Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (63,146)	$ (84,455)	$ (12,676)
Foreign currency translation adjustment	(9,241)	10,607	(3,849)
Foreign currency hedge	658	(1,802)	481
Defined benefit pension plans
Net actuarial gain (loss) arising during period	109	3,226	(10,518)
Prior service cost arising during period	(669)	0	0
Amortization of net actuarial (gain) loss	(78)	71	0
Other comprehensive income (loss), before tax	(9,221)	12,102	(13,886)
Tax (provision) benefit attributable to other comprehensive income (loss)	(3,045)	(2,898)	3,260
Other comprehensive income (loss), net of tax	(12,266)	9,204	(10,626)
Total comprehensive loss	$ (75,412)	$ (75,251)	$ (23,302)