Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (9,205)	$ (10,399)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	1,437	1,312
Defined benefit plans, net of tax:
Amortization of prior service cost, net of tax provision of $5 and $7 for the three months ended March 31, 2018 and 2017, respectively	19	29
Other comprehensive income (loss), net of tax	1,456	1,341
Comprehensive loss	$ (7,749)	$ (9,058)