| In millions, except per share items | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Operating Activities | | | | | | | | |
| Net income | 88.1 | 89.6 | 89.4 | 70.0 | 54.3 | 52.1 | 54.1 | 53.0 |
| |
| Adjustments to reconcile net income to net cash from operating activities: | | | | | | | | |
| Depreciation of premises and equipment | 5.8 | 5.8 | 5.0 | 5.1 | 5.9 | 6.2 | 6.1 | 6.1 |
| Deferred income tax (benefit) expense | 2.2 | 2.6 | 4.9 | -1.2 | 14.9 | 3.8 | 6.6 | 4.6 |
| Stock-compensation expense | 3.1 | 3.3 | 2.5 | 2.2 | 2.1 | 2.0 | 1.8 | 1.5 |
| Increase in value of bank-owned life insurance | -3.9 | -4.4 | -3.8 | -3.1 | -2.7 | -3.1 | -3.4 | -3.1 |
| Loans originated for sale | -42.4 | -28.2 | -18.8 | -15.2 | -16.5 | -18.0 | -17.8 | -8.8 |
| Proceeds from the sale of loans originated for sale | 42.8 | 28.9 | 20.9 | 14.0 | 19.3 | 16.6 | 18.7 | 8.3 |
| Gain on sale of loans | -0.3 | -0.4 | -0.6 | -0.4 | -0.5 | -0.4 | -0.4 | -0.2 |
| Change in accrued interest receivable | 0.2 | -4.2 | 0.9 | -1.5 | -0.8 | -1.0 | -0.4 | 0.0 |
| Change in other assets | -8.7 | -13.8 | -2.0 | 5.4 | -2.1 | -1.6 | -1.0 | -8.3 |
| Change in other liabilities | 11.7 | 12.0 | 7.6 | 4.3 | 3.0 | 5.6 | -8.5 | 1.4 |
| Net Cash Provided by Operating Activities | 102.3 | 89.8 | 105.0 | 77.6 | 76.1 | 65.3 | 47.9 | 53.4 |
| |
| Investing Activities | | | | | | | | |
| Net decrease (increase) in loans | 77.0 | -3.9 | -30.1 | -95.3 | -85.5 | -183.5 | -100.1 | -43.7 |
| Purchases | 560.7 | 461.4 | 209.6 | -130.9 | -159.3 | -196.2 | -175.3 | -31.3 |
| Proceeds from sales of securities available-for-sale | | 30.3 | 70.4 | | 5.8 | 30.9 | 0.4 | 6.7 |
| Proceeds from maturities and calls | 291.6 | 138.9 | 75.7 | 56.8 | 68.9 | 92.2 | 68.9 | 55.5 |
| Purchases | -0.2 | -2.3 | -11.1 | -35.4 | -27.7 | | | |
| Proceeds from maturities and calls | | | 11.7 | 8.4 | | | | |
| Purchases of premises and equipment | -3.3 | -5.5 | -4.7 | -10.2 | -6.6 | -5.5 | -3.0 | -2.3 |
| Proceeds from the disposals of premises and equipment | | | | 3.9 | 3.1 | | | |
| Proceeds from bank-owned life insurance policies | 2.2 | 2.0 | 2.4 | 0.4 | | | | |
| Net Cash Provided by (Used in) Investing Activities | -191.2 | -285.3 | -108.8 | -168.5 | -171.7 | -261.3 | -184.1 | -24.7 |
| |
| Financing Activities | | | | | | | | |
| Net (decrease) increase in short-term borrowings | 16.5 | 84.7 | -50.7 | 7.7 | 3.9 | 93.4 | 14.8 | -2.9 |
| Purchases of treasury stock | -58.7 | -36.5 | -19.4 | -20.3 | | -10.0 | -7.1 | -28.0 |
| Proceeds from exercise of stock options | 0.7 | 0.2 | 0.5 | 1.2 | 0.7 | 1.2 | 3.0 | 0.6 |
| Dividends paid | -36.1 | -36.7 | -35.5 | -29.6 | -27.1 | -25.7 | -25.3 | -24.5 |
| Net Cash (Used in) Provided by Financing Activities | 194.9 | 584.0 | 20.9 | 131.4 | 89.9 | 214.0 | 58.1 | 33.7 |
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| Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract] | | | | | | | | |
| Supplemental Cash Flow Information: | | | | | | | | |
| Goodwill | | | | | | | | |
| Core deposit intangible | | | | | | | | |