Revenue from servicing real estate mortgages held by others.

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The maximum percentage ownership of common stock or equity participation in the investee under the equity method of accounting.

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The minimum percentage ownership of common stock or equity participation in the investee under the equity method of accounting.

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Loan loss guarantee reserve

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Loan loss accrual

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Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

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This element represent the minimum sum of age plus years of service with the company to be eligible for receipt of retirement benefits upon departure from the company.

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Amount of valuation allowance for receivables classified as other, due within one year or the normal operating cycle, if longer.

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Amount of allowance for credit loss for right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

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Amount, before allowance for credit loss, of right to consideration in exchange for good or service transferred to customer, when right is conditioned on something other than passage of time.

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

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Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, with jurisdictional netting.

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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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Amount of investment in equity method investee and investment in and advance to affiliate.

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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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Amount of lessee's right to use underlying asset under operating lease.

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The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Amount of valuation and qualifying accounts and reserves.

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Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) yr	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2017 USD ($)
Mortgage Banking [Abstract]
Mortgage servicing rights	$ 424.3	$ 376.4
Mortgage-backed Securities Held-to-maturity, Fair Value Disclosure	$ 459.6	423.7
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)	$ (4.6)	(2.4)	$ (4.1)
Bank Servicing Fees.	80.0	63.0	49.6
Operating Lease, Right-of-Use Asset	707.4	804.4
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	430.8	404.2
Loan loss guarantee reserve	36.7			$ 15.1
Retained earnings	3,975.9	3,588.3		3,573.4
Contract with Customer, Asset, Allowance for Credit Loss	(2.1)			(1.7)
Contract with Customer, Asset, before Allowance for Credit Loss	345.7	419.3
Contract with Customer, Asset, after Allowance for Credit Loss	347.8	419.3
Loan loss accrual	22.1	20.6
Allowance for Doubtful Other Receivables, Current		(68.1)		(71.7)
Deferred Income Tax Assets, Net	296.5	245.4		250.9
Allowance For Doubtful Accounts, Current. [Member]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	66.5	68.1	$ 52.0		$ 51.3
Cumulative Effect, Period of Adoption, Adjustment
Loan loss guarantee reserve				15.1
Retained earnings				(14.9)
Contract with Customer, Asset, Allowance for Credit Loss				(1.7)
Allowance for Doubtful Other Receivables, Current				(3.6)
Deferred Income Tax Assets, Net				$ 5.5
ASC Topic 326 Opening Balance Adjustment \| Allowance For Doubtful Accounts, Current. [Member]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	71.7
JLL Spark Global Venture funds [Domain]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 69.9	$ 42.9
Share-based Payment Arrangement [Member]
Share Based Compensation Arrangement By Share Based Payment Award Sum Of Age Plus Years Of Service Minimum \| yr	65