Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 23,578	$ 55,086	$ 47,241
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	677	(838)	(79)
Release of cumulative translation adjustment	(258)	132	(82)
Net change in foreign currency translation adjustment	419	(706)	(161)
Unrealized losses on available-for-sale securities	(25)	0	(2)
Comprehensive income	$ 23,972	$ 54,380	$ 47,078