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Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2023 USD ($) yr | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
Mortgage Banking [Abstract] |  |  |  |
Identified intangibles, net of accumulated amortization | $ 785.0 | $ 858.5 |  |
Mortgage-backed Securities Held-to-maturity, Fair Value Disclosure | $ 698.3 | 695.3 |  |
Real Estate Investments, Net [Abstract] |  |  |  |
Minimum ownership percentage in real estate ventures (in hundredths) | 1.00% |  |  |
Maximum ownership percentage in real estate ventures (in hundredths) | 10.00% |  |  |
Foreign Currency Translation [Abstract] |  |  |  |
Net foreign currency gains (losses) | $ (10.6) | (6.4) | $ (8.1) |
Bank Servicing Fees. | 129.6 | 119.0 | 101.8 |
Loan loss guarantee reserve | 23.4 | 24.8 |  |
Loan loss accrual | 30.9 | 29.0 |  |
Allowance For Doubtful Accounts, Current. [Member] |  |  |  |
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount | $ 70.7 | 66.7 | 67.6 | $ 66.5
Share-based Payment Arrangement [Member] |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award Sum Of Age Plus Years Of Service Minimum | yr | 65 |  |  |
ASC Topic 326 Opening Balance Adjustment | Allowance For Doubtful Accounts, Current. [Member] |  |  |  |
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount |  |  | $ 67.6 |
Mortgage servicing rights [Member] |  |  |  |
Mortgage Banking [Abstract] |  |  |  |
Identified intangibles, net of accumulated amortization | $ 492.0 | $ 505.1 |  |

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