Fair Value (Fair value measurement non-recurring) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other real estate owned	$ 11,908	$ 10,777
Premises, furniture and equipment held for sale	4,422	1,977
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	77,727	44,560
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for sale	0	0
Other real estate owned	11,908	10,777
Commercial servicing rights | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights		291
Premises, furniture and equipment held for sale | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Premises, furniture and equipment held for sale	4,422	1,977
Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	21,545	23,469
Loans held for sale	77,727	44,560
Other real estate owned	11,908	10,777
Nonrecurring Basis | Year-to- Date (Gains) Losses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	804	3,469
Loans held for sale	(835)	190
Other real estate owned	1,847	737
Nonrecurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Loans held for sale	0	0
Other real estate owned	0	0
Nonrecurring Basis | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Loans held for sale	77,727	44,560
Other real estate owned	0	0
Nonrecurring Basis | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	21,545	23,469
Loans held for sale	0	0
Other real estate owned	11,908	10,777
Nonrecurring Basis | Commercial servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights		291
Nonrecurring Basis | Commercial servicing rights | Year-to- Date (Gains) Losses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights		(21)
Nonrecurring Basis | Commercial servicing rights | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights		0
Nonrecurring Basis | Commercial servicing rights | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights		0
Nonrecurring Basis | Commercial servicing rights | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing rights		291
Nonrecurring Basis | Premises, furniture and equipment held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Premises, furniture and equipment held for sale	4,422	1,977
Nonrecurring Basis | Premises, furniture and equipment held for sale | Year-to- Date (Gains) Losses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Premises, furniture and equipment held for sale	(74)	192
Nonrecurring Basis | Premises, furniture and equipment held for sale | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Premises, furniture and equipment held for sale	0	0
Nonrecurring Basis | Premises, furniture and equipment held for sale | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Premises, furniture and equipment held for sale	0	0
Nonrecurring Basis | Premises, furniture and equipment held for sale | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Premises, furniture and equipment held for sale	4,422	1,977
Nonrecurring Basis | Commercial | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	6,772	3,212
Nonrecurring Basis | Commercial | Commercial | Year-to- Date (Gains) Losses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	237	1,119
Nonrecurring Basis | Commercial | Commercial | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Commercial | Commercial | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Commercial | Commercial | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	6,772	3,212
Nonrecurring Basis | Commercial | Commercial real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	420	9,480
Nonrecurring Basis | Commercial | Commercial real estate | Year-to- Date (Gains) Losses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	72	322
Nonrecurring Basis | Commercial | Commercial real estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Commercial | Commercial real estate | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Commercial | Commercial real estate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	420	9,480
Nonrecurring Basis | Agricultural and agricultural real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	11,821	8,406
Nonrecurring Basis | Agricultural and agricultural real estate | Year-to- Date (Gains) Losses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	495	2,028
Nonrecurring Basis | Agricultural and agricultural real estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Agricultural and agricultural real estate | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Agricultural and agricultural real estate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	11,821	8,406
Nonrecurring Basis | Residential real estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	590	1,137
Nonrecurring Basis | Residential real estate | Year-to- Date (Gains) Losses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Residential real estate | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Residential real estate | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Residential real estate | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	590	1,137
Nonrecurring Basis | Consumer
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	1,942	1,234
Nonrecurring Basis | Consumer | Year-to- Date (Gains) Losses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Consumer | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Consumer | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	0	0
Nonrecurring Basis | Consumer | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	$ 1,942	$ 1,234