Other Comprehensive Income Loss Net Of Tax	-127.80	-191.00	-25.30	-9.80	17.40	-49.90	-5.30	-3.30	25.40	28.80	-2.40	2.90	14.90	20.20	14.80	-4.40	-2.60	-17.20	NA	-0.97	4.59
Net Income Loss	64.10	-33.40	51.10	47.10	42.50	51.40	46.90	48.30	36.70	29.30	52.40	49.10	37.90	41.60	40.40	41.40	41.70	36.70	34.27	27.26	21.87
Comprehensive Income Net Of Tax	-63.70	-224.40	25.80	37.30	59.90	1.50	41.60	45.00	62.10	58.10	50.00	52.00	52.80	61.80	55.20	37.00	39.10	19.50	21.28	26.29	26.46
Interest Income Expense After Provision For Loan Loss	239.60	116.70	131.30	126.90	118.80	125.80	125.20	117.80	103.00	94.10	124.40	122.90	121.50	112.30	117.30	108.00	100.90	97.70	97.31	97.35	76.97
Noninterest Expense	210.30	207.20	102.20	105.90	99.00	98.40	97.40	99.50	95.60	100.30	90.70	99.30	112.10	93.80	99.40	90.70	84.90	85.90	85.07	94.66	80.40
Noninterest Income	51.00	49.20	37.40	39.70	35.30	38.10	33.90	44.70	39.70	43.70	35.20	40.80	39.40	34.50	34.30	36.20	37.60	35.20	37.19	38.27	37.18

	2022-06-30	2022-03-31	2021-12-31	2021-09-30	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Assets	32061.80	33162.20	19671.90	19372.20	18940.50	18443.40	17648.70	17069.50	16471.40	14411.40	14644.20	14701.60	14414.60	13498.20	13300.20	13355.80	12235.70	12273.40	12213.25	12206.47	12236.34
Liabilities	28789.90	29721.10	17685.30	17387.40	16969.60	16510.00	15688.90	15091.90	14472.50	12455.30	12630.30	12719.00	12466.00	11761.30	11606.30	11701.40	10777.40	10841.00	10785.64	10787.06	10830.96
Liabilities And Stockholders Equity	32061.80	33162.20	19671.90	19372.20	18940.50	18443.40	17648.70	17069.50	16471.40	14411.40	14644.20	14701.60	14414.60	13498.20	13300.20	13355.80	12235.70	12273.40	12213.25	12206.47	12236.34
Stockholders Equity	3271.90	3441.10	1986.60	1984.80	1970.90	1933.40	1959.80	1977.60	1998.90	1956.10	2013.90	1982.60	1948.60	1736.90	1693.90	1654.40	1458.30	1432.40	1427.62	1419.41	1405.38
Tier One Risk Based Capital	2451.40	2446.70	1469.00	1442.60	1415.60	1396.40	1369.00	1378.30	1393.10	1367.70	1422.30	1385.20	1346.30	1237.90	1212.00	1181.20	1086.80	1058.00	1040.30	1026.02	1011.14

		2022-06-30	2022-03-31	2021-12-31	2021-09-30	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents		1059.30	3811.30	2344.80	2233.50	1948.40	2196.00	2276.80	1860.60	1425.00	869.20	1076.80	1269.60	1128.90	955.20	822.00	965.00	712.00	NA	758.90	NA	NA
Available For Sale Securities Debt Securities		7741.10	6283.80	4820.50	4403.60	3957.80	4020.10	4008.70	3453.50	3317.60	3000.30	2960.00	2732.20	2609.70	2572.00	2270.70	2158.80	2178.00	2280.70	2208.70	2111.70	2080.19

