Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income, Net of Tax (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (973)	$ 6,053	$ (4,851)	$ 7,716
Year-to-date change	5,659	(12,610)	9,537	(14,273)
Ending balance	4,686	(6,557)	4,686	(6,557)
Unrealized gains on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	1,127	15,039	(2,799)	16,961
Year-to-date change	6,274	(12,812)	10,200	(14,734)
Ending balance	7,401	2,227	7,401	2,227
Post-retirement obligations
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(2,100)	(8,986)	(2,052)	(9,245)
Year-to-date change	(615)	202	(663)	461
Ending balance	$ (2,715)	$ (8,784)	$ (2,715)	$ (8,784)

- Definition

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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