Accumulated Other Comprehensive Income - Balances in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	$ (921)	$ (1,173)
Change in net unrealized holding gains on securities, before reclassification, net of tax expense	90	820
Reclassification for previously unrealized net losses (gains) recognized in income, net of tax expense (benefit)	(28)	16
Net gain (loss) on pension and postretirement plans, net of tax expense (benefit)	83	(584)
Ending Balance	(776)	(921)
Holding gains (losses) on securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	45	(791)
Change in net unrealized holding gains on securities, before reclassification, net of tax expense	90	820
Reclassification for previously unrealized net losses (gains) recognized in income, net of tax expense (benefit)	(28)	16
Ending Balance	107	45
Pension and Post employment costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	(966)	(382)
Net gain (loss) on pension and postretirement plans, net of tax expense (benefit)	83	(584)
Ending Balance	$ (883)	$ (966)