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Loans - Schedule of Loans by Class (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Sep. 30, 2021 | Dec. 31, 2018
Loans and Leases Receivable |  |  |  |
Loans and Leases Receivable, Deferred Income | $ (12.3) | $ (21.0) |  |
Mortgage loans held for sale, at fair value | 30.1 | 74.0 |  |
Total loans | 9,331.7 | 9,807.5 |  |
Accounts Receivable, Allowance for Credit Loss | (122.3) | (144.3) | $ (144.3) | $ (73.0)
Loans and Leases Receivable, Net Amount | 9,209.4 | 9,663.2 |  |
Less loans charged-off | 14.7 | (55.5) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 16.6 | 20.9 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 30.0 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance | 144.3 | 73.0 |  |
Provision for Loan, Lease, and Other Losses | (14.7) | 55.5 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 9.3 | 6.7 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 122.3 | 144.3 |  |
Commercial Real Estate Portfolio Segment [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 3,971.5 | 3,743.2 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (54.8) |
Less loans charged-off | 8.7 | (20.1) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 2.3 | 0.4 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 15.3 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 19.5 |  |
Provision for Loan, Lease, and Other Losses | (8.7) | 20.1 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.1 | 0.3 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 43.9 | 54.8 |  |
Residential Real Estate Construction Financing Receivable [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 262.0 | 250.9 |  |
Total loans | 262.0 | 250.9 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (1.6) |
Less loans charged-off | (0.9) | (1.0) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.1 | 0.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 0.9 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 1.5 |  |
Provision for Loan, Lease, and Other Losses | 0.9 | 1.0 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.0 | 0.0 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 2.4 | 1.6 |  |
Commercial Real Estate Construction [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 498.0 | 523.5 |  |
Total loans | 498.0 | 523.5 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (7.3) |
Less loans charged-off | 1.3 | (3.3) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.1 | 0.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 1.3 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 2.7 |  |
Provision for Loan, Lease, and Other Losses | (1.3) | 3.3 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.1 | 0.0 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 6.0 | 7.3 |  |
Real Estate Construction Financing Receivable [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 1,007.8 | 1,039.4 |  |
Residential Mortgage [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 1,538.2 | 1,396.3 |  |
Agricultural Real Estate Financing Receivable [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 213.9 | 220.6 |  |
Total loans | 213.9 | 220.6 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (2.7) |
Less loans charged-off | 0.1 | (0.4) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.7 | 0.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 1.8 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 0.5 |  |
Provision for Loan, Lease, and Other Losses | (0.1) | 0.4 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.0 | 0.0 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 1.9 | 2.7 |  |
Real Estate Financing Receivable [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 6,731.4 | 6,399.5 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (80.5) |
Less loans charged-off | 7.7 | (22.9) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 4.5 | 0.9 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 28.5 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 28.9 |  |
Provision for Loan, Lease, and Other Losses | (7.7) | 22.9 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 1.0 | 1.1 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 69.3 | 80.5 |  |
Indirect consumer |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 737.6 | 805.1 |  |
Total loans | 737.6 | 805.1 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (16.7) |
Less loans charged-off | 1.4 | (5.4) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 3.5 | 4.1 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 8.8 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 4.5 |  |
Provision for Loan, Lease, and Other Losses | (1.4) | 5.4 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 2.5 | 2.1 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 14.3 | 16.7 |  |
Other consumer |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 129.2 | 150.6 |  |
Total loans | 129.2 | 150.6 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (4.6) |
Less loans charged-off | (1.7) | (1.6) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 2.9 | 3.9 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 3.0 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 2.9 |  |
Provision for Loan, Lease, and Other Losses | 1.7 | 1.6 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 1.2 | 1.0 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 4.6 | 4.6 |  |
Credit card consumer |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 64.9 | 70.2 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (2.6) |
Less loans charged-off | (0.6) | (1.8) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 1.8 | 2.8 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 0.3 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 2.5 |  |
Provision for Loan, Lease, and Other Losses | 0.6 | 1.8 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.8 | 0.8 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 2.2 | 2.6 |  |
Total consumer loans |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 931.7 | 1,025.9 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (23.9) |
Less loans charged-off | (0.9) | (8.8) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 8.2 | 10.8 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 12.1 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 9.9 |  |
Provision for Loan, Lease, and Other Losses | 0.9 | 8.8 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 4.5 | 3.9 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 21.1 | 23.9 |  |
Commercial Portfolio Segment [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 1,475.5 | 2,153.9 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (39.2) |
Less loans charged-off | 7.7 | (24.0) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 3.7 | 9.1 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 10.0 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 32.6 |  |
Provision for Loan, Lease, and Other Losses | (7.7) | 24.0 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 3.8 | 1.7 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 31.6 | 39.2 |  |
Agricultural Financing Receivable [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 203.9 | 247.6 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (0.7) |
