Entity tax identification number Entity Tax Identification Number EBP, Employer Contribution Vesting EBP, Employer Contribution Vesting [Table Text Block] EBP, Employer Contribution Vesting Rollover 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] Mutual funds Mutual Fund [Member] Pretax, maximum annual compensation to total compensation, percentage EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage 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 Total investments at fair value EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value EBP, Empoyer Contribution, Participant Eligible Compensation [Axis] EBP, Empoyer Contribution, Participant Eligible Compensation [Axis] EBP, Empoyer Contribution, Participant Eligible Compensation EBP, Compensation 3 EBP, Compensation 3 [Member] EBP, Compensation 3 Money market funds Money Market Funds [Member] Level 1 Fair Value, Inputs, Level 1 [Member] EBP, Investment, Fair Value and NAV [Abstract] Assets EBP, Asset [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Employer Discretionary Contributions Employer Discretionary Contributions [Member] Employer Discretionary Contributions Additions: EBP, Change in Net Asset Available for Benefit, Increase [Abstract] EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Statement of Change in Net Asset Available for Benefit [Table] Payment of Benefits EBP, Payment to Participant [Policy Text Block] Assets acquired due to plan merger (Note 1) EBP, Change in Net Asset Available for Benefit, Transfer to (from) Plan EBP, Vesting Period [Domain] EBP, Vesting Period [Domain] EBP, Vesting Period [Domain] Amendment Flag Amendment Flag EBP, Vesting Period 2 EBP, Vesting Period 2 [Member] EBP, Vesting Period 2 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] EBP, Investment, Fair Value and NAV EBP, Investment, Fair Value and NAV [Table Text Block] Life insurance premiums EBP, Change in Net Asset Available for Benefit, Decrease from Payment for Insurance Contract, Excluded from Plan Asset Oppenheimer Holdings Inc. - Common stock Common Stock [Member] Investments [Domain] Investments [Domain] Use of Estimates EBP, Use of Estimate [Policy Text Block] Schedule H, Line 4i – Schedule of Assets (Held At End of Year) EBP, Schedule of Asset Held for Investment [Text Block] Cover [Abstract] EBP, Compensation 1 EBP, Compensation 1 [Member] EBP, Compensation 1 Employer Employer contribution amount EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash Minimum Minimum [Member] Interest from notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Investment Type [Axis] Investment Type [Axis] Total contributions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Employees EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Net realized and unrealized gains 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 the 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] Other EBP, Change in Net Asset Available for Benefit, Increase from Other EBP, Change in Net Asset Available for Benefit, Increase from Other EBP, Schedule of Asset Held for Investment [Line Items] EBP, Schedule of Asset Held for Investment [Line Items] Contributions EBP, Contribution [Policy Text Block] EBP, Vesting Period 4 EBP, Vesting Period 4 [Member] EBP, Vesting Period 4 EBP, Employer Contribution, Type [Domain] EBP, Employer Contribution, Type [Domain] EBP, Employer Contribution, Type [Domain] 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 Allowance for credit loss EBP, Note Receivable from Participant, Allowance for Credit Loss EBP, Vesting Period [Axis] EBP, Vesting Period [Axis] EBP, Vesting Period Investment income: EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Vesting percentage EBP, Employer Contribution Vesting Percentage Company contribution and/ or investment earning percentage vesting to the participant in Company Matching Contributions, Fixed Rate Contributions, Discretionary Profit-Sharing Contributions, Qualified Non-Elective Contributions, and Disability Contributions, upon completion of minimum service period or attainment of maximum vesting age Investment, Identifier [Axis] Investment, Identifier [Axis] Administrative expenses EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Total EBP, Asset Held for Investment Risk and Uncertainties EBP, Risk and Uncertainty [Policy Text Block] Document Information [Line Items] Document Information [Line Items] Cash surrender value life insurance policies Cash Surrender Value [Member] EBP 001 EBP 001 [Member] EBP 001 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] EBP, Investment, Employer, Common Stock, to Total Asset, Percentage EBP, Investment, Employer, Common Stock, to Total Asset, Percentage EBP, Vesting Period 3 EBP, Vesting Period 3 [Member] EBP, Vesting Period 3 EBP, Tax Status [Table] EBP, Tax Status [Table] Net Increase in Net Assets Available for Plan Benefits EBP, Change in Net Asset Available for Benefit, Increase (Decrease) EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] Employer contributions receivable EBP, Employer Contribution, Receivable Participant - directed investments at fair value: EBP, Investment, Fair Value [Abstract] Benefits paid to participants and beneficiaries 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 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] EBP, Statement of Net Asset Available for Benefit [Abstract] EBP, Compensation 2 EBP, Compensation 2 [Member] EBP, Compensation 2 Vesting period EBP, Employer Contribution Vesting Service Period Minimum Vesting service period for company contribution and/ or investment earning to the participant in Company Matching Contributions, Fixed Rate Contributions, Discretionary Profit-Sharing Contributions, Qualified Non-Elective Contributions, and Disability Contributions. EBP, Accounting Policy [Line Items] EBP, Accounting Policy [Line Items] EBP, Tax Status [Abstract] Cash EBP, Noninterest-Bearing Cash Expenses EBP, Expense [Policy Text Block] Participant loan, current value EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Investment Valuation and Income Recognition EBP, Investment [Policy Text Block] Document Type Document Type Entity Central Index Key Entity Central Index Key EBP, Vesting Period 5 EBP, Vesting Period 5 [Member] EBP, Vesting Period 5 Participant loan, interest rate EBP, Asset Held for Investment, Participant Loan, Interest Rate EBP, Tax Status [Line Items] EBP, Tax Status [Line Items] EBP, Employer Contribution, Type [Axis] EBP, Employer Contribution, Type [Axis] EBP, Employer Contribution, Type Participant compensation matched, minimum service period EBP, Requisite Service Period EBP, Requisite Service Period EBP, Subsequent Event [Table] EBP, Subsequent Event [Table] Deductions: EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Forfeited nonvested account, decrease from employer contribution EBP, Forfeited Nonvested Account, Decrease from Employer Contribution Notes receivable from participants EBP, Note Receivable from Participant Summary of Significant Accounting Policies EBP, Summary of Accounting Policy [Text Block] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Entity Registrant Name Entity Registrant Name EBP, Compensation 5 EBP, Compensation 5 [Member] EBP, Compensation 5 EBP, Subsequent Event [Abstract] Subsequent Events EBP, Subsequent Event [Text Block] Tax Status EBP, Tax Status [Text Block] EBP, Vesting Period 1 EBP, Vesting Period 1 [Member] EBP, Vesting Period 1 Maximum borrowing, to total account, percentage EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage EBP, Empoyer Contribution, Participant Eligible Compensation [Domain] EBP, Empoyer Contribution, Participant Eligible Compensation [Domain] EBP, Empoyer Contribution, Participant Eligible Compensation [Domain] EBP, Subsequent Event [Line Items] EBP, Subsequent Event [Line Items] Document Information [Table] Document Information [Table] Note Receivable from Participants EBP, Note Receivable from Participant [Policy Text Block] EBP, Vesting Period 6 EBP, Vesting Period 6 [Member] EBP, Vesting Period 6 EBP, Compensation 4 EBP, Compensation 4 [Member] EBP, Compensation 4 Total investment income EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Net Assets Available for Plan Benefits Net assets available for benefits at beginning of year Net assets available for benefits at 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] Forfeited nonvested account EBP, Forfeited Nonvested Account 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]