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Loans - Schedule of Contractual Aging of Loans by Portfolio (Details) - USD ($) $ in Millions | 6 Months Ended |
--- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Dec. 31, 2019
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Total Loans |  |  | $ 8,936.2
Accrued interest reversal | $ 0.2 | $ 0.4 |
Credit card |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.5 |  | 2.1
Current Loans | 69.1 |  | 79.5
Nonaccrual Loans | 0.0 |  | 0.0
Total Loans | 70.6 |  | 81.6
Commercial real estate |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 7.1 |  | 7.2
Current Loans | 3,573.7 |  | 3,467.6
Nonaccrual Loans | 13.0 |  | 13.0
Total Loans | 3,593.8 |  | 3,487.8
Indirect consumer |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 4.9 |  | 10.0
Current Loans | 795.0 |  | 773.0
Nonaccrual Loans | 2.0 |  | 1.6
Total Loans | 801.9 |  | 784.6
Direct and advance lines |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.9 |  | 1.8
Current Loans | 167.7 |  | 176.7
Nonaccrual Loans | 0.7 |  | 0.5
Total Loans | 169.3 |  | 179.0
Land acquisition & development |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 16.5 |  | 1.8
Current Loans | 268.1 |  | 298.9
Nonaccrual Loans | 0.7 |  | 1.4
Total Loans | 285.3 |  | 302.1
Residential construction |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 5.8 |  | 2.3
Current Loans | 240.4 |  | 241.8
Nonaccrual Loans | 0.0 |  | 0.0
Total Loans | 246.2 |  | 244.1
Commercial construction |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.0 |  | 0.0
Current Loans | 459.3 |  | 431.0
Nonaccrual Loans | 0.5 |  | 0.5
Total Loans | 459.8 |  | 431.5
Total construction loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 22.3 |  | 4.1
Current Loans | 967.8 |  | 971.7
Nonaccrual Loans | 1.2 |  | 1.9
Total Loans | 991.3 |  | 977.7
Residential |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 8.2 |  | 6.3
Current Loans | 1,275.4 |  | 1,235.2
Nonaccrual Loans | 4.0 |  | 4.6
Total Loans | 1,287.6 |  | 1,246.1
Agricultural |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.0 |  | 1.3
Current Loans | 215.8 |  | 220.1
Nonaccrual Loans | 7.4 |  | 5.2
Total Loans | 224.2 |  | 226.6
Total real estate loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 38.6 |  | 18.9
Current Loans | 6,032.7 |  | 5,894.6
Nonaccrual Loans | 25.6 |  | 24.7
Total Loans | 6,096.9 |  | 5,938.2
Total consumer loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 7.3 |  | 13.9
Current Loans | 1,031.8 |  | 1,029.2
Nonaccrual Loans | 2.7 |  | 2.1
Total Loans | 1,041.8 |  | 1,045.2
Commercial |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 15.8 |  | 9.7
Current Loans | 2,614.3 |  | 1,650.3
Nonaccrual Loans | 18.5 |  | 13.7
Total Loans | 2,648.6 |  | 1,673.7
Agricultural |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 2.8 |  | 1.0
Current Loans | 276.9 |  | 275.7
Nonaccrual Loans | 3.1 |  | 2.4
Total Loans | 282.8 |  | 279.1
Other, including overdrafts |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.0 |  | 0.0
Current Loans | 3.7 |  | 0.0
Nonaccrual Loans | 0.0 |  | 0.0
Total Loans | 3.7 |  | 0.0
Loans And Leases Held For Investment [Member] |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 64.5 |  | 43.5
Current Loans | 9,959.4 |  | 8,849.8
Nonaccrual Loans | 49.9 |  | 42.9
Total Loans | 10,073.8 |  | 8,936.2
30 to 59 Days Past Due | Credit card |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.6 |  | 0.8
30 to 59 Days Past Due | Commercial real estate |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 5.1 |  | 5.5
30 to 59 Days Past Due | Indirect consumer |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 3.6 |  | 7.6
30 to 59 Days Past Due | Direct and advance lines |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.5 |  | 1.2
30 to 59 Days Past Due | Land acquisition & development |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 15.8 |  | 0.7
30 to 59 Days Past Due | Residential construction |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 4.7 |  | 1.5
30 to 59 Days Past Due | Commercial construction |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.0 |  | 0.0
30 to 59 Days Past Due | Total construction loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 20.5 |  | 2.2
30 to 59 Days Past Due | Residential |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 4.6 |  | 3.8
30 to 59 Days Past Due | Agricultural |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.0 |  | 0.8
