Loans - Risk Category, Class of Loans and Recorded Investment (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	$ 1,262,912	$ 1,226,081
Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	62,766	60,736
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	499,070	486,828
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	582,576	569,331
Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	70,779	61,903
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	47,721	47,283
Pass [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,179,493	1,103,938
Pass [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	58,318	54,994
Pass [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	460,210	414,023
Pass [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	544,711	527,891
Pass [Member] | Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	70,156	61,123
Pass [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	46,098	45,907
Special Mention [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	10,751	16,577
Special Mention [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	593	1,717
Special Mention [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	8,702	12,137
Special Mention [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	622	1,686
Special Mention [Member] | Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	336	587
Special Mention [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	498	450
Substandard [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	18,435	22,665
Substandard [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Substandard [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	16,435	22,180
Substandard [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,290	36
Substandard [Member] | Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	263	193
Substandard [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	447	256
Doubtful [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Doubtful [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Doubtful [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Doubtful [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Doubtful [Member] | Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Doubtful [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Nonaccrual [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	28,724	40,955
Nonaccrual [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,454	1,342
Nonaccrual [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	6,339	17,234
Nonaccrual [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	20,696	22,099
Nonaccrual [Member] | Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Nonaccrual [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	235	280
Pass-Troubled Debt Restructures [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	7,038	8,616
Pass-Troubled Debt Restructures [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	1,838	2,103
Pass-Troubled Debt Restructures [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	5,167	6,513
Pass-Troubled Debt Restructures [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	33	0
Pass-Troubled Debt Restructures [Member] | Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Pass-Troubled Debt Restructures [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	0	0
Troubled Debt Restructures [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	18,471	33,330
Troubled Debt Restructures [Member] | Construction and Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	563	580
Troubled Debt Restructures [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	2,217	14,741
Troubled Debt Restructures [Member] | Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	15,224	17,619
Troubled Debt Restructures [Member] | Commercial and Financial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	24	0
Troubled Debt Restructures [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Financing Receivables	$ 443	$ 390