Foreign Exchange Risk Management - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Gross notional amount	$ 107,400,000		$ 107,400,000		$ 118,600,000
Recognized gains from forward contracts	8,200,000	$ 37,200,000	11,000,000	$ 43,100,000
Foreign currency transaction losses before tax	$ (23,300,000)	$ (12,900,000)	$ (14,400,000)	$ (18,300,000)