Cover - shares	6 Months Ended
	Jun. 30, 2020	Jul. 30, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
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	Common Stock
Trading Symbol	OPY
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0000791963
Current Fiscal Year End Date	--12-31
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false
Class A Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		12,465,084
Class B Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		99,665