Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 19,808	$ (7,230)	$ (63,559)
Other comprehensive income (loss), net of tax :
Change in foreign currency translation adjustments	(85)	(304)	27
Pension benefit plan	(980)	(1,063)	(84)
Total comprehensive income (loss)	$ 18,743	$ (8,597)	$ (63,616)