Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Basic weighted average number of shares outstanding (in shares)	11,016,430	11,980,115	11,054,306	12,222,527
Net dilutive effect of share-based awards, treasury stock method (in shares)	0	0	857,073	919,011
Diluted weighted average number of shares outstanding (in shares)	11,016,430	11,980,115	11,911,379	13,141,538
Net income (loss) attributable to Oppenheimer Holdings Inc.	$ (9,400)	$ (3,874)	$ 5,217	$ 5,418
Earnings (Loss) per share attributable to Oppenheimer Holdings Inc., Basic (in dollars per share)	$ (0.85)	$ (0.32)	$ 0.47	$ 0.44
Earnings (Loss) per share attributable to Oppenheimer Holdings Inc., Diluted (in dollars per share)	$ (0.85)	$ (0.32)	$ 0.44	$ 0.41
Class A Stock
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Number of anti-dilutive stock options granted	1,138,992	1,267,733	281,810	4,100