v3.25.2
Loans Held for Investment - Schedule of Contractual Aging of Loans by Portfolio (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Dec. 31, 2024
Loans and Leases Receivable, Troubled Debt Restructuring [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
Financing Receivable, Allowance for Credit Loss, Writeoff 13.0 $ 16.3 23.8 $ 27.3 114.7
Financing Receivable, Nonaccrual, Interest Income (1.1) (0.5) (1.5) (0.8)  
Accrued interest reversal (1.0) (0.2) (2.5) (2.0)  
Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year 622.5   622.5   1,368.4
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 1,277.1   1,277.1   1,369.8
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 1,240.8   1,240.8   1,946.9
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 1,638.9   1,638.9   1,397.5
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 1,317.1   1,317.1   1,084.8
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 2,487.3   2,487.3   1,901.0
Financing Receivable, Excluding Accrued Interest, Revolving 69.7   69.7   75.2
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 97.5   97.5   119.6
Financing Receivable, Allowance for Credit Loss, Writeoff     2.8   25.4
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 real estate | Pass          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 483.3   483.3   1,208.5
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 1,097.8   1,097.8   1,340.2
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 1,162.6   1,162.6   1,909.1
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 1,562.9   1,562.9   1,344.1
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 1,174.0   1,174.0   1,069.7
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 2,322.1   2,322.1   1,778.3
Financing Receivable, Excluding Accrued Interest, Revolving 69.6   69.6   74.1
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 97.1   97.1   109.8
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 7,969.4   7,969.4   8,833.8
Commercial real estate | Other Assets Especially Mentioned          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 116.1   116.1   78.4
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 137.4   137.4   17.5
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 45.5   45.5   15.8
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 39.7   39.7   16.1
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 96.8   96.8   4.9
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 111.5   111.5   79.2
Financing Receivable, Excluding Accrued Interest, Revolving 0.1   0.1   0.6
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   9.8
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 547.1   547.1   222.3
Commercial real estate | Substandard          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 21.2   21.2   81.5
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 41.4   41.4   12.1
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 27.0   27.0   22.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 36.3   36.3   37.3
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 46.3   46.3   10.2
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 53.7   53.7   43.5
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.5
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.4   0.4   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 226.3   226.3   207.1
Commercial real estate | Doubtful          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 1.9   1.9    
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 0.5   0.5    
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 5.7   5.7    
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 0.0   0.0    
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.0   0.0    
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.0   0.0    
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0    
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0    
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 8.1   8.1    
Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year 163.3   163.3   443.7
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 353.8   353.8   233.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 108.8   108.8   326.6
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 238.2   238.2   76.5
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 35.1   35.1   17.3
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 28.3   28.3   20.9
Financing Receivable, Excluding Accrued Interest, Revolving 73.6   73.6   124.8
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 3.5   3.5   1.8
Financing Receivable, Allowance for Credit Loss, Writeoff         13.2
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 | Pass          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 143.4   143.4   438.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 349.5   349.5   233.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 108.5   108.5   320.2
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 228.0   228.0   76.5
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 33.4   33.4   17.3
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 28.3   28.3   20.9
Financing Receivable, Excluding Accrued Interest, Revolving 73.4   73.4   124.8
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 3.5   3.5   1.8
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 968.0   968.0   1,232.5
Total construction loans | Other Assets Especially Mentioned          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 10.4   10.4   2.1
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 1.1   1.1   0.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 0.2   0.2   6.4
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 0.1   0.1   0.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 11.8   11.8   8.5
Total construction loans | Substandard          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 9.5   9.5    
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 1.9   1.9    
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 0.1   0.1    
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 10.1   10.1    
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 1.7   1.7    
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.0   0.0    
Financing Receivable, Excluding Accrued Interest, Revolving 0.2   0.2    
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0    
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 23.5   23.5    
Total construction loans | Doubtful          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 0.0   0.0   3.6
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 1.3   1.3   0.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 1.3   1.3   3.6
Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year 18.7   18.7   23.9
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 31.0   31.0   75.3
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 77.1   77.1   414.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 412.0   412.0   489.4
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 471.9   471.9   441.3
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 644.8   644.8   257.4
Financing Receivable, Excluding Accrued Interest, Revolving 496.1   496.1   477.8
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 5.9   5.9   12.5
Financing Receivable, Allowance for Credit Loss, Writeoff     0.7   1.0
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 | Performing Financial Instruments [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 18.2   18.2   22.6
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 29.8   29.8   73.8
