| In millions, except per share items | Jun-30-23 | Mar-31-23 | Jun-30-22 | Mar-31-22 | Dec-31-21 | Sep-30-21 | Jun-30-21 | Mar-31-21 |
| | 10-Q | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q |
| Cash Flows from Operating Activities | | | | | | | | |
| Net income | | | 112.6 | 111.3 | 124.4 | 117.4 | 117.1 | 110.8 |
| |
| Adjustments to reconcile net income to net cash from operating activities: | | | | | | | | |
| Depreciation | | | 5.5 | 5.5 | 5.5 | 5.6 | 5.8 | 5.9 |
| Amortization of premiums and discounts on securities, net | | | 2.8 | 4.2 | 6.2 | 7.5 | 7.3 | 6.4 |
| Amortization of operating lease right-of-use assets | | | 5.4 | 4.5 | 4.6 | 4.4 | 4.1 | 4.2 |
| Other amortization and accretion, net | | | -7.2 | -10.6 | -13.9 | -16.0 | -15.6 | -11.6 |
| Stock based compensation | | | 8.5 | 8.3 | 8.7 | 9.3 | 8.0 | 7.1 |
| Origination of loans designated for sale | | | -328.8 | -384.2 | -490.4 | -540.0 | -590.8 | -602.3 |
| Sale of loans designated for sale | | | 368.3 | 437.1 | 543.4 | 579.7 | 621.2 | 588.6 |
| Provision for credit losses | | | | | | | | |
| Deferred income taxes | | | 3.0 | 2.4 | 3.8 | 4.7 | 3.2 | -4.8 |
| Gains on sale of securities | | | | | 0.4 | | 0.1 | |
| Gains on sale of loans | | | -9.9 | -12.0 | -15.3 | -15.8 | -18.0 | -17.4 |
| Gains on sale and write-downs of other real estate owned | | | -1.6 | -0.7 | -0.6 | | 1.2 | 1.4 |
| Losses on disposition of fixed assets and write-downs upon transfer of bank premises to other real estate owned | | | 0.7 | 0.5 | 0.8 | 0.7 | 0.9 | 0.9 |
| Changes in operating assets and liabilities, net of effects from acquired companies: | | | | | | | | |
| Net decrease in other assets | | | -32.3 | -31.6 | -42.4 | -2.9 | -12.0 | -24.7 |
| Net decrease in other liabilities | | | 35.3 | 24.2 | 28.9 | -4.9 | -11.1 | 16.8 |
| Net cash provided by operating activities | | | 171.2 | 162.0 | 154.6 | 147.1 | 111.9 | 83.1 |
| |
| Cash Flows from Investing Activities | | | | | | | | |
| Maturities and repayments of debt securities available-for-sale | | | 422.4 | 485.9 | 546.3 | 509.5 | 457.7 | 377.2 |
| Maturities and repayments of debt securities held-to-maturity | | | 108.9 | 116.1 | 132.9 | 125.7 | 115.6 | 110.3 |
| Proceeds from sale of debt securities available-for-sale | | | | 111.0 | 85.0 | 57.2 | 60.6 | |
| Purchases of debt securities available-for-sale | | | -1,150.9 | -1,353.2 | -1,145.2 | -1,051.7 | -1,059.6 | -792.6 |
| Purchases of debt securities held-to-maturity | | | -411.2 | -352.1 | -377.2 | -235.1 | -172.0 | -160.0 |
| Maturities of time deposits with other banks | | | 1.7 | 0.5 | | | | |
| Net new loans and principal repayments | | | 86.7 | 442.7 | 566.3 | 685.1 | 698.3 | -24.9 |
| Purchases of loans held for investment | | | | -370.6 | -259.3 | -236.7 | -38.8 | |
| Proceeds from sale of other real estate owned | | | 14.9 | 8.0 | 5.6 | | 9.0 | 6.1 |
| Additions to other real estate owned | | | -1.8 | -2.2 | -2.5 | -2.7 | -3.9 | -3.2 |
| Proceeds from sale of FHLB and Federal Reserve Bank Stock | | | | | | 5.4 | | 14.0 |
| Purchase of FHLB and Federal Reserve Bank Stock | | | | -6.3 | -3.0 | | -2.1 | -2.1 |
| Additions to bank premises and equipment | | | -6.2 | -4.8 | -4.3 | -1.9 | -1.4 | -1.4 |
| Net cash provided by (used in) investing activities | | | -944.8 | -676.0 | -412.5 | -89.6 | 86.7 | -366.6 |
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| Cash Flows from Financing Activities | | | | | | | | |
| Net increase in deposits | | | 295.3 | 800.8 | 640.1 | 924.4 | 840.0 | 1,168.6 |
| Stock based employee benefit plans | | | 7.0 | 8.1 | 5.0 | 4.5 | 1.7 | 1.4 |
| Dividends paid | | | -33.9 | -30.5 | -22.5 | -14.9 | -7.2 | |
| Net cash provided by financing activities | | | 226.1 | 757.2 | 591.6 | 860.6 | 725.9 | 948.0 |
| Net increase in cash and cash equivalents | | | -547.5 | 243.2 | 333.6 | 918.1 | 924.5 | 664.5 |
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| Supplemental disclosure of cash flow information: | | | | | | | | |
| Cash paid during the period for interest | | | 7.3 | 8.0 | 10.0 | 12.0 | 14.3 | 17.0 |
| Cash paid during the period for taxes | | | 22.8 | | 30.9 | 34.2 | 41.9 | |
| Supplemental disclosure of non-cash investing activities: | | | | | | | | |