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Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Deferred tax assets: |  |  |
Loans, principally due to allowance for credit losses | $ 56.7 | $ 54.8 |
Loan discount | 21.7 | 32.5 |
Investment securities, unrealized losses | 118.1 | 157.9 |
Deferred compensation | 18.6 | 26.8 |
Non-performing loan interest | 2.2 | 2.6 |
Net operating loss carryforwards | 1.1 | 1.5 |
Lease liabilities | 11.0 | 12.0 |
Other | 4.8 | 2.4 |
Deferred tax assets | 264.2 | 323.2 |
Deferred tax liabilities: |  |  |
Fixed assets, principally differences in bases and depreciation | (19.8) | (17.3) |
Deferred loan costs | (4.1) | (3.3) |
Investment in joint venture partnership, principally due to differences in depreciation of partnership assets | (2.4) | (1.3) |
Right of use assets | (10.3) | (11.3) |
Prepaid amounts | (0.9) | (0.9) |
Government agency stock dividends | (1.3) | (1.2) |
Goodwill and other intangibles | (68.1) | (68.2) |
Mortgage servicing rights | (6.9) | (7.4) |
Other | (0.4) | (1.8) |
Deferred tax liabilities | (114.2) | (112.7) |
Deferred Tax Liabilities, Net | 150.0 | 210.5 |
Operating Loss Carryforwards [Line Items] |  |  |
Deferred Income Tax Expense (Benefit) | 20.4 | (4.7) | $ 5.0
Tax Credit Carryforward, Amount | 2.4 |  |
Other real estate owned write-downs and carrying costs | 1.4 | 1.5 |
Deferred Tax Assets, Derivative Instruments | 0.3 | 0.5 |
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Reserves | 10.7 | 8.8 |
Deferred Tax Assets, Contract Incentives | 7.5 | 8.5 |
Deferred Tax Assets, Discount on Acquired Investment Securities | $ 10.1 | $ 13.4 |

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