Fair Value (Quantitative Information About Level 3 Fair Value Measurements) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Securities available for sale		$ 2,216,753
Premises, furniture and equipment held for sale	$ 7,258	$ 1,977
Commercial Servicing Rights | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	13.44%	13.04%
Commercial Servicing Rights | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	16.96%	15.49%
Recurring Basis | Interest rate lock commitments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative financial instruments	$ 725	$ 1,738
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held for sale	67,224	0
Securities available for sale	0	0
Derivative financial instruments	0	0
Level 3 | Interest rate lock commitments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative financial instruments	725	1,738
Level 3 | Recurring Basis | Interest rate lock commitments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative financial instruments	725	1,738
Valuation Technique, Discounted Cash Flow | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Loans held for sale	67,224
Servicing rights	$ 7,143
Valuation Technique, Discounted Cash Flow | Level 3 | Commercial Servicing Rights
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Servicing rights		291
Valuation Technique, Discounted Cash Flow | Level 3 | Interest rate lock commitments
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative financial instruments		$ 1,738
Valuation Technique, Discounted Cash Flow | Level 3 | Interest rate lock commitments | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input		0.00
Valuation Technique, Discounted Cash Flow | Level 3 | Interest rate lock commitments | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input		0.99
Valuation Technique, Discounted Cash Flow | Measurement Input, Closing Ratio | Level 3 | Interest rate lock commitments | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.91	0.89
Valuation Technique, Discounted Cash Flow | Measurement Input, Closing Ratio | Level 3 | Interest rate lock commitments | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.00
Valuation Technique, Discounted Cash Flow | Measurement Input, Closing Ratio | Level 3 | Interest rate lock commitments | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative asset, measurement input	0.99
Valuation Technique, Modified Appraised Value | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Other real estate owned	$ 6,153	$ 10,777
Valuation Technique, Modified Appraised Value | Level 3 | Commercial
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent impaired loans	12,932	3,212
Valuation Technique, Modified Appraised Value | Level 3 | Commercial Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent impaired loans	405	9,480
Valuation Technique, Modified Appraised Value | Level 3 | Agricultural and Agricultural Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent impaired loans	11,070	8,406
Valuation Technique, Modified Appraised Value | Level 3 | Residential Real Estate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent impaired loans	478	1,137
Valuation Technique, Modified Appraised Value | Level 3 | Consumer
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Collateral dependent impaired loans	624	1,234
Valuation Technique, Modified Appraised Value | Level 3 | Recurring Basis | Premises, Furniture and Equipment Held for Sale
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Premises, furniture and equipment held for sale	$ 7,258	$ 1,977
Valuation Technique, Modified Appraised Value | Measurement Input, Appraised Value | Level 3 | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	0.00%	0.00%
Valuation Technique, Modified Appraised Value | Measurement Input, Appraised Value | Level 3 | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	10.00%	10.00%
Valuation Technique, Modified Appraised Value | Measurement Input, Appraised Value | Level 3 | Premises, Furniture and Equipment Held for Sale | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	0.00%	0.00%
Valuation Technique, Modified Appraised Value | Measurement Input, Appraised Value | Level 3 | Premises, Furniture and Equipment Held for Sale | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	10.00%	10.00%
Valuation Technique, Modified Appraised Value | Consumer | Measurement Input, Discount Rate | Level 3 | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	0.00%	0.00%
Valuation Technique, Modified Appraised Value | Consumer | Measurement Input, Discount Rate | Level 3 | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	14.00%	12.00%
Valuation Technique, Modified Appraised Value | Residential Real Estate | Measurement Input, Appraised Value | Level 3 | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	0.00%	0.00%
Valuation Technique, Modified Appraised Value | Residential Real Estate | Measurement Input, Appraised Value | Level 3 | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	24.00%	12.00%
Valuation Technique, Modified Appraised Value | Commercial | Measurement Input, Appraised Value | Level 3 | Commercial | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	0.00%	0.00%
Valuation Technique, Modified Appraised Value | Commercial | Measurement Input, Appraised Value | Level 3 | Commercial | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	8.00%	15.00%
Valuation Technique, Modified Appraised Value | Commercial | Measurement Input, Appraised Value | Level 3 | Commercial real estate | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	0.00%	0.00%
Valuation Technique, Modified Appraised Value | Commercial | Measurement Input, Appraised Value | Level 3 | Commercial real estate | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	19.00%	12.00%
Valuation Technique, Modified Appraised Value | Agricultural and Agricultural Real Estate | Measurement Input, Appraised Value | Level 3 | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	0.00%	0.00%
Valuation Technique, Modified Appraised Value | Agricultural and Agricultural Real Estate | Measurement Input, Appraised Value | Level 3 | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Pretax discount rate (percent)	24.00%	10.00%
Interest rate lock commitments | Valuation Technique, Discounted Cash Flow | Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative financial instruments	$ 725