Income Taxes - Income Tax (Benefit) Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S.:
Federal	$ (1.2)	$ 0.1	$ 0.7
State and local	1.0	0.4	(0.2)
Foreign	133.4	85.5	120.1
Total current	133.2	86.0	120.6
U.S.:
Federal	(48.7)	1.9	6.4
State and local	0.4	(0.2)	(5.2)
Foreign	(78.3)	(59.1)	(46.7)
Total deferred	(126.6)	(57.4)	(45.5)
Income tax expense	$ 6.6	$ 28.6	$ 75.1