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Loans - Schedule of Recorded Investment in Impaired Loans (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2020 | Dec. 31, 2017
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Total Recorded Investment | $ 63.5 |  |  |  |
Average Recorded Investment |  | $ 64.7 | $ 74.0 |  |
Accounts Receivable, Allowance for Credit Loss | 144.3 | 73.0 | 73.0 | $ 73.0 | $ 72.1
Provision charged (credited) to operating expense | (56.9) | (13.9) | (8.6) |  |
Less loans charged-off | (20.9) | (23.6) | (19.7) |  |
Add back recoveries of loans previously charged-off |  | 9.7 | 12.0 |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 17.5 |  |  |  |
Individually evaluated for impairment |  | 3.6 | 6.8 |  |
Collectively evaluated for impairment |  | 69.4 | 66.2 |  |
Loans and Leases Receivable, Allowance | 144.3 | 73.0 | 73.0 |  |
Individually evaluated for impairment |  | 64.7 | 64.8 |  |
Collectively evaluated for impairment |  | 8,871.5 | 8,410.0 |  |
Loans And Leases Receivable Held For Investment, Evaluated for Impairment |  | 8,936.2 | 8,474.8 |  |
Impaired Financing Receivable, Interest Income, Accrual Method | 0.0 | 0.3 | 0.3 |  |
Business Assets Pledged as Collateral |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 7.4 |  |  |  |
Real Property Pledged as Collateral |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 8.6 |  |  |  |
Other Property |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 1.5 |  |  |  |
Real Estate |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  | 28.9 | 31.0 |  | 31.7
Provision charged (credited) to operating expense |  | (1.3) | (0.7) |  |
Less loans charged-off |  | (3.5) | (3.7) |  |
Add back recoveries of loans previously charged-off |  | 2.7 | 3.7 |  |
Individually evaluated for impairment |  | 1.7 | 1.3 |  |
Collectively evaluated for impairment |  | 27.2 | 29.7 |  |
Loans and Leases Receivable, Allowance |  | 28.9 | 31.0 |  |
Individually evaluated for impairment |  | 41.1 | 41.8 |  |
Collectively evaluated for impairment |  | 5,897.1 | 5,546.1 |  |
Loans And Leases Receivable Held For Investment, Evaluated for Impairment |  | 5,938.2 | 5,587.9 |  |
Total consumer loans |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  | 9.9 | 8.7 |  | 8.7
Provision charged (credited) to operating expense |  | (10.6) | (6.8) |  |
Less loans charged-off |  | (13.0) | (11.3) |  |
Add back recoveries of loans previously charged-off |  | 3.6 | 4.5 |  |
Individually evaluated for impairment |  | 0.0 | 0.0 |  |
Collectively evaluated for impairment |  | 9.9 | 8.7 |  |
Loans and Leases Receivable, Allowance |  | 9.9 | 8.7 |  |
Individually evaluated for impairment |  | 0.0 | 0.0 |  |
Collectively evaluated for impairment |  | 1,045.2 | 1,070.2 |  |
Loans And Leases Receivable Held For Investment, Evaluated for Impairment |  | 1,045.2 | 1,070.2 |  |
Commercial Portfolio Segment [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  | 32.6 | 31.3 |  | 30.5
Provision charged (credited) to operating expense |  | (4.5) | (1.9) |  |
Less loans charged-off |  | (6.6) | (4.7) |  |
Add back recoveries of loans previously charged-off |  | 3.4 | 3.6 |  |
Individually evaluated for impairment |  | 1.7 | 5.2 |  |
Collectively evaluated for impairment |  | 30.9 | 26.1 |  |
Loans and Leases Receivable, Allowance |  | 32.6 | 31.3 |  |
Individually evaluated for impairment |  | 17.3 | 19.9 |  |
Collectively evaluated for impairment |  | 1,656.4 | 1,540.4 |  |
Loans And Leases Receivable Held For Investment, Evaluated for Impairment |  | 1,673.7 | 1,560.3 |  |
Agriculture |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  | 1.6 | 2.0 |  | 1.2
Provision charged (credited) to operating expense |  | (0.1) | (0.6) |  |
Less loans charged-off |  | (0.5) | 0.0 |  |
