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)	$ 64,743	$ 74,564	$ (3,519)
Other comprehensive income (loss), before tax:
Change in foreign currency translation adjustments	37,454	(10,278)	(25,841)
Unrealized gain (loss) on derivatives
Unrealized derivative (loss) gain arising during period	(3,425)	1,871	(25)
Less: Reclassification adjustments for losses included in net loss	2,958	0	(923)
Unrealized (loss) gain on derivatives	(6,383)	1,871	898
Defined benefit pension plan - net (loss) gain arising during period	(57)	(45)	904
Total other comprehensive income (loss), before tax	31,014	(8,452)	(24,039)
Income tax expense (benefit) related to items in other comprehensive loss	2,333	(800)	(375)
Total other comprehensive income (loss), net of tax	33,347	(9,252)	(24,414)
Comprehensive income (loss), net of tax	$ 98,090	$ 65,312	$ (27,933)