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           Commitments And Contingent Liabilities (Detail) (USD $) 
        In Thousands, unless otherwise specified  | 
        
           Dec. 31, 2012 
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           Dec. 31, 2011 
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           Dec. 31, 2010 
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|---|---|---|---|
| Commitments to extend credit | $ 860,421 | $ 697,939 | $ 538,719 | 
| Credit card arrangements | 25,699 | 19,686 | 17,601 | 
| Standby letters of credit and financial guarantees | 36,374 | 42,937 | 47,103 | 
| Total | $ 922,494 | $ 760,562 | $ 603,423 | 
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- Definition 
          The minimum amount the entity agreed to spend under commitment to extend credit. No definition available. 
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- Definition 
          The minimum amount the entity agreed to spend under commitment to credit card arrangement. No definition available. 
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- Definition 
          The minimum amount the entity commited to spend for standby letters of credit and financial guarantees. No definition available. 
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- Definition 
          Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions. No definition available. 
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