Entity tax identification number Entity Tax Identification Number Rollovers EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Maximum Maximum [Member] Legal Entity [Axis] Legal Entity [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] EBP, Description of Plan [Table] EBP, Description of Plan [Table] Registered investment companies Mutual Fund [Member] General loan, borrowing term EBP, Note Receivable From Participant, General Loan, Maximum Borrowing Term EBP, Note Receivable From Participant, General Loan, Maximum Borrowing Term Vesting Schedule EBP, Employer Contribution, Vesting Schedule [Table Text Block] EBP, Employer Contribution, Vesting Schedule Income recognition EBP, Income Recognition [Policy Text Block] EBP, Income Recognition Subsequent Event Subsequent Event [Member] EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Related Party and Party-in-Interest Transactions [Table] Maximum annual compensation to total compensation percentage EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage Self-directed brokerage accounts EBP, Self-Directed Brokerage Account [Member] Total deductions EBP, Change in Net Asset Available for Benefit, Decrease Maximum borrowing amount EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Fair Value Measurements EBP, Investment, Fair Value and NAV [Text Block] Minimum borrowing amount EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Cost EBP, Asset Held for Investment, Participant Loan, Cost EBP, Asset Held for Investment, Participant Loan, Cost Investments, at fair value EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Less than 1 year EBP, Employer Contribution, Vesting In Less Than One Year [Member] EBP, Employer Contribution, Vesting In Less Than One Year Subsequent Event Type [Domain] Subsequent Event Type [Domain] Money markets and other cash equivalents Money Market Funds [Member] Level 1 Fair Value, Inputs, Level 1 [Member] EBP, Vesting [Axis] EBP, Vesting [Axis] EBP, Vesting EBP, Investment, Fair Value and NAV [Abstract] Requisite service period, minimum hours EBP, Requisite Service Period, Minimum Hours EBP, Requisite Service Period, Minimum Hours Statistical Measurement [Axis] Statistical Measurement [Axis] EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Increase in net assets as a result of the transfer of assets EBP, Change in Net Asset Available for Benefit, Transfer to (from) Plan Payment of benefits EBP, Payment to Participant [Policy Text Block] Amendment Flag Amendment Flag Basis of Accounting EBP, Basis of Accounting [Policy Text Block] EBP, Schedule of Asset Held for Investment [Table] EBP, Schedule of Asset Held for Investment [Table] EBP, Description of Plan and Accounting Change [Abstract] Receivables EBP, Receivable [Abstract] EBP, Investment, Fair Value and NAV EBP, Investment, Fair Value and NAV [Table Text Block] Corrective distributions EBP, Change in Net Assets Available for Benefit, Decrease from Corrective Distribution EBP, Change in Net Assets Available for Benefit, Decrease from Corrective Distribution Investments [Domain] Investments [Domain] Use of Estimates EBP, Use of Estimate [Policy Text Block] Unsettled trades EBP, Unsettled Trades EBP, Unsettled Trades Schedule H, Line 4i – Schedule of Assets (Held At End of Year) EBP, Schedule of Asset Held for Investment [Text Block] Cover [Abstract] Risks and Uncertainties EBP, Risk and Uncertainty [Text Block] Employer EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Minimum Minimum [Member] Investment Type [Axis] Investment Type [Axis] Interest income on notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant 4 years but less than 5 EBP, Employer Contribution, Vesting Between Four And Five Years [Member] EBP, Employer Contribution, Vesting Between Four And Five Years Total contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Participant EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Vesting percentage EBP, Employer Contribution, Vesting Percentage EBP, Employer Contribution, Vesting Percentage Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment EBP, Description of Plan [Line Items] EBP, Description of Plan [Line Items] Plan number EBP, Plan Number EBP, Investment, Fair Value and NAV [Line Items] EBP, Investment, Fair Value and NAV [Line Items] Description of Plan EBP, Description of Plan [Text Block] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Change in Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Statement of Net Asset Available for Benefit [Table] EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] Interest EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Investment Contributions EBP, Contribution [Policy Text Block] Common stock – Columbia Banking System, Inc. EBP, Employer, Common Stock [Member] EBP, Schedule of Asset Held for Investment [Abstract] EBP, Accounting Policy [Table] EBP, Accounting Policy [Table] Total additions EBP, Change in Net Asset Available for Benefit, Increase Investment, Identifier [Axis] Investment, Identifier [Axis] Administrative expenses EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Asset held for investment EBP, Asset Held for Investment 1 year but less than 2 EBP, Employer Contribution, Vesting Between One And Two Years [Member] EBP, Employer Contribution, Vesting Between One And Two Years Document Information [Line Items] Document Information [Line Items] EBP, Risk and Uncertainty [Line Items] EBP, Risk and Uncertainty [Line Items] EBP, Risk and Uncertainty [Table] EBP, Risk and Uncertainty [Table] EBP, Employer Contribution, Participant Compensation Matched, Percentage EBP, Employer Contribution, Participant Compensation Matched, Percentage EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Level 2 Fair Value, Inputs, Level 2 [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] EBP, Tax Status [Table] EBP, Tax Status [Table] CHANGE IN NET ASSETS EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Related Party Transactions and Exempt Party-in-Interest Transactions EBP, Related Party and Party-in-Interest Transactions [Text Block] EBP, Related Party and Party-in-Interest Transactions [Abstract] EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] Total receivables EBP, Receivable Employer contributions - match EBP, Employer Contribution, Receivable Automatic deferral rate EBP, Participant Contribution, Automatic, Deferral Rate Investment income EBP, Investment, Fair Value [Abstract] Benefits paid to participants EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Dividends EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment 5 years or more EBP, Employer Contribution, Vesting In Five Years Or More [Member] EBP, Employer Contribution, Vesting In Five Years Or More Current Value EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] ASSETS Assets [Abstract] EBP, Statement of Net Asset Available for Benefit [Abstract] EBP, Accounting Policy [Line Items] EBP, Accounting Policy [Line Items] EBP, Tax Status [Abstract] Expenses EBP, Expense [Policy Text Block] Participant Loan EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Investment valuation EBP, Investment [Policy Text Block] Participant contributions EBP, Participant Contribution, Receivable Total Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] Document Type Document Type Plan Termination EBP, Plan Termination [Text Block] Entity Central Index Key Entity Central Index Key Participant loan interest rate EBP, Asset Held for Investment, Participant Loan, Interest Rate Collective trusts Common Collective Trust [Member] NET ASSETS AVAILABLE FOR BENEFITS EBP, Net Asset Available for Benefit [Abstract] EBP, Risk and Uncertainty [Abstract] EBP, Tax Status [Line Items] EBP, Tax Status [Line Items] EBP, Subsequent Event [Table] EBP, Subsequent Event [Table] DEDUCTIONS FROM NET ASSETS ATTRIBUTED TO EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Forfeitures used to fund matching contributions EBP, Forfeited Nonvested Account, Decrease from Employer Contribution Notes receivable from participants EBP, Note Receivable from Participant Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Summary of Significant Accounting Policies EBP, Summary of Accounting Policy [Text Block] Entity Registrant Name Entity Registrant Name Forfeitures EBP, Forfeitures [Policy Text Block] EBP, Forfeitures 2 years but less than 3 EBP, Employer Contribution, Vesting Between Two And Three Years [Member] EBP, Employer Contribution, Vesting Between Two And Three Years EBP, Subsequent Event [Abstract] Subsequent Events EBP, Subsequent Event [Text Block] Subsequent events EBP, Subsequent Event [Policy Text Block] Tax Status EBP, Tax Status [Text Block] Maximum borrowing, to total account, percentage EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage EBP, Subsequent Event [Line Items] EBP, Subsequent Event [Line Items] Document Information [Table] Document Information [Table] 3 years but less than 4 EBP, Employer Contribution, Vesting Between Three And Four Years [Member] EBP, Employer Contribution, Vesting Between Three And Four Years EBP, Vesting [Domain] EBP, Vesting [Domain] EBP, Vesting [Domain] Note receivable from participants EBP, Note Receivable from Participant [Policy Text Block] Net investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment EBP, Related Party and Party-in-Interest Transactions [Line Items] EBP, Related Party and Party-in-Interest Transactions [Line Items] Level 3 Fair Value, Inputs, Level 3 [Member] NET ASSETS AVAILABLE FOR BENEFITS Beginning of year End of year EBP, Net Asset Available for Benefit Entity [Domain] Entity [Domain] Contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] EBP 001 EBP 001 [Member] EBP 001 Forfeited nonvested accounts EBP, Forfeited Nonvested Account Employer contribution, matching percentage EBP, Employer Contribution, Matching Percentage NAV Fair Value Measured at Net Asset Value Per Share [Member] EBP, Investment, Fair Value and NAV [Table] EBP, Investment, Fair Value and NAV [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Statement of Net Asset Available for Benefit [Line Items]