Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (9,889)	$ 1,057	$ 17,762
Other comprehensive income (loss)
Foreign currency translation adjustment	2,391	5,105	(27,622)
Reclassification adjustment for foreign currency translation included in net income (loss)	17,201
Pension liability, net of tax expense (benefit) of $14 in 2017, ($95) in 2016, and $113 in 2015	41	(169)	200
Total other comprehensive income (loss)	19,633	4,936	(27,422)
Comprehensive income (loss)	$ 9,744	$ 5,993	$ (9,660)