Loans and Other Repossessed Assets Acquired (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Decrease In Accretable Yield	$ 1,100,000
Troubled Debt Restructuring, Debtor, Current Period, Gain (Loss) on Restructuring, Net of Tax	3,800,000	3,500,000
Maximum Amount of Criticized And Classified Commercial Loans	500,000
Net Impairment of Acquired Loans	4,600,000
Loans In Foreclosure [Member]
Homogenous Loans In Foreclosure	7,100,000
Specific Allowance Related To Homogenous Loans	181,000
Residential Land [Member]
Troubled Debt Restructuring, Debtor, Current Period, Gain (Loss) on Restructuring, Net of Tax	257,000
Commercial Business [Member]
Troubled Debt Restructuring, Debtor, Current Period, Gain (Loss) on Restructuring, Net of Tax	683,000	687,000
Commercial Real Estate [Member]
Troubled Debt Restructuring, Debtor, Current Period, Gain (Loss) on Restructuring, Net of Tax	1,700,000	1,700,000
Commercial Land [Member]
Troubled Debt Restructuring, Debtor, Current Period, Gain (Loss) on Restructuring, Net of Tax	499,000	499,000
Home Equity Loans [Member]
Troubled Debt Restructuring, Debtor, Current Period, Gain (Loss) on Restructuring, Net of Tax	500,000	502,000
Manufactured Housing [Member]
Troubled Debt Restructuring, Debtor, Current Period, Gain (Loss) on Restructuring, Net of Tax	$ 134,000	$ 135,000