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Investment Tax Credit (Narrative) (Details) - USD ($) | Dec. 31, 2023 | Feb. 28, 2023 | Dec. 31, 2022 | Dec. 31, 2021
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Asset Acquisition [Line Items] |  |  |  |
Unfunded affordable housing tax credit commitments | $ 114,082,000 |  | $ 81,632,000 |
Proportional amortization | 210,873,000 |  | 143,719,000 |
Tax credit impairment adjustment | $ 0 |  | $ 0 | $ 0
Umpqua Bank and Columbia Banking System Merger |  |  |  |
Asset Acquisition [Line Items] |  |  |  |
Unfunded affordable housing tax credit commitments |  | $ 40,900,000 |  |
Proportional amortization |  | $ 47,200,000 |  |

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- Definition Amount of investment in qualified affordable housing projects. + References Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Topic 323 -SubTopic 740 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481543/323-740-50-2 + Details
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- Definition Amount of commitment or contingent commitments to qualified affordable housing project investments. + References Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Topic 323 -SubTopic 740 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481543/323-740-50-2 + Details
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