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Loans Held for Investment - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | $ 0.0 | $ (5.2) | $ 5.1 | $ (53.7)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 135.5 | 146.1 | 144.3 | 73.0
Loans Charged-Off | (2.1) | (6.4) | (11.8) | (15.1)
Recoveries Collected | 1.5 | 1.8 | 7.2 | 5.1
Ending balance | 135.1 | 145.5 | 135.1 | 145.5
Loans and Leases Receivable, Allowance |  |  | (4.6) |
Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 30.0
Non-owner occupied |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (1.1) | (1.5) | (1.6) | (11.4)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 22.9 | 23.6 | 25.5 | 8.8
Loans Charged-Off | 0.0 | 0.0 | 0.0 | 0.0
Recoveries Collected | 0.0 | 0.1 | 0.1 | 0.1
Ending balance | 24.0 | 25.2 | 24.0 | 25.2
Non-owner occupied | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 4.9
Owner occupied |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.6) | (0.1) | 0.0 | (5.7)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 16.6 | 19.1 | 18.3 | 10.0
Loans Charged-Off | 0.0 | (0.2) | (2.3) | (0.3)
Recoveries Collected | 0.0 | 0.1 | 0.0 | 0.2
Ending balance | 16.0 | 19.1 | 16.0 | 19.1
Owner occupied | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 3.5
Multi-family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.2) | (2.3) | (0.8) | (3.2)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 11.6 | 8.5 | 11.0 | 0.7
Loans Charged-Off | 0.0 | 0.0 | 0.0 | 0.0
Recoveries Collected | 0.0 | 0.0 | 0.0 | 0.0
Ending balance | 11.8 | 10.8 | 11.8 | 10.8
Multi-family | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 6.9
Commercial real estate |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.7) | (3.9) | (0.8) | (20.3)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 51.1 | 51.2 | 54.8 | 19.5
Loans Charged-Off | 0.0 | (0.2) | (2.3) | (0.3)
Recoveries Collected | 0.0 | 0.2 | 0.1 | 0.3
Ending balance | 51.8 | 55.1 | 51.8 | 55.1
Commercial real estate | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 15.3
Agricultural |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | 0.0 | 0.0 | (0.1) | 0.0
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 0.4 | 0.9 | 0.7 | 1.6
Loans Charged-Off | 0.0 | 0.0 | (0.2) | (0.1)
Recoveries Collected | 0.0 | 0.0 | 0.0 | 0.0
Ending balance | 0.4 | 0.9 | 0.4 | 0.9
Agricultural | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | (0.6)
Commercial and floor plans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.3) | (1.2) | (4.9) | (20.0)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 29.0 | 41.0 | 34.2 | 25.5
Loans Charged-Off | (0.1) | (3.3) | (2.2) | (4.7)
Recoveries Collected | 0.2 | 0.2 | 2.3 | 1.0
Ending balance | 29.4 | 36.7 | 29.4 | 36.7
Commercial and floor plans | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | (5.1)
Commercial purpose secured by 1-4 family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.2) | (0.2) | (0.8) | (2.8)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 4.4 | 5.1 | 4.7 | 5.9
Loans Charged-Off | 0.0 | 0.0 | (0.1) | (0.1)
Recoveries Collected | 0.0 | 0.1 | 0.4 | 0.2
Ending balance | 4.2 | 5.0 | 4.2 | 5.0
Commercial purpose secured by 1-4 family | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | (3.8)
Land acquisition & development |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.2) | (0.5) | (0.8) | (0.3)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 1.0 | 1.5 | 1.3 | 1.9
Loans Charged-Off | 0.0 | 0.0 | (0.1) | (0.5)
Recoveries Collected | 0.1 | 0.2 | 0.5 | 0.2
Ending balance | 0.9 | 1.2 | 0.9 | 1.2
Land acquisition & development | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | (0.1)
Residential construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.3) | (0.3) | (0.3) | (1.0)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 1.5 | 1.3 | 1.6 | 1.5
Loans Charged-Off | 0.0 | 0.0 | (0.1) | 0.0
Recoveries Collected | 0.0 | 0.0 | 0.0 | 0.0
Ending balance | 1.8 | 1.6 | 1.8 | 1.6
Residential construction | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | (0.9)
Commercial construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (1.3) | (0.8) | (0.6) | (3.1)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 8.0 | 6.3 | 7.3 | 2.7
Loans Charged-Off | 0.0 | 0.0 | (0.1) | 0.0
Recoveries Collected | 0.0 | 0.0 | 0.1 | 0.0
Ending balance | 6.7 | 7.1 | 6.7 | 7.1
Commercial construction | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 1.3
Total construction |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (1.2) | (0.6) | (1.1) | (3.8)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 10.5 | 9.1 | 10.2 | 6.1
Loans Charged-Off | 0.0 | 0.0 | (0.3) | (0.5)
Recoveries Collected | 0.1 | 0.2 | 0.6 | 0.2
Ending balance | 9.4 | 9.9 | 9.4 | 9.9
Total construction | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 0.3
