Fair Value - Assets and Liabilities Measured At Fair Value On a Non-Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Impaired loans:
Total impaired loans	$ 14,404	$ 15,393
Foreclosed assets
Foreclosed assets, net	1,572	2,370
Financial instruments measured at fair value on a non-recurring basis [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan servicing rights	5	9
Impaired loans:
Total impaired loans
Foreclosed assets
Foreclosed assets, net
Financial instruments measured at fair value on a non-recurring basis [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loan servicing rights
Impaired loans:
Total impaired loans	7,349	6,809
Foreclosed assets
Foreclosed assets, net	1,414	1,209
Financial instruments measured at fair value on a non-recurring basis [Member] | Commercial Real Estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 2) [Member]
Impaired loans:
Total impaired loans
Financial instruments measured at fair value on a non-recurring basis [Member] | Commercial Real Estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 2) [Member] | Non-owner occupied [Member]
Impaired loans:
Total impaired loans
Foreclosed assets
Foreclosed assets, net
Financial instruments measured at fair value on a non-recurring basis [Member] | Commercial Real Estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 2) [Member] | Owner occupied [Member]
Impaired loans:
Total impaired loans
Financial instruments measured at fair value on a non-recurring basis [Member] | Commercial Real Estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 2) [Member] | Land [Member]
Impaired loans:
Total impaired loans
Foreclosed assets
Foreclosed assets, net
Financial instruments measured at fair value on a non-recurring basis [Member] | Commercial Real Estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 3) [Member]
Impaired loans:
Total impaired loans	121	108
Financial instruments measured at fair value on a non-recurring basis [Member] | Commercial Real Estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 3) [Member] | Non-owner occupied [Member]
Impaired loans:
Total impaired loans	1,839	2,887
Foreclosed assets
Foreclosed assets, net	967
Financial instruments measured at fair value on a non-recurring basis [Member] | Commercial Real Estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 3) [Member] | Owner occupied [Member]
Impaired loans:
Total impaired loans	1,293	516
Financial instruments measured at fair value on a non-recurring basis [Member] | Commercial Real Estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 3) [Member] | Land [Member]
Impaired loans:
Total impaired loans	159	233
Foreclosed assets
Foreclosed assets, net	447	1,209
Financial instruments measured at fair value on a non-recurring basis [Member] | Real estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 2) [Member] | Multi-family residential [Member]
Impaired loans:
Total impaired loans
Financial instruments measured at fair value on a non-recurring basis [Member] | Real estate [Member] | Fair Value Measurements Using Significant Other Observable Inputs (Level 3) [Member] | Multi-family residential [Member]
Impaired loans:
Total impaired loans	$ 3,937	$ 3,065