Goodwill and Other Intangible Assets - Intangible Assets by Asset Type (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets [Line Items]
Gross Carrying Amount	$ 2,702.6	$ 2,694.5
Accumulated Amortization	(1,990.4)	(1,797.5)
Net Carrying Amount	712.2	897.0
Customer relationships and contracts
Intangible Assets [Line Items]
Gross Carrying Amount	2,071.0	2,106.8
Accumulated Amortization	(1,625.5)	(1,490.8)
Net Carrying Amount	445.5	616.0
Trade name
Intangible Assets [Line Items]
Gross Carrying Amount	422.1	422.2
Accumulated Amortization	(237.3)	(216.3)
Net Carrying Amount	184.8	205.9
Internally developed software
Intangible Assets [Line Items]
Gross Carrying Amount	205.8	162.6
Accumulated Amortization	(125.4)	(89.6)
Net Carrying Amount	80.4	73.0
Other
Intangible Assets [Line Items]
Gross Carrying Amount	3.7	2.9
Accumulated Amortization	(2.2)	(0.8)
Net Carrying Amount	$ 1.5	$ 2.1