Earnings per share - Summary of Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share [Abstract]
Basic weighted average number of shares outstanding	13,607,998	13,597,330
Net dilutive effect of warrant, treasury method
Net dilutive effect of share-based awards, treasury method	420,717
Diluted weighted average number of shares outstanding	14,028,715	13,597,330
Net income (loss) for the period	$ 3,893	$ (3,883)
Net income attributable to non-controlling interest, net of tax	230	774
Net income (loss) attributable to Oppenheimer Holdings Inc.	$ 3,663	$ (4,657)
Basic profit (loss) per share	$ 0.27	$ (0.34)
Diluted profit (loss) per share	$ 0.26	$ (0.34)