Dividends paid per share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Statistical Measurement [Domain] Statistical Measurement [Domain] Net Amount Security Loaned, Subject to Master Netting Arrangement, after Offset and Deduction Commodity contracts Commodity Contract [Member] Financial Instruments, Estimate Not Practicable, Fair Value [Line Items] Financial Instruments, Estimate Not Practicable, Fair Value [Line Items] [Line Items] for Financial Instruments, Estimate Not Practicable, Fair Value [Table] Award Timing Predetermined Award Timing Predetermined [Flag] 2026 Lessee, Operating Lease, Liability, to be Paid, Remainder of Fiscal Year Schedule of Investments in Company-Sponsored Funds Schedule Of Sponsored Fund Investments Table [Table Text Block] Schedule of sponsored fund investments. Asset Class [Axis] Asset Class [Axis] Entity File Number Entity File Number Less : Segment Reporting Information, Income (Loss) before Income Taxes [Abstract] Additional paid-in capital Additional Paid-in Capital [Member] Cash Collateral Received Security Borrowed, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash Not Offset Tabular List, Table Tabular List [Table Text Block] Leases [Abstract] Leases [Abstract] Notes Receivable, Five Years and Older Notes Receivable, Five Years and Older [Member] Notes Receivable, Five Years and Older [Member] Organization And Basis Of Presentation [Line Items] Organization And Basis Of Presentation [Line Items] Organization and basis of presentation. Investments Fair Value, Estimate Not Practicable, Investment Fair Value, Estimate Not Practicable, Investment Clearing organizations Fair Value Estimate Not Practicable Receivables From Clearing Organizations Fair value estimate not practicable receivables from clearing organizations. Payables to customers Fair Value Estimate Not Practicable Payables To Customers This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Measurement Basis [Axis] Measurement Basis [Axis] Basic (in dollars per share) (Loss) Earnings per share attributable to Oppenheimer Holdings Inc. - Basic (in dollars per share) Earnings Per Share, Basic Other (1) Other Expenses Adjustment to Compensation: Adjustment to Compensation [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Accounts payable and other liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Excess liquid capital under hong kong SFC rules Excess Liquid Capital Under Hong Kong SFC Rules Excess Liquid Capital Under Hong Kong SFC Rules Revenue from contracts with customers Revenue from Contract with Customer [Text Block] Gross amount of recognized liabilities for repurchase agreements and securities loaned Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement Schedule of Stock by Class [Table] Stock, Class of Stock [Table] Deferred tax assets Deferred Tax Assets, Gross Gross Amounts of Recognized Assets Security Purchased under Agreement to Resell, Subject to Master Netting Arrangement, before Offset Schedule of Reported Revenue and Pre-Tax Income (Loss) Schedule of Segment Reporting Information, by Segment [Table Text Block] Bank deposit sweep income Sweep Interest Income From FDIC-Insured Bank Deposits Sweep Interest Income From FDIC-Insured Bank Deposits Adjustment to Compensation, Amount Adjustment to Compensation Amount Concentration risk, percentage Concentration Risk, Percentage Mortgage and other asset-backed securities Collateralized Mortgage Obligations [Member] Other assets Increase (Decrease) in Other Operating Assets Share-based compensation Share-Based Payment Arrangement, Noncash Expense Schedule of Receivable from and Payable to Brokers, Dealers and Clearing Organizations Schedule of Due to (from) Broker-Dealer and Clearing Organization [Table Text Block] Notional derivative asset Derivative Asset, Notional Amount Communications and technology Communications and Information Technology Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Cash paid during the period for income taxes, net Income Taxes Paid Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Fair value of collateral Securities Sold under Agreements to Repurchase, Fair Value of Collateral Dividends declared Dividends, Common Stock, Cash Total Oppenheimer Holdings Inc. stockholders' equity Equity, Attributable to Parent Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Measurement Frequency [Axis] Measurement Frequency [Axis] Insider Trading Policies and Procedures [Line Items] Common stock, authorized (in shares) Common Stock, Shares Authorized Revenue Segment Reporting Information, Revenue for Reportable Segment [Abstract] Hedging Designation [Domain] Hedging Designation [Domain] Payables to brokers, dealers and clearing organizations Increase (Decrease) in Payable to Broker-Dealer and Clearing Organization Uncollectible balance reserved (as a percent) Defaulted Loans, Uncollectible Balance Reserved, Percent Defaulted Loans, Uncollectible Balance Reserved, Percent Total Liabilities and Stockholders' Equity Liabilities and Equity Fair Value, Recurring Fair Value, Recurring [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Cover [Abstract] Cover [Abstract] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Maximum Maximum [Member] Net income attributable to non-controlling interest, net of tax Net Income (Loss) Attributable to Noncontrolling Interest Accounting Policies [Abstract] Accounting Policies [Abstract] Remaining amount authorized for repurchase (in shares) Share Repurchase Program, Remaining Authorized, Number of Shares Securities Borrowed Transactions Securities Borrowed Transactions [Member] Securities borrowed transactions. Gross Amounts Offset on the Balance Sheet Security Sold under Agreement to Repurchase, Subject to Master Netting Arrangement, Asset Offset Schedule of Maturities of Lease Liabilities Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount 2026 Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Financing Receivable, Credit Quality Indicator [Table] Financing Receivable, Credit Quality Indicator [Table] U.S. Agency securities US Government Agencies Debt Securities [Member] Lease liabilities Lease liabilities Present value of lease liabilities Operating Lease, Liability Recognized in Income on Derivatives (pre-tax) Gain (Loss) On Derivatives Pre Tax Recognized In Income Gain (loss) on derivatives pre tax recognized in income. Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Liabilities Liabilities [Abstract] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Pre-tax income (loss) Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Schedule of Revenue Classified by Major Geographic Areas Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Accounts payable and other liabilities Accounts Payable and Other Accrued Liabilities Number of business days for related transactions (in days) Transaction Settlement Period Transaction Settlement Period Receivables from customers Fair Value Estimate Not Practicable Receivables From Customers This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments [Member] Schedule of Variable Interest Entities [Table] Variable Interest Entity [Table] 2024 Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount 2029 Lessee, Operating Lease, Liability, to be Paid, Year Three Net income attributable to non-controlling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Interest Interest Expense, Operating Comprehensive (loss) income attributable to Oppenheimer Holdings Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Name Measure Name Drafts payable Broker-Dealer, Draft Payable Fair value of securities received as collateral, sold and re-pledged under securities loaned Fair value of Securities Received as Collateral, Sold and Re-Pledged under Securities Loaned Fair value of Securities Received as Collateral, Sold and Re-Pledged under Securities Loaned Principal transactions, net Principal transactions, net Principal Transactions Revenue, Net Class of Stock [Line Items] Class of Stock [Line Items] Deferred tax liabilities, net of deferred tax assets of $53,713 ($50,032 in 2025) Deferred Income Tax Liabilities, Net Document Fiscal Period Focus Document Fiscal Period Focus Notes Receivable, Under Five Years Notes Receivable, Under Five Years [Member] Notes Receivable, Under Five Years [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Receivables from brokers, dealers and clearing organizations consisting of: Receivable from Broker-Dealer and Clearing Organization [Abstract] Futures Futures Future [Member] Award Timing Method Award Timing Method [Text Block] Litigation Case [Domain] Litigation Case [Domain] Award Type Award Type [Axis] Total assets Assets Assets Fair value of securities received as collateral Fair Value Of Securities Received As Collateral Under Securities Borrowed Transactions Fair Value Of Securities Received As Collateral Under Securities Borrowed Transactions Trading Symbol Trading Symbol Securities loaned Deposits Received for Securities Loaned, at Carrying Value 2030 Lessee, Operating Lease, Liability, to be Paid, Year Four Financing Receivable, Credit Quality Indicator [Line Items] Financing Receivable, Credit Quality Indicator [Line Items] Regulatory Liability [Axis] Regulatory Liability [Axis] Geographical [Domain] Geographical [Domain] Financing Receivable, Allowance for Credit Loss [Roll Forward] Financing Receivable, Allowance for Credit Loss [Roll Forward] Entity Address, City or Town Entity Address, City or Town Estimated range of loss in excess of amounts accrued Loss Contingency, Range of Possible Loss, Portion Not Accrued Organization And Basis Of Presentation [Table] Organization And Basis Of Presentation [Table] Organization and basis of presentation. Cash flows from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Receivable Type [Axis] Receivable Type [Axis] Other Segment Items Segment Reporting, Other Segment Item, Amount Concentration Risk Type [Axis] Concentration Risk Type [Axis] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Securities sold but not yet purchased Increase (Decrease) in Financial Instruments Sold, Not yet Purchased Income Statement Location [Domain] Statement of Income Location, Balance [Domain] Private equity funds Private Equity Funds [Member] Common Equity Tier 1 ratio (as a percent) Banking Regulation, Common Equity Tier One Ratio Banking Regulation, Common Equity Tier One Ratio Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Oppenheimer Investments Asia Ltd. Oppenheimer Investments Asia [Member] Oppenheimer Investments Asia. Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Financial Instruments - Credit Losses Credit Loss, Financial Instrument [Text Block] Entity Emerging Growth Company Entity Emerging Growth Company Capitalized Contract Cost [Table] Capitalized Contract Cost [Table] Quarterly dividend payable amount per share (in dollars per share) Common Stock, Dividends, Per Share, Declared Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Decrease (increase) in operating assets: Increase (Decrease) in Operating Assets [Abstract] Securities failed to receive Securities Failed-to-Receive Trade date receivables Fair Value Estimate Not Practicable Receivables From Trade Receivables Fair Value Estimate Not Practicable Receivables From Trade Receivables Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Unfunded commitments Unfunded Loan Commitment [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Financial Instruments Security Borrowed, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Net capital Broker-Dealer, Net Capital Common stock, outstanding (in shares) Class A Stock outstanding, beginning of period Class A Stock outstanding, end of period Common Stock, Shares, Outstanding Clearing organizations Receivables from Clearing Organizations Reversal of credit losses Accounts Receivable, Credit Loss Expense (Reversal) Investments Other Assets, Fair Value Disclosure PEO PEO [Member] Regulatory capital required to be maintained Broker-Dealer, Minimum Net Capital Required, Aggregate Indebtedness Standard Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Schedule of Changes in Number of Shares of Class A Stock Outstanding Schedule of Common Stock Outstanding Roll Forward [Table Text Block] Deposits with clearing organizations Fair Value Estimate Not Practicable Deposits With Clearing Organizations This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Issued pursuant to share-based compensation plans Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period UNITED STATES UNITED STATES Regulatory requirements Regulatory Requirements [Text Block] Regulatory requirements. Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Deposits with clearing organizations Deposits With Clearing Organizations Fair Value Deposits with clearing organizations fair value. Variable Interest Entity [Abstract] Variable Interest Entity [Abstract] Variable Interest Entity [Abstract] Retained earnings Retained Earnings [Member] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Total cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income Statement [Abstract] Derivative contracts, total Derivative Asset Income tax (benefit) provision Income Tax Expense (Benefit) Class B Stock Common Class B [Member] Other assets Other Assets Fair Value, Nonrecurring Fair Value, Nonrecurring [Member] Beginning balance Ending balance Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Fair Value Investments, Fair Value Disclosure Document Information [Line Items] Document Information [Line Items] Preferred stock, issued (in shares) Preferred Stock, Shares Issued Intangible assets Intangible Assets, Net (Excluding Goodwill) Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Product and Service [Domain] Product and Service [Domain] Customer Concentration Risk Customer Concentration Risk [Member] Reverse Repurchase Agreements Reverse Repurchase Agreement [Member] Reverse repurchase agreement. Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Commissions from sales and trading Commissions From Sales And Trading [Member] Commissions From Sales And Trading [Member] Securities borrowed Deposits Paid for Securities Borrowed, at Carrying Value Deferred Revenue, Type [Axis] Deferred Revenue, Type [Axis] Deferred Revenue, Type Parent Parent [Member] Net (loss) income Net (loss) income Net income (loss) Net (loss) income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Total Liabilities, Fair Value Disclosure Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Receivables from brokers Due from Correspondent Brokers Securities failed to receive Fair Value Estimate Not Practicable Securities Failed To Receive This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Amortization of right-of-use lease assets Right-of-use lease asset amortization Operating Lease, Right-of-Use Asset, Periodic Reduction Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Municipal obligations Municipal Notes [Member] Commission Commission [Member] Commission [Member] City Area Code City Area Code Schedule of Activity in Allowance for Uncollectibles of Defaulted Notes Financing Receivable, Allowance for Credit Loss [Table Text Block] Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Regulatory Capital Requirements [Line Items] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Net Amount Security Sold under Agreement to Repurchase, Subject to Master Netting Arrangement, after Offset and Deduction Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Schedule of Receivables and Deferred Revenue Balances from Contracts with Customers Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Cash flows from investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Gross Amounts of Recognized Assets Derivative Asset, Security Purchased under Agreement to Resell, and Security Borrowed, Subject to Master Netting Arrangement, before Offset Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Cash used in operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Proceeds from the settlement of company-owned life insurance Proceeds from Insurance Settlement, Investing Activities Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Unrecorded Unconditional Purchase Obligation by Category of Item Purchased [Axis] Shares repurchased as a percent of shares outstanding (as a percent) Stock Repurchase Program Percentage Of Shares Repurchase Of Outstanding Share Percentage of repurchase of class A common stock. Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Sales and settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Subsequent Event Subsequent Event [Member] Basel Three New Requirements Basel Three New Requirements [Member] Basel three new requirement. Other liabilities Other Liabilities Equity securities Equity Securities, FV-NI Goodwill Goodwill Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Schedule of Weighted Average Lease Term and Weighted Average Discount Rate and Operating Lease Costs Lease, Cost [Table Text Block] PEO Total Compensation Amount PEO Total Compensation Amount Money markets Money Market Funds [Member] Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] Securities borrowed Fair Value Estimate Not Practicable Deposits Paid For Securities Borrowed This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Equity Components [Axis] Equity Components [Axis] 2023 Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year Repurchase agreements Security Sold under Agreement to Repurchase, Including Not Subject to Master Netting Arrangement, after Offset and Deduction [Abstract] Operating Lease, Lease Not yet Commenced Operating Lease, Lease Not yet Commenced [Member] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Financial Instruments Derivative Liability, Security Sold under Agreement to Repurchase, and Security Loaned, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Equipment Equipment [Member] Securities owned Increase (Decrease) in Financial Instruments Used in Operating Activities Supplemental disclosure of cash flow information Supplemental Cash Flow Information [Abstract] Other Performance Measure, Amount Other Performance Measure, Amount Entity Address, State or Province Entity Address, State or Province Oppenheimer Europe Ltd Oppenheimer Europe [Member] Oppenheimer Europe. Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Security, Excluded EPS Calculation [Table] Clearing and exchange fees Floor Brokerage, Exchange and Clearance Fees Investment Banking fees Investment Banking Fees [Member] Investment Banking Fees [Member] Loans Loans Receivable, Fair Value Disclosure Real Estate Real Estate [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Interest expense Operating Lease, Interest Expense Operating Lease, Interest Expense Individual: Individual [Axis] Payables to brokers Fair Value Estimate Not Practicable Payable To Correspondent Brokers Fair Value Estimate Not Practicable Payable To Correspondent Brokers Cash dividends paid on Class A non-voting and Class B voting common stock Payments of Ordinary Dividends, Common Stock Net Amount Security Purchased under Agreement to Resell, Subject to Master Netting Arrangement, after Offset and Deduction Entities [Table] Entities [Table] After 2030 Lessee, Operating Lease, Liability, to be Paid, After Year Four Lessee, Operating Lease, Liability, to be Paid, After Year Four Cash provided by/(used in) investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Cash paid during the period for interest Interest Paid, Excluding Capitalized Interest, Operating Activity Document Fiscal Year Focus Document Fiscal Year Focus Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Right-of-use lease assets, net of accumulated amortization of $143,446 ($137,005 in 2025) Right-of-use lease assets, net of accumulated amortization Operating Lease, Right-of-Use Asset Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Depreciation and amortization of furniture, equipment and leasehold improvements Other Depreciation and Amortization Entity Interactive Data Current Entity Interactive Data Current Carrying Value Reported Value Measurement [Member] Equity [Abstract] Equity [Abstract] Segment information Segment Reporting Disclosure [Text Block] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] U.S. Treasury securities US Treasury Securities [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Long-Lived Tangible Asset [Axis] Long-Lived Tangible Asset [Axis] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Repurchase of class A common stock (in shares) Share Repurchase Program, Authorized, Number of Shares Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Amortization of intangible assets Amortization of Intangible Assets Schedule of Disaggregation of Gross Obligation by Class of Collateral Pledged and Remaining Contractual Maturity of Repurchase Agreements and Securities Loaned Transactions Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Table Text Block] Company-owned life insurance Proceeds From Life Insurance Policy, Operating Activities Proceeds From Life Insurance Policy, Operating Activities Notes receivable Increase (Decrease) In Due From Employee Current And Noncurrent The increase (decrease) during the reporting period in the amount from employees for floats, allowances and loans (generally evidenced by promissory notes). Income tax receivable Increase (Decrease) in Income Taxes Receivable Customer [Domain] Customer [Domain] Entity Central Index Key Entity Central Index Key PEO Name PEO Name Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Total revenue Revenue Total Revenues Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Other Other [Member] Other [Member] Schedule of Disaggregation of Defaulted Notes by Year of Default Financing Receivable Credit Quality Indicators [Table Text Block] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Securities