CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 13,902	$ 11,407	$ 28,001	$ 21,786
Other comprehensive income, net of tax:
Foreign currency translation adjustments, net of $0 tax in the three and six months ended June 30, 2017 and 2016	31	37	95	(17)
Unrealized gain on marketable securities, net of $0 tax in the three and six months ended June 30, 2017 and 2016	15	48	98	261
Amortization of defined benefit pension items, net of tax of $14 and $27 in the three and six months ended June 30, 2017, respectively, and $11 and $22 in the three and six months ended June 30, 2016, respectively	49	40	98	80
Total other comprehensive income	95	125	291	324
TOTAL COMPREHENSIVE INCOME	$ 13,997	$ 11,532	$ 28,292	$ 22,110