Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Before Tax Amount
Other comprehensive loss, net	$ (2,136)	$ 1,490	$ (9,280)	$ 156
Tax Benefit (Expense)
Other comprehensive loss, net	499	(573)	2,194	(140)
Net of Tax Amount
Other comprehensive (loss) income	(1,637)	917	(7,086)	16
Net unrealized gains (losses) on available for sale securities
Before Tax Amount
Net unrealized holding (losses) gains arising during period	(2,203)	1,661	(9,705)	2,845
Reclassification adjustment for net gains arising during the period	0	15	0	(2,524)
Other comprehensive loss, net	(2,203)	1,676	(9,705)	321
Tax Benefit (Expense)
Net unrealized holding (losses) gains arising during period	513	(632)	2,283	(1,082)
Reclassification adjustment for net gains arising during the period	0	(6)	0	884
Other comprehensive loss, net	513	(638)	2,283	(198)
Net of Tax Amount
Net unrealized holding (losses) gains arising during period	(1,690)	1,029	(7,422)	1,763
Reclassification adjustment for net gains arising during the period	0	9	0	(1,640)
Other comprehensive (loss) income	(1,690)	1,038	(7,422)	123
Unrealized gains (losses) on derivatives
Before Tax Amount
Other comprehensive loss, net	67	(186)	425	(165)
Tax Benefit (Expense)
Other comprehensive loss, net	(14)	65	(89)	58
Net of Tax Amount
Other comprehensive (loss) income	$ 53	$ (121)	$ 336	$ (107)