Acquisitions and FDIC Indemnification Asset (Details Textual) (USD $)	0 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended			9 Months Ended			12 Months Ended			9 Months Ended
	Jul. 02, 2009	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Jun. 30, 2013	Dec. 31, 2011	Sep. 30, 2013 Commercial And Single Family Residential Mortgage Loans [Member] Minimum [Member]	Sep. 30, 2013 Commercial And Single Family Residential Mortgage Loans [Member] Maximum [Member]	Sep. 30, 2013 First National Bank Of Danville [Member]	Dec. 31, 2009 First National Bank Of Danville [Member]	Jul. 02, 2009 First National Bank Of Danville [Member]	Jul. 02, 2009 First National Bank Of Danville [Member] ASC 310-30 Loans [Member]	Sep. 30, 2013 After Acquisition [Member] Commercial And Single Family Residential Mortgage Loans [Member] Minimum [Member]	Sep. 30, 2013 After Acquisition [Member] Commercial And Single Family Residential Mortgage Loans [Member] Maximum [Member]	Aug. 16, 2013 Bank Of Amercia [Member]
Business Acquisition [Line Items]
Assets acquired											$ 151,800,000
Loans											77,500,000				1,900,000
Investment securities											24,200,000
Cash and cash equivalents											31,000,000				177,700,000
Liabilities											146,300,000
Deposits											145,700,000				189,300,000
Customer related core deposit intangible asset											4,600,000				2,200,000
Cash received (disbursed) from purchase of business unit	14,600,000
Gain on acquisition										5,100,000
Losses on assets, threshold under loss-sharing agreement										29,000,000
Percentage of losses to be reimbursed by the FDIC, on losses up to the threshold amount										80.00%
Percentage of losses to be reimbursed by the FDIC, on losses exceeding the threshold amount										95.00%
Loss Sharing Provisions Period							5 years	10 years					8 years	10 years
Reimbursements from the FDIC		143,000	281,000	2,174,000					18,300,000
Outstanding balance for reimbursement of losses		1,171,000	1,171,000	2,632,000	1,515,000	2,384,000			1,200,000
Net changes in losses and expenses added									493,000
Percentage of loans, acquired and subject to the loss-sharing agreement with the FDIC, which were included in the estimate of future potential losses									80.00%
Contractually required payments receivable	58,400,000											31,600,000
Allowance for credit losses		623,000	623,000									18,400,000
Estimated fair value of the loans	60,700,000											16,700,000
Fixed Assets															5,900,000
Other liabilities															300,000
Goodwill		39,489,000	39,489,000	37,612,000											1,900,000
Goodwill expected tax deductible amount															$ 1,600,000