Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
REVENUE
Commissions	$ 82,850	$ 83,852	$ 166,257	$ 170,569
Advisory fees	77,270	72,783	154,818	142,192
Investment banking	27,904	15,386	56,114	33,407
Proceeds from (Payments for) in Interest-bearing Deposits in Banks	28,853	17,720	54,150	31,846
Interest	13,056	12,829	25,283	23,394
Principal transactions, net	6,400	5,302	9,126	10,675
Other	6,223	8,012	11,338	17,062
Total revenue	242,556	215,884	477,086	429,145
EXPENSES
Compensation and related expenses	151,871	142,657	304,975	286,535
Communications and technology	17,997	18,399	36,685	36,105
Occupancy and equipment costs	14,901	15,161	30,329	30,433
Clearing and exchange fees	5,780	5,916	11,876	11,770
Interest	10,909	6,854	19,872	12,210
Other	28,597	28,534	51,223	60,754
Total expenses	230,055	217,521	454,960	437,807
Income (Loss) before income taxes from continuing operations	12,501	(1,637)	22,126	(8,662)
Income Tax Expense (Benefit)	3,662	(274)	6,578	(1,961)
Net income (loss) from continuing operations	8,839	(1,363)	15,548	(6,701)
Income from discontinued operations	0	89	0	1,065
Income taxes	0	36	0	425
Net income from discontinued operations	0	53	0	640
Net income (loss)	8,839	(1,310)	15,548	(6,061)
Less net income (loss) attributable to non-controlling interest, net of tax	(16)	9	(12)	105
Net income (loss) attributable to Oppenheimer Holdings Inc.	$ 8,855	$ (1,319)	$ 15,560	$ (6,166)
Basic net income (loss) per share attributable to Oppenheimer Holdings Inc.
Continuing operations (in dollars per share)	$ 0.67	$ (0.10)	$ 1.17	$ (0.50)
Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.04
Net loss per share (in dollars per share)	0.67	(0.10)	1.17	(0.46)
Earnings Per Share, Diluted [Abstract]
Continuing operations (in dollars per share)	0.63	(0.10)	1.11	(0.50)
Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.04
Net loss per share (in dollars per share)	$ 0.63	$ (0.10)	$ 1.11	$ (0.46)
Weighted average shares
Basic (in shares)	13,248,812	13,260,855	13,244,245	13,329,670
Diluted (in shares)	14,050,573	13,260,855	14,005,556	13,329,670