Earnings Per Share - Summary of Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Basic weighted average number of shares outstanding (in shares)	13,704,228		13,536,805
Net dilutive effect of share-based awards, treasury method	578,042	[1]	578,152	[1]
Diluted weighted average number of shares outstanding	14,282,270		14,114,957
Net income for the period	$ 6,121		$ 3,420
Net income attributable to noncontrolling interest, net of tax	402		196
Net income attributable to Oppenheimer Holdings Inc.	$ 5,719		$ 3,224
Basic earnings (loss) per share (in dollars per share)	$ 0.42		$ 0.24
Diluted earnings (loss) per share (in dollars per share)	$ 0.40		$ 0.23
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	46,076		55,309

[1] For the three months ended March 31, 2015, the diluted earnings per share computation does not include the anti-dilutive effect of 46,076 shares of Class A Stock granted under share-based compensation arrangements (55,309 shares of Class A Stock granted under share-based compensation arrangements for the three months ended March 31, 2014).