Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (43,637)	$ (53,333)	$ (205)
Other comprehensive income (loss):
Foreign currency translation adjustments, net of zero tax	(7,464)	8,803	(6,640)
Unrealized gain on available-for-sale securities, net of zero tax	1	17	10
Defined benefit pension plans:
Loss arising during the period	(95)	(32)	(72)
Curtailments, settlements and other	0	0	0
Tax	34	11	24
Total other comprehensive income (loss)	(7,524)	8,799	(6,678)
Comprehensive loss	$ (51,161)	$ (44,534)	$ (6,883)