sold but not yet purchased: Financial Instruments Sold, Not yet Purchased, at Fair Value [Abstract] Other comprehensive income (loss), net of tax Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Arrangement Duration Trading Arrangement Duration Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Derivative contracts Disclosure Schedule Of Fair Values Of Outstanding Derivative Contracts Recorded As Liabilities [Abstract] Disclosure schedule of fair values of outstanding derivative contracts recorded as liabilities. Segments [Axis] Segments [Axis] Schedule of Notional Amounts and Fair Values of Derivatives by Product Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Exercise Price Award Exercise Price Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Entity Filer Category Entity Filer Category Local Phone Number Local Phone Number Class of Stock [Domain] Class of Stock [Domain] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Effective income tax rate (as a percent) Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Subsequent Event Type [Axis] Subsequent Event Type [Axis] Stock repurchased (in shares) Repurchased and cancelled Stock Repurchased and Retired During Period, Shares Liabilities Liability [Member] Advisory fees Investment Advisory Fee Revenue Investment Advisory Fee Revenue Assets Assets [Abstract] Other Other Receivable from Broker-Dealer and Clearing Organization Other contracts Other Contract [Member] Payables to brokers, dealers and clearing organizations consisting of: Broker-Dealer, Payable to Other Broker-Dealer and Clearing Organization [Abstract] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Statement of Financial Position Location, Balance [Axis] Statement of Financial Position Location, Balance [Axis] Trade claims Trade Claims [Member] Trade Claims Fair value measurements Fair Value Disclosures [Text Block] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Number of states in which entity operates Number of States in which Entity Operates Entity Address, Address Line One Entity Address, Address Line One Accumulated other comprehensive income (loss) AOCI Attributable to Parent [Member] Investments [Domain] Investments [Domain] Number of broker-dealers Receivables From Brokers-Dealers And Clearing Organizations, Number Of Major Broker-Dealers Receivables From Brokers-Dealers And Clearing Organizations, Number Of Major Broker-Dealers Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] Americas Americas [Member] Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] 2022 Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year Mutual fund and insurance income Mutual fund and insurance income Mutual Fund Income [Member] Mutual Fund Income [Member] Receivables from customers Increase Decrease In Receivable From Customers The change during the period, either increase or decrease, in amounts receivable from customers. The term customers generally excludes other broker-dealers; persons who are principal officers, directors, and stockholders; and persons whose securities or funds are part of the regulatory net capital of the broker-dealer. Another broker-dealer's account can be classified as a customer if the account is carried as an omnibus account in compliance with certain regulations. The accounts of principal officers, directors and stockholders may be combined in the customer captions if they are not material and the combination is disclosed in the oath that is required to accompany the annual audited FOCUS Report. Compensation expenses (1) Employee Benefits and Share-Based Compensation Compensation and related expenses Labor and Related Expense Net dilutive effect of share-based awards, treasury stock method (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Regulated Operations [Abstract] Regulated Operations [Abstract] Gross Amounts Offset on the Balance Sheet Derivative Asset, Security Purchased under Agreement to Resell, and Security Borrowed, Subject to Master Netting Arrangement, Liability Offset Document Quarterly Report Document Quarterly Report Total Assets, Fair Value Disclosure Other debt securities Financial Instrument, Other [Member] Deferred income taxes Deferred Income Taxes and Tax Credits Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Securities owned: Investment Owned, Balance [Abstract] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] 2028 Lessee, Operating Lease, Liability, to be Paid, Year Two Financial Instruments Security Purchased under Agreement to Resell, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Other Other Income [Member] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Investment Type [Axis] Investment Type [Axis] Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Additions Financing Receivable, Excluding Accrued Interest, Additions Financing Receivable, Excluding Accrued Interest, Additions Number of offices providing services Number of stores Number of Stores Restatement Determination Date: Restatement Determination Date [Axis] Issuance of Class A non-voting common stock Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Non-PEO NEO Non-PEO NEO [Member] Outstanding letters of credit Letters of Credit Outstanding, Amount Accounts Receivable Accounts Receivable [Member] Aggregate indebtedness (as a percent) Percentage Of Net Capital To Aggregate Indebtedness Percentage of net capital to aggregate indebtedness. Increase in bank call loans Proceeds from (Payment for) Other Financing Activity Corporate equities Corporate Equities [Member] Corporate Equities Right of use asset, accumulated amortization Operating Lease Right-Of-Use Asset Accumulated Amortization Operating Lease Right-Of-Use Asset Accumulated Amortization Notional derivative liability Derivative Liability, Notional Amount Name Trading Arrangement, Individual Name Net Amounts of Assets Presented on the Balance Sheet Derivative Asset, Security Purchased under Agreement to Resell, and Security Borrowed, Subject to Master Netting Arrangement, after Offset All Award Types Award Type [Domain] Cash and cash equivalents Fair Value, Estimate Not Practicable, Cash And Cash Equivalents Fair Value, Estimate Not Practicable, Cash And Cash Equivalents 2027 Lessee, Operating Lease, Liability, to be Paid, Year One Non-controlling interest (Note 2) Equity, Attributable to Noncontrolling Interest Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Private equity securities Private Equity Securities [Member] Private Equity Securities Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Other Other Income Compensation Amount Outstanding Recovery Compensation Amount Securities sold under agreements to repurchase Fair Value,Estimate not Practicable, Securities sold under Agreements to Repurchase Fair Value,Estimate not Practicable, Securities sold under Agreements to Repurchase Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Accrued compensation Increase (Decrease) in Employee Related Liabilities Share Repurchase Program [Axis] Share Repurchase Program [Axis] Securities failed to deliver Securities Failed-to-Deliver MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Fair value derivative asset Derivative Asset, Subject to Master Netting Arrangement, before Offset of Collateral Name Awards Close in Time to MNPI