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Deferred compensation vesting life.

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Liability related to the OARs.

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Number of stock appreciation rights granted.

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Number of type of employee compensation plans granted under share-based compensation and cash-based compensation plans

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Amount of difference between fair value and exercise price of outstanding and expected to vest stock appreciation rights.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

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Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

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Amount of discretionary contributions made by an employer to a defined contribution plan.

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Maximum amount the employee may contribute to a defined contribution plan.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Percentage of vesting of award under share-based payment arrangement.

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Intrinsic value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Employee Compensation Plans - Additional Information (Narrative) (Details)			12 Months Ended
	Jan. 28, 2021 shares	Jan. 11, 2021 shares	Dec. 31, 2020 USD ($) employee_compensation_plan shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Employee Compensation Plans Granted \| employee_compensation_plan			2
Maximum annual contribution under Defined Contribution Plan			$ 19,500	$ 19,000	$ 18,500
Employer contribution to Defined Contribution Plan			3,500,000	2,400,000	1,800,000
Deferred bonus amounts			$ 10,000,000.0	9,300,000	9,400,000
Vesting period of deferred bonus			5 years
Deferred compensation plans cost			$ 18,100,000	19,400,000	6,100,000
Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of Class A Stock available \| shares			1,279,118
Restricted Stock \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of ESP awards outstanding			$ 41,800,000
Compensation expense relating to the share-based awards			7,700,000	8,100,000	6,000,000.0
Unrecognized compensation cost related to unvested share-based compensation			$ 14,600,000
Cost is expected to be recognized over a weighted average period			1 year 10 months 24 days
Granted, Number of shares \| shares			471,700
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period \| shares			623,981
Restricted Stock \| Subsequent Event [Member] \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of shares \| shares	571,940
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense relating to the share-based awards			$ 25,300	26,200	26,500
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense relating to the share-based awards			$ 8,500,000	$ 3,700,000	$ 650,000
Cost is expected to be recognized over a weighted average period			3 years 1 month 6 days
Aggregate intrinsic value of OARs outstanding and expected to vest			$ 17,500,000
Liability related to the OARs			15,400,000
Total unrecognized compensation cost			$ 9,500,000
Stock Appreciation Rights (SARs) [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period under share based payment		5 years
Number Of Stock Appreciation Rights Granted \| shares		639,050
Minimum [Member] \| Restricted Stock \| Subsequent Event [Member] \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period under share based payment	3 years
Maximum [Member] \| Restricted Stock \| Subsequent Event [Member] \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period under share based payment	5 years
Third Anniversary \| Restricted Stock \| Subsequent Event [Member] \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of shares \| shares	293,690
Fifth Anniversary [Domain] \| Restricted Stock \| Subsequent Event [Member] \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period \| shares	278,250
Oppenheimer Holdings 2014 Incentive Plan (OIP) [Member] \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term granted for options			5 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period			6 months
Oppenheimer Holdings 2014 Incentive Plan (OIP) [Member] \| Minimum [Member] \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period under share based payment			3 years
Oppenheimer Holdings 2014 Incentive Plan (OIP) [Member] \| Maximum [Member] \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period under share based payment			5 years
Oppenheimer Holdings 2014 Incentive Plan (OIP) [Member] \| Second Anniversary \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage under share based payment			25.00%
Oppenheimer Holdings 2014 Incentive Plan (OIP) [Member] \| Third Anniversary \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage under share based payment			25.00%
Oppenheimer Holdings 2014 Incentive Plan (OIP) [Member] \| Fourth Anniversary \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage under share based payment			25.00%
Oppenheimer Holdings 2014 Incentive Plan (OIP) [Member] \| Six Months Before Expiration \| Class A Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage under share based payment			25.00%
Oppenheimer Holdings Inc. Stock Appreciation Right Plan \| Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period under share based payment			5 years
Executive Deferred Compensation Plan and Deferred Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company's deferred compensation liability			$ 52,600,000
CIBC Deferred Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company's deferred compensation liability			$ 21,400,000