Loans - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012 Branch	Jun. 30, 2012	Sep. 30, 2012 Branch	Mar. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount of marketed loans with bulk sales				$ 33,400,000
Charges paid for the execution of loan held for sale	108,000	11,700,000
Transferred to loans held for sale			7,500,000
Number of branches to be sold	2		2
Total of net unearned income, net deferred fees and costs and discounts and premiums	368,000		368,000		21,000
Lendable Collateral	79,900,000		79,900,000		66,700,000
Repayment period of term loan borrowed for company's total asset			3 years
Additional interest income	212,000		1,100,000
Interest income recognized on impaired loans	0		0
Average balance of total impaired loans	49,900,000		66,900,000
Federal Home Loan Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans were pledged to collateralize FHLB	201,200,000		201,200,000		251,400,000
Pledge [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loan borrowed for company's total asset			15.00%
Federal Reserve System Services [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans were pledged to collateralize FHLB	$ 2,900,000		$ 2,900,000		$ 5,400,000