v3.26.1
Loans Held for Investment - Schedule of Recorded Investment in Past Due Loans (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Nonaccrual loans $ 55.5   $ 55.5   $ 59.8
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss 14,281.4   14,281.4   15,201.6
Accrued interest reversal (1.1) $ (1.0) (1.6) $ (2.5)  
Financing Receivable, Excluding Accrued Interest, Nonaccrual 0.0   0.0    
Financing Receivable, Nonaccrual, Interest Income 1.1 $ 1.1 2.4 $ 1.5  
30 to 59 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Nonaccrual loans 1.8   1.8   4.5
60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Nonaccrual loans 3.6   3.6   3.8
Equal to or Greater than 90 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Nonaccrual loans 97.1   97.1   60.5
Commercial          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 5.9   5.9   40.1
Nonaccrual loans 60.0   60.0   35.6
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 7,947.9   7,947.9   8,144.4
Commercial | 30 to 59 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 5.2   5.2   34.1
Commercial | 60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 0.7   0.7   5.7
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 0.0   0.0   0.3
Commercial | Financial Asset, Not Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 7,882.0   7,882.0   8,068.7
Total construction loans          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 0.7   0.7   13.5
Nonaccrual loans 4.7   4.7   4.3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 576.1   576.1   837.2
Total construction loans | 30 to 59 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 0.5   0.5   13.4
Total construction loans | 60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 0.2   0.2   0.1
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 570.7   570.7   819.4
Residential          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 3.2   3.2   10.9
Nonaccrual loans 12.4   12.4   13.9
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 2,044.7   2,044.7   2,108.8
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   8.3
Residential | 60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 1.3   1.3   2.5
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 0.1   0.1   0.1
Residential | Financial Asset, Not Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 2,029.1   2,029.1   2,084.0
Agricultural          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 0.3   0.3   0.2
Nonaccrual loans 21.6   21.6   27.1
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 592.1   592.1   629.0
Agricultural | 30 to 59 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 0.2   0.2   0.2
Agricultural | 60 to 89 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 | 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 570.2   570.2   601.7
Total real estate          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 10.1   10.1   64.7
Nonaccrual loans 98.7   98.7   80.9
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 11,160.8   11,160.8   11,719.4
Total real estate | 30 to 59 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 7.7   7.7   56.0
Total real estate | 60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 2.3   2.3   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 0.1   0.1   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 11,052.0   11,052.0   11,573.8
Indirect consumer          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 5.3   5.3   8.3
Nonaccrual loans 4.1   4.1   5.6
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 369.0   369.0   477.5
Indirect consumer | 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   6.5
Indirect consumer | 60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 1.3   1.3   1.7
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 0.1   0.1   0.1
Indirect consumer | Financial Asset, Not Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 359.6   359.6   463.6
Total consumer loans          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 6.4   6.4   9.4
Nonaccrual loans 4.8   4.8   6.3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 494.3   494.3   609.0
Total consumer loans | 30 to 59 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 4.7   4.7   7.4
Total consumer loans | 60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 1.6   1.6   1.9
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 0.1   0.1   0.1
Total consumer loans | Financial Asset, Not Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 483.1   483.1   593.3
Commercial          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 6.6   6.6   8.9
Nonaccrual loans 37.1   37.1   21.7
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 2,275.6   2,275.6   2,359.6
Commercial | 30 to 59 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 3.2   3.2   3.1
Commercial | 60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 2.3   2.3   4.9
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 1.1   1.1   0.9
Commercial | Financial Asset, Not Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 2,231.9   2,231.9   2,329.0
Agricultural          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 2.5   2.5   1.1
Nonaccrual loans 17.8   17.8   24.6
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 357.3   357.3   520.2
Agricultural | 30 to 59 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 2.3   2.3   0.5
Agricultural | 60 to 89 Days Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 0.2   0.2   0.6
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 337.0   337.0   494.5
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 1.4   1.4   1.7
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 1.4   1.4   1.7
Loans And Leases Held For Investment [Member]          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 25.6   25.6   84.1
Nonaccrual loans 158.4   158.4   133.5
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 14,289.4   14,289.4   15,209.9
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 17.9   17.9   67.0
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 6.4   6.4   15.7
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 1.3   1.3   1.4
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 14,105.4   14,105.4   14,992.3
Consumer Loan          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process 1.1   1.1   1.1
Nonaccrual loans 0.7   0.7   0.7
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 125.3   125.3   131.5
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   0.9
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 0.0   0.0   0.0
Consumer Loan | Financial Asset, Not Past Due          
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]          
Financing Receivable, Loan in Process $ 123.5   $ 123.5   $ 129.7