| **Components of Accumulated Other Comprehensive Income (Detail) (USD $)In Thousands**                                                        | Sep. 30, 2011 | Dec. 31, 2010 |
|----------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Net unrealized gain on securities available for sale                                                                                         | $ 15,921      | $ 2,767       |
| Net unrealized loss on securities available for sale for which a portion of an other-than-temporary impairment has been recognized in income | (1,584)       | (1,001)       |
| Net unrealized loss on cash flow hedges                                                                                                      | (1,474)       | 288           |
| Defined benefit plans                                                                                                                        | (12,263)      | (12,211)      |
| Accumulated Other Comprehensive Income (Loss), Net of Tax, Total                                                                             | $ 600         | $ (10,157)    |

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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Accumulated appreciation or loss, net of tax, in value of the total of available-for-sale securities at the end of an accounting period.
+ References
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| - Definition
Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.
+ References
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| - Definition
The total of net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s) because they have yet to be recognized as components of net periodic benefit cost.
+ References
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| - 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.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.
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