CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
NET INCOME	$ 28,801	$ 19,677	$ 65,561	$ 36,580
OTHER COMPREHENSIVE (LOSS) INCOME, NET OF TAX:
Defined benefit pension plan adjustments	248		819
Foreign currency translation adjustment	(411)	(1,375)	261	(3,109)
Unrealized loss in fair value of investments	(79)	(2)	(224)	(86)
Unrealized gain (loss) in fair value of interest rate swap		47	(24)	152
Total other comprehensive (loss) income, net of tax	(242)	(1,330)	832	(3,043)
TOTAL COMPREHENSIVE INCOME	$ 28,559	$ 18,347	$ 66,393	$ 33,537