Disclosures, Individual Name Real Estate Leases Real Estate Leases [Member] Real Estate Leases Cash Collateral Pledged Security Loaned, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset Variable interest entities ("VIEs") Variable Interest Entities Disclosure [Text Block] Variable interest entities disclosure. Customer securities under customer margin loans that are available to be pledged Customer Securities Under Customer Margin Loans That Are Available To Be Pledged Customer Securities under Customer Margin Loans that are Available to be Pledged Total receivable from brokers, dealers and clearing organizations Fair Value Estimate Not Practicable Receivables From Brokers Dealers And Clearing Organizations This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Revenue settlement period (in days) Revenue From Contract With Customer, Settlement Period Revenue From Contract With Customer, Settlement Period Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Revenue Revenues [Abstract] Net Amounts of Assets Presented on the Balance Sheet Security Purchased under Agreement to Resell, Subject to Master Netting Arrangement, after Offset Credit Loss [Abstract] Credit Loss [Abstract] Clearing organization and other Fair Value Estimate Not Practicable Other Payables To Broker Dealers And Clearing Organizations This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Share-based expense APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Repurchase Agreements Repurchase Agreements [Member] Financial Instruments [Domain] Financial Instruments [Domain] Litigation Case [Axis] Litigation Case [Axis] Liability Class [Axis] Liability Class [Axis] TBAs To Be Announced Security [Member] To be announced security. Purchases and issuances Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Segments [Domain] Segments [Domain] Income Statement Location [Axis] Statement of Income Location, Balance [Axis] Other Fair Value Estimate Not Practicable Receivables From Other Fair Value Estimate Not Practicable Receivables From Other Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Repurchase Agreements and Similar Transactions, Maturity Periods [Domain] Repurchase Agreements and Similar Transactions, Maturity Periods [Domain] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Required percentage of net capital to aggregate customer-related debit items (as a percent) Broker-Deal, Minimum Net Capital Requirement, Parent Broker-Deal, Minimum Net Capital Requirement, Parent Total payables to brokers, dealers and clearing organizations Fair Value Estimate Not Practicable Payables To Broker Dealers And Clearing Organizations This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Statement of Financial Position Location, Balance [Domain] Statement of Financial Position Location, Balance [Domain] Gross Amounts Offset on the Balance Sheet Security Loaned, Subject to Master Netting Arrangement, Asset Offset Securities Borrowed Offsetting Securities Borrowed [Abstract] Bank call loans Broker-Dealer, Bank Loan, Short-Term Trade date receivables Trade Receivable Trade Receivable Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Banking Regulation, Regulatory Capital Requirement, Compliance [Table] Minimum Minimum [Member] Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Company Selected Measure Name Company Selected Measure Name Sovereign obligations Sovereign Debt Securities [Member] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Contract Asset, Type [Domain] Contract Asset, Type [Domain] Contract Asset, Type [Domain] Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Vested employee share plan awards Vested Employee Share Plan Awards The reversal of the pre-tax accumulated compensation cost for stock awards that vested during the period. 2025 Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year Securities owned, including amounts pledged of $1,172,973 ($1,179,503 in 2025), at fair value Securities owned, at fair value Security Owned and Sold, Not yet Purchased Fair Value, Security Owned Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Assets Assets [Member] All Executive Categories All Executive Categories [Member] Stock repurchased and retired during period, per share (in dollars per share) Stock Repurchased and Retired During Period, Per Share Stock Repurchased and Retired During Period, Per Share Common stock ($0.001 par value per share): Class A: shares authorized: 50,000,000; shares issued and outstanding: 10,608,340 and 10,387,575 as of March 31, 2026 and December 31, 2025, respectively Class B: shares authorized, issued and outstanding: 99,665 as of March 31, 2026 and December 31, 2025 Common Stock, Value, Issued Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Notes receivable, net Fair Value, Estimate not Practicable, Notes Receivable, Net Fair Value, Estimate not Practicable, Notes Receivable, Net Diluted (in shares) Diluted weighted average number of shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Commitments and contingencies (Note 13) Commitments and Contingencies Net Amount Derivative Asset, Security Purchased under Agreement to Resell, and Security Borrowed, Subject to Master Netting Arrangement, after Offset and Deduction Increase (decrease) in operating liabilities: Increase (Decrease) in Operating Liabilities [Abstract] Securities sold but not yet purchased, at fair value Security Owned and Sold, Not yet Purchased Fair Value, Security Sold, Not yet Purchased Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Comprehensive (loss) income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Other Revenue Not from Contract with Customer, Other Entity Small Business Entity Small Business Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Commission Commission From Equity Securities Transactions [Member] Commission From Equity Securities Transactions Liberty Capital Group, Individually and on Behalf of All Others Similarly Situated v. Oppenheimer Holdings Inc., Oppenheimer & Co. Inc., and Oppenheimer Asset Management Inc. Liberty Capital Group, Individually and on Behalf of All Others Similarly Situated v. Oppenheimer Holdings Inc., Oppenheimer & Co. Inc., and Oppenheimer Asset Management Inc. [Member] Liberty Capital Group, Individually and on Behalf of All Others Similarly Situated v. Oppenheimer Holdings Inc., Oppenheimer & Co. Inc., and Oppenheimer Asset Management Inc. Customer securities directly with the Options Clearing Corporation to secure obligations and margin requirements under option contracts written by customers Customer securities directly with the Options Clearing Corporation to secure obligations and margin requirements under option contracts written by customers Customer Securities Pledged with the Options Clearing Corporation Non-controlling interest Noncontrolling Interest [Member] Net Amount Derivative Liability, Security Sold under Agreement to Repurchase, and Security Loaned, Subject to Master Netting Arrangement, after Offset and Deduction Document Transition Report Document Transition Report Summary of significant accounting policies and estimates Accounting Standards Update and Change in Accounting Principle [Text Block] Schedule of Assets and Liabilities Not Measured at Fair Value Financial Instruments, Estimate Not