Consolidated statements of comprehensive income (Unaudited) (Parenthetical) - 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 change in unrealized (loss) gain in available-for-sale, tax	$ (780)	$ 1,053	$ (3,319)	$ 1,408
Reclassification adjustment for (gain) loss on securities, tax	0	11	(2)	12
Net change in unrealized gain in hedging activities, tax	69	0	518	0
Reclassification adjustment for (gain) loss on hedging activities, tax	$ 6	$ 0	$ 2	$ 0