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Loans - Schedule of Loans Renegotiated in Troubled Debt Restructurings (Details) | 12 Months Ended
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Dec. 31, 2020 USD ($) note | Dec. 31, 2019 USD ($) note | Dec. 31, 2018 USD ($) note
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Loans renegotiated in troubled debt restructurings | $ 14,500,000 | $ 24,900,000 |
Loans renegotiated in troubled debt restructurings, non-accrual loans | 11,300,000 | 19,400,000 |
Loans renegotiated in troubled debt restructurings, accrual loans | $ 3,200,000 | $ 5,500,000 |
Number of notes under troubled debt restructurings | note | 3 | 11 | 5
Charge-offs directly related to modified loans | $ 0 | $ 0 | $ 0
Financing Receivable, Troubled Debt Restructuring, Postmodification | 300,000 | 10,400,000 | $ 4,100,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance |  | $ 300,000 |
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend | 0 |  |
Balance of notes for which there was a payment default | 0 |  |
Impaired Financing Receivable, Recorded Investment | 63,500,000 |  |
Financing Receivable, Allowance for Credit Loss, Noncurrent | $ 2,900,000 |  |
Commercial Real Estate Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Number of notes under troubled debt restructurings | note | 3 | 4 | 3
Financing Receivable, Troubled Debt Restructuring, Postmodification | $ 300,000 | $ 3,300,000 | $ 3,600,000
Impaired Financing Receivable, Recorded Investment |  | 23,700,000 | 16,300,000
Agricultural Real Estate Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Concessions in troubled debt restructurings, amount |  |  | 0
Financing Receivable, Troubled Debt Restructuring, Postmodification |  |  | 200,000
Impaired Financing Receivable, Recorded Investment |  | 8,200,000 | 12,700,000
Real Estate Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Impaired Financing Receivable, Recorded Investment |  | $ 41,100,000 | $ 41,800,000
Commercial Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Number of notes under troubled debt restructurings | note |  | 1 | 1
Concessions in troubled debt restructurings, amount |  | $ 0 |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  | 5,000,000.0 |
Impaired Financing Receivable, Recorded Investment |  | 17,300,000 | $ 19,900,000
Real Estate Construction Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Impaired Financing Receivable, Recorded Investment |  | $ 3,500,000 | 5,100,000
Agricultural Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Number of notes under troubled debt restructurings | note |  | 6 |
Concessions in troubled debt restructurings, amount |  | $ 0 |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  | 2,100,000 |
Impaired Financing Receivable, Recorded Investment |  | 6,300,000 | $ 3,100,000
522291 Consumer Lending |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Number of notes under troubled debt restructurings | note |  |  | 1
Concessions in troubled debt restructurings, amount |  |  | $ 0
Financing Receivable, Troubled Debt Restructuring, Postmodification |  |  | 300,000
Interest Only Period Concession |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Concessions in troubled debt restructurings, amount |  | 200,000 | 3,600,000
Financing Receivable, Troubled Debt Restructuring, Postmodification | 200,000 |  |
Interest Only Period Concession | Commercial Real Estate Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Concessions in troubled debt restructurings, amount |  | 200,000 | 3,600,000
Financing Receivable, Troubled Debt Restructuring, Postmodification | 200,000 |  |
Extension of terms or maturity |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification | 0 | 200,000 | 0
Extension of terms or maturity | Commercial Real Estate Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification | 0 | 200,000 | 0
Extension of terms or maturity | Agricultural Real Estate Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  |  | 0
Extension of terms or maturity | Commercial Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  | 0 |
Extension of terms or maturity | Agricultural Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  | 0 |
Extension of terms or maturity | 522291 Consumer Lending |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  |  | 0
Interest rate adjustment |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Concessions in troubled debt restructurings, amount |  |  | 0
Financing Receivable, Troubled Debt Restructuring, Postmodification | 0 | 0 |
Interest rate adjustment | Commercial Real Estate Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Concessions in troubled debt restructurings, amount |  |  | 0
Financing Receivable, Troubled Debt Restructuring, Postmodification | 0 | 0 |
Interest rate adjustment | Agricultural Real Estate Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Concessions in troubled debt restructurings, amount |  |  | 0
Interest rate adjustment | Commercial Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  | 0 |
Interest rate adjustment | Agricultural Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  | 0 |
Interest rate adjustment | 522291 Consumer Lending |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Concessions in troubled debt restructurings, amount |  |  | 0
Other |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification | 100,000 | 10,000,000.0 | 500,000
Other | Commercial Real Estate Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification | $ 100,000 | 2,900,000 | 0
Other | Agricultural Real Estate Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  |  | 200,000
Other | Commercial Portfolio Segment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  | 5,000,000.0 |
Other | Agricultural Financing Receivable [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  | $ 2,100,000 |
Other | 522291 Consumer Lending |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring |  |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification |  |  | $ 300,000

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