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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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, depletion and amortization of physical assets used in the normal conduct of business 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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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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Other Financial Information - Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Property and Equipment [Line Items]
Property and equipment, gross	$ 2,046.6	$ 2,124.1
Accumulated depreciation	(1,215.7)	(1,172.4)
Property and equipment, net	830.9	951.7		$ 908.8
Depreciation expense	184.0	193.2	$ 202.8
Computers and equipment
Property and Equipment [Line Items]
Property and equipment, gross	1,041.4	1,100.0
Software
Property and Equipment [Line Items]
Property and equipment, gross	228.6	223.3
Leasehold improvements
Property and Equipment [Line Items]
Property and equipment, gross	216.9	235.2
Furniture and fixtures
Property and Equipment [Line Items]
Property and equipment, gross	48.3	48.6
Building and building improvements
Property and Equipment [Line Items]
Property and equipment, gross	255.0	254.3
Land and land improvements
Property and Equipment [Line Items]
Property and equipment, gross	243.5	243.2
Construction-in-process
Property and Equipment [Line Items]
Property and equipment, gross	$ 12.9	$ 19.5