Accumulated Other Comprehensive Income - Reclassification of Unrealized (Losses) Gains and Impairments on Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gains on sale of securities available-for-securities	$ 180	$ 2	$ 290	$ 4
Tax expense	(326)	(50)	(669)	(202)
Net Unrealized Gains (Losses) on Securities | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gains on sale of securities available-for-securities	180	2	290	4
Tax expense	(62)		(99)	(1)
Impact on net income	$ 118	$ 2	$ 191	$ 3