Fair Value (Estimated fair value financial instruments (incl. carrying amounts)) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Trading securities	$ 0	$ 1,801
Securities available for sale	1,400,756	1,633,902
Held to maturity securities	263,169	237,437
Forward Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	238	1,206
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	88,628	125,270
Time deposits in other financial institutions	3,355
Trading securities	0	1,801
Securities available for sale	2,555	4,084
Held to maturity securities	0	0
Other investments	0	0
Loans held for sale	0	0
Loans, net	0	0
Derivative assets	0	0
Short term borrowings	0	0
Other borrowings	0	0
Derivative liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Demand Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Savings Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Time Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Interest Rate Lock Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Forward Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Agricultural and Agricultural Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Residential Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Consumer
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0
Trading securities	0	0
Securities available for sale	1,393,871	1,626,520
Held to maturity securities	263,169	237,437
Other investments	18,520	21,608
Loans held for sale	54,862	46,665
Loans, net	3,504,038	3,396,662
Derivative assets	152	0
Short term borrowings	256,250	408,756
Other borrowings	339,930	355,923
Derivative liabilities	3,467	3,697
Significant Other Observable Inputs (Level 2) | Demand Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	1,195,457	1,238,581
Significant Other Observable Inputs (Level 2) | Savings Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	2,582,166	2,535,242
Significant Other Observable Inputs (Level 2) | Time Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	885,741	892,676
Significant Other Observable Inputs (Level 2) | Interest Rate Lock Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Significant Other Observable Inputs (Level 2) | Forward Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	238	1,206
Derivative liabilities	307	133
Significant Other Observable Inputs (Level 2) | Commercial
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	962,913	923,272
Significant Other Observable Inputs (Level 2) | Commercial Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	1,541,521	1,505,024
Significant Other Observable Inputs (Level 2) | Agricultural and Agricultural Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	364,591	365,024
Significant Other Observable Inputs (Level 2) | Residential Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	348,728	331,966
Significant Other Observable Inputs (Level 2) | Consumer
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	286,285	271,376
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Time deposits in other financial institutions	0
Trading securities	0	0
Securities available for sale	4,330	3,298
Held to maturity securities	0	0
Other investments	235	235
Loans held for sale	0	0
Loans, net	17,328	33,199
Derivative assets	0	0
Short term borrowings	0	0
Other borrowings	0	0
Derivative liabilities	0	0
Significant Unobservable Inputs (Level 3) | Demand Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Significant Unobservable Inputs (Level 3) | Savings Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Significant Unobservable Inputs (Level 3) | Time Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	0	0
Significant Unobservable Inputs (Level 3) | Interest Rate Lock Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2,993	1,809
Significant Unobservable Inputs (Level 3) | Forward Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Significant Unobservable Inputs (Level 3) | Commercial
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	440	7,229
Significant Unobservable Inputs (Level 3) | Commercial Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	6,585	7,749
Significant Unobservable Inputs (Level 3) | Agricultural and Agricultural Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	4,926	13,062
Significant Unobservable Inputs (Level 3) | Residential Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	2,764	3,396
Significant Unobservable Inputs (Level 3) | Consumer
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	2,613	1,763
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	88,628	125,270
Time deposits in other financial institutions	3,355
Trading securities	0	1,801
Securities available for sale	1,400,756	1,633,902
Held to maturity securities	257,927	237,498
Other investments	18,755	21,843
Loans held for sale	54,862	46,665
Loans, net	3,544,669	3,461,016
Derivative assets	152	0
Short term borrowings	256,250	408,756
Other borrowings	334,916	350,109
Derivative liabilities	3,467	3,697
Carrying Amount | Demand Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	1,195,457	1,238,581
Carrying Amount | Savings Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	2,582,166	2,535,242
Carrying Amount | Time Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	885,741	892,676
Carrying Amount | Interest Rate Lock Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2,993	1,809
Carrying Amount | Forward Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	238	1,206
Derivative liabilities	307	133
Carrying Amount | Commercial
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	974,144	936,305
Carrying Amount | Commercial Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	1,548,517	1,516,352
Carrying Amount | Agricultural and Agricultural Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	368,168	374,203
Carrying Amount | Residential Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	362,769	347,266
Carrying Amount | Consumer
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	291,071	286,890
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	88,628	125,270
Time deposits in other financial institutions	3,355
Trading securities	0	1,801
Securities available for sale	1,400,756	1,633,902
Held to maturity securities	263,169	237,437
Other investments	18,755	21,843
Loans held for sale	54,862	46,665
Loans, net	3,521,366	3,429,861
Derivative assets	152	0
Short term borrowings	256,250	408,756
Other borrowings	339,930	355,923
Derivative liabilities	3,467	3,697
Estimated Fair Value | Demand Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	1,195,457	1,238,581
Estimated Fair Value | Savings Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	2,582,166	2,535,242
Estimated Fair Value | Time Deposits
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deposits	885,741	892,676
Estimated Fair Value | Interest Rate Lock Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative assets	2,993	1,809
Estimated Fair Value | Forward Commitments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative liabilities	307	133
Estimated Fair Value | Commercial
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	963,353	930,501
Estimated Fair Value | Commercial Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	1,548,106	1,512,773
Estimated Fair Value | Agricultural and Agricultural Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	369,517	378,086
Estimated Fair Value | Residential Real Estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	351,492	335,362
Estimated Fair Value | Consumer
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans, net	$ 288,898	$ 273,139