Goodwill and Other Assets Schedule of Intangible Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 1,102.8	$ 1,074.2
Accumulated amortization	(334.2)	(300.4)
Net carrying amount	$ (768.6)	(773.8)
Internally-developed software [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	2 years 3 months
Gross carrying amount	$ 201.5	192.9
Accumulated amortization	(107.7)	(99.8)
Net carrying amount	$ (93.8)	(93.1)
Development costs non-software [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	1 year 3 months
Gross carrying amount	$ 56.3	55.3
Accumulated amortization	(39.1)	(35.1)
Net carrying amount	$ (17.2)	(20.2)
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 5 months
Gross carrying amount	$ 766.4	741.5
Accumulated amortization	(131.8)	(108.2)
Net carrying amount	$ (634.6)	(633.3)
Other intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	1 year 5 months
Gross carrying amount	$ 78.6	84.5
Accumulated amortization	(55.6)	(57.3)
Net carrying amount	(23.0)	(27.2)
Other intangible asset, net [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	336.4	332.7
Accumulated amortization	(202.4)	(192.2)
Net carrying amount	$ (134.0)	$ (140.5)