CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 35,469	$ 26,143	$ 19,311
Short term investments:
Unrealized loss, net of income tax benefit of $11, $8 and $2, respectively	(21)	(16)	(4)
Comprehensive income	$ 35,448	$ 26,127	$ 19,307