Quarterly Information - Schedule of Quarterly Information (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 254,928		$ 244,679		$ 249,689		$ 255,168		$ 293,362		$ 243,376		$ 243,830		$ 239,146		$ 1,004,464		$ 1,019,714		$ 952,612
Income before income taxes	9,595		10,896		136		5,109		23,359		8,163		5,674		6,713		25,736		43,909		(527)
Net income attributable to Oppenheimer Holdings Inc.	$ 2,686		$ 4,470		$ (1,554)		$ 3,224		$ 13,313		$ 5,237		$ 2,848		$ 3,663		$ 8,826		$ 25,061		$ (3,613)
Earnings per share attributable to Oppenheimer Holdings Inc.
Basic earnings per share	$ 0.20		$ 0.33		$ (0.11)		$ 0.24		$ 0.99		$ 0.38		$ 0.21		$ 0.27		$ 0.65		$ 1.85		$ (0.27)
Diluted earnings per share	$ 0.19		$ 0.31		$ (0.11)		$ 0.23		$ 0.94		$ 0.37		$ 0.20		$ 0.26		$ 0.62		$ 1.77		$ (0.27)
Dividends per share	$ 0.11		$ 0.11		$ 0.11		$ 0.11		$ 0.11		$ 0.11		$ 0.11		$ 0.11		$ 0.44		$ 0.44000
Market price of Class A Stock
High	$ 24.7	[1]	$ 24.8	[1]	$ 28.86	[1]	$ 29.75	[1]	$ 24.80	[1]	$ 19.75	[1]	$ 20.00	[1]	$ 21.00	[1]	$ 29.75	[1]	$ 24.80	[1]
Low	$ 19.97	[1]	$ 19.76	[1]	$ 21.28	[1]	$ 22.26	[1]	$ 16.66	[1]	$ 16.52	[1]	$ 16.75	[1]	$ 15.69	[1]	$ 19.76	[1]	$ 15.69	[1]

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