Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
REVENUE
Commissions									$ 336,620	$ 377,317	$ 417,559
Advisory fees									320,746	269,119	280,247
Investment banking									78,215	81,011	102,540
Interest									48,498	47,649	49,032
Principal transactions, net									23,273	20,481	15,180
Other									112,986	62,202	33,243
Total revenue	$ 264,973	$ 226,220	$ 215,884	$ 213,261	$ 218,945	$ 211,804	$ 212,074	$ 214,956	920,338	857,779	897,801
EXPENSES
Compensation and related expenses									602,138	584,710	610,820
Communications and technology									71,978	70,390	66,549
Occupancy and equipment costs									61,164	60,791	62,842
Clearing and exchange fees									23,545	25,126	26,022
Interest									28,354	19,437	16,329
Other									113,423	119,217	117,667
Total expenses	248,403	214,392	217,521	220,286	226,441	213,614	217,320	222,296	900,602	879,671	900,229
Income (loss) before income taxes from continuing operations	16,570	11,828	(1,637)	(7,025)	(7,496)	(1,810)	(5,246)	(7,340)	19,736	(21,892)	(2,428)
Current and Deferred Income Tax Expense (Benefit) from Continuing Operations									(2,134)	(12,262)	406
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	21,168	7,403	(1,363)	(5,338)	(2,424)	(1,059)	(2,855)	(3,292)	21,870	(9,630)	(2,834)
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax									2,071	17,339	9,139
Discontinued Operation, Tax Effect of Discontinued Operation									941	7,218	3,407
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	29	461	53	587	759	413	9,566	(617)	1,130	10,121	5,732
Net income	21,197	7,864	(1,310)	(4,751)	(1,665)	(646)	6,711	(3,909)	23,000	491	2,898
Less net income attributable to noncontrolling interest, net of tax	4	75	9	96	125	66	1,523	(62)	184	1,652	936
Net income (loss) attributable to Oppenheimer Holdings Inc.	$ 21,193	$ 7,789	$ (1,319)	$ (4,847)	$ (1,790)	$ (712)	$ 5,188	$ (3,847)	$ 22,816	$ (1,161)	$ 1,962
Basic net income (loss) per share attributable to Oppenheimer Holdings Inc.
Income (Loss) from Continuing Operations, Per Basic Share	$ 1.61	$ 0.56	$ (0.10)	$ (0.40)	$ (0.28)	$ (0.08)	$ (0.21)	$ (0.25)	$ 1.65	$ (0.72)	$ (0.21)
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0.00	0.03	0.00	0.04	0.05	0.03	0.60	(0.04)	0.07	0.63	0.35
Net income (loss) per share	1.61	0.59	(0.10)	(0.36)	0	0	0	0	1.72	(0.09)	0.14
Income (Loss) from Continuing Operations, Per Diluted Share	1.54	0.54	(0.10)	(0.40)	(0.28)	(0.08)	(0.21)	(0.25)	1.60	(0.72)	(0.21)
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0.00	0.03	0.00	0.04	0.05	0.03	0.60	(0.04)	0.07	0.63	0.35
Earnings Per Share, Diluted	1.54	0.57	(0.10)	(0.36)	0	0	0	0	1.67	(0.09)	0.14
Dividends	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.44000	$ 0.44	$ 440.00
Weighted average shares
Basic									13,246,423	13,368,768	13,640,610
Diluted									13,673,361	13,368,768	13,640,610
Retained Earnings [Member]
EXPENSES
Net income (loss) attributable to Oppenheimer Holdings Inc.									$ 22,816	$ (1,161)	$ 1,962
Basic net income (loss) per share attributable to Oppenheimer Holdings Inc.
Dividends									$ 0.44	$ 0.44	$ 0.44