Quarterly report pursuant to Section 13 or 15(d)

Summary of Investment Securities Held to Maturity (Detail)

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Summary of Investment Securities Held to Maturity (Detail) (USD $)
Sep. 30, 2012
Dec. 31, 2011
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost $ 50,600 $ 59,742,000
Gross Unrealized Gain   219,000
Gross Unrealized Loss   598,000
Estimated Fair Value   59,363,000
Municipal Bonds-Tax Exempt [Member]
    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost   9,815,000
Gross Unrealized Gain   98,000
Gross Unrealized Loss   46,000
Estimated Fair Value   9,867,000
Municipal Bonds - Taxable [Member]
    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost   38,797,000
Gross Unrealized Gain   117,000
Gross Unrealized Loss   522,000
Estimated Fair Value   38,392,000
Mortgage-Backed Securities [Member]
    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost   3,137,000 [1]
Gross Unrealized Gain   2,000 [1]
Gross Unrealized Loss   11,000 [1]
Estimated Fair Value   3,128,000 [1]
U.S. Government Agencies Securities [Member]
    
Schedule of Held-to-maturity Securities [Line Items]    
Amortized Cost   7,993,000
Gross Unrealized Gain   2,000
Gross Unrealized Loss   19,000
Estimated Fair Value   $ 7,976,000
[1] Collateralized by residential mortgages and guaranteed by U.S. government sponsored entities