Earnings Per Share - Summary of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Basic weighted average number of shares outstanding (in shares)		13,690,698	13,630,368	13,713,578	13,595,458
Net dilutive effect of share-based awards, treasury method (in shares)	[1]	0	667,074	625,627	621,789
Diluted weighted average number of shares outstanding (in shares)		13,690,698	14,297,442	14,339,205	14,217,247
Net income (loss) for the period		$ (777)	$ 4,625	$ 5,989	$ 6,792
Net income attributable to noncontrolling interest, net of tax		131	155	883	652
Net income (loss) attributable to Oppenheimer Holdings Inc.		$ (908)	$ 4,470	$ 5,106	$ 6,140
Basic earnings (loss) per share (in dollars per share)		$ (0.07)	$ 0.33	$ 0.37	$ 0.45
Diluted earnings (loss) per share (in dollars per share)		$ (0.07)	$ 0.31	$ 0.36	$ 0.43
Class A Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Number of anti-dilutive warrants, options and restricted shares, for the year		1,304,185		40,309	58,008

[1] For the three and nine months ended September 30, 2015, the diluted earnings per share computation does not include the anti-dilutive effect of 1,304,185 and 40,309 shares of Class A Stock granted under share-based compensation arrangements, respectively (58,008 for both the three and nine months ended September 30, 2014).