Practicable, Fair Value [Table Text Block] [Table Text Block] for Financial Instruments, Estimate Not Practicable, Fair Value [Table] Underlying Securities Award Underlying Securities Amount Maximum loss exposure Variable Interest Entity, Primary Beneficiary, Maximum Loss Exposure, Amount Warrants at fair value Warrants Not Settleable in Cash, Fair Value Disclosure Drafts payable Fair Value Estimate Not Practicable Drafts Payable This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Investment banking Investment Banking Revenue 2 Largest Customers 2 Largest Customers [Member] 2 Largest Customers Income taxes Income Tax Disclosure [Text Block] Allowance for credit loss Accounts Receivable, Allowance for Credit Loss Class A Stock Common Class A [Member] Contractual obligation Contractual Obligation Securities failed to deliver Fair Value Estimate Not Practicable Securities Failed To Deliver This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Gross Amounts Offset on the Balance Sheet Derivative Liability, Security Sold under Agreement to Repurchase, and Security Loaned, Subject to Master Netting Arrangement, Asset Offset Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Hedging Designation [Axis] Hedging Designation [Axis] Schedule of Fair Value Amounts of Derivative Instruments and their Effect on Consolidated Income Statements Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position, Location [Table Text Block] Amortization of notes receivable Amortization Of Notes Receivable The expense charged against earnings for the periodic recognition of the loans to employees. These loans are generally forgiven over a service period of 3 to 5 years and deducted from earnings through amortization. Cash Collateral Pledged Derivative Liability, Security Sold under Agreement to Repurchase, and Security Loaned, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset Total Stockholders' equity Balance at beginning of period Balance at end of period Equity, Including Portion Attributable to Noncontrolling Interest Convertibles note, fair value Convertible Debt, Fair Value Disclosures Document Type Document Type Equity method investments Equity Method Investments, Fair Value Disclosure Level 3 Fair Value, Inputs, Level 3 [Member] Earnings per share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Loss Contingencies [Table] Loss Contingencies [Table] Additional paid-in capital Additional Paid in Capital Product and Service [Axis] Product and Service [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Company-owned life insurance Life Insurance, Corporate or Bank Owned, Amount Total revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Financial Instruments Security Sold under Agreement to Repurchase, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Transfers in (out) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net All Individuals All Individuals [Member] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Brokers and Dealers [Abstract] Broker-Dealer [Abstract] Purchase of furniture, equipment and leasehold improvements Payments to Acquire Property, Plant, and Equipment Name Forgone Recovery, Individual Name Investment banking - advisory Investment Banking, Advisory [Member] Investment Banking, Advisory [Member] Reverse repurchase agreements Offsetting Securities Purchased under Agreements to Resell [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Deferred Revenue, Type [Domain] Deferred Revenue, Type [Domain] Deferred Revenue, Type [Domain] Reconciliation of cash and cash equivalents within the condensed consolidated balance sheets: Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation [Abstract] New Program New Program [Member] New Program [Member] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Bank call loans Fair Value Estimate Not Practicable Bank Loans This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Payments for employee taxes withheld related to vested share-based awards Payment, Tax Withholding, Share-Based Payment Arrangement Software license fees Software License Fees [Member] Software License Fees Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Financial Instruments, Estimate Not Practicable, Fair Value [Table] Financial Instruments, Estimate Not Practicable, Fair Value [Table] Financial Instruments, Estimate Not Practicable, Fair Value [Table] Europe/Middle East Europe / Middle East [Member] Europe / Middle East [Member] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Geographical [Axis] Geographical [Axis] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Total expenses Operating Expenses Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Securities Loaned Security Loaned, Including Not Subject to Master Netting Arrangement, after Offset and Deduction [Abstract] Level 1 Fair Value, Inputs, Level 1 [Member] Period end shares outstanding (in shares) Shares, Outstanding Principal transactions revenue, net Principal or Proprietary Transactions [Member] Diluted (in dollars per share) (Loss) Earnings per share attributable to Oppenheimer Holdings Inc. - Diluted (in dollars per share) Earnings Per Share, Diluted Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Interest Interest Interest Income, Operating Title of 12(b) Security Title of 12(b) Security Derivative contracts Disclosure Schedule Of Fair Values Of Outstanding Derivative Contracts Recorded As Assets [Abstract] Disclosure Schedule Of Fair Values Of Outstanding Derivative Contracts Recorded As Assets Payables to brokers Due to Correspondent Brokers Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Schedule of non-cash financing activities Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Overnight and Open Maturity Overnight and on Demand [Member] Excess capital Broker-Dealer, Excess Net Capital, Alternative Standard Change In Common Stock Outstanding [Roll Forward] Change In Common Stock Outstanding [Roll Forward] Change In Common Stock Outstanding Receivable from brokers and clearing organizations Credit Concentration Receivable From Major Broker Dealers Credit concentration receivable from major broker dealers. (Loss) Earnings per share attributable to Oppenheimer Holdings Inc. Earnings Per Share [Abstract] Consolidation Items [Domain] Consolidation Items [Domain] Organization Business Description and Basis of Presentation [Text Block] Repurchase of Class A non-voting common stock for cancellation Total consideration for repurchase of stock Stock Repurchased and Retired During Period, Value Receivable from and payable to brokers, dealers and clearing organizations Due to and from Broker-Dealers and Clearing Organizations Disclosure [Text Block] Gross Amounts Offset on the Balance Sheet Security Borrowed, Subject to Master Netting Arrangement, Liability Offset Regulatory Liability [Domain] Regulatory Liability [Domain] Regulatory Capital requirement [Domain] Regulatory Capital requirement [Domain] Regulatory Capital requirement [Domain] Less interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Receivables from brokers Fair Value Estimate Not Practicable Due From Correspondent Brokers This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Financial Instruments Derivative Asset, Security Purchased under Agreement to Resell, and Security