Mergers and Acquisitions Mergers and Acquisitions (Details Textual) (USD $)	3 Months Ended		6 Months Ended		1 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Wheatland Bankshares [Member]	Jun. 30, 2013 Wheatland Bankshares [Member]	May 31, 2013 Wheatland Bankshares [Member]
Percentage of Outstanding Common Stock Acquired							100.00%
Total purchase price							$ 39,315,000
Number of Shares Issued for Aquisition							1,455,256
Cash consideration for outstanding shares							11,025,000
Loans receivable							171,199,000
Loans Receivable Acquired, Gross Principal and Contractual Interest Due							176,698,000
Loans Receivable Acquired, Gross Principal and Contractual Interest Due, Expected to be Uncollectible							0
Third-party Acquisition Related Costs						571,000
Net interest income and non-interest income					1,145,000
Net income	$ 22,702,000	$ 18,981,000	$ 43,470,000	$ 35,314,000	$ 311,000