CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 164,413	$ 71,176	$ 193,468
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in 2021, 2020 and 2019	(486)	(183)	(518)
Unrealized gain (loss) on marketable securities, net of $0 tax in 2021, 2020 and 2019	(2,055)	307	849
Unrealized actuarial gain (loss) on pension benefits, net of tax of ($334), ($308) and $497 in 2021, 2020 and 2019, respectively	967	843	(1,772)
Total other comprehensive income (loss)	(1,574)	967	(1,441)
TOTAL COMPREHENSIVE INCOME	$ 162,839	$ 72,143	$ 192,027