Condensed Consolidating Financial Information - Condensed Consolidating Statement of Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
REVENUES
Commissions	$ 109,695	$ 122,138
Advisory fees	70,966	68,205
Investment banking	27,305	33,524
Interest	11,035	12,390
Principal transactions, net	18,555	8,817
Other	8,005	10,094
Total revenue	245,561	255,168
EXPENSES
Compensation and related expenses	163,091	171,950
Communications and technology	17,168	16,734
Occupancy and equipment costs	15,778	15,397
Clearing and exchange fees	6,402	5,892
Interest	3,910	5,164
Other	29,361	34,922
Total expenses	235,710	250,059
Income (loss) before income taxes	9,851	5,109
Income tax provision (benefit)	3,730	1,689
Equity in subsidiaries	0	0
Net income (loss) for the period	6,121	3,420
Less net income attributable to noncontrolling interests	402	196
Net income attributable to Oppenheimer Holdings Inc.	5,719	3,224
Other comprehensive income (loss)	(567)	(87)
Comprehensive income attributable to Oppenheimer Holdings Inc.	5,152	3,137
Eliminations [Member]
REVENUES
Commissions	0	0
Advisory fees	(454)	(370)
Investment banking	0	0
Interest	(2,564)	(2,710)
Principal transactions, net	(54)	0
Other	(75)	(216)
Total revenue	(3,147)	(3,296)
EXPENSES
Compensation and related expenses	0	0
Communications and technology	0	0
Occupancy and equipment costs	(75)	(216)
Clearing and exchange fees	0	0
Interest	(2,564)	(2,710)
Other	(508)	(370)
Total expenses	(3,147)	(3,296)
Income (loss) before income taxes	0	0
Income tax provision (benefit)	0	0
Equity in subsidiaries	(14,544)	(9,623)
Net income (loss) for the period	(14,544)	(9,623)
Less net income attributable to noncontrolling interests	0	0
Net income attributable to Oppenheimer Holdings Inc.	(14,544)	(9,623)
Other comprehensive income (loss)	0	0
Comprehensive income attributable to Oppenheimer Holdings Inc.	(14,544)	(9,623)
Parent Company [Member]
REVENUES
Commissions	0	0
Advisory fees	0	0
Investment banking	0	0
Interest	0	0
Principal transactions, net	0	0
Other	0	0
Total revenue	0	0
EXPENSES
Compensation and related expenses	312	315
Communications and technology	25	27
Occupancy and equipment costs	0	0
Clearing and exchange fees	0	0
Interest	3,281	4,375
Other	288	344
Total expenses	3,906	5,061
Income (loss) before income taxes	(3,906)	(5,061)
Income tax provision (benefit)	(1,480)	(1,911)
Equity in subsidiaries	8,145	6,374
Net income (loss) for the period	5,719	3,224
Less net income attributable to noncontrolling interests	0	0
Net income attributable to Oppenheimer Holdings Inc.	5,719	3,224
Other comprehensive income (loss)	0	0
Comprehensive income attributable to Oppenheimer Holdings Inc.	5,719	3,224
Guarantor Subsidiaries [Member]
REVENUES
Commissions	0	0
Advisory fees	0	0
Investment banking	0	0
Interest	2,566	2,733
Principal transactions, net	0	40
Other	95	216
Total revenue	2,661	2,989
EXPENSES
Compensation and related expenses	0	0
Communications and technology	0	0
Occupancy and equipment costs	0	0
Clearing and exchange fees	0	0
Interest	0	0
Other	68	2
Total expenses	68	2
Income (loss) before income taxes	2,593	2,987
Income tax provision (benefit)	847	(138)
Equity in subsidiaries	6,399	3,249
Net income (loss) for the period	8,145	6,374
Less net income attributable to noncontrolling interests	0	0
Net income attributable to Oppenheimer Holdings Inc.	8,145	6,374
Other comprehensive income (loss)	0	0
Comprehensive income attributable to Oppenheimer Holdings Inc.	8,145	6,374
Non-Guarantor Subsidiaries [Member]
REVENUES
Commissions	109,695	122,138
Advisory fees	71,420	68,575
Investment banking	27,305	33,524
Interest	11,033	12,367
Principal transactions, net	18,609	8,777
Other	7,985	10,094
Total revenue	246,047	255,475
EXPENSES
Compensation and related expenses	162,779	171,635
Communications and technology	17,143	16,707
Occupancy and equipment costs	15,853	15,613
Clearing and exchange fees	6,402	5,892
Interest	3,193	3,499
Other	29,513	34,946
Total expenses	234,883	248,292
Income (loss) before income taxes	11,164	7,183
Income tax provision (benefit)	4,363	3,738
Equity in subsidiaries	0	0
Net income (loss) for the period	6,801	3,445
Less net income attributable to noncontrolling interests	402	196
Net income attributable to Oppenheimer Holdings Inc.	6,399	3,249
Other comprehensive income (loss)	(567)	(87)
Comprehensive income attributable to Oppenheimer Holdings Inc.	$ 5,832	$ 3,162