Add back recoveries of loans previously charged-off |  | 0.0 | 0.2 |  |
Individually evaluated for impairment |  | 0.2 | 0.3 |  |
Collectively evaluated for impairment |  | 1.4 | 1.7 |  |
Loans and Leases Receivable, Allowance |  | 1.6 | 2.0 |  |
Individually evaluated for impairment |  | 6.3 | 3.1 |  |
Collectively evaluated for impairment |  | 272.8 | 251.7 |  |
Loans And Leases Receivable Held For Investment, Evaluated for Impairment |  | 279.1 | 254.8 |  |
Other Segments |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  | 0.0 | 0.0 |  | $ 0.0
Provision charged (credited) to operating expense |  | 0.0 | 0.0 |  |
Less loans charged-off |  | 0.0 | 0.0 |  |
Add back recoveries of loans previously charged-off |  | 0.0 | 0.0 |  |
Other |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Individually evaluated for impairment |  | 0.0 | 0.0 |  |
Collectively evaluated for impairment |  | 0.0 | 0.0 |  |
Loans and Leases Receivable, Allowance |  | 0.0 | 0.0 |  |
Individually evaluated for impairment |  | 0.0 | 0.0 |  |
Collectively evaluated for impairment |  | 0.0 | 1.6 |  |
Loans And Leases Receivable Held For Investment, Evaluated for Impairment |  | 0.0 | 1.6 |  |
Commercial Real Estate Portfolio Segment [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 12.9 | 8.6 |  |
Recorded Investment With Allowance |  | 10.8 | 7.7 |  |
Total Recorded Investment |  | 23.7 | 16.3 |  |
Related Allowance |  | 0.7 | 0.7 |  |
Accounts Receivable, Allowance for Credit Loss | 54.8 |  |  | 19.5 |
Less loans charged-off | (0.4) |  |  |  |
Unpaid Total Principal Balance |  | 29.2 | 22.2 |  |
Land Acquisition And Development Construction Financing Receivable [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 0.4 | 0.4 |  |
Recorded Investment With Allowance |  | 2.6 | 3.5 |  |
Total Recorded Investment |  | 3.0 | 3.9 |  |
Related Allowance |  | 0.5 | 0.2 |  |
Accounts Receivable, Allowance for Credit Loss | 1.3 |  |  | 1.9 |
Less loans charged-off | (0.5) |  |  |  |
Unpaid Total Principal Balance |  | 9.2 | 10.0 |  |
Residential Real Estate Construction Financing Receivable [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 0.0 | 0.6 |  |
Recorded Investment With Allowance |  | 0.0 | 0.4 |  |
Total Recorded Investment |  | 0.0 | 1.0 |  |
Related Allowance |  | 0.0 | 0.1 |  |
Accounts Receivable, Allowance for Credit Loss | 1.6 |  |  | 1.5 |
Less loans charged-off | 0.0 |  |  |  |
Unpaid Total Principal Balance |  | 0.1 | 1.1 |  |
Commercial Real Estate Construction [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 0.5 | 0.2 |  |
Recorded Investment With Allowance |  | 0.0 | 0.0 |  |
Total Recorded Investment |  | 0.5 | 0.2 |  |
Related Allowance |  | 0.1 | 0.0 |  |
Accounts Receivable, Allowance for Credit Loss | 7.3 |  |  | 2.7 |
Less loans charged-off | 0.0 |  |  |  |
Unpaid Total Principal Balance |  | 1.0 | 0.7 |  |
Real Estate Construction Financing Receivable [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 0.9 | 1.2 |  |
Recorded Investment With Allowance |  | 2.6 | 3.9 |  |
Total Recorded Investment |  | 3.5 | 5.1 |  |
Related Allowance |  | 0.6 | 0.3 |  |
Unpaid Total Principal Balance |  | 10.3 | 11.8 |  |
Agricultural Real Estate Financing Receivable [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 5.2 | 12.5 |  |
Recorded Investment With Allowance |  | 3.0 | 0.2 |  |
Total Recorded Investment |  | 8.2 | 12.7 |  |
Related Allowance |  | 0.2 | 0.0 |  |
Accounts Receivable, Allowance for Credit Loss | 2.7 |  |  | 0.5 |
Less loans charged-off | 0.0 |  |  |  |
Unpaid Total Principal Balance |  | 8.6 | 12.9 |  |
Real Estate Financing Receivable [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 22.9 | 28.0 |  |
Recorded Investment With Allowance |  | 18.2 | 13.8 |  |
