Earnings Per Share - Summary of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended			6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016		Jun. 30, 2017	Jun. 30, 2016
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net loss from continuing operations		$ (1,363)	$ (2,855)	[1]	$ (6,701)	$ (6,147)	[1]
Net income from discontinued operations		53	9,566	[1]	640	8,949	[1]
Net income (loss)		(1,310)	6,711	[1]	(6,061)	2,802	[1]
Less net income attributable to noncontrolling interest, net of tax		9	1,523	[1]	105	1,461	[1]
Net income (loss) attributable to Oppenheimer Holdings Inc.		$ (1,319)	$ 5,188	[1]	$ (6,166)	$ 1,341	[1]
Basic weighted average number of shares outstanding (in shares)		13,260,855	13,367,248	[1]	13,329,670	13,373,537	[1]
Net dilutive effect of share-based awards, treasury method (in shares)	[2]	0	0		0	0
Diluted weighted average number of shares outstanding (in shares)		13,260,855	13,367,248		13,329,670	13,373,537
Basic net income (loss) per share attributable to Oppenheimer Holdings Inc.
Continuing operations, basic (in dollars per share)		$ (0.10)	$ (0.21)	[1]	$ (0.50)	$ (0.46)	[1]
Discontinued operations, basic (in dollars per share)		0.00	0.60	[1]	0.04	0.56	[1]
Basic (in dollars per share)		(0.10)	0.39	[1]	(0.46)	0.10	[1]
Diluted net income (loss) per share attributable to Oppenheimer Holdings Inc.
Continuing operations, diluted (in dollars per share)		(0.10)	(0.21)	[1]	(0.50)	(0.46)	[1]
Discontinued operations, diluted (in dollars per share)		0.00	0.60	[1]	0.04	0.56	[1]
Diluted (in dollars per share)		$ (0.10)	$ 0.39	[1]	$ (0.46)	$ 0.10	[1]
Class A Stock [Member]
Diluted net income (loss) per share attributable to Oppenheimer Holdings Inc.
Number of anti-dilutive warrants, options and restricted shares, for the year (in shares)		1,336,424	1,271,124		1,336,424	1,271,124

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[2] For both the three and six months ended June 30, 2017, the diluted net income (loss) per share computation does not include the anti-dilutive effect of 1,336,424 shares of Class A Stock granted under share-based compensation arrangements (1,271,124 for the three and six months ended June 30, 2016).