CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 42,034	$ 14,820	$ 123,713	$ 43,898
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in each of the three and nine months ended September 30, 2021 and 2020	(154)	(51)	(212)	(364)
Unrealized gain (loss) on marketable securities, net of $0 tax in each of the three and nine months ended September 30, 2021 and 2020	7	(633)	(904)	981
Amortization of defined benefit pension items, net of tax of $6 and $147 in the three and nine months ended September 30, 2021, respectively, and $37 and $92 in the three and nine months ended September 30, 2020, respectively	53	49	30	158
Total other comprehensive income (loss)	(94)	(635)	(1,086)	775
TOTAL COMPREHENSIVE INCOME	$ 41,940	$ 14,185	$ 122,627	$ 44,673