Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (17,076)	$ (43,637)	$ (53,333)
Other comprehensive income (loss):
Foreign currency translation adjustments, net of zero tax	(745)	(7,464)	8,803
Unrealized gain on available-for-sale securities, net of zero tax	0	1	17
Defined benefit pension plans:
Loss arising during the period	0	(95)	(32)
Tax	0	34	11
Total other comprehensive income (loss)	(745)	(7,524)	8,799
Comprehensive loss	$ (17,821)	$ (51,161)	$ (44,534)