| 
           Foreclosed Properties (Detail) (USD $) 
        In Thousands, unless otherwise specified  | 
        12 Months Ended | ||
|---|---|---|---|
| 
           Dec. 31, 2012 
         | 
        
           Dec. 31, 2011 
         | 
        
           Dec. 31, 2010 
         | 
      |
| Balance at beginning of year | $ 12,275 | $ 6,966 | $ 12,525 | 
| Transfers from loans and capitalized expenses | 2,695 | 9,029 | 5,447 | 
| Foreclosed properties sold | (2,967) | (3,334) | (7,995) | 
| Writedowns and partial liquidations | (2,318) | (386) | (3,011) | 
| Balance at end of year | $ 9,685 | $ 12,275 | $ 6,966 | 
| X | ||||||||||
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- Definition 
          The value of properties held for sale acquired from customer under loan arrangement. No definition available. 
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| X | ||||||||||
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- Definition 
          The Value of foreclosed properties sold during the period. No definition available. 
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| X | ||||||||||
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- Definition 
          The Value of foreclosed properties transferred from loans and capitalised during the period. No definition available. 
  | 
        
| X | ||||||||||
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- Definition 
          The value of write down and partial liquidations during the period. No definition available. 
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