Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income		$ 16,169	$ 13,524
Other comprehensive income:
Unrealized gain (loss) on securities, net of tax	[1]	(5,848)	952
Comprehensive income		$ 10,321	$ 14,476

[1] Data presented for 2018 includes debt securities only compared to 2017 which includes both debt and equity securities.