Comprehensive Income (Loss) - Components of Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrealized gains (losses) on available for sale securities
Unrealized holding gains (losses) arising during period, Before Tax Amount	$ (1,406)	$ (1,816)	$ (375)
Reclassification adjustment for net gains realized in net income, Before Tax Amount	(2,524)	(370)	(241)
Net unrealized gains (losses) on available for sale securities, Before Tax Amount	(3,930)	(2,186)	(616)
Unrealized gain on derivatives, Before Tax Amount	57	1,033
Change in pension liabilities, Before Tax Amount	(27)	70	3
Other comprehensive income (loss), net, Before Tax Amount	(3,900)	(1,083)	(613)
Unrealized holding gains (losses) arising during period, Tax benefit (Expense)	503	778	155
Reclassification adjustment for net gains realized in net income, (Expense)	884	137	84
Net unrealized gains (losses) on available for sale securities, Tax Benefit (Expense)	1,387	915	239
Unrealized gain on derivatives, Tax Benefit (Expense)	(20)	(361)
Change in pension liabilities, Tax Benefit (Expense)	11	(28)	1
Other comprehensive income (loss), net, Tax Benefit (Expense)	1,378	526	240
Unrealized holding gains (losses) arising during period, Net of Tax Amount	(903)	(1,038)	(220)
Reclassification adjustment for net gains realized in net income, Net of Tax Amount	(1,640)	(233)	(157)
Net unrealized gains (losses) on available for sale securities, Net of Tax Amount	(2,543)	(1,271)	(377)
Unrealized gain on derivatives, Net of Tax Amount	37	672	0
Change in pension liabilities, Net of Tax Amount	(16)	42	4
Other comprehensive loss	$ (2,522)	$ (557)	$ (373)