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 75.8   75.8   409.1
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 407.0   407.0   487.3
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 469.6   469.6   440.2
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 639.1   639.1   252.5
Financing Receivable, Excluding Accrued Interest, Revolving 496.1   496.1   477.8
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 5.8   5.8   12.5
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 2,141.4   2,141.4   2,175.8
Residential | Nonperforming Financial Instruments [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 0.5   0.5   1.3
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 1.2   1.2   1.5
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 1.3   1.3   4.9
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 5.0   5.0   2.1
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 2.3   2.3   1.1
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 5.7   5.7   4.9
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.1   0.1   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 16.1   16.1   15.8
Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year 47.8   47.8   132.6
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 107.3   107.3   61.4
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 54.6   54.6   131.2
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 119.0   119.0   117.4
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 107.3   107.3   78.9
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 176.0   176.0   145.7
Financing Receivable, Excluding Accrued Interest, Revolving 23.3   23.3   33.4
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.3   0.3   0.5
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 635.6   635.6   701.1
Agricultural | Pass          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 37.0   37.0   118.6
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 93.8   93.8   53.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 46.1   46.1   104.7
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 111.5   111.5   107.9
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 92.9   92.9   66.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 149.7   149.7   144.1
Financing Receivable, Excluding Accrued Interest, Revolving 22.2   22.2   33.4
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.3   0.3   0.5
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 553.5   553.5   628.2
Agricultural | Other Assets Especially Mentioned          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 4.1   4.1   1.1
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 10.6   10.6   0.2
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 1.7   1.7   6.8
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 4.2   4.2   6.1
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 8.1   8.1   8.5
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 15.3   15.3   0.7
Financing Receivable, Excluding Accrued Interest, Revolving 1.1   1.1   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 45.1   45.1   23.4
Agricultural | Substandard          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 6.7   6.7   12.9
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 2.9   2.9   8.2
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 6.8   6.8   19.7
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 3.3   3.3   3.4
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 6.3   6.3   4.4
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 11.0   11.0   0.9
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 37.0   37.0   49.5
Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 24.7   24.7   31.5
Nonaccrual loans 121.9   121.9   79.4
Financing Receivable, Allowance for Credit Loss, Writeoff 3.2 10.1 3.5 13.3 39.6
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 12,548.6   12,548.6   13,400.5
Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year 31.5   31.5   267.7
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 217.2   217.2   128.3
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 99.6   99.6   168.6
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 133.8   133.8   69.5
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 54.0   54.0   44.8
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 71.0   71.0   46.1
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Allowance for Credit Loss, Writeoff     4.8   8.5
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 607.1   607.1   725.0
Indirect consumer | Performing Financial Instruments [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 31.3   31.3   266.8
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 216.3   216.3   127.2
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 98.8   98.8   167.5
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 132.6   132.6   68.9
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 53.3   53.3   44.4
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 70.3   70.3   45.6
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 602.6   602.6   720.4
Indirect consumer | Nonperforming Financial Instruments [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 0.2   0.2   0.9
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 0.9   0.9   1.1
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 0.8   0.8   1.1
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 1.2   1.2   0.6
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.7   0.7   0.4
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.7   0.7   0.5
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 4.5   4.5   4.6
Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 10.9   10.9   15.0
Nonaccrual loans 4.4   4.4   4.5
Financing Receivable, Allowance for Credit Loss, Writeoff 5.6 4.0 10.3 7.8 15.4
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 741.5   741.5   936.6
Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year 181.4   181.4   473.5
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 380.1   380.1   373.9
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 304.7   304.7   392.9
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 337.5   337.5   324.2
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 261.9   261.9   173.7
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 315.6   315.6   259.2
Financing Receivable, Excluding Accrued Interest, Revolving 727.9   727.9   821.6
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 20.8   20.8   10.4
Financing Receivable, Allowance for Credit Loss, Writeoff 2.2 2.2 5.1 6.2 59.4
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 | Pass          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 166.9   166.9   438.8
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 340.4   340.4   353.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 287.2   287.2   375.9
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 317.6   317.6   316.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 251.9   251.9   165.9
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 312.2   312.2   255.2
Financing Receivable, Excluding Accrued Interest, Revolving 660.9   660.9   767.3
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 7.1   7.1   8.9
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 2,344.2   2,344.2   2,681.0
Commercial | Other Assets Especially Mentioned          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 6.7   6.7   3.9
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 11.0   11.0   13.9
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 8.7   8.7   3.1
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 4.9   4.9   2.2
