Consolidated statements of comprehensive income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 21,377	$ 8,388	$ 63,196	$ 29,380
Other comprehensive (loss) income, net of tax:
Net change in unrealized (loss) gain in available-for-sale securities, net of taxes of ($1,348), $170, ($4,667) and $1,577	(3,749)	265	(12,845)	2,446
Reclassification adjustment for (gain) loss on securities included in net income, net of taxes of $0, $100, ($2) and $111		(154)	7	(173)
Net change in unrealized gain in hedging activities, net of taxes of $60, $52, $577 and $52	169	81	1,638	81
Reclassification adjustment for (gain) loss on hedging activities, net of taxes of $23, $59, $22 and $59	(69)	91	(62)	91
Total other comprehensive (loss) income, net of tax	(3,649)	283	(11,262)	2,445
Comprehensive income	$ 17,728	$ 8,671	$ 51,934	$ 31,285