Income Taxes - Provision/(Benefit) For Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
U.S. federal	$ (4.4)	$ (67.2)	$ (2.0)
Foreign	72.9	54.0	38.2
State and local	1.7	(10.6)	(0.6)
Total current	70.2	(23.8)	35.6
Deferred
U.S. federal	7.6	3.6	(38.3)
Foreign	(44.9)	(50.2)	(11.1)
State and local	(3.1)	2.8	0.1
Total deferred	(40.4)	(43.8)	(49.3)
Income tax (benefit) expense	$ 29.8	$ (67.6)	$ (13.7)