Specific Allocation for Impaired Loans By Class (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance with no related allowance	$ 103
Unpaid Principal Balance	7,976	6,459
Recorded Investment with no related allowance	103
Recorded Investment	7,834	6,304
Unpaid Principal Balance with an allowance recorded	7,873	6,459
Recorded Investment with an allowance recorded	7,731	6,304
Related Allowance	1,460	846
Commercial and Industrial
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance with an allowance recorded	1,133	1,170
Recorded Investment with an allowance recorded	1,133	1,170
Related Allowance	551	301
Construction & Development
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance with an allowance recorded	551	1,392
Recorded Investment with an allowance recorded	409	1,237
Related Allowance	61	355
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance with an allowance recorded	5,030	3,755
Recorded Investment with an allowance recorded	5,030	3,755
Related Allowance	356	48
Residential Real Estate
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance with no related allowance	103
Recorded Investment with no related allowance	103
Unpaid Principal Balance with an allowance recorded	865	142
Recorded Investment with an allowance recorded	865	142
Related Allowance	218	142
Consumer Loan
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance with an allowance recorded	294
Recorded Investment with an allowance recorded	294
Related Allowance	$ 274