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Income Taxes (Details) - USD ($) $ in Millions | 6 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Jun. 30, 2023 | Sep. 30, 2022 | Feb. 28, 2023
Income Tax Contingency [Line Items] |  |  |
Deferred Tax Assets, Net | $ 362.9 |  |
Effective Tax Rate as a Percentage of pre-tax Income (loss) | 25.50% | 25.10% |
Umpqua Bank and Columbia Banking System Merger |  |  |
Income Tax Contingency [Line Items] |  |  |
Deferred Tax Assets, Net |  |  | $ 254.9
State and Local Jurisdiction |  |  |
Income Tax Contingency [Line Items] |  |  |
Operating Loss Carryforwards | $ 2.7 |  |

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- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482685/740-10-50-2 + Details
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