Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 28, 2022	Jun. 30, 2021
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-12043
Entity Registrant Name	OPPENHEIMER HOLDINGS INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	98-0080034
Entity Address, Address Line One	85 Broad Street,
Entity Address, City or Town	New York,
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10004
City Area Code	212
Local Phone Number	668-8000
Title of 12(b) Security	Class A non-voting common stock
Trading Symbol	OPY
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 640.2
Documents Incorporated by Reference	The Company's definitive Proxy Statement for the 2022 Annual Meeting of Stockholders to be filed by the Company pursuant to Regulation 14A is incorporated into Items 10, 11, 12, 13 and 14 of Part III of this Form 10-K.
Entity Central Index Key	0000791963
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
Class A Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		12,322,073,000
Class B Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		99,665,000