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Loans - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2020 | Sep. 30, 2019
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | $ 5.2 | $ 2.6 | $ 53.7 | $ 10.1
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 146.1 | 74.2 | 73.0 | 73.0
Loans Charged-Off | (6.4) | (4.7) | (15.1) | (16.3)
Recoveries Collected | 1.8 |  | 5.1 |
Ending balance | 145.5 | $ 75.0 | 145.5 | $ 75.0
Loans and Leases Receivable, Allowance |  |  | 52.5 |
Non-owner occupied |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 1.5 |  | 11.4 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 23.6 |  | 8.8 |
Loans Charged-Off | 0.0 |  | 0.0 |
Recoveries Collected | 0.1 |  | 0.1 |
Ending balance | 25.2 |  | 25.2 |
Owner occupied |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.1 |  | 5.7 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 19.1 |  | 10.0 |
Loans Charged-Off | (0.2) |  | (0.3) |
Recoveries Collected | 0.1 |  | 0.2 |
Ending balance | 19.1 |  | 19.1 |
Multi-family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 2.3 |  | 3.2 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 8.5 |  | 0.7 |
Loans Charged-Off | 0.0 |  | 0.0 |
Recoveries Collected | 0.0 |  | 0.0 |
Ending balance | 10.8 |  | 10.8 |
Commercial real estate |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 3.9 |  | 20.3 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 51.2 |  | 19.5 |
Loans Charged-Off | (0.2) |  | (0.3) |
Recoveries Collected | 0.2 |  | 0.3 |
Ending balance | 55.1 |  | 55.1 |
Agricultural |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.0 |  | 0.0 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 0.9 |  | 1.6 |
Loans Charged-Off | 0.0 |  | (0.1) |
Recoveries Collected | 0.0 |  | 0.0 |
Ending balance | 0.9 |  | 0.9 |
Commercial and floor plans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 1.2 |  | 20.0 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 41.0 |  | 25.5 |
Loans Charged-Off | (3.3) |  | (4.7) |
Recoveries Collected | 0.2 |  | 1.0 |
Ending balance | 36.7 |  | 36.7 |
Commercial purpose secured by 1-4 family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.2 |  | 2.8 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 5.1 |  | 5.9 |
Loans Charged-Off | 0.0 |  | (0.1) |
Recoveries Collected | 0.1 |  | 0.2 |
Ending balance | 5.0 |  | 5.0 |
Land acquisition & development |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.5 |  | 0.3 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 1.5 |  | 1.9 |
Loans Charged-Off | 0.0 |  | (0.5) |
Recoveries Collected | 0.2 |  | 0.2 |
Ending balance | 1.2 |  | 1.2 |
Residential construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.3 |  | 1.0 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 1.3 |  | 1.5 |
Loans Charged-Off | 0.0 |  | 0.0 |
Recoveries Collected | 0.0 |  | 0.0 |
Ending balance | 1.6 |  | 1.6 |
Commercial construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.8 |  | 3.1 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 6.3 |  | 2.7 |
Loans Charged-Off | 0.0 |  | 0.0 |
Recoveries Collected | 0.0 |  | 0.0 |
Ending balance | 7.1 |  | 7.1 |
Total construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.6 |  | 3.8 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 9.1 |  | 6.1 |
Loans Charged-Off | 0.0 |  | (0.5) |
Recoveries Collected | 0.2 |  | 0.2 |
Ending balance | 9.9 |  | 9.9 |
Residential 1-4 family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 1.1 |  | 3.3 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 10.3 |  | 1.8 |
Loans Charged-Off | 0.0 |  | 0.0 |
Recoveries Collected | 0.0 |  | 0.1 |
Ending balance | 9.2 |  | 9.2 |
Home equity and HELOC |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.0 |  | 0.1 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 1.5 |  | 1.0 |
Loans Charged-Off | 0.0 |  | 0.0 |
Recoveries Collected | 0.0 |  | 0.1 |
Ending balance | 1.5 |  | 1.5 |
Residential |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 1.1 |  | 3.4 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 11.8 |  | 2.8 |
Loans Charged-Off | 0.0 |  | 0.0 |
Recoveries Collected | 0.0 |  | 0.2 |
Ending balance | 10.7 |  | 10.7 |
Agricultural |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.2 |  | 0.6 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 3.1 |  | 0.5 |
Loans Charged-Off | 0.0 |  | 0.0 |
Recoveries Collected | 0.0 |  | 0.0 |
Ending balance | 2.9 |  | 2.9 |
Total real estate loans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 3.2 |  | 21.3 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 75.2 |  | 28.9 |
Loans Charged-Off | (0.2) |  | (0.8) |
Recoveries Collected | 0.4 |  | 0.7 |
Ending balance | 78.6 |  | 78.6 |
Indirect consumer |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.7 |  | 5.1 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 16.4 |  | 4.5 |
Loans Charged-Off | (0.8) |  | (3.2) |
Recoveries Collected | 0.7 |  | 1.8 |
