Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Assets, carrying amount
Cash and cash equivalents	$ 34,396	$ 32,778	$ 26,572	$ 55,223
Loans held for sale, carrying amount	6,765	5,106
Loans net, carrying amount	955,876	969,545
FHLB stock, carrying amount	14,391	14,391
Interest receivable, carrying amount	3,635	3,846
Liabilities, carrying amount
Deposits, carrying amount	1,167,727	1,184,009
FHLB advances, carrying amount	81,525	74,675
Other borrowings, carrying amount	11,427	11,606
Interest payable, carrying amount	247	236
Assets, fair value
Cash and cash equivalents, fair value	34,396	32,778
Loans held for sale, fair value	6,883	5,235
Loans, fair value	978,047	993,539
FHLB stock, fair value	14,391	14,391
Interest receivable, fair value	3,635	3,846
Liabilities, fair value
Deposits, fair value	1,166,770	1,195,825
FHLB advances, fair value	82,289	75,688
Other borrowings, fair value	12,341	12,648
Interest payable, fair value	247	236
Fair Value, Inputs, Level 1
Assets, fair value
Cash and cash equivalents, fair value	34,396	32,778
Liabilities, fair value
Deposits, fair value	619,218	606,066
Fair Value, Inputs, Level 2
Assets, fair value
Loans held for sale, fair value	6,883	5,235
FHLB stock, fair value	14,391	14,391
Interest receivable, fair value	3,635	3,846
Liabilities, fair value
FHLB advances, fair value	82,289	75,688
Other borrowings, fair value	12,341	12,648
Interest payable, fair value	247	236
Fair Value, Inputs, Level 3
Assets, fair value
Loans, fair value	978,047	993,539
Liabilities, fair value
Deposits, fair value	$ 547,552	$ 589,759