Less loans charged-off | 0.2 | 0.2 |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.2 | 0.1 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 0.6 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 1.6 |  |
Provision for Loan, Lease, and Other Losses | (0.2) | (0.2) |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.0 | 0.0 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 0.3 | 0.7 |  |
Other, including overdrafts |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 1.5 | 1.6 |  |
Loans held for investment |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 9,344.0 | 9,828.5 |  |
FIBK Commercial Real Estate Non Owner Occupied Loans |  |  |  |
Loans and Leases Receivable |  |  |  |
Total loans | 1,893.6 | 1,674.5 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (25.5) |
Less loans charged-off | 8.3 | (11.7) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.0 |  |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 4.9 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 8.8 |  |
Provision for Loan, Lease, and Other Losses | (8.3) | 11.7 |  |
Financing Receivable, Allowance for Credit Loss, Recovery |  | 0.1 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 17.3 | 25.5 |  |
FIBK Commercial Real Estate Non Owner Occupied Loans | Cumulative-Effect Adjustment, Consolidation of Variable Interest Entity |  |  |  |
Loans and Leases Receivable |  |  |  |
Financing Receivable, Allowance for Credit Loss, Writeoff |  | 0.0 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.1 |  |  |
Commercial Real Estate Owner Occupied |  |  |  |
Loans and Leases Receivable |  |  |  |
Total loans | 1,656.7 | 1,705.0 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (18.3) |
Less loans charged-off | 2.7 | (5.0) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 2.3 | 0.4 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 3.5 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 10.0 |  |
Provision for Loan, Lease, and Other Losses | (2.7) | 5.0 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.0 | 0.2 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 13.3 | 18.3 |  |
Commercial Real Estate Multifamily |  |  |  |
Loans and Leases Receivable |  |  |  |
Total loans | 421.2 | 363.7 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (11.0) |
Less loans charged-off | (2.3) | (3.4) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.0 | 0.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 6.9 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 0.7 |  |
Provision for Loan, Lease, and Other Losses | 2.3 | 3.4 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.0 | 0.0 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 13.3 | 11.0 |  |
Land Acquisition And Development Construction Financing Receivable [Member] |  |  |  |
Loans and Leases Receivable |  |  |  |
Loans held for investment | 247.8 | 265.0 |  |
Total loans | 247.8 | 265.0 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (1.3) |
Less loans charged-off | 0.1 | 0.4 |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 1.2 | 0.5 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 0.1 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 1.9 |  |
Provision for Loan, Lease, and Other Losses | (0.1) | (0.4) |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.5 | 0.4 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 0.5 | 1.3 |  |
Construction Loans |  |  |  |
Loans and Leases Receivable |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (10.2) |
Less loans charged-off | 0.5 | (3.9) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 1.4 | 0.5 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 0.3 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 6.1 |  |
Provision for Loan, Lease, and Other Losses | (0.5) | 3.9 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.6 | 0.4 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 8.9 | 10.2 |  |
Residential Real Estate 1-4 Family |  |  |  |
Loans and Leases Receivable |  |  |  |
Total loans | 1,143.6 | 1,012.3 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (11.4) |
Less loans charged-off | (2.0) | 1.1 |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.0 | 0.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | (10.6) |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 1.8 |  |
Provision for Loan, Lease, and Other Losses | 2.0 | (1.1) |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.0 | 0.1 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 13.4 | 11.4 |  |
Home Equity Loan |  |  |  |
Loans and Leases Receivable |  |  |  |
Total loans | 394.6 | 384.0 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (1.4) |
Less loans charged-off | 0.4 | 0.4 |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.1 | 0.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | (0.5) |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 1.0 |  |
Provision for Loan, Lease, and Other Losses | (0.4) | (0.4) |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.3 | 0.3 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 1.2 | 1.4 |  |
Residential Real Estate |  |  |  |
Loans and Leases Receivable |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (12.8) |
Less loans charged-off | (1.6) | 1.5 |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.1 | 0.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | (11.1) |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 2.8 |  |
Provision for Loan, Lease, and Other Losses | 1.6 | (1.5) |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.3 | 0.4 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 14.6 | 12.8 |  |
Commercial and Floor Plans |  |  |  |
Loans and Leases Receivable |  |  |  |
Total loans | 1,132.7 | 1,814.5 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (34.2) |
Less loans charged-off | 7.3 | (20.4) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 3.0 | 8.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 5.1 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 25.5 |  |
Provision for Loan, Lease, and Other Losses | (7.3) | 20.4 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 3.2 | 1.4 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 27.1 | 34.2 |  |
Commercial Purpose Secured by 1-4 Family |  |  |  |
Loans and Leases Receivable |  |  |  |
Total loans | 269.6 | 272.8 |  |
Accounts Receivable, Allowance for Credit Loss |  |  | (4.7) |
Less loans charged-off | 0.5 | (2.5) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.3 | 0.1 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 3.8 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 5.9 |  |
Provision for Loan, Lease, and Other Losses | (0.5) | 2.5 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.5 | 0.2 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | 4.4 | 4.7 |  |
Commercial Borrower |  |  |  |
Loans and Leases Receivable |  |  |  |
Accounts Receivable, Allowance for Credit Loss |  |  | $ (0.3) |
Less loans charged-off | (0.1) | (1.1) |  |
Financing Receivable, Allowance for Credit Loss, Writeoff | 0.4 | 1.0 |  |
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method |  | 1.1 |  |
Accounts Receivable, Allowance for Credit Loss, Beginning Balance |  | 1.2 |  |
Provision for Loan, Lease, and Other Losses | 0.1 | 1.1 |  |
Financing Receivable, Allowance for Credit Loss, Recovery | 0.1 | 0.1 |  |
Financing Receivable, Allowance for Credit Loss, Ending Balance | $ 0.1 | $ 0.3 |  |

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