Loans and Allowance for Loan Losses - Loans by Credit Quality Indicators (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	$ 1,075,487,000	$ 1,041,189,000	$ 1,035,288,000
Commercial and Industrial [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	286,887,000	285,322,000
Commercial and Industrial [Member] \| Grades 1-4 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	208,750,000	180,314,000
Commercial and Industrial [Member] \| Grades 5-7 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	75,339,000	101,832,000
Commercial and Industrial [Member] \| Grades 8-9 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	2,798,000	3,176,000
Commercial Vacant Land, Land Development, and Residential Construction [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	40,741,000	48,099,000
Commercial Vacant Land, Land Development, and Residential Construction [Member] \| Grades 1-4 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	8,089,000	6,526,000
Commercial Vacant Land, Land Development, and Residential Construction [Member] \| Grades 5-7 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	27,022,000	37,697,000
Commercial Vacant Land, Land Development, and Residential Construction [Member] \| Grades 8-9 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	5,630,000	3,876,000
Commercial Real Estate - Owner Occupied [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	258,656,000	259,277,000
Commercial Real Estate - Owner Occupied [Member] \| Grades 1-4 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	157,824,000	150,467,000
Commercial Real Estate - Owner Occupied [Member] \| Grades 5-7 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	97,819,000	102,988,000
Commercial Real Estate - Owner Occupied [Member] \| Grades 8-9 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	3,013,000	5,822,000
Commercial Real Estate - Non-Owner Occupied [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	368,301,000	324,886,000
Commercial Real Estate - Non-Owner Occupied [Member] \| Grades 1-4 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	205,586,000	154,127,000
Commercial Real Estate - Non-Owner Occupied [Member] \| Grades 5-7 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	130,040,000	128,041,000
Commercial Real Estate - Non-Owner Occupied [Member] \| Grades 8-9 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	32,675,000	42,718,000
Commercial Real Estate - Multi-Family and Residential Rental [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	53,178,000	50,922,000
Commercial Real Estate - Multi-Family and Residential Rental [Member] \| Grades 1-4 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	31,755,000	24,015,000
Commercial Real Estate - Multi-Family and Residential Rental [Member] \| Grades 5-7 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	18,230,000	22,082,000
Commercial Real Estate - Multi-Family and Residential Rental [Member] \| Grades 8-9 [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	3,193,000	4,825,000
Retail Home Equity and Other [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	36,575,000	38,917,000
Retail 1-4 Family Mortgages [Member]
Financing Receivable Credit Quality Indicator [Line Items]
Total loans	$ 31,149,000	$ 33,766,000