Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ 2,378	$ (52,982)	$ (19,342)
Other Comprehensive Income (Loss), net of tax
Net unrealized gains (losses) on available-for-sale securities	316	279	(3,130)
Defined benefit plan adjustments	(395)	(1,185)	(3,755)
Foreign currency translation	4,857	(1,480)	(4,236)
Other Comprehensive Income (Loss), net of tax	4,778	(2,386)	(11,121)
Comprehensive Income (Loss), net of tax	$ 7,156	$ (55,368)	$ (30,463)