Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive (Loss) Income
Beginning Balance	$ (33,977)	$ (19,495)
Other comprehensive loss before reclassifications	12,580	(13,416)
Amounts reclassified from accumulated other comprehensive loss		(1,066)
Other comprehensive income (loss)	12,580	(14,482)	$ (13,601)
Ending Balance	$ (21,397)	(33,977)	$ (19,495)
Currency translation adjustment
Accumulated Other Comprehensive (Loss) Income
Amounts reclassified from accumulated other comprehensive loss		$ (1,100)