Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (9,723)	$ (13,860)	$ (30,230)	$ (34,377)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	510	(929)	(1,457)	3,197
Defined benefit plans, net of tax:
Amortization of prior service cost, net of tax provision of $5 and $7 for the three months ended September 30, 2018 and 2017, respectively; net of tax provision of $15 and $22 for the nine months ended September 30, 2018 and 2017, respectively	19	31	57	91
Other comprehensive income (loss), net of tax	529	(898)	(1,400)	3,288
Comprehensive loss	$ (9,194)	$ (14,758)	$ (31,630)	$ (31,089)