Credit Quality of Loans and Allowance for Loan Losses, Part II (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	$ 7,222,000	$ 7,313,000	$ 7,276,000	$ 8,813,000	$ 8,813,000
Provision for loan losses	300,000	650,000	1,550,000	3,150,000	3,925,000
Recoveries	86,000	48,000	247,000	256,000	310,000
Loans charged-off	(234,000)	(682,000)	(1,699,000)	(4,890,000)	(5,772,000)
Balance, end of period	7,374,000	7,329,000	7,374,000	7,329,000	7,276,000
Ending Balance: individually evaluated for impairment	660,000		660,000		682,000
Loans [Abstract]
Loans: ending balance	808,833,000		808,833,000		746,305,000
Ending balance: individually evaluated for impairment	8,442,000		8,442,000		6,942,000
Number of industry segment concentration above threshold limit			1
Threshold percentage of loan portfolio (in hundredths)			10.00%
Loans exposure in oil and gas industry	133,100,000		133,100,000
Exposure in the oil and gas industry specified as percentage of total loans (in hundredths)	16.50%		16.50%
Commercial, Financial and Agricultural [Member]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period			1,734,000	1,664,000	1,664,000
Provision for loan losses			574,000		1,027,000
Recoveries			169,000		152,000
Loans charged-off			(683,000)		(1,109,000)
Balance, end of period	1,794,000		1,794,000		1,734,000
Ending Balance: individually evaluated for impairment	461,000		461,000		240,000
Loans [Abstract]
Loans: ending balance	266,046,000		266,046,000		223,283,000
Ending balance: individually evaluated for impairment	2,302,000		2,302,000		2,341,000
Real Estate Construction [Member]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period			1,661,000	2,963,000	2,963,000
Provision for loan losses			378,000		1,128,000
Recoveries			9,000		14,000
Loans charged-off			0		(2,444,000)
Balance, end of period	2,048,000		2,048,000		1,661,000
Ending Balance: individually evaluated for impairment	40,000		40,000		2,000
Loans [Abstract]
Loans: ending balance	57,727,000		57,727,000		52,712,000
Ending balance: individually evaluated for impairment	926,000		926,000		901,000
Commercial Real Estate [Member]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period			2,215,000	2,565,000	2,565,000
Provision for loan losses			282,000		895,000
Recoveries			0		1,000
Loans charged-off			(495,000)		(1,246,000)
Balance, end of period	2,002,000		2,002,000		2,215,000
Ending Balance: individually evaluated for impairment	64,000		64,000		321,000
Loans [Abstract]
Loans: ending balance	293,579,000		293,579,000		280,798,000
Ending balance: individually evaluated for impairment	3,144,000		3,144,000		2,271,000
Percentage of CRE loans secured by owner-occupied commercial properties (in hundredths)	61.00%		61.00%
Loans on nonaccrual status	4,100,000		4,100,000
Nonaccrual status of loans specified as percentage of total loans (in hundredths)	1.20%		1.20%
Residential Real Estate [Member]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period			936,000	862,000	862,000
Provision for loan losses			114,000		353,000
Recoveries			3,000		4,000
Loans charged-off			(126,000)		(283,000)
Balance, end of period	927,000		927,000		936,000
Ending Balance: individually evaluated for impairment	0		0		21,000
Loans [Abstract]
Loans: ending balance	110,735,000		110,735,000		113,582,000
Ending balance: individually evaluated for impairment	1,771,000		1,771,000		1,142,000
Consumer [Member]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period			710,000	730,000	730,000
Provision for loan losses			197,000		513,000
Recoveries			66,000		138,000
Loans charged-off			(395,000)		(671,000)
Balance, end of period	578,000		578,000		710,000
Ending Balance: individually evaluated for impairment	95,000		95,000		98,000
Loans [Abstract]
Loans: ending balance	73,334,000		73,334,000		69,980,000
Ending balance: individually evaluated for impairment	299,000		299,000		287,000
Finance Leases Commercial [Member]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period			19,000	29,000	29,000
Provision for loan losses			4,000		8,000
Recoveries			0		1,000
Loans charged-off			0		(19,000)
Balance, end of period	23,000		23,000		19,000
Ending Balance: individually evaluated for impairment	0		0		0
Loans [Abstract]
Loans: ending balance	5,041,000		5,041,000		4,276,000
Ending balance: individually evaluated for impairment	0		0		0
Other [Member]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period			1,000	0	0
Provision for loan losses			1,000		1,000
Recoveries			0		0
Loans charged-off			0		0
Balance, end of period	2,000		2,000		1,000
Ending Balance: individually evaluated for impairment	0		0		0
Loans [Abstract]
Loans: ending balance	2,371,000		2,371,000		1,674,000
Ending balance: individually evaluated for impairment	$ 0		$ 0		$ 0