Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheet (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$ 66,918	$ 63,807	$ 123,042	$ 98,294
Cash segregated for regulatory and other purposes	1,517	18,594
Deposits with clearing organizations	50,258	36,510
Receivable from brokers, dealers and clearing organizations	338,103	314,475
Receivable from customers, net of allowance for credit losses	890,260	864,189
Income tax receivable	6,329	4,240
Securities purchased under agreements to resell	0	251,606
Securities owned, including amounts pledged of $501,643 ($518,123 in 2014), at fair value	955,363	843,155
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $35,596 and $9,062, respectively ($42,211 and $8,606, respectively, in 2014)	34,995	34,932
Office facilities, net	28,269	29,589
Loans held for sale, at fair value	95,876	19,243
Mortgage servicing rights	28,391	30,140	29,226	28,879
Subordinated Loan Receivable	0	0
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Other assets	118,518	107,386
Deferred Tax Assets, Net	0	0
Investment in subsidiaries	0	0
Intercompany receivables	0	0
Total assets	2,784,386	2,787,455
Liabilities
Drafts payable	34,615	35,373
Bank call loans	101,400	59,400
Payable to brokers, dealers and clearing organizations	350,230	257,161
Payable to customers	704,087	652,256
Securities sold under agreements to repurchase	397,389	687,440
Securities sold, but not yet purchased, at fair value	184,649	92,510
Accrued compensation	102,668	165,134
Accounts payable and other liabilities	203,493	141,352
Income tax payable	0	0
Senior secured notes	150,000	150,000
Subordinated indebtedness	0	0
Deferred tax liabilities, net of deferred tax assets of $62,254 ($68,622 in 2014)	19,186	13,097
Intercompany payables	0	0
Total liabilities	2,247,717	2,253,723
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	530,179	527,644
Noncontrolling interest	6,490	6,088
Total stockholders' equity	536,669	533,732	530,582
Total liabilities and stockholders' equity	2,784,386	2,787,455
Net accumulated depreciation	105,809	103,547
Notes Receivable, Accumulated Amortization	35,596	42,211
Notes Receivable, Allowance for Credit Losses	9,062	8,606
Allowance for credit losses	2,439	2,427
Amounts pledged	501,643	518,123
Eliminations [Member]
ASSETS
Cash and cash equivalents	0	0
Cash segregated for regulatory and other purposes	0	0
Deposits with clearing organizations	0	0
Receivable from brokers, dealers and clearing organizations	0	0
Receivable from customers, net of allowance for credit losses	0	0
Income tax receivable	(50,390)	(51,134)
Securities purchased under agreements to resell		0
Securities owned, including amounts pledged of $501,643 ($518,123 in 2014), at fair value	0	0
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $35,596 and $9,062, respectively ($42,211 and $8,606, respectively, in 2014)	0	0
Office facilities, net	0	0
Loans held for sale, at fair value	0	0
Mortgage servicing rights	0	0
Subordinated Loan Receivable	(112,558)	(112,558)
Intangible assets	0	0
Goodwill	0	0
Other assets	0	0
Deferred Tax Assets, Net	(23,188)	(28,300)
Investment in subsidiaries	(1,121,169)	(1,109,833)
Intercompany receivables	(84,727)	(87,442)
Total assets	(1,392,032)	(1,389,267)
Liabilities
Drafts payable	0	0
Bank call loans	0	0
Payable to brokers, dealers and clearing organizations	0	0
Payable to customers	0	0
Securities sold under agreements to repurchase	0	0
Securities sold, but not yet purchased, at fair value	0	0
Accrued compensation	0	0
Accounts payable and other liabilities	0	0
Income tax payable	(50,390)	(51,134)
Senior secured notes	0	0
Subordinated indebtedness	(112,558)	(112,558)
Deferred tax liabilities, net of deferred tax assets of $62,254 ($68,622 in 2014)	(23,188)	(28,300)
Intercompany payables	(84,727)	(87,442)
Total liabilities	(270,863)	(279,434)
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	(1,121,169)	(1,109,833)
Noncontrolling interest	0	0
Total stockholders' equity	(1,121,169)	(1,109,833)
Total liabilities and stockholders' equity	(1,392,032)	(1,389,267)
Parent Company [Member]
ASSETS
Cash and cash equivalents	1	439	598	448
Cash segregated for regulatory and other purposes	0	0
Deposits with clearing organizations	0	0
Receivable from brokers, dealers and clearing organizations	0	0
Receivable from customers, net of allowance for credit losses	0	0
Income tax receivable	29,280	28,070
