Accumulated Other Comprehensive Income - Balances in Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	$ (1,173)	$ (381)
Change in net unrealized holding gains (losses) on securities, before reclassification, net of tax expense (benefit)	820	(1,068)
Reclassification for previously unrealized net (gains) losses recognized in income, net of tax benefit	16	(3)
Net gain (loss) on pension and postretirement plans, net of tax expense	(584)	277
Net postretirement plan transition cost, net of tax expense		2
Ending Balance	(921)	(1,173)
Holding gains (losses) on securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	(791)	280
Change in net unrealized holding gains (losses) on securities, before reclassification, net of tax expense (benefit)	820	(1,068)
Reclassification for previously unrealized net (gains) losses recognized in income, net of tax benefit	16	(3)
Ending Balance	45	(791)
Pension and Post employment costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	(382)	(661)
Net gain (loss) on pension and postretirement plans, net of tax expense	(584)	277
Net postretirement plan transition cost, net of tax expense		2
Ending Balance	$ (966)	$ (382)

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income (loss) for actuarial gain (loss) related to pension and other postretirement benefit plans.

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- Definition

Amount after tax of reclassification adjustment from accumulated other comprehensive income (loss) for net transition asset (obligation) related to pension and other postretirement benefit plans.

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