CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 16,506	$ 12,809	$ 44,507	$ 34,595
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net of $0 tax in the three and nine months ended September 30, 2017 and 2016	2	(254)	97	(271)
Unrealized gain (loss) on marketable securities, net of $0 tax in the three and nine months ended September 30, 2017 and 2016	47	(145)	145	116
Amortization of defined benefit pension items, net of tax of $14 and $41 in the three and nine months ended September 30, 2017, respectively, and $11 and $33 in the three and nine months ended September 30, 2016, respectively	50	41	148	121
Total other comprehensive income (loss)	99	(358)	390	(34)
TOTAL COMPREHENSIVE INCOME	$ 16,605	$ 12,451	$ 44,897	$ 34,561