Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Mar. 02, 2020	Jun. 30, 2017
Document Information [Line Items]
Entity Registrant Name	OPPENHEIMER HOLDINGS INC
Entity Central Index Key	0000791963
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 347.2
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		12,986,606
Class B Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		99,665