CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 46,248	$ 39,798
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in each of the three months ended March 31, 2022 and 2021	(269)	(18)
Unrealized loss on marketable securities, net of $0 tax in each of the three months ended March 31, 2022 and 2021	(4,181)	(580)
Amortization of defined benefit pension items, net of tax of $3 and $135 in the three months ended March 31, 2022 and 2021, respectively	18	(75)
Total other comprehensive loss	(4,432)	(673)
TOTAL COMPREHENSIVE INCOME	$ 41,816	$ 39,125