CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income (loss)	$ (295,697)	$ 446,906	$ 109,493
Other comprehensive Income (loss):
Foreign currency translation	8,450	(192)	91
Unrealized gain on marketable securities, net of tax	95	1,137	203
Defined benefit pension obligations, net of tax	(8,363)	(6,322)	(696)
Other comprehensive income (loss)	182	(5,377)	(402)
Comprehensive income (loss)	$ (295,515)	$ 441,529	$ 109,091