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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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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Property, Equipment, and Capitalized Software (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	$ 532.0	$ 495.2
Less accumulated depreciation	(377.3)	(351.7)
Property, equipment, and capitalized software, net	154.7	143.5
Depreciation expense	81.2	76.0	$ 67.6
Computer equipment [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	70.1	83.5
Capitalized software [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	328.3	294.8
Furniture and fixtures [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	33.7	29.6
Leasehold improvements [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	92.1	77.3
Telephone equipment [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	2.3	2.1
Construction in progress [Member]
Property, Plant and Equipment, Net [Abstract]
Property, equipment, and capitalized software, at cost	$ 5.5	$ 7.9