Redeemable Noncontrolling Interests (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Redeemable Noncontrolling Interest [Abstract]
Document Period End Date	Mar. 31, 2018
Balance at January 1	$ 492.1	$ 44.1
Other comprehensive income	0.0	(18.6)
Redemption value adjustment	17.5	39.4
Redemption of shares	0.0	(1.7)
Reclassification of noncontrolling interest		386.7
Balance at March 31	$ 509.6	$ 449.9