Residential 1-4 family |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.2) | (1.1) | (1.8) | (3.3)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 13.4 | 10.3 | 11.4 | 1.8
Loans Charged-Off | 0.0 | 0.0 | 0.0 | 0.0
Recoveries Collected | 0.0 | 0.0 | 0.0 | 0.1
Ending balance | 13.2 | 9.2 | 13.2 | 9.2
Residential 1-4 family | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 10.6
Home equity and HELOC |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.1) | 0.0 | (0.2) | (0.1)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 1.4 | 1.5 | 1.4 | 1.0
Loans Charged-Off | 0.0 | 0.0 | (0.1) | 0.0
Recoveries Collected | 0.1 | 0.0 | 0.3 | 0.1
Ending balance | 1.4 | 1.5 | 1.4 | 1.5
Residential |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.3) | (1.1) | (1.6) | (3.4)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 14.8 | 11.8 | 12.8 | 2.8
Loans Charged-Off | 0.0 | 0.0 | (0.1) | 0.0
Recoveries Collected | 0.1 | 0.0 | 0.3 | 0.2
Ending balance | 14.6 | 10.7 | 14.6 | 10.7
Residential | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 11.1
Agricultural |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.1) | (0.2) | (0.4) | (0.6)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 3.0 | 3.1 | 2.7 | 0.5
Loans Charged-Off | 0.0 | 0.0 | 0.0 | 0.0
Recoveries Collected | 0.0 | 0.0 | 0.0 | 0.0
Ending balance | 3.1 | 2.9 | 3.1 | 2.9
Agricultural | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 1.8
Total real estate loans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.7) | (3.2) | (0.1) | (21.3)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 79.4 | 75.2 | 80.5 | 28.9
Loans Charged-Off | 0.0 | (0.2) | (2.7) | (0.8)
Recoveries Collected | 0.2 | 0.4 | 1.0 | 0.7
Ending balance | 78.9 | 78.6 | 78.9 | 78.6
Total real estate loans | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 28.5
Indirect consumer |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.1) | (0.7) | (0.3) | (5.1)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 15.8 | 16.4 | 16.7 | 4.5
Loans Charged-Off | (0.8) | (0.8) | (2.9) | (3.2)
Recoveries Collected | 0.5 | 0.7 | 1.9 | 1.8
Ending balance | 15.4 | 17.0 | 15.4 | 17.0
Indirect consumer | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 8.8
Direct and advance lines |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.5) | (0.6) | (1.2) | (1.3)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 4.6 | 5.1 | 4.6 | 2.9
Loans Charged-Off | (0.8) | (1.1) | (2.0) | (3.1)
Recoveries Collected | 0.4 | 0.2 | 0.9 | 0.7
Ending balance | 4.7 | 4.8 | 4.7 | 4.8
Direct and advance lines | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 3.0
Credit card |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.4) | (0.6) | 0.0 | (1.0)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 1.6 | 2.0 | 2.6 | 2.5
Loans Charged-Off | (0.4) | (0.6) | (1.4) | (2.2)
Recoveries Collected | 0.2 | 0.2 | 0.6 | 0.6
Ending balance | 1.8 | 2.2 | 1.8 | 2.2
Credit card | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 0.3
Total consumer loans |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.8) | (1.9) | (0.9) | (7.4)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 22.0 | 23.5 | 23.9 | 9.9
Loans Charged-Off | (2.0) | (2.5) | (6.3) | (8.5)
Recoveries Collected | 1.1 | 1.1 | 3.4 | 3.1
Ending balance | 21.9 | 24.0 | 21.9 | 24.0
Total consumer loans | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | 12.1
Credit card |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | 0.0 | (0.3) | (0.2) | (1.0)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 0.3 | 0.4 | 0.3 | 1.2
Loans Charged-Off | 0.0 | (0.4) | (0.3) | (0.9)
Recoveries Collected | 0.0 | 0.0 | 0.1 | 0.1
Ending balance | 0.3 | 0.3 | 0.3 | 0.3
Credit card | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | (1.1)
Commercial |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | (0.1) | (1.1) | (5.5) | (23.8)
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 33.7 | 46.5 | 39.2 | 32.6
Loans Charged-Off | (0.1) | (3.7) | (2.6) | (5.7)
Recoveries Collected | 0.2 | 0.3 | 2.8 | 1.3
Ending balance | 33.9 | 42.0 | 33.9 | 42.0
Commercial | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | (10.0)
Agriculture Portfolio Segment [Member] |  |  |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |  |  |
(Reversal of) provision for credit losses | 0.0 | 0.0 |  | 0.0
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance | 0.4 | 0.9 |  |
Loans Charged-Off | 0.0 | 0.0 |  | (0.1)
Recoveries Collected | 0.0 | 0.0 |  | 0.0
Ending balance | $ 0.4 | $ 0.9 | $ 0.4 | 0.9
Agriculture Portfolio Segment [Member] | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | (0.6)
Consumer Home Equity and HELOC | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Financing Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |
Beginning balance |  |  |  | $ 0.5

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