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Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Millions | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Mar. 01, 2020 | Jan. 01, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018
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Entity Information [Line Items] |  |  |  |  |  |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss | $ 145.5 | $ 146.1 |  |  |  | $ 73.0 | $ 75.0 | $ 74.2 |  | $ 73.0
Off-Balance Sheet, Credit Loss, Liability |  |  |  |  |  | 0.0 |  |  |  |
Credit Extension Commitments | 2,173.2 |  |  |  |  | 2,067.0 |  |  |  |
Unused Credit Card Lines |  |  |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |  |  |
Credit Extension Commitments | 691.9 |  |  |  |  | 671.8 |  |  |  |
Standby Letter of Credit |  |  |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |  |  |
Credit Extension Commitments | 58.8 |  |  |  |  | 42.7 |  |  |  |
Cumulative Effect, Period of Adoption, Adjusted Balance [Member] |  |  |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  |  | $ 2.3 |  | $ 103.0 | 0.0 |  |  | $ 0.0 | 0.0
Off-Balance Sheet, Credit Loss, Liability | 1.2 | 3.5 |  | $ 0.0 | 2.3 | 1.2 | $ 0.0 | $ 0.0 | $ 0.0 | $ 0.0
Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss | 30.0 |  |  |  | 30.0 |  |  |  |  |
Off-Balance Sheet, Credit Loss, Liability |  |  |  |  | $ 2.3 |  |  |  |  |
Agricultural |  |  |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss | 0.9 | $ 0.9 |  |  |  | $ 1.6 |  |  |  |
Agricultural | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |  |  |
Entity Information [Line Items] |  |  |  |  |  |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss | $ (0.6) |  |  |  |  |  |  |  |  |

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