Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 57,304	$ 40,440	$ 19,224
Change in net unrealized loss on investments, net of tax	(261)	(462)	(57)
Reclassification adjustment for net change realized and included in net income, net of tax	289	44	112
Total change in unrealized gain (loss) on marketable securities, net of tax	28	(418)	55
Change in net unrealized loss, net of tax	(40)	0	0
Other comprehensive (loss) income, net of tax	(12)	(418)	55
Comprehensive income	$ 57,292	$ 40,022	$ 19,279