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Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Jun. 30, 2024 | Dec. 31, 2023 | Jun. 30, 2023 | Dec. 31, 2022
Entity Information [Line Items] |  |  |  |  |  |  |  |
Off-Balance Sheet, Credit Loss, Liability | $ 5.6 | $ 18.8 | $ 5.6 | $ 18.8 | $ 5.8 | $ 18.4 | $ 20.8 | $ 16.2
Provision for credit loss expense | (20.0) | (3.2) | (47.0) | (25.3) |  |  |  |
Credit Extension Commitments | 3,290.7 |  | 3,290.7 |  |  | 4,069.2 |  |
Unused Credit Card Lines |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |
Credit Extension Commitments | 861.4 |  | 861.4 |  |  | 814.0 |  |
Standby Letter of Credit |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |
Credit Extension Commitments | 88.7 |  | 88.7 |  |  | $ 97.1 |  |
Cumulative effect, period of adoption, adjusted balance |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |
Provision for credit loss expense | $ (0.2) | $ (2.0) | $ (12.8) | $ 2.6 |  |  |  |

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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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