Total Recorded Investment |  | 41.1 | 41.8 |  |
Related Allowance |  | 1.7 | 1.3 |  |
Average Recorded Investment |  | 41.4 | 50.0 |  |
Accounts Receivable, Allowance for Credit Loss | 80.5 |  |  | 28.9 |
Less loans charged-off | (0.9) |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 8.9 |  |  |  |
Unpaid Total Principal Balance |  | 55.0 | 55.7 |  |
Impaired Financing Receivable, Interest Income, Accrual Method |  | 0.1 | 0.1 |  |
Real Estate Financing Receivable [Member] | Business Assets Pledged as Collateral |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 1.3 |  |  |  |
Real Estate Financing Receivable [Member] | Real Property Pledged as Collateral |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 6.5 |  |  |  |
Real Estate Financing Receivable [Member] | Other Property |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 1.1 |  |  |  |
Agricultural Financing Receivable [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 2.3 | 2.5 |  |
Recorded Investment With Allowance |  | 4.0 | 0.6 |  |
Total Recorded Investment |  | 6.3 | 3.1 |  |
Related Allowance |  | 0.2 | 0.3 |  |
Average Recorded Investment |  | 4.6 | 2.1 |  |
Accounts Receivable, Allowance for Credit Loss | 0.7 |  |  | 1.6 |
Less loans charged-off | (0.1) |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 0.8 |  |  |  |
Unpaid Total Principal Balance |  | 6.9 | 3.2 |  |
Impaired Financing Receivable, Interest Income, Accrual Method |  | 0.0 | 0.0 |  |
Agricultural Financing Receivable [Member] | Business Assets Pledged as Collateral |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 0.0 |  |  |  |
Agricultural Financing Receivable [Member] | Real Property Pledged as Collateral |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 0.8 |  |  |  |
Agricultural Financing Receivable [Member] | Other Property |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 0.0 |  |  |  |
Residential Real Estate |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 3.9 | 5.7 |  |
Recorded Investment With Allowance |  | 1.8 | 2.0 |  |
Total Recorded Investment |  | 5.7 | 7.7 |  |
Related Allowance |  | 0.2 | 0.3 |  |
Accounts Receivable, Allowance for Credit Loss | 12.8 |  |  | 2.8 |
Less loans charged-off | 0.0 |  |  |  |
Unpaid Total Principal Balance |  | 6.9 | 8.8 |  |
Commercial Portfolio Segment [Member] |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 12.0 | 5.5 |  |
Recorded Investment With Allowance |  | 5.3 | 14.4 |  |
Total Recorded Investment |  | 17.3 | 19.9 |  |
Related Allowance |  | 1.7 | 5.2 |  |
Average Recorded Investment |  | 18.7 | 21.9 |  |
Accounts Receivable, Allowance for Credit Loss | 39.2 |  |  | $ 32.6 |
Less loans charged-off | (9.1) |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 7.8 |  |  |  |
Unpaid Total Principal Balance |  | 25.5 | 24.1 |  |
Impaired Financing Receivable, Interest Income, Accrual Method |  | 0.2 | 0.2 |  |
Commercial Portfolio Segment [Member] | Business Assets Pledged as Collateral |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 6.1 |  |  |  |
Commercial Portfolio Segment [Member] | Real Property Pledged as Collateral |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | 1.3 |  |  |  |
Commercial Portfolio Segment [Member] | Other Property |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Loans and Leases Receivable, Collateral for Secured Borrowings | $ 0.4 |  |  |  |
Loans held for investment |  |  |  |  |
Impaired Financing Receivable, Unpaid Principal Balance |  |  |  |  |
Recorded Investment With No Allowance |  | 37.2 | 36.0 |  |
Recorded Investment With Allowance |  | 27.5 | 28.8 |  |
Total Recorded Investment |  | 64.7 | 64.8 |  |
Related Allowance |  | 3.6 | 6.8 |  |
Unpaid Total Principal Balance |  | $ 87.4 | $ 83.0 |  |

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