Foreign Currency Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule of gains (losses) on foreign currency forward contracts
Net gains (loss) on foreign currency forward contracts	$ (157)	$ (2,715)	$ 2,242	$ (3,055)