Loans Leases and Other Real Estate Owned - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held for Sale	$ 2,708,000	$ 2,708,000	$ 2,021,000
Loans and leases	1,184,142,000	1,184,142,000	1,277,090,000	1,307,586,000
Equipment Lease Paid down		3,273,000
Non-accrual loans	143,877,000	143,877,000	96,592,000
Allowance for loan and lease losses	33,756,000	33,756,000	7,315,000
Interest income actually recognized	1,034,000	1,155,000	903,000
Performing restructured loans	144,872,000	144,872,000	96,423,000
Financing Receivable Troubled Debt Restructurings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	3,738,000	3,738,000	5,296,000
Interest income that would have been recorded if non-accrual loans had been current in accordance with original terms		5,864,000
Interest income actually recognized		1,209
Financing Receivable Troubled Debt Restructurings | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Performing restructured loans	8,611,000	8,611,000	7,253,000
Non Accrual Loans | Financing Receivable Troubled Debt Restructurings
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	2,195	2,195	392,000
Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	276,779,000	276,779,000	291,874,000	292,381,000
Non-accrual loans	7,644,000	7,644,000	2,372,000
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	619,417,000	619,417,000	675,549,000	695,800,000
Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	242,212,000	242,212,000	258,689,000	265,805,000
Allowance for loan and lease losses	3,063,000	3,063,000	2,270,000
Interest income actually recognized	48,000	62,000	95,000
Performing restructured loans	14,499,000	14,499,000	15,354,000
Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	45,734,000	45,734,000	50,978,000	53,600,000
Non-accrual loans	659,000	659,000	651,000
Allowance for loan and lease losses	60,000	60,000	60,000
Interest income actually recognized	0	0	0
Performing restructured loans	119,000	119,000	119,000
Consumer Portfolio Segment | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	45,075,000	45,075,000	50,327,000
Commercial and Industrial | Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loan portfolio		12,017,000
Percentage of Increase in loan portfolio	4.30%	4.30%
Loans and leases	266,015,000	266,015,000	278,032,000
Agricultural | Commercial, financial and agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loan portfolio		195,000
Percentage of Increase in loan portfolio	19.00%	19.00%
Loans and leases	1,223,000	1,223,000	1,028,000
Agricultural | Commercial, financial and agricultural | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage Loan Portfolio	1.00%	1.00%
Commercial construction, land and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	228,220,000	228,220,000	250,859,000
Commercial construction, land and land development | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loan portfolio		22,639,000
Percentage of Increase in loan portfolio	9.00%	9.00%
Loans and leases	228,220,000	228,220,000	250,859,000
Non-accrual loans	102,176,000	102,176,000	59,382,000
Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	391,197,000	391,197,000	424,690,000
Other commercial real estate | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loan portfolio		33,493,000
Percentage of Increase in loan portfolio	7.90%	7.90%
Loans and leases	391,197,000	391,197,000	424,690,000
Non-accrual loans	17,230,000	17,230,000	15,275,000
Residential Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	13,624,000	13,624,000	13,509,000
Residential Construction | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loan portfolio		115,000,000
Percentage of Increase in loan portfolio	0.90%	0.90%
Loans and leases	13,624,000	13,624,000	13,509,000
Non-accrual loans	484,000	484,000	497,000
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	228,588,000	228,588,000	245,180,000
Residential Mortgage | Residential real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loan portfolio		16,592,000
Percentage of Increase in loan portfolio	6.80%	6.80%
Loans and leases	228,588,000	228,588,000	245,180,000
Non-accrual loans	15,684,000	15,684,000	18,415,000
Residential Mortgage | Residential real estate | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential mortgage loans terms to maturity		15 years
Consumer | Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loan portfolio		3,562,000
Percentage of Increase in loan portfolio	8.00%	8.00%
Loans and leases	41,151,000	41,151,000	44,713,000
Consumer Other Financing Receivable | Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in loan portfolio		1,682,000
Percentage of Increase in loan portfolio	26.80%	26.80%
Loans and leases	$ 4,583,000	$ 4,583,000	$ 6,265,000