Redeemable Noncontrolling Interests - Table 2 (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Noncontrolling Interest [Abstract]
Net income attributable to nonredeemable noncontrolling interests	$ 16.9	$ 15.0	$ 53.2	$ 43.3
Net income attributable to redeemable noncontrolling interests	3.8	4.2	10.3	9.9
Net income attributable to noncontrolling interests	$ 20.7	$ 19.2	$ 63.5	$ 53.2