Consolidated Statements of Comprehensive Income/(Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 84,936	$ (29,615)	$ (84,867)
Other comprehensive income (loss)
Foreign currency translation adjustments	(52,873)	14,650	35,361
Derivative adjustments
Fair valuation of derivatives	7,736	(1,032)	(3,748)
Reclassification adjustment for loss (gain) on derivatives included in net loss	(2,001)	637	3,222
Total other comprehensive income (loss)	(47,138)	14,255	34,835
Total comprehensive income (loss)	$ 37,798	$ (15,360)	$ (50,032)