Condensed consolidating financial information - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
REVENUES
Commissions									$ 417,559	$ 469,829	$ 486,767
Advisory fees									280,247	281,680	274,178
Investment banking									102,540	125,598	97,977
Interest									51,031	49,244	53,216
Principal transactions, net									20,503	29,699	43,768
Other									56,505	48,414	63,808
Total revenue	$ 230,360	$ 213,536	$ 238,928	$ 245,561	$ 254,928	$ 244,679	$ 249,689	$ 255,168	928,385	1,004,464	1,019,714
EXPENSES
Compensation and related expenses									623,226	664,641	675,936
Communications and technology									66,910	67,170	65,817
Occupancy and equipment costs									63,144	63,012	66,758
Clearing and exchange fees									26,022	24,709	24,481
Interest									17,323	17,801	26,142
Other									125,049	141,395	116,671
Total expenses									921,674	978,728	975,805
Income before income tax provision	(4,243)	(1,527)	2,630	9,851	9,595	10,896	136	5,109	6,711	25,736	43,909
Income tax provision (benefit)									3,813	16,175	17,756
Equity in earnings of subsidiaries									0	0	0
Net income for the year									2,898	9,561	26,153
Less net income attributable to noncontrolling interest									936	735	1,092
Net income attributable to Oppenheimer Holdings Inc.	$ (3,144)	$ (908)	$ 295	$ 5,719	$ 2,686	$ 4,470	$ (1,554)	$ 3,224	1,962	8,826	25,061
Other comprehensive income									17	(2,627)	1,502
Total comprehensive income									1,979	6,199	26,563
Reportable Legal Entities | Parent
REVENUES
Commissions									0	0	0
Advisory fees									0	0	0
Investment banking									0	0	0
Interest									0	0	5
Principal transactions, net									0	0	0
Other									0	0	0
Total revenue									0	0	5
EXPENSES
Compensation and related expenses									1,185	1,047	1,124
Communications and technology									142	145	119
Occupancy and equipment costs									0	0	0
Clearing and exchange fees									0	0	0
Interest									13,125	14,401	17,500
Other									1,663	4,626	1,309
Total expenses									16,115	20,219	20,052
Income before income tax provision									(16,115)	(20,219)	(20,047)
Income tax provision (benefit)									(6,030)	(7,917)	(7,110)
Equity in earnings of subsidiaries									12,047	21,128	37,998
Net income for the year									1,962	8,826	25,061
Less net income attributable to noncontrolling interest									0	0	0
Net income attributable to Oppenheimer Holdings Inc.									1,962	8,826	25,061
Other comprehensive income									0	0	(3)
Total comprehensive income									1,962	8,826	25,058
Reportable Legal Entities | Guarantor Subsidiaries
REVENUES
Commissions									0	0	0
Advisory fees									1,296	1,139	825
Investment banking									0	0	0
Interest									10,237	10,482	11,128
Principal transactions, net									0	164	79
Other									370	477	180
Total revenue									11,903	12,262	12,212
EXPENSES
Compensation and related expenses									0	0	0
Communications and technology									0	0	0
Occupancy and equipment costs									0	0	0
Clearing and exchange fees									0	0	0
Interest									0	0	0
Other									892	733	522
Total expenses									892	733	522
Income before income tax provision									11,011	11,529	11,690
Income tax provision (benefit)									5,553	3,971	5,638
Equity in earnings of subsidiaries									6,589	13,570	31,946
Net income for the year									12,047	21,128	37,998
Less net income attributable to noncontrolling interest									0	0	0
Net income attributable to Oppenheimer Holdings Inc.									12,047	21,128	37,998
Other comprehensive income									0	0	0
Total comprehensive income									12,047	21,128	37,998
Reportable Legal Entities | Non-Guarantor Subsidiaries
REVENUES
Commissions									417,559	469,829	486,767
Advisory fees									282,633	283,785	276,913
Investment banking									102,540	125,598	97,977
Interest									51,055	49,193	53,401
Principal transactions, net									20,567	29,535	43,689
Other									56,435	48,362	63,808
Total revenue									930,789	1,006,302	1,022,555
EXPENSES
Compensation and related expenses									622,041	663,594	674,812
Communications and technology									66,768	67,025	65,698
Occupancy and equipment costs									63,444	63,437	66,938
Clearing and exchange fees									26,022	24,709	24,481
Interest									14,459	13,831	19,960
Other									126,240	139,280	118,400
Total expenses									918,974	971,876	970,289
Income before income tax provision									11,815	34,426	52,266
Income tax provision (benefit)									4,290	20,121	19,228
Equity in earnings of subsidiaries									0	0	0
Net income for the year									7,525	14,305	33,038
Less net income attributable to noncontrolling interest									936	735	1,092
Net income attributable to Oppenheimer Holdings Inc.									6,589	13,570	31,946
Other comprehensive income									17	(2,627)	1,505
Total comprehensive income									6,606	10,943	33,451
Eliminations
REVENUES
Commissions									0	0	0
Advisory fees									(3,682)	(3,244)	(3,560)
Investment banking									0	0	0
Interest									(10,261)	(10,431)	(11,318)
Principal transactions, net									(64)	0	0
Other									(300)	(425)	(180)
Total revenue									(14,307)	(14,100)	(15,058)
EXPENSES
Compensation and related expenses									0	0	0
Communications and technology									0	0	0
Occupancy and equipment costs									(300)	(425)	(180)
Clearing and exchange fees									0	0	0
Interest									(10,261)	(10,431)	(11,318)
Other									(3,746)	(3,244)	(3,560)
Total expenses									(14,307)	(14,100)	(15,058)
Income before income tax provision									0	0	0
Income tax provision (benefit)									0	0	0
Equity in earnings of subsidiaries									(18,636)	(34,698)	(69,944)
Net income for the year									(18,636)	(34,698)	(69,944)
Less net income attributable to noncontrolling interest									0	0	0
Net income attributable to Oppenheimer Holdings Inc.									(18,636)	(34,698)	(69,944)
Other comprehensive income									0	0	0
Total comprehensive income									$ (18,636)	$ (34,698)	$ (69,944)