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 4.4   4.4   6.2
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.8   0.8   0.6
Financing Receivable, Excluding Accrued Interest, Revolving 43.1   43.1   19.1
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 79.6   79.6   49.0
Commercial | Substandard          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 7.3   7.3   30.8
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 26.2   26.2   5.4
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 8.3   8.3   12.8
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 8.7   8.7   5.5
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 5.2   5.2   1.6
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 2.6   2.6   3.4
Financing Receivable, Excluding Accrued Interest, Revolving 23.9   23.9   35.2
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 13.7   13.7   1.5
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 95.9   95.9   96.2
Commercial | Doubtful          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 0.5   0.5   0.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 2.5   2.5   1.6
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 0.5   0.5   1.1
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 6.3   6.3   0.5
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.4   0.4   0.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 10.2   10.2   3.2
Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year 83.5   83.5   136.7
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 58.2   58.2   61.4
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 27.3   27.3   40.4
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 35.0   35.0   16.8
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 12.5   12.5   14.9
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 8.8   8.8   5.9
Financing Receivable, Excluding Accrued Interest, Revolving 313.6   313.6   410.4
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 2.5   2.5   1.4
Financing Receivable, Allowance for Credit Loss, Writeoff 2.0 $ 0.0 4.9 $ 0.0 0.3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 541.4   541.4   687.9
Agricultural | Pass          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 52.6   52.6   109.6
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 50.0   50.0   34.1
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 23.0   23.0   39.4
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 31.0   31.0   16.6
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 11.7   11.7   13.5
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 8.3   8.3   5.8
Financing Receivable, Excluding Accrued Interest, Revolving 269.9   269.9   379.4
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.9   0.9   1.1
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 447.4   447.4   599.5
Agricultural | Other Assets Especially Mentioned          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 13.9   13.9   4.1
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 2.7   2.7   1.4
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 1.0   1.0   0.9
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 3.9   3.9   0.2
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.8   0.8   0.9
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.0   0.0   0.1
Financing Receivable, Excluding Accrued Interest, Revolving 37.1   37.1   5.1
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 1.5   1.5   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 60.9   60.9   12.7
Agricultural | Substandard          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 11.1   11.1   4.1
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 5.4   5.4   25.9
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 0.7   0.7   0.1
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 0.1   0.1   0.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.0   0.0   0.5
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.5   0.5   0.0
Financing Receivable, Excluding Accrued Interest, Revolving 4.6   4.6   25.9
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.1   0.1   0.3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 22.5   22.5   56.8
Agricultural | Doubtful          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 5.9   5.9   18.9
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 0.1   0.1   0.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 2.6   2.6   0.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving 2.0   2.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 10.6   10.6   18.9
Other, including overdrafts          
Loans and Leases Receivable, Troubled Debt Restructuring [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
Loans And Leases Held For Investment [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [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
Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year 28.9   28.9   46.9
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 35.4   35.4   25.5
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 18.9   18.9   18.7
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 13.9   13.9   10.1
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 7.4   7.4   4.2
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 7.1   7.1   5.3
Financing Receivable, Excluding Accrued Interest, Revolving 22.8   22.8   23.2
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.1
Financing Receivable, Allowance for Credit Loss, Writeoff     2.0   3.9
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 134.4   134.4   134.0
Consumer Loan | Performing Financial Instruments [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 28.9   28.9   46.5
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 35.2   35.2   25.4
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 18.8   18.8   18.5
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 13.8   13.8   10.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 7.3   7.3   4.2
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 7.0   7.0   5.2
Financing Receivable, Excluding Accrued Interest, Revolving 22.8   22.8   23.2
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.1
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 133.8   133.8   133.1
Consumer Loan | Nonperforming Financial Instruments [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year 0.0   0.0   0.4
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year 0.2   0.2   0.1
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year 0.1   0.1   0.2
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year 0.1   0.1   0.1
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year 0.1   0.1   0.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year 0.1   0.1   0.1
Financing Receivable, Excluding Accrued Interest, Revolving 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan 0.0   0.0   0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process 0.6   0.6   0.9
Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [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, Year One, Originated, Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Revolving         77.6
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan         0.0
Financing Receivable, Allowance for Credit Loss, Writeoff     3.5   3.0
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] | Performing Financial Instruments [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Revolving         76.6
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan         0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process         76.6
