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Loans Held for Investment - Schedule of Recorded Investment in Past Due Loans (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024 | Dec. 31, 2024
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | $ 0.0 |  | $ 0.0 |  | $ 1.2
Nonaccrual loans | 130.3 |  | 130.3 |  | 56.9
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss | 16,353.4 |  | 16,353.4 |  | 17,844.9
Accrued interest reversal | (1.0) | $ (0.2) | (2.5) | $ (2.0) |
Financing Receivable, Excluding Accrued Interest, Nonaccrual | 0.0 | 0.0 | 0.0 | 0.0 |
Financing Receivable, Nonaccrual, Interest Income | 1.1 | $ 0.5 | 1.5 | $ 0.8 |
30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Nonaccrual loans | 29.5 |  | 29.5 |  | 13.5
60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Nonaccrual loans | 9.7 |  | 9.7 |  | 6.2
Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Nonaccrual loans | 74.7 |  | 74.7 |  | 40.5
Commercial |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 5.4 |  | 5.4 |  | 7.7
Nonaccrual loans | 81.0 |  | 81.0 |  | 55.4
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 8,750.9 |  | 8,750.9 |  | 9,263.2
Commercial | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.9 |  | 0.9 |  | 4.9
Commercial | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 4.4 |  | 4.4 |  | 2.8
Commercial | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.1 |  | 0.1 |  | 0.0
Commercial | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 8,664.5 |  | 8,664.5 |  | 9,200.1
Total construction loans |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 9.6 |  | 9.6 |  | 3.7
Nonaccrual loans | 4.0 |  | 4.0 |  | 3.3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 1,004.6 |  | 1,004.6 |  | 1,244.6
Total construction loans | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 9.3 |  | 9.3 |  | 3.7
Total construction loans | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.3 |  | 0.3 |  | 0.0
Total construction loans | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.0
Total construction loans | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 991.0 |  | 991.0 |  | 1,237.6
Residential |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 3.3 |  | 3.3 |  | 9.7
Nonaccrual loans | 16.1 |  | 16.1 |  | 15.4
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 2,157.5 |  | 2,157.5 |  | 2,191.6
Residential | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1.8 |  | 1.8 |  | 6.6
Residential | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1.5 |  | 1.5 |  | 2.7
Residential | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.4
Residential | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,138.1 |  | 2,138.1 |  | 2,166.5
Agricultural |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 6.4 |  | 6.4 |  | 10.4
Nonaccrual loans | 20.8 |  | 20.8 |  | 5.3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 635.6 |  | 635.6 |  | 701.1
Agricultural | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 5.1 |  | 5.1 |  | 7.6
Agricultural | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1.2 |  | 1.2 |  | 2.8
Agricultural | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.1 |  | 0.1 |  | 0.0
Agricultural | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 608.4 |  | 608.4 |  | 685.4
Total real estate |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 24.7 |  | 24.7 |  | 31.5
Nonaccrual loans | 121.9 |  | 121.9 |  | 79.4
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 12,548.6 |  | 12,548.6 |  | 13,400.5
Total real estate | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 17.1 |  | 17.1 |  | 22.8
Total real estate | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 7.4 |  | 7.4 |  | 8.3
Total real estate | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.2 |  | 0.2 |  | 0.4
Total real estate | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 12,402.0 |  | 12,402.0 |  | 13,289.6
Indirect consumer |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 9.7 |  | 9.7 |  | 11.7
Nonaccrual loans | 3.9 |  | 3.9 |  | 3.9
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 607.1 |  | 607.1 |  | 725.0
Indirect consumer | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 7.0 |  | 7.0 |  | 8.4
Indirect consumer | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2.1 |  | 2.1 |  | 2.6
Indirect consumer | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.6 |  | 0.6 |  | 0.7
Indirect consumer | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 593.5 |  | 593.5 |  | 709.4
Credit Card Receivable [Member] |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 2.2
Nonaccrual loans | 0.0 |  | 0.0 |  | 0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 0.0 |  | 0.0 |  | 77.6
Credit Card Receivable [Member] | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.7
Credit Card Receivable [Member] | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.5
Credit Card Receivable [Member] | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 1.0
Credit Card Receivable [Member] | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 75.4
Total consumer loans |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 10.9 |  | 10.9 |  | 15.0
Nonaccrual loans | 4.4 |  | 4.4 |  | 4.5
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 741.5 |  | 741.5 |  | 936.6
Total consumer loans | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 7.8 |  | 7.8 |  | 9.7
Total consumer loans | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2.4 |  | 2.4 |  | 3.3
Total consumer loans | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.7 |  | 0.7 |  | 2.0
Total consumer loans | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 726.2 |  | 726.2 |  | 917.1
Commercial |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 7.6 |  | 7.6 |  | 14.8
Nonaccrual loans | 44.4 |  | 44.4 |  | 33.5
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 2,529.9 |  | 2,529.9 |  | 2,829.4
Commercial | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 3.9 |  | 3.9 |  | 11.2
Commercial | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 3.2 |  | 3.2 |  | 3.0
Commercial | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.5 |  | 0.5 |  | 0.6
Commercial | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2,477.9 |  | 2,477.9 |  | 2,781.1
Agricultural |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 10.4 |  | 10.4 |  | 5.2
Nonaccrual loans | 22.0 |  | 22.0 |  | 20.9
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 541.4 |  | 541.4 |  | 687.9
Agricultural | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 10.4 |  | 10.4 |  | 2.4
Agricultural | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 2.8
Agricultural | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.0
Agricultural | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 509.0 |  | 509.0 |  | 661.8
Other, including overdrafts |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.0
Nonaccrual loans | 0.0 |  | 0.0 |  | 0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 2.0 |  | 2.0 |  | 1.6
Other, including overdrafts | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.0
Other, including overdrafts | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.0
Other, including overdrafts | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.0 |  | 0.0 |  | 0.0
Other, including overdrafts | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 2.0 |  | 2.0 |  | 1.6
Loans And Leases Held For Investment [Member] |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 53.6 |  | 53.6 |  | 66.5
Nonaccrual loans | 192.7 |  | 192.7 |  | 138.3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 16,363.4 |  | 16,363.4 |  | 17,856.0
Loans And Leases Held For Investment [Member] | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 39.2 |  | 39.2 |  | 46.1
Loans And Leases Held For Investment [Member] | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 13.0 |  | 13.0 |  | 17.4
Loans And Leases Held For Investment [Member] | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1.4 |  | 1.4 |  | 3.0
Loans And Leases Held For Investment [Member] | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 16,117.1 |  | 16,117.1 |  | 17,651.2
Consumer Loan |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 1.2 |  | 1.2 |  | 1.1
Nonaccrual loans | 0.5 |  | 0.5 |  | 0.6
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process | 134.4 |  | 134.4 |  | 134.0
Consumer Loan | 30 to 59 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.8 |  | 0.8 |  | 0.6
Consumer Loan | 60 to 89 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.3 |  | 0.3 |  | 0.2
Consumer Loan | Equal to or Greater than 90 Days Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | 0.1 |  | 0.1 |  | 0.3
Consumer Loan | Financial Asset, Not Past Due |  |  |  |  |
Loans and Leases Receivable Recorded Investment, Past Due [Line Items] |  |  |  |  |
Financing Receivable, Loan in Process | $ 132.7 |  | $ 132.7 |  | $ 132.3

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