30 to 59 Days Past Due | Total real estate loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 30.2 |  | 12.3
30 to 59 Days Past Due | Total consumer loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 4.7 |  | 9.6
30 to 59 Days Past Due | Commercial |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 7.1 |  | 4.8
30 to 59 Days Past Due | Agricultural |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.5 |  | 0.9
30 to 59 Days Past Due | Other, including overdrafts |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 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] |  |  |
Past Due | 43.5 |  | 27.6
60 to 89 Days Past Due | Credit card |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.3 |  | 0.5
60 to 89 Days Past Due | Commercial real estate |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.2 |  | 1.1
60 to 89 Days Past Due | Indirect consumer |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.1 |  | 1.9
60 to 89 Days Past Due | Direct and advance lines |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.2 |  | 0.5
60 to 89 Days Past Due | Land acquisition & development |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.4 |  | 0.8
60 to 89 Days Past Due | Residential construction |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.6 |  | 0.8
60 to 89 Days Past Due | Commercial construction |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.0 |  | 0.0
60 to 89 Days Past Due | Total construction loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.0 |  | 1.6
60 to 89 Days Past Due | Residential |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 3.3 |  | 1.4
60 to 89 Days Past Due | Agricultural |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.0 |  | 0.5
60 to 89 Days Past Due | Total real estate loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 5.5 |  | 4.6
60 to 89 Days Past Due | Total consumer loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.6 |  | 2.9
60 to 89 Days Past Due | Commercial |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 5.6 |  | 2.6
60 to 89 Days Past Due | Agricultural |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.6 |  | 0.1
60 to 89 Days Past Due | Other, including overdrafts |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 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] |  |  |
Past Due | 13.3 |  | 10.2
Equal to or Greater than 90 Days Past Due | Credit card |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.6 |  | 0.8
Equal to or Greater than 90 Days Past Due | Commercial real estate |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.8 |  | 0.6
Equal to or Greater than 90 Days Past Due | Indirect consumer |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.2 |  | 0.5
Equal to or Greater than 90 Days Past Due | Direct and advance lines |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.2 |  | 0.1
Equal to or Greater than 90 Days Past Due | Land acquisition & development |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.3 |  | 0.3
Equal to or Greater than 90 Days Past Due | Residential construction |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.5 |  | 0.0
Equal to or Greater than 90 Days Past Due | Commercial construction |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.0 |  | 0.0
Equal to or Greater than 90 Days Past Due | Total construction loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.8 |  | 0.3
Equal to or Greater than 90 Days Past Due | Residential |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.3 |  | 1.1
Equal to or Greater than 90 Days Past Due | Agricultural |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.0 |  | 0.0
Equal to or Greater than 90 Days Past Due | Total real estate loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 2.9 |  | 2.0
Equal to or Greater than 90 Days Past Due | Total consumer loans |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 1.0 |  | 1.4
Equal to or Greater than 90 Days Past Due | Commercial |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 3.1 |  | 2.3
Equal to or Greater than 90 Days Past Due | Agricultural |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 0.7 |  | 0.0
Equal to or Greater than 90 Days Past Due | Other, including overdrafts |  |  |
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items] |  |  |
Past Due | 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] |  |  |
Past Due | $ 7.7 |  | $ 5.7

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