CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 14,820	$ 17,099	$ 43,898	$ 35,177
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, 2020 and 2019	(51)	27	(364)	(245)
Unrealized gain (loss) on marketable securities, net of $0 tax in each of the three and nine months ended September 30, 2020 and 2019	(633)	208	981	799
Amortization of defined benefit pension items, net of tax of $37 and $92 in the three and nine months ended September 30, 2020, respectively, and $5 and $15 in the three and nine months ended September 30, 2019, respectively	49	17	158	51
Total other comprehensive income (loss)	(635)	252	775	605
TOTAL COMPREHENSIVE INCOME	$ 14,185	$ 17,351	$ 44,673	$ 35,782