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Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Entity Information |  |  |
Off-Balance Sheet, Credit Loss, Liability | $ 18.4 | $ 16.2 | $ 3.8
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal) | (31.1) | (68.4) | $ 14.7
Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |
Entity Information |  |  |
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal) | 2.2 | 12.4 |
Unused Credit Card Lines |  |  |
Entity Information |  |  |
Credit extension commitments | 814.0 | 827.6 |
Standby Letters of Credit |  |  |
Entity Information |  |  |
Credit extension commitments | 97.1 | 93.8 |
Commitments to Extend Credit |  |  |
Entity Information |  |  |
Credit extension commitments | $ 4,069.2 | $ 5,173.3 |

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- Definition Credit Extension Commitments + References No definition available. + Details
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- Definition Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479344/326-20-45-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482454/460-10-45-1 + Details
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- Definition Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 + Details
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