Goodwill and Other Intangible Assets - Schedule of Changes in the Carrying Amount of Goodwill by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill net book value, beginning balance	$ 446.4	$ 446.8
Foreign exchange and other adjustments	1.0	(0.4)
Goodwill net book value, ending balance	447.4	446.4
U.S.
Goodwill [Line Items]
Goodwill net book value, beginning balance	429.2	429.2
Foreign exchange and other adjustments	0.0	0.0
Goodwill net book value, ending balance	429.2	429.2
International
Goodwill [Line Items]
Goodwill net book value, beginning balance	17.2	17.6
Foreign exchange and other adjustments	1.0	(0.4)
Goodwill net book value, ending balance	$ 18.2	$ 17.2