Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 6,064	$ 7,460	$ 9,094	$ 8,749
Other comprehensive income (loss), net of taxes:
Foreign currency translation	2,514	(1,429)	3,304	52
Net change in market value of investments	7	3	24	120
Other comprehensive income (loss)	2,521	(1,426)	3,328	172
Comprehensive income	$ 8,585	$ 6,034	$ 12,422	$ 8,921