Borrowed, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Market value of securities Firm's Securities Fair Value, Collateral for Bank Loans Firm's Securities Fair Value, Collateral for Bank Loans Tier 1 capital ratio required (as a percent) Tier One Capital Ratio Required Under Crd Fourth Tier One Capital Ratio required for capital adequacy purposes under the Capital Requirements Directive (DRD IV) in the European Union. Award Timing Disclosures [Line Items] Contract Asset, Type [Axis] Contract Asset, Type [Axis] Contract Asset, Type [Axis] Corporate equities Gross Amounts of Recognized Liabilities Security Loaned, Subject to Master Netting Arrangement, before Offset Notes Receivable Notes Receivable [Member] Measurement Frequency [Domain] Measurement Frequency [Domain] Uncollectible balance period (in years) Defaulted Loans, Uncollectible Balance, Period Defaulted Loans, Uncollectible Balance, Period Unfunded Commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments Total lease payments Lessee, Operating Lease, Liability, to be Paid Payables to brokers, dealers and clearing organizations Total Broker-Dealer, Payable to Other Broker-Dealer and Clearing Organization Share Repurchase Program, March (2024) Share Repurchase Program, March (2024) [Member] Share Repurchase Program, March (2024) U.S. Treasury securities Gross Amounts of Recognized Liabilities Security Sold under Agreement to Repurchase, Subject to Master Netting Arrangement, before Offset Stockholders' Equity Equity [Text Block] Financial Instruments Security Loaned, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Uncollected balance of defaulted notes Total Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss Notes receivable, net Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss Securities sold under agreements to repurchase Securities Sold under Agreements to Repurchase Net (loss) income attributable to Oppenheimer Holdings Inc. Net (loss) income attributable to Oppenheimer Holdings Inc. Net Income (Loss) Attributable to Parent Expiration Date Trading Arrangement Expiration Date Schedule of Gross Amounts and Offsetting Amounts of Reverse Repurchase Agreements, Repurchase Agreements, Securities Borrowed and Securities Loaned Transactions Offsetting Securities Purchased Under Agreements To Resell Securities Borrowed Securities Sold Under Agreements To Repurchase Securities Loaned Table [Table Text Block] Offsetting securities purchased under agreements to resell securities borrowed securities sold under agreements to repurchase securities loaned. Total capital ratio (as a percent) Total Capital Ratio Calculated Under Crd Fourth Total Capital Ratio calculated for capital adequacy purposes under the Capital Requirements Directive (DRD IV) in the European Union. Clearing organizations and other Other Payable to Broker-Dealer and Clearing Organization Net Amounts of Assets Presented on the Balance Sheet Security Borrowed, Subject to Master Netting Arrangement, after Offset Stockholders' equity Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Advisory fees Advisory Fees [Member] Advisory Fees [Member] Paid-in-kind interest Interest Income, Operating, Paid in Kind Net Amount Security Borrowed, Subject to Master Netting Arrangement, after Offset and Deduction Furniture, equipment and leasehold improvements, net of accumulated depreciation of $104,464 ($101,962 in 2025) Property, Plant and Equipment, Net Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Preferred stock, authorized (in shares) Preferred Stock, Shares Authorized Total other sources of revenue Revenue Not from Contract with Customer Repurchase of Class A non-voting common stock for cancellation Payments for Repurchase of Common Stock Income tax payable Taxes Payable Adoption Date Trading Arrangement Adoption Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Bank deposit sweep income Bank Deposit Sweep Income [Member] Bank Deposit Sweep Income [Member] Contract assets (receivables) Contract with Customer, Asset, after Allowance for Credit Loss Deposits with clearing organizations Deposits with Clearing Organizations and Others, Securities Total Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract] Asia Asia [Member] Entity Current Reporting Status Entity Current Reporting Status Cash Collateral Pledged Security Sold under Agreement to Repurchase, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset Customer [Axis] Customer [Axis] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Pre-tax (loss) income Operating Income (Loss) Consolidated Entities [Domain] Consolidated Entities [Domain] Retained earnings Retained Earnings (Accumulated Deficit) Net Amounts of Liabilities Presented on the Balance Sheet Derivative Liability, Security Sold under Agreement to Repurchase, and Security Loaned, Subject to Master Netting Arrangement, after Offset Major Types of Debt and Equity Securities [Axis] Financial Instrument [Axis] Financial Instrument [Axis] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Executive Category: Executive Category [Axis] Foreign exchange forward contracts Foreign Exchange Forward [Member] Regulatory Capital requirement [Axis] Regulatory Capital requirement [Axis] Regulatory Capital requirement Current Fiscal Year End Date Current Fiscal Year End Date Class of Stock [Axis] Class of Stock [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Commissions Brokerage Commissions Revenue Gross Amounts of Recognized Liabilities Derivative Liability, Security Sold under Agreement to Repurchase, and Security Loaned, Subject to Master Netting Arrangement, before Offset Payables to customers Increase (Decrease) in Payables to Customers Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Number of customers Receivable from Customer in Brokerage, Number of Customers Receivable from Customer in Brokerage, Number of Customers Wealth Management Wealth Management Segment [Member] Wealth Management Segment Service period (in years) Financing Receivable, Service Period Service period. Statement [Table] Statement [Table] Derivative contracts, total Derivative Liability Non-cash items included in net (loss) income: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Total Offsetting Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed [Abstract] Cash flows from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Drafts payable Increase Decrease In Draft Payable The increase (decrease) in cash during the reporting period in drafts payable. Equipment Leases Equipment Leases [Member] Equipment Leases Deferred revenue (payables) Contract with Customer, Liability Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis and Changes in Level 3 Assets and Liabilities Measured at Fair Value on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Number of anti-dilutive stock options granted (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Weighted average shares outstanding Weighted Average Number of Shares Outstanding, Diluted [Abstract] Investment banking - capital markets Investment Banking, Capital Markets [Member] Investment Banking, Capital Markets [Member] Lease not yet commenced, amount Leases not yet commenced Unrecorded Unconditional Purchase Obligation All Adjustments to Compensation All Adjustments to Compensation [Member] Fair