Supplementary Data Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Furniture and equipment	$ 653.5	$ 654.6
Leasehold improvements	571.3	554.6
Internal-use computer software	513.5	470.1
Land and buildings	139.1	144.9
Total property and equipment, gross	1,877.4	1,824.2
Less: accumulated depreciation and amortization	(1,201.6)	(1,133.9)
Total property and equipment, net	675.8	690.3
Depreciation	$ 197.6	$ 204.7	$ 192.5

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software.

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Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

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