Credit Card Receivable [Member] | Nonperforming Financial Instruments [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year         0.0
Financing Receivable, Excluding Accrued Interest, Revolving         1.0
Financing Receivable, Excluding Accrued Interest, Revolving, Converted to Term Loan         0.0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Fee, and Loan in Process         1.0
30 to 59 Days Past Due          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Nonaccrual loans 29.5   29.5   13.5
30 to 59 Days Past Due | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.9   0.9   4.9
30 to 59 Days Past Due | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 9.3   9.3   3.7
30 to 59 Days Past Due | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 1.8   1.8   6.6
30 to 59 Days Past Due | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 5.1   5.1   7.6
30 to 59 Days Past Due | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 17.1   17.1   22.8
30 to 59 Days Past Due | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 7.0   7.0   8.4
30 to 59 Days Past Due | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 7.8   7.8   9.7
30 to 59 Days Past Due | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 3.9   3.9   11.2
30 to 59 Days Past Due | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 10.4   10.4   2.4
30 to 59 Days Past Due | Other, including overdrafts          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   0.0
30 to 59 Days Past Due | Loans And Leases Held For Investment [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 39.2   39.2   46.1
30 to 59 Days Past Due | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.8   0.8   0.6
30 to 59 Days Past Due | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   0.7
60 to 89 Days Past Due          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Nonaccrual loans 9.7   9.7   6.2
60 to 89 Days Past Due | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 4.4   4.4   2.8
60 to 89 Days Past Due | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.3   0.3   0.0
60 to 89 Days Past Due | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 1.5   1.5   2.7
60 to 89 Days Past Due | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 1.2   1.2   2.8
60 to 89 Days Past Due | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 7.4   7.4   8.3
60 to 89 Days Past Due | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 2.1   2.1   2.6
60 to 89 Days Past Due | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 2.4   2.4   3.3
60 to 89 Days Past Due | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 3.2   3.2   3.0
60 to 89 Days Past Due | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   2.8
60 to 89 Days Past Due | Other, including overdrafts          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   0.0
60 to 89 Days Past Due | Loans And Leases Held For Investment [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 13.0   13.0   17.4
60 to 89 Days Past Due | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.3   0.3   0.2
60 to 89 Days Past Due | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   0.5
Equal to or Greater than 90 Days Past Due          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Nonaccrual loans 74.7   74.7   40.5
Equal to or Greater than 90 Days Past Due | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.1   0.1   0.0
Equal to or Greater than 90 Days Past Due | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   0.0
Equal to or Greater than 90 Days Past Due | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   0.4
Equal to or Greater than 90 Days Past Due | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.1   0.1   0.0
Equal to or Greater than 90 Days Past Due | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.2   0.2   0.4
Equal to or Greater than 90 Days Past Due | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.6   0.6   0.7
Equal to or Greater than 90 Days Past Due | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.7   0.7   2.0
Equal to or Greater than 90 Days Past Due | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.5   0.5   0.6
Equal to or Greater than 90 Days Past Due | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   0.0
Equal to or Greater than 90 Days Past Due | Other, including overdrafts          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   0.0
Equal to or Greater than 90 Days Past Due | Loans And Leases Held For Investment [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 1.4   1.4   3.0
Equal to or Greater than 90 Days Past Due | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.1   0.1   0.3
Equal to or Greater than 90 Days Past Due | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 0.0   0.0   1.0
Financial Asset, Not Past Due | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 8,664.5   8,664.5   9,200.1
Financial Asset, Not Past Due | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 991.0   991.0   1,237.6
Financial Asset, Not Past Due | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 2,138.1   2,138.1   2,166.5
Financial Asset, Not Past Due | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 608.4   608.4   685.4
Financial Asset, Not Past Due | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 12,402.0   12,402.0   13,289.6
Financial Asset, Not Past Due | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 593.5   593.5   709.4
Financial Asset, Not Past Due | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 726.2   726.2   917.1
Financial Asset, Not Past Due | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 2,477.9   2,477.9   2,781.1
Financial Asset, Not Past Due | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 509.0   509.0   661.8
Financial Asset, Not Past Due | Other, including overdrafts          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 2.0   2.0   1.6
Financial Asset, Not Past Due | Loans And Leases Held For Investment [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 16,117.1   16,117.1   17,651.2
Financial Asset, Not Past Due | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process 132.7   132.7   132.3
Financial Asset, Not Past Due | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Loan in Process $ 0.0   0.0   75.4
Year One, Originated, Current Fiscal Year          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     2.1   22.5
Year One, Originated, Current Fiscal Year | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.2
Year One, Originated, Current Fiscal Year | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff         0.0
Year One, Originated, Current Fiscal Year | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year One, Originated, Current Fiscal Year | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.2
Year One, Originated, Current Fiscal Year | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.5
Year One, Originated, Current Fiscal Year | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.1   0.7
Year One, Originated, Current Fiscal Year | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   21.6
Year One, Originated, Current Fiscal Year | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     2.0   0.0
Year One, Originated, Current Fiscal Year | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.1   0.2
Year One, Originated, Current Fiscal Year | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year Two, Originated, Fiscal Year Before Current Fiscal Year          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     5.3   10.7
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   5.7
