| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Interest Income | | | | | | | | |
| Loans including fees: | | | | | | | | |
| Nontaxable | 25.9 | 12.4 | 13.9 | 15.9 | 16.3 | 14.0 | 12.3 | 11.6 |
| |
| Investment securities: | | | | | | | | |
| Taxable | 204.0 | 98.0 | 99.0 | 113.8 | 80.2 | 63.0 | 57.0 | 361.8 |
| Nontaxable | 43.6 | 37.6 | 33.9 | 29.2 | 26.7 | 28.9 | 28.6 | 25.8 |
| Total interest income | 1,454.2 | 638.6 | 663.3 | 730.4 | 632.0 | 495.3 | 447.1 | 399.2 |
| |
| Interest Expense | | | | | | | | |
| Deposits | 49.1 | 11.0 | 28.2 | 69.4 | 41.3 | 20.4 | 17.3 | 14.2 |
| Federal funds purchased and interbank borrowings | 5.0 | | 1.3 | 5.7 | 4.8 | 2.0 | 0.7 | 0.3 |
| Securities sold under agreements to repurchase | 0.8 | 0.4 | 0.9 | 2.5 | 2.0 | 1.3 | 1.5 | 1.5 |
| Federal Home Loan Bank advances | 51.5 | 21.1 | 27.3 | 37.5 | 34.9 | 24.8 | 15.5 | 8.1 |
| Other borrowings | 19.8 | 9.8 | 9.6 | 11.1 | 11.5 | 9.8 | 9.4 | 9.0 |
| Total interest expense | 126.3 | 42.2 | 67.2 | 126.1 | 94.4 | 58.2 | 44.4 | 33.1 |
| Net interest income | 1,327.9 | 596.4 | 596.1 | 604.3 | 537.6 | 437.2 | 402.7 | 366.1 |
| Net interest income after provision for credit losses | 1,183.1 | 626.0 | 553.2 | 599.5 | 530.6 | 434.1 | 401.7 | 363.2 |
| |
| Noninterest Income | | | | | | | | |
| Wealth management fees | 69.1 | 40.4 | 36.8 | 37.1 | 36.9 | 37.3 | 34.6 | |
| Service charges on deposit accounts | 72.5 | 31.7 | 32.6 | 44.9 | 44.0 | 41.3 | 41.6 | 43.4 |
| Debit card and ATM fees | 40.2 | 23.8 | 22.7 | 21.7 | 20.2 | 17.7 | 16.8 | 21.3 |
| Mortgage banking revenue | 23.0 | 42.6 | 62.8 | 26.6 | 17.7 | 18.4 | 20.2 | |
| Investment product fees | 31.7 | 24.6 | 21.6 | 21.8 | 20.5 | 21.0 | 18.8 | 17.9 |
| Capital markets income | 26.0 | 22.0 | 22.5 | 13.3 | 4.9 | 6.5 | 3.2 | 1.1 |
| Company-owned life insurance | 14.6 | 10.6 | 12.0 | 11.5 | 10.6 | 8.7 | 8.5 | 8.6 |
| Debt securities gains (losses), net | -0.1 | 4.3 | 10.8 | 1.9 | 2.1 | | | |
| Other income | 32.1 | 14.3 | 17.5 | 20.5 | 24.4 | 23.3 | 24.8 | 19.9 |
| Total noninterest income | 399.8 | 214.2 | 239.3 | 199.3 | 195.3 | 183.4 | 252.8 | 230.6 |
| |
| Noninterest Expense | | | | | | | | |
| Salaries and employee benefits | 575.6 | 284.1 | 293.6 | 289.5 | 281.3 | 246.7 | 252.9 | 243.9 |
| Occupancy | 100.4 | 54.8 | 55.3 | 55.3 | 51.9 | 46.5 | 50.9 | 53.2 |
| Equipment | 27.6 | 16.7 | 16.7 | 16.9 | 14.9 | 13.6 | 13.4 | 13.2 |
| Marketing | 32.3 | 12.7 | 10.9 | 15.9 | 15.8 | 13.2 | 14.6 | 10.4 |
| Technology | 84.9 | 47.0 | 41.1 | 37.6 | 36.2 | 32.3 | 32.0 | 27.3 |
| Communication | 18.8 | 10.1 | 9.7 | 10.7 | 10.8 | 9.3 | 10.0 | 9.6 |
| Professional fees | 39.0 | 20.1 | 15.8 | 22.9 | 14.5 | 16.8 | 15.7 | 11.8 |
| FDIC assessment | 19.3 | 6.1 | 6.7 | 6.0 | 10.6 | 9.5 | 8.7 | 7.5 |
| Amortization of intangibles | 25.9 | 11.3 | 14.1 | 16.9 | 14.4 | 11.8 | 12.5 | 11.7 |
| Amortization of tax credit investments | 11.0 | 6.8 | 18.8 | 2.7 | 22.9 | 11.7 | | |
| Other expense | 76.5 | 31.7 | 27.2 | 34.1 | 43.8 | 30.8 | 28.7 | 31.0 |
| Total noninterest expense | 1,038.2 | 501.4 | 536.9 | 508.5 | 517.3 | 448.8 | 454.1 | 430.9 |
| Income (loss) before income taxes | 544.7 | 338.9 | 255.6 | 290.4 | 208.7 | 168.7 | 200.4 | 162.9 |
| Income tax expense (benefit) | 116.4 | 61.3 | 29.1 | 52.2 | 17.9 | 72.9 | 66.2 | 46.2 |
| Net income (loss) | 428.3 | 277.5 | 226.4 | 238.2 | 190.8 | 95.7 | 134.3 | 116.7 |
| Net income (loss) applicable to common shareholders | 414.2 | 277.5 | 226.4 | | | | | |
| |
| Net income (loss) per common share - basic (in dollars per share) | $1.51 | $1.68 | $1.37 | $1.39 | $1.23 | $0.69 | $1.05 | $1.01 |
| Net income (loss) per common share - diluted (in dollars per share) | $1.50 | $1.67 | $1.36 | $1.38 | $1.22 | $0.69 | $1.05 | $1.00 |
| |
| Weighted average number of common shares outstanding - basic (in shares) | 275.2 | 165.2 | 165.5 | 171.9 | 155.7 | 137.8 | 127.7 | 115.7 |
| Weighted average number of common shares outstanding - diluted (in shares) | 276.7 | 165.9 | 166.2 | 172.7 | 156.5 | 138.5 | 128.3 | 116.3 |
| |
| Dividends per common share (in dollars per share) | $0.56 | $0.56 | $0.56 | $0.52 | $0.52 | $0.52 | $0.52 | $0.48 |