Merger with MidCarolina (Details) (USD $)	6 Months Ended
	Jun. 30, 2013 Branch	Dec. 31, 2012	Dec. 31, 2011	Jul. 01, 2011
Merger with MidCarolina [Abstract]
Effective date of completion of merger	Jul. 01, 2011
Date of acquisition agreement	Dec. 15, 2010
Number of branches added during expansion of business	8
Number of shares received by the stockholder of acquiree entity in exchange of acquirer entity's common stock (in shares)	0.33
Shares exchange ratio on acquisition	0.33
Number of additional common stock issued in connection with merger (in shares)	1,626,157
Amortization period of core deposit	9 years
Liabilities assumed [Abstract]
Goodwill resulting from merger with MidCarolina	$ 39,043,000	$ 39,043,000
Preferred shares issued (in shares)	5,000
Direct costs related to acquisition expense	0	251,000	1,600,000
Acquired loan portfolio at fair value	367,400,000
Discount on acquired loan portfolio at fair value	39,900,000
Performing portion of acquired loan portfolio estimated at fair value	286,500,000
Details the acquired loans that are accounted for in accordance with FASB ASC 310-30 [Abstract]
Contractually required principal and interest at acquisition				56,681,000
Contractual cash flows not expected to be collected (nonaccretable difference)				17,472,000
Expected cash flows at acquisition				39,209,000
Interest component of expected cash flows (accretable discount)				1,663,000
Fair value of acquired loans accounted for under FASB ASC 310-30				37,546,000
MidCarolina [Member]
Merger with MidCarolina [Abstract]
Amortization period of core deposit	108 months
Consideration Paid [Abstract]
Common shares issued (1,626,157)				29,905,000
Cash paid to Shareholders				12,000
Fair Value of Options				132,000
Preferred shares issued (5,000)				5,000,000
Value of consideration				35,049,000
Assets acquired [Abstract]
Cash and cash equivalents				34,783,000
Investment securities				51,442,000
Loans held for sale				113,000
Loans, net of unearned income				328,123,000
Premises and equipment, net				5,708,000
Deferred income taxes				15,310,000
Core deposit intangible	6,556,000			6,556,000
Other real estate owned				3,538,000
Other assets				13,535,000
Total assets				459,108,000
Liabilities assumed [Abstract]
Deposits				420,248,000
FHLB advances				9,858,000
Other borrowings				6,546,000
Other liabilities				3,982,000
Total Liabilities				440,634,000
Net assets acquired				18,474,000
Goodwill resulting from merger with MidCarolina				$ 16,575,000
Series A Preferred Stock [Member] | MidCarolina [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Number of perpetual Series A preferred stock received in exchange on merger (in shares)	1