CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 41,247	$ 19,422	$ 90,415	$ 57,373
Other comprehensive income:
Change in unrealized (loss) gain on available-for-sale investments, net of tax	(129)		145
Comprehensive income	$ 41,118	$ 19,422	$ 90,560	$ 57,373