Accumulated Other Comprehensive Income (Loss) - Reclassification of Unrealized Losses and Impairments on Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gains (losses) on sale of securities available-for-securities	$ 2	$ (8)	$ 4	$ (25)
Tax (expense) benefit	(50)	(171)	(202)	(375)
Holding gains (losses) on securities | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gains (losses) on sale of securities available-for-securities	2	(8)	4	(25)
Tax (expense) benefit		3	(1)	9
Impact on net income	$ 2	$ (5)	$ 3	$ (16)