Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Additional Information (Detail)

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Fair Value Measurements - Additional Information (Detail) (USD $)
9 Months Ended
Sep. 30, 2012
Jun. 30, 2012
Dec. 31, 2011
Sep. 30, 2011
Jun. 30, 2011
Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Loans Held for Sale $ 10,736,000 $ 5,138,000 $ 22,587,000 $ 37,202,000 $ 44,105,000 $ 36,620,000
Maturities of term federal funds 90 days          
Zero Coupon Municipal Bond [Member]
           
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Zero coupon tax credit municipal bond is recorded at estimated fair value 788,000          
Significant Observable Inputs With No Active Market With Identical Characteristics [Member] | Small Business Administration Loans Held For Sale [Member] | Nonrecurring Basis [Member]
           
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Loans Held for Sale 4,800,000   5,100,000      
Significant Unobservable Inputs [Member] | Non-Performing Loans Held For Sale [Member] | Nonrecurring Basis [Member]
           
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Loans Held for Sale $ 4,400,000   $ 15,000,000