Summary of Significant Accounting Policies - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Unrealized losses on cash flow hedge instruments	$ (0.6)	$ (0.9)
Currency translation adjustments	(70.5)	(35.8)
Unrealized losses on defined benefit plans	(2.6)	(2.3)
Total	$ (73.7)	$ (39.0)