Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Balance at the beginning of the period	$ 130.6	$ 130.6	$ 127.8
Current period additions/adjustments	33.8	1.0	6.8
Impairment			(0.7)
Foreign currency impact	5.4	(1.0)	(3.3)
Balance at the end of the period	$ 169.8	$ 130.6	$ 130.6