Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
ASSETS
Cash and cash equivalents	$ 77,942	$ 98,294	$ 105,357	$ 135,366
Cash and securities segregated for regulatory and other purposes	19,106	36,323
Deposits with clearing organizations	31,611	23,679
Receivable from brokers, dealers and clearing organizations	380,943	364,873
Receivable from customers, net of allowance for credit losses	883,133	868,869
Income tax receivable	7,801	6,562
Securities purchased under agreements to resell	250,000	184,825
Securities owned, including amounts pledged of $498,928 ($586,625 in 2013), at fair value	806,772	856,088
Notes receivable, net	37,673	40,751
Office facilities, net	30,518	32,939
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Loans held for sale	20,095	75,989
Mortgage servicing rights	29,496	28,879	28,121	26,983
Other assets	131,064	165,060
Total assets	2,875,743	2,952,720
Liabilities
Drafts payable	24,316	48,198
Bank call loans	135,500	118,200
Payable to brokers, dealers and clearing organizations	204,950	223,315
Payable to customers	689,363	626,564
Securities sold under agreements to repurchase	688,310	757,491
Securities sold, but not yet purchased, at fair value	128,262	76,314
Accrued compensation	138,782	180,119
Accounts payable and other liabilities	170,175	192,552
Senior secured notes	150,000	195,000
Deferred tax liabilities, net	13,519	7,096
Total liabilities	2,343,177	2,424,849
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	526,561	522,518
Non-controlling interest	6,005	5,353
Total stockholders' equity	532,566	527,871	515,273
Total liabilities and stockholders' equity	2,875,743	2,952,720
Eliminations [Member]
ASSETS
Income tax receivable	(45,477)	(39,704)
Subordinated loan receivable	(112,558)	(112,558)
Deferred tax assets, net	(26,432)	(30,483)
Investment in subsidiaries	(1,262,944)	(1,274,360)
Intercompany receivables	(62,703)	(64,501)
Total assets	(1,510,114)	(1,521,606)
Liabilities
Accounts payable and other liabilities		(88)
Income tax payable	(45,477)	(39,704)
Subordinated indebtedness	(112,558)	(112,558)
Deferred tax liabilities, net	(26,432)	(30,483)
Intercompany payables	(62,703)	(64,501)
Total liabilities	(247,170)	(247,334)
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	(1,262,944)	(1,274,272)
Total stockholders' equity	(1,262,944)	(1,274,272)
Total liabilities and stockholders' equity	(1,510,114)	(1,521,606)
Parent Company [Member]
ASSETS
Cash and cash equivalents	1,162	448	232	35
Income tax receivable	26,600	19,494
Deferred tax assets, net	21	678
Other assets	1,839	2,797
Investment in subsidiaries	561,539	546,755
Intercompany receivables	93,926	153,528
Total assets	685,087	723,700
Liabilities
Accounts payable and other liabilities	6,086	3,742
Income tax payable	2,440	2,440
Senior secured notes	150,000	195,000
Total liabilities	158,526	201,182
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	526,561	522,518
Total stockholders' equity	526,561	522,518
Total liabilities and stockholders' equity	685,087	723,700
Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	5,123	30,901	32,441	40,658
Income tax receivable	27,371	27,589
Securities owned, including amounts pledged of $498,928 ($586,625 in 2013), at fair value	5,694	2,225
Subordinated loan receivable	112,558	112,558
Office facilities, net	20,310	21,250
Deferred tax assets, net	309	309
Other assets	27,077	27,113
Investment in subsidiaries	881,012	910,230
Intercompany receivables	(19,048)	(68,920)
Total assets	1,060,406	1,063,255
Liabilities
Accounts payable and other liabilities	58,392	59,289
Income tax payable	22,189	22,189
Deferred tax liabilities, net	12
Intercompany payables	62,703	64,501
Total liabilities	143,296	145,979
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	917,110	917,276
Total stockholders' equity	917,110	917,276
Total liabilities and stockholders' equity	1,060,406	1,063,255
Non-Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	71,657	66,945	72,684	94,673
Cash and securities segregated for regulatory and other purposes	19,106	36,323
Deposits with clearing organizations	31,611	23,679
Receivable from brokers, dealers and clearing organizations	380,943	364,873
Receivable from customers, net of allowance for credit losses	883,133	868,869
Income tax receivable	(693)	(817)
Securities purchased under agreements to resell	250,000	184,825
Securities owned, including amounts pledged of $498,928 ($586,625 in 2013), at fair value	801,078	853,863
Notes receivable, net	37,673	40,751
Office facilities, net	10,208	11,689
Deferred tax assets, net	26,102	29,496
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Loans held for sale	20,095	75,989
Mortgage servicing rights	29,496	28,879
Other assets	102,148	135,150
Investment in subsidiaries	(179,607)	(182,625)
Intercompany receivables	(12,175)	(20,107)
Total assets	2,640,364	2,687,371
Liabilities
Drafts payable	24,316	48,198
Bank call loans	135,500	118,200
Payable to brokers, dealers and clearing organizations	204,950	223,315
Payable to customers	689,363	626,564
Securities sold under agreements to repurchase	688,310	757,491
Securities sold, but not yet purchased, at fair value	128,262	76,314
Accrued compensation	138,782	180,119
Accounts payable and other liabilities	105,697	129,609
Income tax payable	20,848	15,075
Subordinated indebtedness	112,558	112,558
Deferred tax liabilities, net	39,939	37,579
Total liabilities	2,288,525	2,325,022
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	345,834	356,996
Non-controlling interest	6,005	5,353
Total stockholders' equity	351,839	362,349
Total liabilities and stockholders' equity	$ 2,640,364	$ 2,687,371