Supplemental Guarantor Condensed Consolidated Financial Statements - Condensed Consolidating Statement of Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
REVENUES
Commissions									$ 469,829	$ 486,767		$ 469,865
Advisory fees									281,680	274,178		222,732
Investment banking									125,598	97,977		89,477
Interest									49,244	53,216		57,662
Principal transactions, net									29,699	43,768		54,311
Other									48,414	63,808		58,565
Total revenue	254,928	244,679	249,689	255,168	293,362	243,376	243,830	239,146	1,004,464	1,019,714		952,612
EXPENSES
Compensation and related expenses									664,641	675,936		626,411
Communications and technology									67,170	65,817		63,359
Occupancy and equipment costs									63,012	66,758		62,818
Clearing and exchange fees									24,709	24,481		23,750
Interest									17,801	26,142		35,086
Other									141,395	116,671		141,715
Total expenses									978,728	975,805		953,139
Income (loss) before income taxes	9,595	10,896	136	5,109	23,359	8,163	5,674	6,713	25,736	43,909		(527)
Income tax provision (benefit)									16,175	17,756		324
Equity in earnings of subsidiaries									0	0	[1]	0
Net income (loss) for the year									9,561	26,153		(851)
Less net income attributable to non-controlling interest									735	1,092		2,762
Net income (loss) attributable to Oppenheimer Holdings Inc.	2,686	4,470	(1,554)	3,224	13,313	5,237	2,848	3,663	8,826	25,061		(3,613)
Other comprehensive income (loss)									(2,627)	1,502		415
Total comprehensive income									6,199	26,563		(3,198)
Eliminations
REVENUES
Commissions									0	0		0
Advisory fees									(3,244)	(3,560)		(2,494)
Investment banking									0	0		0
Interest									(10,431)	(11,318)		(11,860)
Principal transactions, net									0	0		0
Other									(425)	(180)		(168)
Total revenue									(14,100)	(15,058)		(14,522)
EXPENSES
Compensation and related expenses									0	0		0
Communications and technology									0	0		0
Occupancy and equipment costs									(425)	(180)		(168)
Clearing and exchange fees									0	0		0
Interest									(10,431)	(11,318)		(11,861)
Other									(3,244)	(3,560)		(2,493)
Total expenses									(14,100)	(15,058)		(14,522)
Income (loss) before income taxes									0	0		0
Income tax provision (benefit)									0	0		0
Equity in earnings of subsidiaries									(34,698)	(69,944)	[1]	(9,525)
Net income (loss) for the year									(34,698)	(69,944)		(9,525)
Less net income attributable to non-controlling interest									0	0		0
Net income (loss) attributable to Oppenheimer Holdings Inc.									(34,698)	(69,944)		(9,525)
Other comprehensive income (loss)									0	0		0
Total comprehensive income									(34,698)	(69,944)		(9,525)
Guarantor Subsidiaries
REVENUES
Commissions									0	0		0
Advisory fees									1,139	825		0
Investment banking									0	0		0
Interest									10,482	11,128		12,070
Principal transactions, net									164	79		752
Other									477	180		168
Total revenue									12,262	12,212		12,990
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									733	522		60
Total expenses									733	522		60
Income (loss) before income taxes									11,529	11,690		12,930
Income tax provision (benefit)									3,971	5,638		6,093
Equity in earnings of subsidiaries									13,570	31,946	[1]	0
Net income (loss) for the year									21,128	37,998		6,837
Less net income attributable to non-controlling interest									0	0		0
Net income (loss) attributable to Oppenheimer Holdings Inc.									21,128	37,998		6,837
Other comprehensive income (loss)									0	0		0
Total comprehensive income									21,128	37,998		6,837
Non-Guarantor Subsidiaries
REVENUES
Commissions									469,829	486,767		469,865
Advisory fees									283,785	276,913		225,226
Investment banking									125,598	97,977		89,477
Interest									49,193	53,401		57,452
Principal transactions, net									29,535	43,689		53,559
Other									48,362	63,808		58,565
Total revenue									1,006,302	1,022,555		954,144
EXPENSES
Compensation and related expenses									663,594	674,812		626,014
Communications and technology									67,025	65,698		63,278
Occupancy and equipment costs									63,437	66,938		62,986
Clearing and exchange fees									24,709	24,481		23,750
Interest									13,831	19,960		29,447
Other									139,280	118,400		142,673
Total expenses									971,876	970,289		948,148
Income (loss) before income taxes									34,426	52,266		5,996
Income tax provision (benefit)									20,121	19,228		546
Equity in earnings of subsidiaries									0	0	[1]	0
Net income (loss) for the year									14,305	33,038		5,450
Less net income attributable to non-controlling interest									735	1,092		2,762
Net income (loss) attributable to Oppenheimer Holdings Inc.									13,570	31,946		2,688
Other comprehensive income (loss)									(2,627)	1,505		415
Total comprehensive income									10,943	33,451		3,103
Parent
REVENUES
Commissions									0	0		0
Advisory fees									0	0		0
Investment banking									0	0		0
Interest									0	5		0
Principal transactions, net									0	0		0
Other									0	0		0
Total revenue									0	5		0
EXPENSES
Compensation and related expenses									1,047	1,124		397
Communications and technology									145	119		81
Occupancy and equipment costs									0	0		0
Clearing and exchange fees									0	0		0
Interest									14,401	17,500		17,500
Other									4,626	1,309		1,475
Total expenses									20,219	20,052		19,453
Income (loss) before income taxes									(20,219)	(20,047)		(19,453)
Income tax provision (benefit)									(7,917)	(7,110)		(6,315)
Equity in earnings of subsidiaries									21,128	37,998	[1]	9,525
Net income (loss) for the year									8,826	25,061		(3,613)
Less net income attributable to non-controlling interest									0	0		0
Net income (loss) attributable to Oppenheimer Holdings Inc.									8,826	25,061		(3,613)
Other comprehensive income (loss)									0	(3)		0
Total comprehensive income									$ 8,826	$ 25,058		$ (3,613)

[1] The Company revised amounts in Equity in Earnings of Subsidiaries in the Condensed Consolidating Statement of Operations to properly reflect investments in subsidiaries. Offsetting amounts were adjusted in the eliminations column.