Condensed Consolidating Financial Information - Condensed Consolidating Statement of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
REVENUES
Commissions	$ 110,862	$ 120,252	$ 349,062	$ 364,272
Advisory fees	70,957	60,117	209,592	177,417
Investment banking	33,841	21,362	94,164	62,377
Interest	12,449	14,439	37,387	39,916
Principal transactions, net	4,272	10,347	24,883	33,596
Other	12,298	16,859	34,448	48,774
Total revenue	244,679	243,376	749,536	726,352
EXPENSES
Compensation and related expenses	161,334	161,081	493,135	480,296
Communications and technology	15,991	16,999	50,261	48,881
Occupancy and equipment costs	15,801	16,405	47,105	51,111
Clearing and exchange fees	5,969	6,099	17,885	18,434
Interest	4,127	6,164	13,703	20,169
Other	30,561	28,465	111,306	86,911
Total expenses	233,783	235,213	733,395	705,802
Income (loss) before income taxes	10,896	8,163	16,141	20,550
Income tax provision (benefit)	6,271	2,655	9,349	8,083
Net income (loss) for the period	4,625	5,508	6,792	12,467
Less net income attributable to non-controlling interests, net of tax	155	271	652	719
Net income attributable to Oppenheimer Holdings Inc.	4,470	5,237	6,140	11,748
Other comprehensive income (loss)	(1,608)	656	(1,356)	1,156
Comprehensive income attributable to Oppenheimer Holdings Inc.	2,862	5,893	4,784	12,904
Consolidation, Eliminations [Member]
REVENUES
Advisory fees	(321)	(533)	(1,002)	(1,720)
Interest	(2,565)	(3,143)	(7,861)	(8,578)
Other	(66)	(42)	(346)	(126)
Total revenue	(2,952)	(3,718)	(9,209)	(10,424)
EXPENSES
Occupancy and equipment costs	(66)	(42)	(346)	(126)
Interest	(2,565)	(3,143)	(7,861)	(8,578)
Other	(321)	(533)	(1,002)	(1,720)
Total expenses	(2,952)	(3,718)	(9,209)	(10,424)
Equity in subsidiaries	(6,415)	(8,335)	(16,139)	(21,173)
Net income attributable to Oppenheimer Holdings Inc.	(6,415)	(8,335)	(16,139)	(21,173)
Comprehensive income attributable to Oppenheimer Holdings Inc.	(6,415)	(8,335)	(16,139)	(21,173)
Non-Guarantor Subsidiaries [Member]
REVENUES
Interest		14,805
EXPENSES
Occupancy and equipment costs		16,447
Guarantor Subsidiaries [Member]
REVENUES
Interest		2,777
Parent Company [Member]
REVENUES
Interest				5
Total revenue		0		5
EXPENSES
Compensation and related expenses	207	207	822	902
Communications and technology	37	23	111	81
Interest	3,281	4,375	11,120	13,125
Other	235	285	4,396	1,045
Total expenses	3,760	4,890	16,449	15,153
Income (loss) before income taxes	(3,760)	(4,890)	(16,449)	(15,148)
Income tax provision (benefit)	(1,816)	(1,792)	(6,450)	(5,723)
Net income (loss) for the period	(1,944)	(3,098)	(9,999)	(9,425)
Equity in subsidiaries	6,415	8,335	16,139	21,173
Net income attributable to Oppenheimer Holdings Inc.	4,471	5,237	6,140	11,748
Other comprehensive income (loss)		0		(3)
Comprehensive income attributable to Oppenheimer Holdings Inc.	4,471	5,237	6,140	11,745
Guarantor Subsidiaries [Member]
REVENUES
Interest	2,580		7,901	8,370
Principal transactions, net	(161)	26	10	38
Other	85	42	375	126
Total revenue	2,504	2,845	8,286	8,534
EXPENSES
Interest	8		8
Other	17	4	30	23
Total expenses	25	4	38	23
Income (loss) before income taxes	2,479	2,841	8,248	8,511
Income tax provision (benefit)	1,326	1,808	2,457	3,702
Net income (loss) for the period	1,153	1,033	5,791	4,809
Net income attributable to Oppenheimer Holdings Inc.	1,153	1,033	5,791	4,809
Comprehensive income attributable to Oppenheimer Holdings Inc.	1,153	1,033	5,791	4,809
Non-Guarantor Subsidiaries [Member]
REVENUES
Commissions	110,862	120,252	349,062	364,272
Advisory fees	71,278	60,650	210,594	179,137
Investment banking	33,841	21,362	94,164	62,377
Interest	12,434		37,347	40,119
Principal transactions, net	4,433	10,321	24,873	33,558
Other	12,279	16,859	34,419	48,774
Total revenue	245,127	244,249	750,459	728,237
EXPENSES
Compensation and related expenses	161,127	160,874	492,313	479,394
Communications and technology	15,954	16,976	50,150	48,800
Occupancy and equipment costs	15,867		47,451	51,237
Clearing and exchange fees	5,969	6,099	17,885	18,434
Interest	3,403	4,932	10,436	15,622
Other	30,630	28,709	107,882	87,563
Total expenses	232,950	234,037	726,117	701,050
Income (loss) before income taxes	12,177	10,212	24,342	27,187
Income tax provision (benefit)	6,761	2,639	13,342	10,104
Net income (loss) for the period	5,416	7,573	11,000	17,083
Less net income attributable to non-controlling interests, net of tax	155	271	652	719
Net income attributable to Oppenheimer Holdings Inc.	5,261	7,302	10,348	16,364
Other comprehensive income (loss)	(1,608)	656	(1,356)	1,159
Comprehensive income attributable to Oppenheimer Holdings Inc.	$ 3,653	$ 7,958	$ 8,992	$ 17,523