CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 10,845	$ 15,381	$ 18,078	$ 29,581
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in each of the three and six months ended June 30, 2019 and 2018	(250)	37	(272)	0
Unrealized gain (loss) on marketable securities, net of $0 tax in each of the three and six months ended June 30, 2019 and 2018	257	226	591	(12)
Amortization of defined benefit pension items, net of tax of $5 and $9 in the three and six months ended June 30, 2019, respectively, and $9 and $18 in the three and six months ended June 30, 2018, respectively	18	31	34	63
Total other comprehensive income	25	294	353	51
TOTAL COMPREHENSIVE INCOME	$ 10,870	$ 15,675	$ 18,431	$ 29,632