Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Consolidated Statements of Comprehensive Loss
Net loss	$ (142,390)	$ (178,530)	$ (509,116)
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	(44)	(90)	(906)
Unrealized pension actuarial gains (losses), net of tax	6,118	(9,005)	1,242
Total other comprehensive loss, net of tax	$ (136,316)	$ (187,625)	$ (508,780)