Consolidated statements of comprehensive income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 22,065	$ 11,239	$ 41,819	$ 20,992
Other comprehensive (loss) income, net of tax:
Net change in unrealized (loss) gain in available-for-sale securities, net of taxes of ($780), $1,053, ($3,319) and $1,408	(2,026)	1,631	(9,096)	2,180
Reclassification adjustment for (gain) loss on securities included in net income, net of taxes of $0, $11, ($2) and $12		(18)	7	(18)
Net change in unrealized gain in hedging activities, net of taxes of $69, $0, $518 and $0	196		1,469
Reclassification adjustment for (gain) loss on hedging activities, net of taxes of $6, $0, $2 and $0	(25)		7
Total other comprehensive (loss) income, net of tax	(1,855)	1,613	(7,613)	2,162
Comprehensive income	$ 20,210	$ 12,852	$ 34,206	$ 23,154