Consolidated statements of comprehensive income (loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 8,388	$ 1,207	$ 29,380	$ 31,581
Other comprehensive income, net of tax:
Net change in unrealized gain (loss) in available-for-sale securities, net of taxes of $170, $38, $1,577 and $807	265	(1,524)	2,446	10,246
Reclassification adjustment for gain (loss) on sale of securities included in net income, net of tax expenses of $100, $57, $111 and $298	(154)	(359)	(173)	(4,109)
Net change in unrealized gain in hedging activities, net of taxes of $111, $0, $111, and $0	172		172
Comprehensive income (loss)	$ 8,671	$ (676)	$ 31,825	$ 37,718