Accumulated Other Comprehensive Income - Balances in Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized holding gains (losses) arising during the period, tax expense	$ 173	$ 103
Reclassification for previously unrealized net losses (gains) recognized in income,tax expense (benefit)	2	(1)
Holding gains (losses) on securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized holding gains (losses) arising during the period, tax expense	173	103
Reclassification for previously unrealized net losses (gains) recognized in income,tax expense (benefit)	$ 2	$ (1)