Condensed Consolidating Financial Information - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
REVENUES
Commissions	$ 103,556	$ 116,062	$ 213,251	$ 238,200
Advisory fees	72,243	70,430	143,209	138,635
Investment banking	29,020	26,799	56,325	60,323
Interest	12,030	12,548	23,065	24,938
Principal transactions, net	1,710	11,794	20,265	20,611
Other	20,369	12,056	28,374	22,150
Total revenue	238,928	249,689	484,489	504,857
EXPENSES
Compensation and related expenses	158,214	159,851	321,305	331,801
Communications and technology	16,407	17,536	33,575	34,270
Occupancy and equipment costs	15,984	15,907	31,762	31,304
Clearing and exchange fees	6,231	6,024	12,633	11,916
Interest	4,505	4,412	8,415	9,576
Other	34,957	45,823	64,318	80,745
Total expenses	236,298	249,553	472,008	499,612
Income (loss) before income taxes	2,630	136	12,481	5,245
Income tax provision (benefit)	1,985	1,389	5,715	3,078
Equity in subsidiaries	0	0	0	0
Net income (loss) for the period	645	(1,253)	6,766	2,167
Less net income attributable to noncontrolling interests	350	301	752	497
Net income (loss) attributable to Oppenheimer Holdings Inc.	295	(1,554)	6,014	1,670
Other comprehensive income (loss)	1,317	339	750	252
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	1,612	(1,215)	6,764	1,922
Eliminations [Member]
REVENUES
Commissions	0	0	0	0
Advisory fees	(411)	(311)	(865)	(681)
Investment banking	0	0	0	0
Interest	(2,565)	(2,586)	(5,129)	(5,296)
Principal transactions, net	(30)	0	(84)	0
Other	(76)	(64)	(151)	(280)
Total revenue	(3,082)	(2,961)	(6,229)	(6,257)
EXPENSES
Compensation and related expenses	0	0	0	0
Communications and technology	0	0	0	0
Occupancy and equipment costs	(76)	(64)	(151)	(280)
Clearing and exchange fees	0	0	0	0
Interest	(2,565)	(2,586)	(5,129)	(5,296)
Other	(441)	(311)	(949)	(681)
Total expenses	(3,082)	(2,961)	(6,229)	(6,257)
Income (loss) before income taxes	0	0	0	0
Income tax provision (benefit)	0	0	0	0
Equity in subsidiaries	(3,551)	(5,189)	(18,095)	(14,812)
Net income (loss) for the period	(3,551)	(5,189)	(18,095)	(14,812)
Less net income attributable to noncontrolling interests		0	0	0
Net income (loss) attributable to Oppenheimer Holdings Inc.	(3,551)	(5,189)	(18,095)	(14,812)
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	(3,551)	(5,189)	(18,095)	(14,812)
Non-Guarantor Subsidiaries [Member]
REVENUES
Interest		12,546		24,913
EXPENSES
Occupancy and equipment costs		15,971
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
EXPENSES
Compensation and related expenses	263	300	575	615
Communications and technology	42	47	67	74
Occupancy and equipment costs	0	0	0	0
Clearing and exchange fees	0	0	0	0
Interest	3,281	3,464	6,562	7,839
Other	258	3,817	546	4,161
Total expenses	3,844	7,628	7,750	12,689
Income (loss) before income taxes	(3,844)	(7,628)	(7,750)	(12,689)
Income tax provision (benefit)	(1,521)	(2,723)	(3,001)	(4,634)
Equity in subsidiaries	2,618	3,351	10,763	9,725
Net income (loss) for the period	295	(1,554)	6,014	1,670
Less net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to Oppenheimer Holdings Inc.	295	(1,554)	6,014	1,670
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	295	(1,554)	6,014	1,670
Guarantor Subsidiaries [Member]
REVENUES
Commissions	0	0	0	0
Advisory fees	0	0	0	0
Investment banking	0	0	0	0
Interest	2,557	2,588	5,123	5,321
Principal transactions, net	0	131	0	171
Other	96	74	191	290
Total revenue	2,653	2,793	5,314	5,782
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	0	0	0
Other	45	11	113	13
Total expenses	45	11	113	13
Income (loss) before income taxes	2,608	2,782	5,201	5,769
Income tax provision (benefit)	923	1,269	1,770	1,131
Equity in subsidiaries	933	1,838	7,332	5,087
Net income (loss) for the period	2,618	3,351	10,763	9,725
Less net income attributable to noncontrolling interests	0	0	0	0
Net income (loss) attributable to Oppenheimer Holdings Inc.	2,618	3,351	10,763	9,725
Other comprehensive income (loss)	0	0	0	0
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	2,618	3,351	10,763	9,725
Non-Guarantor Subsidiaries [Member]
REVENUES
Commissions	103,556	116,062	213,251	238,200
Advisory fees	72,654	70,741	144,074	139,316
Investment banking	29,020	26,799	56,325	60,323
Interest	12,038		23,071
Principal transactions, net	1,740	11,663	20,349	20,440
Other	20,349	12,046	28,334	22,140
Total revenue	239,357	249,857	485,404	505,332
EXPENSES
Compensation and related expenses	157,951	159,551	320,730	331,186
Communications and technology	16,365	17,489	33,508	34,196
Occupancy and equipment costs	16,060		31,913	31,584
Clearing and exchange fees	6,231	6,024	12,633	11,916
Interest	3,789	3,534	6,982	7,033
Other	35,095	42,306	64,608	77,252
Total expenses	235,491	244,875	470,374	493,167
Income (loss) before income taxes	3,866	4,982	15,030	12,165
Income tax provision (benefit)	2,583	2,843	6,946	6,581
Equity in subsidiaries	0	0	0	0
Net income (loss) for the period	1,283	2,139	8,084	5,584
Less net income attributable to noncontrolling interests	350	301	752	497
Net income (loss) attributable to Oppenheimer Holdings Inc.	933	1,838	7,332	5,087
Other comprehensive income (loss)	1,317	339	750	252
Comprehensive income (loss) attributable to Oppenheimer Holdings Inc.	$ 2,250	$ 2,177	$ 8,082	$ 5,339