Supplementary Data Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 01, 2018
Property and Equipment [Abstract]
Depreciation	$ 204.7	$ 192.5	$ 165.3
Property, Plant and Equipment [Line Items]
Furniture and equipment	654.6	694.3
Leasehold improvements	554.6	634.9
Internal-use computer software	470.1	422.0
Land and buildings	144.9	143.3
Total property and equipment, gross	1,824.2	1,894.5
Less: accumulated depreciation and amortization	(1,133.9)	(1,116.4)
Total property and equipment, net	$ 690.3	$ 778.1		$ 159.7

Property and Equipment [Abstract]

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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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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount before accumulated depreciation of equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities. Examples include, but are not limited to, desks, chairs, tables, and bookcases.

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

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Amount before accumulated depreciation of additions or improvements to assets held under a lease arrangement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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