Derivative Financial Instruments - Effect of Derivative on Statement of Operations (Details) - Designated as Hedging Instrument - Cash Flow Hedging - Foreign Currency Forward Contract - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative [Line Items]
Realized gains (losses) recognized in cost of services	$ (0.1)	$ 0.0
Unrealized gains (losses) recognized in other comprehensive income	(0.3)	0.0
Net derivative gains (losses)	$ (0.4)	$ 0.0