Condensed Consolidating Financial Information - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
REVENUES
Commissions	$ 101,243	$ 110,862	$ 314,494	$ 349,062
Advisory fees	69,557	70,957	212,766	209,592
Investment banking	16,548	33,841	72,873	94,164
Interest	14,384	12,449	37,449	37,387
Principal transactions, net	(3,339)	4,272	16,926	24,883
Other	15,143	12,298	43,517	34,448
Total revenue	213,536	244,679	698,025	749,536
EXPENSES
Compensation and related expenses	142,746	161,334	464,051	493,135
Communications and technology	16,475	15,991	50,050	50,261
Occupancy and equipment costs	16,158	15,801	47,920	47,105
Clearing and exchange fees	6,909	5,969	19,542	17,885
Interest	4,541	4,127	12,956	13,703
Other	28,234	30,561	92,552	111,306
Total expenses	215,063	233,783	687,071	733,395
Income (loss) before income tax provision (benefit)	(1,527)	10,896	10,954	16,141
Income tax provision (benefit)	(750)	6,271	4,965	9,349
Equity in earnings of subsidiaries	0	0	0	0
Net income (loss) for the period	(777)	4,625	5,989	6,792
Less net income attributable to noncontrolling interests	131	155	883	652
Net income (loss) attributable to Oppenheimer Holdings Inc.	(908)	4,470	5,106	6,140
Other comprehensive income (loss)	(916)	(1,608)	(166)	(1,356)
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	(1,824)	2,862	4,940	4,784
Eliminations [Member]
REVENUES
Commissions	0	0	0	0
Advisory fees	(381)	(321)	(1,246)	(1,002)
Investment banking	0	0	0	0
Interest	(2,565)	(2,565)	(7,694)	(7,861)
Principal transactions, net	(239)	(161)	(323)	0
Other	(74)	(66)	(225)	(346)
Total revenue	(3,259)	(3,113)	(9,488)	(9,209)
EXPENSES
Compensation and related expenses	0	0	0	0
Communications and technology	0	0	0	0
Occupancy and equipment costs	(74)	(66)	(225)	(346)
Clearing and exchange fees	0	0	0	0
Interest	(2,565)	(2,565)	(7,694)	(7,861)
Other	(620)	(482)	(1,569)	(1,002)
Total expenses	(3,259)	(3,113)	(9,488)	(9,209)
Income (loss) before income tax provision (benefit)	0	0	0	0
Income tax provision (benefit)	0	0	0	0
Equity in earnings of subsidiaries	(2,051)	(11,675)	(20,146)	(26,487)
Net income (loss) for the period	(2,051)	(11,675)	(20,146)	(26,487)
Less net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to Oppenheimer Holdings Inc.	(2,051)	(11,675)	(20,146)	(26,487)
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	(2,051)	(11,675)	(20,146)	(26,487)
Parent Company [Member]
REVENUES
Commissions	0	0	0	0
Advisory fees	0	0	0	0
Investment banking	0	0	0	0
Interest	0	0	0	0
Principal transactions, net	0	0	0	0
Other	0	0	0	0
Total revenue	0	0	0	0
EXPENSES
Compensation and related expenses	254	207	829	822
Communications and technology	27	37	94	111
Occupancy and equipment costs	0	0	0	0
Clearing and exchange fees	0	0	0	0
Interest	3,282	3,281	9,844	11,120
Other	234	235	780	4,396
Total expenses	3,797	3,760	11,547	16,449
Income (loss) before income tax provision (benefit)	(3,797)	(3,760)	(11,547)	(16,449)
Income tax provision (benefit)	(1,343)	(1,816)	(4,344)	(6,450)
Equity in earnings of subsidiaries	1,546	6,414	12,309	16,139
Net income (loss) for the period	(908)	4,470	5,106	6,140
Less net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to Oppenheimer Holdings Inc.	(908)	4,470	5,106	6,140
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	(908)	4,470	5,106	6,140
Guarantor Subsidiaries [Member]
REVENUES
Commissions	0	0	0	0
Advisory fees	0	0	0	0
Investment banking	0	0	0	0
Interest	2,557	2,580	7,680	7,901
Principal transactions, net	0	0	0	10
Other	96	85	287	375
Total revenue	2,653	2,665	7,967	8,286
EXPENSES
Compensation and related expenses	0	0	0	0
Communications and technology	0	0	0	0
Occupancy and equipment costs	0	0	0	0
Clearing and exchange fees	0	0	0	0
Interest	0	8	0	8
Other	252	178	365	30
Total expenses	252	186	365	38
Income (loss) before income tax provision (benefit)	2,401	2,479	7,602	8,248
Income tax provision (benefit)	1,360	1,326	3,130	2,457
Equity in earnings of subsidiaries	505	5,261	7,837	10,348
Net income (loss) for the period	1,546	6,414	12,309	16,139
Less net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to Oppenheimer Holdings Inc.	1,546	6,414	12,309	16,139
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	1,546	6,414	12,309	16,139
Non-Guarantor Subsidiaries [Member]
REVENUES
Commissions	101,243	110,862	314,494	349,062
Advisory fees	69,938	71,278	214,012	210,594
Investment banking	16,548	33,841	72,873	94,164
Interest	14,392	12,434	37,463	37,347
Principal transactions, net	(3,100)	4,433	17,249	24,873
Other	15,121	12,279	43,455	34,419
Total revenue	214,142	245,127	699,546	750,459
EXPENSES
Compensation and related expenses	142,492	161,127	463,222	492,313
Communications and technology	16,448	15,954	49,956	50,150
Occupancy and equipment costs	16,232	15,867	48,145	47,451
Clearing and exchange fees	6,909	5,969	19,542	17,885
Interest	3,824	3,403	10,806	10,436
Other	28,368	30,630	92,976	107,882
Total expenses	214,273	232,950	684,647	726,117
Income (loss) before income tax provision (benefit)	(131)	12,177	14,899	24,342
Income tax provision (benefit)	(767)	6,761	6,179	13,342
Equity in earnings of subsidiaries	0	0	0	0
Net income (loss) for the period	636	5,416	8,720	11,000
Less net income attributable to noncontrolling interests	131	155	883	652
Net income (loss) attributable to Oppenheimer Holdings Inc.	505	5,261	7,837	10,348
Other comprehensive income (loss)	(916)	(1,608)	(166)	(1,356)
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	$ (411)	$ 3,653	$ 7,671	$ 8,992