CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 39,798	$ 15,886
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in each of the three months ended March 31, 2021 and 2020	(18)	(283)
Unrealized loss on marketable securities, net of $0 tax in each of the three months ended March 31, 2021 and 2020	(580)	(952)
Amortization of defined benefit pension items, net of tax of $135 and $31 in the three months ended March 31, 2021, and 2020, respectively	(75)	51
Total other comprehensive loss	(673)	(1,184)
TOTAL COMPREHENSIVE INCOME	$ 39,125	$ 14,702