Credit Quality of Loans and Allowance for Loan Losses, Part II (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period	$ 7,078,000	$ 6,752,000	$ 7,276,000	$ 8,813,000	$ 8,813,000
Provision for loan losses	575,000	900,000	1,250,000	2,500,000	3,925,000
Recoveries	95,000	122,000	161,000	208,000	310,000
Loans charged-off	(526,000)	(461,000)	(1,465,000)	(4,208,000)	(5,772,000)
Balance, end of period	7,222,000	7,313,000	7,222,000	7,313,000	7,276,000
Ending Balance: individually evaluated for impairment	442,000		442,000		682,000
Loans [Abstract]
Loans: Ending Balance	751,455,000		751,455,000		746,305,000	[1]
Ending Balance: Individually Evaluated for Impairment	7,462,000		7,462,000		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	127,500,000		127,500,000
Exposure in the oil and gas industry specified as percentage of total loans (in hundredths)	17.00%		17.00%
Loans on nonaccrual status	7,370,000		7,370,000		6,229,000
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			384,000		1,027,000
Recoveries			103,000		152,000
Loans charged-off			(565,000)		(1,109,000)
Balance, end of period	1,656,000		1,656,000		1,734,000
Ending Balance: individually evaluated for impairment	235,000		235,000		240,000
Loans [Abstract]
Loans: Ending Balance	233,629,000		233,629,000		223,283,000
Ending Balance: Individually Evaluated for Impairment	1,890,000		1,890,000		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			357,000		1,128,000
Recoveries			9,000		14,000
Loans charged-off			0		(2,444,000)
Balance, end of period	2,027,000		2,027,000		1,661,000
Ending Balance: individually evaluated for impairment	33,000		33,000		2,000
Loans [Abstract]
Loans: Ending Balance	55,111,000		55,111,000		52,712,000
Ending Balance: Individually Evaluated for Impairment	576,000		576,000		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			246,000		895,000
Recoveries			0		1,000
Loans charged-off			(495,000)		(1,246,000)
Balance, end of period	1,966,000		1,966,000		2,215,000
Ending Balance: individually evaluated for impairment	60,000		60,000		321,000
Loans [Abstract]
Loans: Ending Balance	271,141,000		271,141,000		280,798,000
Ending Balance: Individually Evaluated for Impairment	2,974,000		2,974,000		2,271,000
Percentage of CRE loans secured by owner-occupied commercial properties (in hundredths)	63.00%		63.00%
Nonaccrual status of loans specified as percentage of total loans (in hundredths)	1.10%		1.10%
Commercial Real Estate [Member] | Secured Loans Receivable [Member]
Loans [Abstract]
Loans: Ending Balance	255,800,000		255,800,000
Loans on nonaccrual status	3,600,000		3,600,000
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			103,000		353,000
Recoveries			2,000		4,000
Loans charged-off			(84,000)		(283,000)
Balance, end of period	957,000		957,000		936,000
Ending Balance: individually evaluated for impairment	15,000		15,000		21,000
Loans [Abstract]
Loans: Ending Balance	112,343,000		112,343,000		113,582,000
Ending Balance: Individually Evaluated for Impairment	1,717,000		1,717,000		1,142,000
Consumer Loan [Member]
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of period			710,000	730,000	730,000
Provision for loan losses			156,000		513,000
Recoveries			47,000		138,000
Loans charged-off			(321,000)		(671,000)
Balance, end of period	592,000		592,000		710,000
Ending Balance: individually evaluated for impairment	99,000		99,000		98,000
Loans [Abstract]
Loans: Ending Balance	72,859,000		72,859,000		69,980,000
Ending Balance: Individually Evaluated for Impairment	305,000		305,000		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			3,000		8,000
Recoveries			0		1,000
Loans charged-off			0		(19,000)
Balance, end of period	22,000		22,000		19,000
Ending Balance: individually evaluated for impairment	0		0		0
Loans [Abstract]
Loans: Ending Balance	3,974,000		3,974,000		4,276,000
Ending Balance: Individually Evaluated for Impairment	0		0		0
Other Loan Receivable [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	2,398,000		2,398,000		1,674,000
Ending Balance: Individually Evaluated for Impairment	0		0		0
Commercial Real Estate (Including Construction) Loans [Member] | Secured Loans Receivable [Member]
Loans [Abstract]
Loans: Ending Balance	$ 314,500,000		$ 314,500,000

[1] Derived from audited financial statements.