Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (7,230)	$ (63,559)	$ (61,662)
Other comprehensive income (loss), net of tax :
Change in foreign currency translation adjustments	(304)	27	8
Pension benefit plan	(1,063)	(84)	532
Total comprehensive income (loss)	$ (8,597)	$ (63,616)	$ (61,122)