Fair Values of off-Balance Sheet Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Assets:
Cash and cash equivalents	$ 36,712	$ 23,181	$ 134,288	$ 33,976
Securities available-for-sale	233,621	212,529
Securities held-to-maturity	8,478	6,002
Other securities	2,638	2,645
Loans, net	388,560	383,417
Liabilities:
Noninterest-bearing deposits	110,051	107,129
Interest-bearing deposits	511,882	466,265
Subordinated debentures	10,310	10,310
FHLB and other borrowings	16,781	27,032
Estimated Fair Value
Assets:
Cash and cash equivalents	36,712	23,181
Securities available-for-sale	233,621	212,529
Securities held-to-maturity	9,996	6,002
Other securities	2,638	2,645
Loans, net	400,908	396,905
Liabilities:
Noninterest-bearing deposits	110,051	107,129
Interest-bearing deposits	512,258	467,198
Subordinated debentures	10,310	10,310
FHLB and other borrowings	$ 16,781	$ 27,032

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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