Fair Value - Additional Information (Detail) (USD $) | 6 Months Ended | ||
|---|---|---|---|
Jun. 30, 2012 | Dec. 31, 2011 | Jun. 30, 2011 | |
| Fair Value Measurements [Line Items] | |||
| Impaired loans gross carrying amount | $ 31,686,000 | $ 29,124,000 | |
| Impaired loans, valuation allowance | 7,516,000 | 7,443,000 | 7,666,000 |
| Increase in provision for loan losses | $ 73,000 | $ 1,699,000 | |
Minimum | |||
| Fair Value Measurements [Line Items] | |||
| Loans classified as Level 3, other unobservable inputs additional discounts | 5.00% | ||
Maximum | |||
| Fair Value Measurements [Line Items] | |||
| Loans classified as Level 3, other unobservable inputs additional discounts | 10.00% | ||