Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 48,292	$ 38,062	$ 25,170
Unrealized gains (losses) on investments, net of tax	7,887	(3,638)	(1,427)
Comprehensive income	$ 56,179	$ 34,424	$ 23,743