Ending balance | 17.0 |  | 17.0 |
Direct and advance lines |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.6 |  | 1.3 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 5.1 |  | 2.9 |
Loans Charged-Off | (1.1) |  | (3.1) |
Recoveries Collected | 0.2 |  | 0.7 |
Ending balance | 4.8 |  | 4.8 |
Credit card |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.6 |  | 1.0 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 2.0 |  | 2.5 |
Loans Charged-Off | (0.6) |  | (2.2) |
Recoveries Collected | 0.2 |  | 0.6 |
Ending balance | 2.2 |  | 2.2 |
Total consumer loans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 1.9 |  | 7.4 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 23.5 |  | 9.9 |
Loans Charged-Off | (2.5) |  | (8.5) |
Recoveries Collected | 1.1 |  | 3.1 |
Ending balance | 24.0 |  | 24.0 |
Credit card |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.3 |  | 1.0 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 0.4 |  | 1.2 |
Loans Charged-Off | (0.4) |  | (0.9) |
Recoveries Collected | 0.0 |  | 0.1 |
Ending balance | 0.3 |  | 0.3 |
Commercial |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 1.1 |  | 23.8 |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 46.5 |  | 32.6 |
Loans Charged-Off | (3.7) |  | (5.7) |
Recoveries Collected | 0.3 |  | 1.3 |
Ending balance | 42.0 |  | 42.0 |
Agriculture Portfolio Segment [Member] |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
Provision for credit losses | 0.0 |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 0.9 |  |  |
Loans Charged-Off | 0.0 |  |  |
Recoveries Collected | 0.0 |  |  |
Ending balance | 0.9 |  | 0.9 |
Cumulative Effect, Period of Adoption, Adjustment [Member] |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 30.0 |  | 30.0 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Non-owner occupied |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 4.9 |  | 4.9 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Owner occupied |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 3.5 |  | 3.5 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Multi-family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 6.9 |  | 6.9 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Commercial real estate |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 15.3 |  | 15.3 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Agricultural |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | (0.6) |  | (0.6) |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Commercial and floor plans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | (5.1) |  | (5.1) |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Commercial purpose secured by 1-4 family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | (3.8) |  | (3.8) |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Land acquisition & development |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | (0.1) |  | (0.1) |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Residential construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | (0.9) |  | (0.9) |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Commercial construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 1.3 |  | 1.3 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Total construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 0.3 |  | 0.3 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Residential 1-4 family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 10.6 |  | 10.6 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Home equity and HELOC |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 0.5 |  | 0.5 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Residential |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 11.1 |  | 11.1 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Agricultural |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 1.8 |  | 1.8 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Total real estate loans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 28.5 |  | 28.5 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Indirect consumer |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 8.8 |  | 8.8 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Direct and advance lines |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 3.0 |  | 3.0 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Credit card |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 0.3 |  | 0.3 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Total consumer loans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | 12.1 |  | 12.1 |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Credit card |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | (1.1) |  | (1.1) |
Cumulative Effect, Period of Adoption, Adjustment [Member] | Commercial |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Ending balance | $ (10.0) |  | $ (10.0) |

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