Quarterly information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 230,360		$ 213,536		$ 238,928		$ 245,561		$ 254,928		$ 244,679		$ 249,689		$ 255,168		$ 928,385		$ 1,004,464		$ 1,019,714
Income (loss) before income tax provision (benefit)	(4,243)		(1,527)		2,630		9,851		9,595		10,896		136		5,109		6,711		25,736		43,909
Net income (loss) attributable to Oppenheimer Holdings Inc.	$ (3,144)		$ (908)		$ 295		$ 5,719		$ 2,686		$ 4,470		$ (1,554)		$ 3,224		$ 1,962		$ 8,826		$ 25,061
Earnings (loss) per share attributable to Oppenheimer Holdings Inc.
Basic earnings (loss) per share (in dollars per share)	$ (0.23)		$ (0.07)		$ 0.02		$ 0.42		$ 0.20		$ 0.33		$ (0.11)		$ 0.24		$ 0.14		$ 0.65		$ 1.85
Diluted earnings (loss) per share (in dollars per share)	(0.23)		(0.07)		0.02		0.40		0.19		0.31		(0.11)		0.23		0.14		0.62		$ 1.77
Dividends per share (in dollars per share)	0.11		0.11		0.11		0.11		0.11		0.11		0.11		0.11		0.44		0.44
Market price of Class A Stock
High (in dollars per share)	20.98	[1]	26.80	[1]	27.99	[1]	24.41	[1]	24.7	[2]	24.8	[2]	28.86	[2]	29.75	[2]	27.99	[1]	29.75	[2]
Low (in dollars per share)	$ 15.60	[1]	$ 17.40	[1]	$ 22.30	[1]	$ 19.04	[1]	$ 19.97	[2]	$ 19.76	[2]	$ 21.28	[2]	$ 22.26	[2]	$ 15.6	[1]	$ 19.76	[2]

[1] The price quotations above were obtained from the New York Stock Exchange website.

[2] The price quotations above were obtained from the New York Stock Exchange website.