Redeemable Noncontrolling Interests (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Redeemable Noncontrolling Interest [Abstract]
Document Period End Date	Jun. 30, 2018
Balance at January 1	$ 492.1	$ 44.1
Other comprehensive income	(12.1)	(18.6)
Redemption value adjustment	(8.1)	39.4
Redemption of shares	(3.3)	(2.6)
Reclassification of noncontrolling interest	0.0	386.7
Balance at June 30	$ 468.6	$ 449.0