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Loans Held for Investment - Schedule of Recorded Investment in Impaired Loans (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Jun. 30, 2024 | Jun. 30, 2023 | Jun. 30, 2024 | Jun. 30, 2023 | Mar. 31, 2024 | Dec. 31, 2023 | Mar. 31, 2023 | Dec. 31, 2022
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Provision charged to operating expense | $ (9.0) | $ (11.7) | $ (14.3) | $ (26.9) |  |  |  |
Accounts Receivable, Allowance for Credit Loss | 232.8 | 224.6 | 232.8 | 224.6 | $ 227.7 | $ 227.7 | $ 226.1 | $ 220.1
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal) | 18.6 | 9.9 | 27.0 | 22.1 |  |  |  |
Impaired Financing Receivable, Interest Income, Accrual Method | 0.0 | 0.0 | 0.0 | 0.0 |  |  |  |
Total real estate |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Provision charged to operating expense | 3.3 | (20.4) | 8.0 | (33.8) |  |  |  |
Accounts Receivable, Allowance for Credit Loss | 139.7 | 158.7 | 139.7 | 158.7 | 152.9 | 160.1 | 147.5 | 138.7
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 13,544.3 |  | 13,544.3 |  |  | 13,656.8 |  |
Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Provision charged to operating expense | (12.1) | 4.5 | (23.3) | 5.3 |  |  |  |
Accounts Receivable, Allowance for Credit Loss | 69.2 | 49.5 | 69.2 | 49.5 | 58.0 | 50.2 | 54.4 | 54.9
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 3,052.9 |  | 3,052.9 |  |  | 2,906.8 |  |
Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Provision charged to operating expense | (1.2) | (0.2) | (0.7) | 0.9 |  |  |  |
Accounts Receivable, Allowance for Credit Loss | 5.4 | $ 2.7 | 5.4 | $ 2.7 | $ 4.2 | 4.4 | $ 2.4 | $ 3.2
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 698.2 |  | 698.2 |  |  | 769.4 |  |
Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 9,054.5 |  | 9,054.5 |  |  | 8,869.2 |  |
Residential |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 2,246.4 |  | 2,246.4 |  |  | 2,244.3 |  |
Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 723.5 |  | 723.5 |  |  | 716.8 |  |
Total construction loans |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 1,519.9 |  | 1,519.9 |  |  | 1,826.5 |  |
Collateral [Member] |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 103.9 |  | 103.9 |  |  | 52.6 |  |
Collateral [Member] | Total real estate |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 39.7 |  | 39.7 |  |  | 45.3 |  |
Collateral [Member] | Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 63.2 |  | 63.2 |  |  | 6.6 |  |
Collateral [Member] | Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 1.0 |  | 1.0 |  |  | 0.7 |  |
Collateral [Member] | Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 27.4 |  | 27.4 |  |  | 26.6 |  |
Collateral [Member] | Residential |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 1.9 |  | 1.9 |  |  | 0.5 |  |
Collateral [Member] | Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 1.0 |  | 1.0 |  |  | 1.2 |  |
Collateral [Member] | Total construction loans |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 9.4 |  | 9.4 |  |  | 17.0 |  |
Business Assets [Member] | Collateral [Member] |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 62.4 |  | 62.4 |  |  | 5.2 |  |
Business Assets [Member] | Collateral [Member] | Total real estate |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Business Assets [Member] | Collateral [Member] | Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 62.4 |  | 62.4 |  |  | 4.5 |  |
Business Assets [Member] | Collateral [Member] | Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.7 |  |
Business Assets [Member] | Collateral [Member] | Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Business Assets [Member] | Collateral [Member] | Residential |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Business Assets [Member] | Collateral [Member] | Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Business Assets [Member] | Collateral [Member] | Total construction loans |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Real Property [Member] | Collateral [Member] |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 40.7 |  | 40.7 |  |  | 46.7 |  |
Real Property [Member] | Collateral [Member] | Total real estate |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 39.7 |  | 39.7 |  |  | 45.3 |  |
Real Property [Member] | Collateral [Member] | Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.1 |  | 0.1 |  |  | 1.4 |  |
Real Property [Member] | Collateral [Member] | Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.9 |  | 0.9 |  |  | 0.0 |  |
Real Property [Member] | Collateral [Member] | Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 27.4 |  | 27.4 |  |  | 26.6 |  |
Real Property [Member] | Collateral [Member] | Residential |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 1.9 |  | 1.9 |  |  | 0.5 |  |
Real Property [Member] | Collateral [Member] | Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 1.0 |  | 1.0 |  |  | 1.2 |  |
Real Property [Member] | Collateral [Member] | Total construction loans |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 9.4 |  | 9.4 |  |  | 17.0 |  |
Other Property [Member] | Collateral [Member] |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.8 |  | 0.8 |  |  | 0.7 |  |
Other Property [Member] | Collateral [Member] | Total real estate |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Other Property [Member] | Collateral [Member] | Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.7 |  | 0.7 |  |  | 0.7 |  |
Other Property [Member] | Collateral [Member] | Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.1 |  | 0.1 |  |  | 0.0 |  |
Other Property [Member] | Collateral [Member] | Commercial |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Other Property [Member] | Collateral [Member] | Residential |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Other Property [Member] | Collateral [Member] | Agricultural |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 0.0 |  | 0.0 |  |  | 0.0 |  |
Other Property [Member] | Collateral [Member] | Total construction loans |  |  |  |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Impaired [Line Items] |  |  |  |  |  |  |  |
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | $ 0.0 |  | $ 0.0 |  |  | $ 0.0 |  |

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