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Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) yr	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Mortgage Banking [Abstract]
Identified intangibles, net of accumulated amortization	$ 724.1	$ 785.0
Mortgage-backed Securities Held-to-maturity, Fair Value Disclosure	$ 708.9	698.3
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)	$ (1.5)	(10.6)	$ (6.4)
Loan loss guarantee reserve	28.5	23.4
Loan loss accrual	30.0	30.9
Allowance For Doubtful Accounts, Current. [Member]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	$ 60.8	70.7	66.7	$ 67.6
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			$ 66.7
Mortgage servicing rights [Member]
Mortgage Banking [Abstract]
Identified intangibles, net of accumulated amortization	$ 471.1	$ 492.0

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Amount, before tax, of realized and unrealized gain (loss) from foreign currency transaction.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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Fair value of securitized, pay-through debt securities collateralized by real estate mortgage loans classified as held-to-maturity.

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