Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Earnings Per Share [Abstract]
Basic weighted average number of shares outstanding (in shares)	10,519,431	11,270,589	10,874,055	11,901,727
Net dilutive effect of share-based awards, treasury stock method (in shares)	920,798	919,836	872,282	907,273
Diluted weighted average number of shares outstanding (in shares)	11,440,229	12,190,425	11,746,337	12,809,000
Net income attributable to Oppenheimer Holdings Inc.	$ 13,861	$ 4,520	$ 19,079	$ 9,938
Earnings per share attributable to Oppenheimer Holdings Inc., Basic (in dollars per share)	$ 1.32	$ 0.40	$ 1.75	$ 0.84
Earnings per share attributable to Oppenheimer Holdings Inc., Diluted (in dollars per share)	$ 1.21	$ 0.37	$ 1.62	$ 0.78
Class A Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of anti-dilutive stock options granted (in shares)	286,185	398,198	277,435	22,250