	2022-06-30	2022-03-31	2021-12-31	2021-09-30	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Property Plant And Equipment Gross	NA	NA	495.80	NA	NA	NA	491.30	NA	NA	NA	475.10	NA	NA	NA	422.00	NA	NA	NA	404.20	NA	NA
Accumulated Depreciation Depletion And Amortization Property Plant And Equipment	NA	NA	196.20	NA	NA	NA	179.00	NA	NA	NA	169.10	NA	NA	NA	176.80	NA	NA	NA	162.30	NA	NA
Amortization Of Intangible Assets	4.10	3.60	2.50	2.40	2.50	2.50	2.60	2.70	2.70	2.90	2.90	3.00	3.00	2.30	2.40	2.00	1.70	1.80	1.86	1.89	1.06
Property Plant And Equipment Net	442.70	444.40	299.60	297.30	299.10	305.50	312.30	307.80	309.50	308.50	306.00	302.80	321.10	298.20	245.20	244.20	233.70	240.20	241.90	242.94	243.15
Goodwill	1099.80	1137.60	621.60	621.60	621.60	621.60	621.60	621.60	621.60	621.60	621.60	622.60	623.50	546.30	546.70	546.40	445.60	445.60	444.70	445.03	444.33
Indefinite Lived Intangible Assets Excluding Goodwill	105.10	109.60	41.30	43.70	46.10	48.60	51.20	53.80	56.50	59.20	62.10	65.00	67.90	54.60	56.90	NA	NA	NA	49.10	NA	NA
Finite Lived Intangible Assets Net	105.10	109.60	41.30	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	54.60	NA	59.30	45.60	47.30	49.10	50.97	52.84
Held To Maturity Securities Accumulated Unrecognized Holding Loss	270.00	208.80	35.70	8.90	9.10	13.70	NA	NA	0.00	0.00	0.00	0.00	0.10	0.50	8.30	19.40	17.50	16.40	12.70	10.35	9.54
Held To Maturity Securities Fair Value	2860.50	3029.10	1667.50	1632.50	1701.90	855.60	55.00	58.40	71.10	72.60	94.50	97.20	100.80	118.00	400.70	407.40	432.80	455.50	483.35	510.40	535.14
Held To Maturity Securities	3131.60	3220.30	1687.60	1618.10	1685.50	866.30	51.60	55.00	67.90	70.20	92.30	94.90	98.80	117.00	406.80	417.80	440.90	462.30	484.50	505.99	529.44
Available For Sale Debt Securities Amortized Cost Basis	8193.80	6575.10	4859.30	4408.80	3949.40	4011.00	3932.70	3369.20	3229.00	2946.70	2945.50	2714.70	2596.50	2579.00	2305.20	2213.20	2226.20	2325.00	2229.30	2110.20	2076.11
Held To Maturity Securities Accumulated Unrecognized Holding Gain	0.50	19.20	15.60	23.30	25.50	3.00	3.40	3.40	3.20	2.40	2.20	2.30	2.10	1.50	2.20	9.00	9.40	9.60	11.50	14.77	15.25
Held To Maturity Securities Accumulated Unrecognized Holding Loss	270.00	208.80	35.70	8.90	9.10	13.70	NA	NA	0.00	0.00	0.00	0.00	0.10	0.50	8.30	19.40	17.50	16.40	12.70	10.35	9.54
Held To Maturity Securities Continuous Unrealized Loss Position Fair Value	NA	NA	1067.70	801.30	771.30	851.50	NA	NA	NA	NA	NA	0.00	19.70	NA	307.30	274.90	271.40	287.70	268.30	105.93	107.15
Held To Maturity Securities Debt Maturities Next Rolling Twelve Months Fair Value	10.10	355.30	687.20	667.40	688.10	335.70	8.40	8.90	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Held To Maturity Securities Debt Maturities Rolling After Ten Years Fair Value	1764.10	443.80	340.50	328.60	339.60	179.00	1.40	1.50	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Held To Maturity Securities Debt Maturities Rolling Year Six Through Ten Fair Value	718.40	956.00	276.20	266.80	276.00	146.90	16.20	16.10	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Held To Maturity Securities Debt Maturities Rolling Year Two Through Five Fair Value	367.90	1274.00	363.60	369.70	398.20	194.00	29.00	31.90	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	0.00	NA	216.90	88.80	76.80	73.70	87.70	28.07	18.65
Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	NA	NA	1067.70	801.30	771.30	851.50	NA	NA	NA	NA	NA	NA	19.70	NA	90.40	186.10	194.60	214.00	180.60	77.86	88.50

		2022-06-30	2022-03-31	2021-12-31	2021-09-30	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Long Term Debt		NA	NA	98.70	NA	NA	NA	98.60	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Long Term Debt And Capital Lease Obligations		NA	NA	112.40	NA	NA	NA	112.40	NA	NA	NA	13.90	NA	NA	NA	15.80	NA	NA	NA	13.10	NA	NA

	2022-06-30	2022-03-31	2021-12-31	2021-09-30	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Net Cash Provided By Used In Operating Activities	204.30	64.90	76.90	99.30	35.60	70.50	105.50	153.60	-32.10	41.30	70.60	8.60	0.50	47.60	48.30	74.20	34.30	63.40	59.99	6.14	15.52
Net Cash Provided By Used In Investing Activities	-1685.90	1522.50	-246.10	-199.20	-715.50	-959.20	-233.70	-256.20	-1406.10	26.20	-167.90	-106.00	245.00	12.10	-77.70	1.30	20.80	-126.70	-174.61	5.49	49.22
Net Cash Provided By Used In Financing Activities	-1270.40	-120.90	280.50	385.00	432.30	807.90	544.40	538.20	1994.00	-275.10	-95.50	238.10	-71.80	73.50	-113.60	177.50	-87.30	48.60	-9.23	-48.58	47.08

	2022-06-30	2022-03-31	2021-12-31	2021-09-30	2021-06-30	2021-03-31	2020-12-31	2020-09-30	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30
Credit And Debit Card	19.50	14.80	11.30	12.20	11.40	10.20	11.10	10.50	9.30	10.20	10.80	10.80	10.50	9.40	9.80	10.10	12.90	10.50	12.30	12.40	10.20
Deposit Account	6.30	7.70	4.40	4.40	3.90	3.80	4.30	4.30	3.60	5.40	5.40	5.30	5.40	5.00	5.20	5.70	5.30	5.60	6.00	5.90	5.10
Financial Service Other	3.60	4.30	2.80	1.40	1.60	2.10	2.10	5.00	2.90	4.70	4.40	4.20	4.20	4.30	4.00	3.40	3.80	3.90	3.70	3.60	3.40