Accumulated Other Comprehensive Income - Balances in Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized holding gains arising during the period, tax expense	$ (192)	$ 112	$ (90)	$ 280
Reclassification for previously unrealized net losses recognized in income, tax benefit	2	(6)	1	(6)
Holding gains (losses) on securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized holding gains arising during the period, tax expense	(192)	112	(90)	280
Reclassification for previously unrealized net losses recognized in income, tax benefit	$ 2	$ (6)	$ 1	$ (6)