Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 12,872	$ 13,616	$ 28,517	$ 28,952
Other comprehensive income (loss):
Foreign currency translation adjustment	17	(31)	(69)	58
Tax benefit (provision)	(8)	7	24	(23)
Comprehensive income	$ 12,881	$ 13,592	$ 28,472	$ 28,987