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	$ 19,754	$ 9,753
Other comprehensive (loss) income, net of tax:
Net change in unrealized (loss) gain in available-for-sale securities, net of taxes of $2,539 and $354	(7,070)	550
Reclassification adjustment for loss (gain) on securities included in net income, net of taxes of $2 and $0	7	(1)
Net change in unrealized gain in hedging activities, net of taxes of $449 and $0	1,273
Reclassification adjustment for loss on hedging activities, net of taxes of $8 and $0	32
Total other comprensive (loss) income, net of tax	(5,758)	549
Comprehensive income	$ 13,996	$ 10,302