Allowance for Loan Losses - Aging of Past Due Loans (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Accruing 30-89 Days Past Due	$ 6,627	$ 6,690
Non Accrual	3,745	4,471
Accrual Greater Than 90 Days
Total Past Due	10,372	11,161
Current Loans	1,220,676	1,100,627
Total loans, net	1,231,048	1,111,788	1,064,923
Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Non Accrual	1,500	1,500
Accrual Greater Than 90 Days
Total Past Due	1,500	1,500
Current Loans	31,250	37,118
Total loans, net	32,750	38,618	38,318
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Accruing 30-89 Days Past Due	392	1,256
Non Accrual	501	676
Accrual Greater Than 90 Days
Total Past Due	893	1,932
Current Loans	86,575	86,543
Total loans, net	87,468	88,475	78,567
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Accruing 30-89 Days Past Due	3,174	3,450
Non Accrual	448	674
Accrual Greater Than 90 Days
Total Past Due	3,622	4,124
Current Loans	662,544	572,341
Total loans, net	666,166	576,465	562,252
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Accruing 30-89 Days Past Due	1,907	864
Non Accrual	1,270	1,597
Accrual Greater Than 90 Days
Total Past Due	3,177	2,461
Current Loans	306,114	279,396
Total loans, net	309,291	281,857	262,426
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Accruing 30-89 Days Past Due	7	32
Non Accrual	2	24
Accrual Greater Than 90 Days
Total Past Due	9	56
Current Loans	8,719	7,394
Total loans, net	8,728	7,450	6,661
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Accruing 30-89 Days Past Due	1,147	1,088
Non Accrual	24
Accrual Greater Than 90 Days
Total Past Due	1,171	1,088
Current Loans	125,474	117,835
Total loans, net	$ 126,645	$ 118,923	$ 116,699