CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 39,147	$ 59,544	$ 57,266
Other comprehensive income:
Foreign currency translation adjustments, net of $0 tax in 2015, 2014 and 2013	(191)	(79)	(29)
Unrealized gain (loss) on marketable securities, net of $0 tax in 2015, 2014 and 2013	(180)	(127)	72
Unrealized actuarial loss on pension benefits, net of tax of $96, $128 and $61 in 2015, 2014 and 2013, respectively	(344)	(460)	(220)
Total other comprehensive loss	(715)	(666)	(177)
Total comprehensive income	38,432	58,878	57,089
Foreign currency translation adjustment, tax	0	0	0
Unrealized gain on marketable securities, tax	0	0	0
Unrealized actuarial loss on pension benefits, tax	$ 96	$ 128	$ 61