Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 34,014	$ 21,386	$ 17,890	$ 19,400	$ 18,806	$ 19,701	$ 16,956	$ 16,169	$ 92,690	$ 71,632	$ 46,231
Other comprehensive income:
Unrealized gain (loss) on securities, net of tax									13,043	(4,243)	4,104
Comprehensive income	$ 33,610	$ 23,862	$ 23,068	$ 25,193					$ 105,733	$ 67,389	$ 50,335