Income Taxes (Components of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense (benefit):
Federal	$ 0.7	$ 0.6	$ (0.2)
State	(0.9)	(0.2)	(1.1)
Foreign	28.1	18.6	10.9
Deferred tax expense (benefit):
Federal	(13.5)	(26.9)	(20.1)
State	3.8	(1.0)	(0.5)
Foreign	(2.4)	5.2	(3.8)
Income tax expense (benefit)	$ 15.8	$ (3.7)	$ (14.8)