Accumulated Other Comprehensive Loss - Schedule of Changes in Component of Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Securities Available for Sale [Member]	Sep. 30, 2013 Securities Available for Sale [Member]	Sep. 30, 2014 Adjustments Related to Pension Benefits [Member]	Dec. 31, 2013 Adjustments Related to Pension Benefits [Member]	Sep. 30, 2013 Adjustments Related to Pension Benefits [Member]	Dec. 31, 2012 Adjustments Related to Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, Beginning Balance			$ (1,304)	$ (859)	$ (1,129)	$ 1,770	$ (175)	$ (175)	$ (2,629)	$ (2,629)
Unrealized holding gains (losses), net of tax	101	(501)	1,016	(3,194)	1,016	(3,194)
Reclassification adjustment, net of tax	60		45		45
Change during period	161	(501)	1,061	(3,194)	1,061	(3,194)
Accumulated other comprehensive loss, Ending Balance	$ (243)	$ (4,053)	$ (243)	$ (4,053)	$ (68)	$ (1,424)	$ (175)	$ (175)	$ (2,629)	$ (2,629)

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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 and reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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