Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Basic weighted average number of shares outstanding (in shares)	11,270,589	12,690,386	11,901,727	12,653,310
Net dilutive effect of share-based awards, treasury method (in shares)	919,836	973,828	907,273	886,063
Diluted weighted average number of shares outstanding (in shares)	12,190,425	13,664,214	12,809,000	13,539,373
Net income attributable to Oppenheimer Holdings Inc.	$ 4,520	$ 26,250	$ 9,938	$ 96,067
Basic (in dollars per share)	$ 0.40	$ 2.07	$ 0.84	$ 7.59
Diluted (in dollars per share)	$ 0.37	$ 1.92	$ 0.78	$ 7.10
Class A Stock
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Number of anti-dilutive stock options granted	398,198	0	22,250	0