value derivative liability Derivative Liability, Subject to Master Netting Arrangement, before Offset of Collateral Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Capital Markets Capital Markets Capital Markets Segment [Member] Capital Markets Segment Amendment Flag Amendment Flag Tier 1 capital ratio (as a percent) Tier One Capital Ratio Calculated Under Crd Fourth Tier One Capital Ratio calculated for capital adequacy purposes under the Capital Requirements Directive (DRD IV) in the European Union. Securities loaned Fair Value Estimate Not Practicable Deposits Received For Securities Loaned This item represents a financial instrument (as defined) for which it is not practicable to estimate fair value. Such disclosure may be for an individual financial instrument or a class of financial instruments. Leases Lessee, Operating Leases [Text Block] Termination Date Trading Arrangement Termination Date Cash provided by financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Measure: Measure [Axis] Allowance for credit loss Beginning balance Ending balance Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest Receivable [Domain] Receivable [Domain] Employee share plan issuance Employee Share Plan Issuance The grant date fair value of stock issued upon the vesting of stock awards. Weighted average discount rate (as a percent) Operating Lease, Weighted Average Discount Rate, Percent Receivables from brokers, dealers and clearing organizations Total Receivable from Broker-Dealer and Clearing Organization Total capital ratio required (as a percent) Total Capital Ratio Required Under Crd Fourth Total Capital Ratio Required for capital adequacy purposes under the Capital Requirements Directive (DRD IV) in the European Union. Long-Lived Tangible Asset [Domain] Long-Lived Tangible Asset [Domain] Basic (in shares) Basic weighted average number of shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Securities Financing Transaction [Axis] Securities Financing Transaction [Axis] Schedule of Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Capitalized Contract Cost [Line Items] Capitalized Contract Cost [Line Items] Subsequent Events [Abstract] Subsequent Events [Abstract] Segment Reporting [Abstract] Segment Reporting [Abstract] Receivables from customers, net of allowance for credit losses of $154 ($131 in 2025) Receivable from Customer in Brokerage Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Entity Tax Identification Number Entity Tax Identification Number Schedule of Total Assets and Liabilities of VIEs Schedule of Variable Interest Entities [Table Text Block] Net capital Liquid Capital Under Hong Kong SFC Rules Liquid Capital Under Hong Kong SFC Rules Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Consolidated Entities [Axis] Consolidated Entities [Axis] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, issued (in shares) Common Stock, Shares, Issued Common Stock, Shares, Issued Income tax receivable Income Taxes Receivable, Current Number Of Reportable Segments Not Disclosed Flag Number Of Reportable Segments Not Disclosed Flag Number Of Reportable Segments Not Disclosed Flag Net Amounts of Liabilities Presented on the Balance Sheet Security Loaned, Subject to Master Netting Arrangement, after Offset Weighted average remaining lease term (in years) Operating Lease, Weighted Average Remaining Lease Term Receivable from customers Credit Concentration, Receivable from Customer in Brokerage Credit Concentration, Receivable from Customer in Brokerage Payables to customers Broker-Dealer, Payable to Customer Common equity tier 1 ratio required (as a percent) Common Equity Tier One Ratio Required Under Crd Fourth Common Equity Tier One Ratio required for capital adequacy purposes under the Capital Requirements Directive (DRD IV) in the European Union. Securities sold under agreements to repurchase Increase (Decrease) in Payables under Repurchase Agreements Receivables from brokers, dealers and clearing organizations Increase (Decrease) in Receivable from Broker-Dealer and Clearing Organization Occupancy and equipment costs Occupancy, Net Cash Collateral Received Security Purchased under Agreement to Resell, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash Not Offset Convertible bonds Convertible Debt Securities [Member] Litigation settlement amount awarded to other party Litigation Settlement, Amount Awarded to Other Party Trading Arrangement: Trading Arrangement [Axis] Income tax payable Increase (Decrease) in Income Taxes Payable Total Shareholder Return Amount Total Shareholder Return Amount Loss Contingencies [Line Items] Loss Contingencies [Line Items] Subsequent events Subsequent Events [Text Block] Deposits with clearing organizations Increase (Decrease) in Deposit Assets Currency translation adjustment Currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Insider Trading Arrangements [Line Items] Corporate/Other Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] 2021 and prior Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year Security Exchange Name Security Exchange Name Net Amounts of Liabilities Presented on the Balance Sheet Security Sold under Agreement to Repurchase, Subject to Master Netting Arrangement, after Offset Corporate equities Equity Securities [Member] Re-pledged amounts under securities loans agreements Customer Securities under Customer Margin Loans that are Available to be Pledged, Re-pledged Amount Customer Securities under Customer Margin Loans that are Available to be Pledged, Re-pledged Amount Total liabilities Liabilities Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Expenses Operating Expenses [Abstract] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Gross Amounts of Recognized Assets Security Borrowed, Subject to Master Netting Arrangement, before Offset Asset Class [Domain] Asset Class [Domain] Total realized and unrealized gain (losses) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Cash Collateral Received Derivative Asset, Security Purchased under Agreement to Resell, and Security Borrowed, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash Not Offset Collateralized transactions Collateralized Transaction [Text Block] Collateralized Transaction Statement [Line Items] Statement [Line Items] Consolidation Items [Axis] Consolidation Items [Axis] Amounts pledged Pledged Securities Owned And Pledged As Collateral Amount Eligible To Be Repledged By Counterparty Carrying Value Pledged securities owned and pledged as collateral amount eligible to be repledged by counterparty carrying value. Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Securities Financing Transaction [Domain] Securities Financing Transaction [Domain] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalent Common Stock Common Stock [Member] Accrued compensation Employee-related Liabilities Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Corporate debt and other obligations Corporate debt and other obligations Corporate Debt Securities [Member] Oppenheimer Oppenheimer [Member] Oppenheimer. Net (decrease)/increase in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Gross Amounts Offset on the Balance Sheet Security Purchased under Agreement to Resell, Subject to Master Netting Arrangement, Liability Offset