CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
NET INCOME	$ 14,099	$ 10,379
Other comprehensive income, net of tax:
Foreign currency translation adjustments, net of $0 tax in each of the three months ended March 31, 2017 and 2016	64	(54)
Unrealized gain on marketable securities, net of $0 tax in each of the three months ended March 31, 2017 and 2016	83	213
Amortization of defined benefit pension items, net of tax of $13 and $11 in the three months ended March 31, 2017 and 2016, respectively	49	40
Total other comprehensive income	196	199
TOTAL COMPREHENSIVE INCOME	$ 14,295	$ 10,578