Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Before Tax Amount
Other comprehensive loss, net	$ (2,807)	$ 270	$ (12,087)	$ 426
Tax Benefit (Expense)
Other comprehensive loss, net	794	(98)	2,988	(238)
Net of Tax Amount
Other comprehensive (loss) income	(2,013)	172	(9,099)	188
Net unrealized gains (losses) on available for sale securities
Before Tax Amount
Net unrealized holding (losses) gains arising during period	(2,816)	267	(12,521)	3,112
Reclassification adjustment for net gains arising during the period	0	0	0	(2,524)
Other comprehensive loss, net	(2,816)	267	(12,521)	588
Tax Benefit (Expense)
Net unrealized holding (losses) gains arising during period	797	(97)	3,080	(1,179)
Reclassification adjustment for net gains arising during the period	0	0	0	884
Other comprehensive loss, net	797	(97)	3,080	(295)
Net of Tax Amount
Net unrealized holding (losses) gains arising during period	(2,019)	170	(9,441)	1,933
Reclassification adjustment for net gains arising during the period	0	0	0	(1,640)
Other comprehensive (loss) income	(2,019)	170	(9,441)	293
Unrealized gains on derivatives
Before Tax Amount
Other comprehensive loss, net	9	3	434	(162)
Tax Benefit (Expense)
Other comprehensive loss, net	(3)	(1)	(92)	57
Net of Tax Amount
Other comprehensive (loss) income	$ 6	$ 2	$ 342	$ (105)