Fair Value Measurement (Narrative) (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
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| Fair Value Disclosures [Abstract] | ||||
| Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset | $ 6 | $ 5 | $ 17 | $ 17 |
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||||
| Net increase (decrease) in fair value | (3) | 4 | (6) | 11 |
| Unrealized losses arising during the period | (14) | (8) | (15) | 0 |
| Changes in unrealized gains and losses on junior subordinated debentures carried at fair value, net of taxes | (10) | (6) | (11) | 0 |
| Location, Statement of Income, Balance [Axis]: colb:ResidentialMortgageBankingRevenueLossNet | ||||
| Fair Value, Option, Quantitative Disclosures [Line Items] | ||||
| Net increase (decrease) in fair value | $ (1) | $ 0 | $ 14 | $ 1 |
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- Definition Amount of contractually specified servicing fee, late fee, and ancillary fee recognized as income for servicing asset and servicing liability. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References No definition available.
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- Definition For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, after tax, before reclassification adjustment, of unrealized gain (loss) from increase (decrease) in instrument-specific credit risk of financial liability measured under fair value option. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, before tax and reclassification adjustment, of unrealized gain (loss) from increase (decrease) in instrument-specific credit risk of financial liability measured under fair value option. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Details
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