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Goodwill and Core Deposit Intangibles - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items] |  |  |
2023 | $ 15.6 |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Gross other intangible assets, at beginning of the period |  | $ 106.0 | $ 106.0
Provisional amounts established through acquisition | 72.9 |  |
Finite-Lived Intangible Assets, Period Increase (Decrease) | (1.4) |  |
Accumulated amortization | (76.5) | (64.7) |
Net other intangible assets, end of period | 101.0 | 41.3 |
Core Deposits |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
2023 | 13.7 |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Gross other intangible assets, at beginning of the period |  | 106.0 | 106.0
Provisional amounts established through acquisition | 50.1 |  |
Finite-Lived Intangible Assets, Period Increase (Decrease) | (1.4) |  |
Accumulated amortization | (75.2) | (64.7) |
Net other intangible assets, end of period | 79.5 | 41.3 |
OCRI |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
2023 | 1.9 |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Gross other intangible assets, at beginning of the period |  | 0.0 | $ 0.0
Provisional amounts established through acquisition | 22.8 |  |
Finite-Lived Intangible Assets, Period Increase (Decrease) | 0.0 |  |
Accumulated amortization | (1.3) | 0.0 |
Net other intangible assets, end of period | $ 21.5 | $ 0.0 |

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