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Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)
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3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Sep. 30, 2012
Point
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Sep. 30, 2011
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Sep. 30, 2012
Point
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Sep. 30, 2011
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Dec. 31, 2011
Point
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Sep. 30, 2012
Construction
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Sep. 30, 2011
Construction
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Sep. 30, 2012
Construction
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Sep. 30, 2011
Construction
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Dec. 31, 2011
Construction
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Sep. 30, 2012
Qualitative Factor Economic Condition
Point
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Dec. 31, 2011
Qualitative Factor Economic Condition
Point
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Sep. 30, 2012
Qualitative Factor Past Due Loans
Point
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Dec. 31, 2011
Qualitative Factor Past Due Loans
Point
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Sep. 30, 2012
Qualitative Factor Other Internal and External Factors
Point
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Dec. 31, 2011
Qualitative Factor Other Internal and External Factors
Point
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Sep. 30, 2012
Overall Qualitative Factor
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Dec. 31, 2011
Overall Qualitative Factor
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Sep. 30, 2012
Installment Loans
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Sep. 30, 2012
Bank Overdrafts
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Sep. 30, 2012
Partial charge-off loan
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Sep. 30, 2012
Minimum
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| Accounts, Notes, Loans and Financing Receivable [Line Items] | ||||||||||||||||||||||
| Days principal payments should be past due for recognition of income on a loan be discontinued and previously accrued interest is reversed | 90 days | 90 days | ||||||||||||||||||||
| Period of performance borrower need to demonstrate for a loan be restored to accrual status | 6 months | |||||||||||||||||||||
| Loan partial charge-off | $ 259,000 | $ 403,000 | $ 897,000 | $ 1,388,000 | $ 0 | $ 0 | $ 0 | $ 0 | $ 371,000 | |||||||||||||
| Loans charge off period | 90 days | 45 days | ||||||||||||||||||||
| Value of significant property | 200,000 | |||||||||||||||||||||
| Loan portfolio risk factor | 1.15 | 1.15 | 1.15 | 1.20 | 1.20 | 1.20 | 1.20 | 1.20 | 1.20 | |||||||||||||
| Increase in estimated allowance for loan losses | 306,000 | 317,000 | ||||||||||||||||||||
| Days loans are past due to be nonperforming loans | 90 days | |||||||||||||||||||||
| TDR loans, commitments to lend additional funds | $ 33,000 | $ 33,000 | $ 192,000 | |||||||||||||||||||