| In millions, except per share items | Jun-30-23 | Mar-31-23 | Dec-31-22 | Sep-30-22 | Jun-30-22 | Mar-31-22 | Dec-31-21 | Sep-30-21 |
| | 10-Q | 10-Q | 8-K | 10-Q | 10-Q | 10-Q | 10-K | 10-Q |
| Interest income | | | | | | | | |
| Interest and fees on loans | 621.1 | 558.7 | 498.8 | 402.7 | 320.5 | 285.7 | 289.1 | 285.6 |
| Interest-bearing deposits with banks | 16.9 | 13.5 | | 15.6 | 5.8 | 1.7 | 2.3 | 2.0 |
| Federal funds sold and securities purchased under resale agreements | 0.0 | 0.1 | | 1.8 | 1.4 | 0.4 | | |
| Investment securities | 51.2 | 59.9 | 53.1 | 38.6 | 36.5 | 32.4 | 27.2 | 25.2 |
| Federal Home Loan Bank and Federal Reserve Bank stock | 3.5 | 3.7 | 2.9 | 2.1 | 1.8 | 1.8 | 1.8 | 1.8 |
| Brokerage customer receivables | 0.3 | 0.3 | 0.3 | 0.3 | 0.2 | 0.2 | 0.2 | 0.2 |
| Total interest income | 697.2 | 639.7 | 580.7 | 466.5 | 372.0 | 328.3 | 328.0 | 322.5 |
| |
| Interest expense | | | | | | | | |
| Interest on deposits | 213.5 | 144.8 | 95.4 | 45.9 | 19.0 | 14.9 | 16.6 | 19.3 |
| Interest on Federal Home Loan Bank advances | 17.4 | 19.1 | | 6.8 | 4.9 | 4.8 | 4.9 | 4.9 |
| Interest on subordinated notes | 5.5 | 5.5 | | 5.5 | 5.5 | 5.5 | 5.5 | 5.5 |
| Interest on junior subordinated debentures | 5.5 | 5.5 | | 5.5 | 5.5 | 5.5 | 5.5 | 5.5 |
| Total interest expense | 249.6 | 181.7 | 123.9 | 65.0 | 34.2 | 29.0 | 32.0 | 35.0 |
| Net interest income | 447.5 | 458.0 | 456.8 | 401.4 | 337.8 | 299.3 | 296.0 | 287.5 |
| Provision for credit losses | 28.5 | 23.0 | | 6.4 | 20.4 | 4.1 | 9.3 | -7.9 |
| Net interest income after provision for credit losses | 419.0 | 435.0 | 409.2 | 395.0 | 317.4 | 295.2 | 286.7 | 295.4 |
| |
| Non-interest income | | | | | | | | |
| Revenue from contracts with customers | | | | | | | | |
| Mortgage banking | 30.0 | 18.3 | | 27.2 | 33.3 | 77.2 | 53.1 | 55.8 |
| Gains (losses) on investment securities, net | | 1.4 | -6.7 | | -7.8 | -2.8 | | |
| Fees from covered call options | 2.6 | 10.4 | 8.0 | 1.4 | 1.1 | 3.7 | 1.1 | 1.2 |
| Trading gains, net | 0.1 | 0.8 | | 0.0 | 0.2 | 3.9 | 0.2 | 0.1 |
| Operating lease income, net | 12.2 | 13.0 | 12.4 | 12.6 | 15.0 | 15.5 | 14.2 | 12.8 |
| Other | 20.7 | 21.0 | | 15.9 | 13.9 | 18.6 | 18.9 | 23.4 |
| Total non-interest income | 113.0 | 107.8 | 93.8 | 101.5 | 102.9 | 162.8 | 133.8 | 136.5 |
| |
| Non-interest expense | | | | | | | | |
| Salaries and employee benefits | 184.9 | 176.8 | | 176.1 | 167.3 | 172.4 | 167.1 | 170.9 |
| Software and equipment | 26.2 | 24.7 | | 24.1 | 24.3 | 22.8 | 23.7 | 22.0 |
| Occupancy, net | 19.2 | 18.5 | | 17.7 | 17.7 | 17.8 | 18.3 | 18.2 |
| Data processing | 9.7 | 9.4 | | 7.8 | 8.0 | 7.5 | 7.2 | 7.1 |
| Advertising and marketing | 17.8 | 11.9 | 14.3 | 16.6 | 16.6 | 11.9 | 14.0 | 13.4 |
| Professional fees | 8.9 | 8.2 | | 7.5 | 7.9 | 8.4 | 7.6 | 7.1 |
| Amortization of other acquisition-related intangible assets | 1.5 | 1.2 | 1.4 | 1.5 | 1.6 | 1.6 | 1.8 | 1.9 |
| FDIC insurance | 9.0 | 8.7 | | 7.2 | 6.9 | 7.7 | 7.3 | 6.8 |
| Other | 33.4 | 30.2 | | 28.3 | 29.3 | 25.5 | 26.8 | 26.3 |
| Total non-interest expense | 320.6 | 299.2 | 307.8 | 296.5 | 288.7 | 284.3 | 283.4 | 282.1 |
| Income tax expense | 56.7 | 63.4 | 50.4 | 57.1 | 37.1 | 46.3 | 38.3 | 40.6 |
| Net income | 154.8 | 180.2 | 144.8 | 143.0 | 94.5 | 127.4 | 98.8 | 109.1 |
| Preferred stock dividends | 7.0 | 7.0 | | 7.0 | 7.0 | 7.0 | 35.0 | 7.0 |
| Net income applicable to common shares | 147.8 | 173.2 | 137.8 | 136.0 | 87.5 | 120.4 | 91.8 | 102.1 |
| |
| Net income per common share-Basic (usd per share) | $2.41 | $2.84 | $2.27 | $2.24 | $1.51 | $2.11 | $1.61 | $1.79 |
| Net income per common share-Diluted (usd per share) | $2.38 | $2.80 | $2.23 | $2.21 | $1.49 | $2.07 | $1.58 | $1.77 |
| |
| Cash dividends declared per common share (usd per share) | $0.40 | $0.40 | $340.00 | $0.34 | $0.34 | $0.34 | $0.31 | $0.31 |
| |
| Weighted average common shares outstanding (in shares) | 61.2 | 61.0 | 60.8 | 60.7 | 58.1 | 57.2 | 57.0 | 57.0 |
| Dilutive potential common shares (in shares) | 0.9 | 0.9 | | 0.8 | 0.8 | 0.9 | 0.1 | 0.8 |
| Average common shares and dilutive common shares (in shares) | 62.1 | 61.8 | 60.8 | 61.6 | 58.8 | 58.1 | 57.8 | 57.8 |