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff         0.0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.2   0.2
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.2   5.9
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.2   2.0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.7   2.6
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.5   2.2
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     2.9   0.0
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.5   0.6
Year Two, Originated, Fiscal Year Before Current Fiscal Year | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year Three, Originated, Two Years before Current Fiscal Year          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     3.8   18.7
Year Three, Originated, Two Years before Current Fiscal Year | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year Three, Originated, Two Years before Current Fiscal Year | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff         13.1
Year Three, Originated, Two Years before Current Fiscal Year | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.1   0.2
Year Three, Originated, Two Years before Current Fiscal Year | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.1   13.3
Year Three, Originated, Two Years before Current Fiscal Year | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.5   3.4
Year Three, Originated, Two Years before Current Fiscal Year | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.8   4.3
Year Three, Originated, Two Years before Current Fiscal Year | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.9   1.1
Year Three, Originated, Two Years before Current Fiscal Year | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year Three, Originated, Two Years before Current Fiscal Year | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.3   0.9
Year Three, Originated, Two Years before Current Fiscal Year | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year Four, Originated, Three Years before Current Fiscal Year          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     2.2   21.4
Year Four, Originated, Three Years before Current Fiscal Year | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.2   19.4
Year Four, Originated, Three Years before Current Fiscal Year | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff         0.0
Year Four, Originated, Three Years before Current Fiscal Year | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.3   0.1
Year Four, Originated, Three Years before Current Fiscal Year | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.5   19.5
Year Four, Originated, Three Years before Current Fiscal Year | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.2   1.1
Year Four, Originated, Three Years before Current Fiscal Year | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.3   1.3
Year Four, Originated, Three Years before Current Fiscal Year | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.4   0.3
Year Four, Originated, Three Years before Current Fiscal Year | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.3
Year Four, Originated, Three Years before Current Fiscal Year | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.1   0.2
Year Four, Originated, Three Years before Current Fiscal Year | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year Five, Originated, Four Years before Current Fiscal Year          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     3.3   0.9
Year Five, Originated, Four Years before Current Fiscal Year | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     2.5   0.0
Year Five, Originated, Four Years before Current Fiscal Year | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff         0.1
Year Five, Originated, Four Years before Current Fiscal Year | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.1   0.3
Year Five, Originated, Four Years before Current Fiscal Year | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     2.6   0.4
Year Five, Originated, Four Years before Current Fiscal Year | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.4   0.4
Year Five, Originated, Four Years before Current Fiscal Year | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.4   0.4
Year Five, Originated, Four Years before Current Fiscal Year | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.3   0.1
Year Five, Originated, Four Years before Current Fiscal Year | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year Five, Originated, Four Years before Current Fiscal Year | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Year Five, Originated, Four Years before Current Fiscal Year | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Originated, More than Five Years before Current Fiscal Year          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     2.4   3.3
Originated, More than Five Years before Current Fiscal Year | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.1   0.1
Originated, More than Five Years before Current Fiscal Year | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff         0.0
Originated, More than Five Years before Current Fiscal Year | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.2
Originated, More than Five Years before Current Fiscal Year | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.1   0.3
Originated, More than Five Years before Current Fiscal Year | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.5   1.1
Originated, More than Five Years before Current Fiscal Year | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.5   2.9
Originated, More than Five Years before Current Fiscal Year | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.8   0.1
Originated, More than Five Years before Current Fiscal Year | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Originated, More than Five Years before Current Fiscal Year | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.0   1.8
Originated, More than Five Years before Current Fiscal Year | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     4.7   34.2
Revolving | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff         0.0
Revolving | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     3.5   3.1
Revolving | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     1.2   31.1
Revolving | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.1
Revolving | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     3.5   3.0
Revolving, Converted to Term          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   3.0
Revolving, Converted to Term | Commercial real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving, Converted to Term | Total construction loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff         0.0
Revolving, Converted to Term | Residential          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving, Converted to Term | Total real estate          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving, Converted to Term | Indirect consumer          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving, Converted to Term | Total consumer loans          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.1
Revolving, Converted to Term | Commercial          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   2.9
Revolving, Converted to Term | Agricultural          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.0
Revolving, Converted to Term | Consumer Loan          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     0.0   0.1
Revolving, Converted to Term | Credit Card Receivable [Member]          
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]          
Financing Receivable, Allowance for Credit Loss, Writeoff     $ 0.0   $ 0.0