Acquisition (Details Textual) (USD $)	12 Months Ended				12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 Heartland [Member]	Jul. 17, 2012 Heartland [Member]	Dec. 31, 2012 Heartland Bancshares Inc [Member]
Acquisition (Textual) [Abstract]
Date of acquisition agreement	Jul. 17, 2012
Exchange ratio per share to Heartland shareholder						$ 0.81
Market closing price per share						$ 16.83
Transaction value is estimated						$ 26,900,000
Costs related to the acquisition					1,500,000
Common stock outstanding	8,617,466	7,421,544				1,442,449
Common stock issued					1,168,383
Net tangible assets acquired						26,900,000
Net intangible assets acquired	2,332,000					2,300,000
Purchase price of the business assets	2,647,000					10,800,000
Acquisition of goodwill	13,838,000					13,800,000
Core deposit intangible amortization period					7 years
Loan portfolio acquired						131,100,000
Discount on loan portfolio acquired						16,500,000
Performing portion of the loan portfolio acquired						95,400,000
Estimated fair value of performing portion of the loan portfolio						91,600,000
Increased the allowance for loan losses	3,524,000	5,282,000	11,554,000				0
Allowances for loan losses							0
Acquisition (Additional Textual) [Abstract]
Net of allowance	$ 18,270,000	$ 18,882,000	$ 19,064,000	$ 16,015,000