Securities purchased under agreements to resell		0
Securities owned, including amounts pledged of $501,643 ($518,123 in 2014), at fair value	0	0
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $35,596 and $9,062, respectively ($42,211 and $8,606, respectively, in 2014)	0	0
Office facilities, net	0	0
Loans held for sale, at fair value	0	0
Mortgage servicing rights	0	0
Subordinated Loan Receivable	0	0
Intangible assets	0	0
Goodwill	0	0
Other assets	1,634	1,686
Deferred Tax Assets, Net	287	18
Investment in subsidiaries	572,836	565,257
Intercompany receivables	84,727	87,442
Total assets	688,765	682,912
Liabilities
Drafts payable	0	0
Bank call loans	0	0
Payable to brokers, dealers and clearing organizations	0	0
Payable to customers	0	0
Securities sold under agreements to repurchase	0	0
Securities sold, but not yet purchased, at fair value	0	0
Accrued compensation	0	0
Accounts payable and other liabilities	6,146	2,828
Income tax payable	2,440	2,440
Senior secured notes	150,000	150,000
Subordinated indebtedness	0	0
Deferred tax liabilities, net of deferred tax assets of $62,254 ($68,622 in 2014)	0	0
Intercompany payables	0	0
Total liabilities	158,586	155,268
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	530,179	527,644
Noncontrolling interest	0	0
Total stockholders' equity	530,179	527,644
Total liabilities and stockholders' equity	688,765	682,912
Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	1,993	1,557	58,197	30,901
Cash segregated for regulatory and other purposes	0	0
Deposits with clearing organizations	0	0
Receivable from brokers, dealers and clearing organizations	0	0
Receivable from customers, net of allowance for credit losses	0	0
Income tax receivable	27,439	27,304
Securities purchased under agreements to resell		0
Securities owned, including amounts pledged of $501,643 ($518,123 in 2014), at fair value	5,080	5,806
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $35,596 and $9,062, respectively ($42,211 and $8,606, respectively, in 2014)	0	0
Office facilities, net	19,748	20,181
Loans held for sale, at fair value	0	0
Mortgage servicing rights	0	0
Subordinated Loan Receivable	112,558	112,558
Intangible assets	0	0
Goodwill	0	0
Other assets	3,384	3,803
Deferred Tax Assets, Net	309	309
Investment in subsidiaries	548,333	544,576
Intercompany receivables		0
Total assets	718,844	716,094
Liabilities
Drafts payable	0	0
Bank call loans	0	0
Payable to brokers, dealers and clearing organizations	0	0
Payable to customers	0	0
Securities sold under agreements to repurchase	0	0
Securities sold, but not yet purchased, at fair value	0	0
Accrued compensation	0	0
Accounts payable and other liabilities	35,805	35,800
Income tax payable	22,189	22,189
Senior secured notes	0	0
Subordinated indebtedness	0	0
Deferred tax liabilities, net of deferred tax assets of $62,254 ($68,622 in 2014)	73	88
Intercompany payables	71,592	76,492
Total liabilities	129,659	134,569
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	589,185	581,525
Noncontrolling interest	0	0
Total stockholders' equity	589,185	581,525
Total liabilities and stockholders' equity	718,844	716,094
Non-Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	64,924	61,811	64,247	66,945
Cash segregated for regulatory and other purposes	1,517	18,594
Deposits with clearing organizations	50,258	36,510
Receivable from brokers, dealers and clearing organizations	338,103	314,475
Receivable from customers, net of allowance for credit losses	890,260	864,189
Income tax receivable	0	0
Securities purchased under agreements to resell		251,606
Securities owned, including amounts pledged of $501,643 ($518,123 in 2014), at fair value	950,283	837,349
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $35,596 and $9,062, respectively ($42,211 and $8,606, respectively, in 2014)	34,995	34,932
Office facilities, net	8,521	9,408
Loans held for sale, at fair value	95,876	19,243
Mortgage servicing rights	28,391	30,140
Subordinated Loan Receivable	0	0
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Other assets	113,500	101,897
Deferred Tax Assets, Net	22,592	27,973
Investment in subsidiaries	0	0
Intercompany receivables	0	0
Total assets	2,768,809	2,777,716
Liabilities
Drafts payable	34,615	35,373
Bank call loans	101,400	59,400
Payable to brokers, dealers and clearing organizations	350,230	257,161
Payable to customers	704,087	652,256
Securities sold under agreements to repurchase	397,389	687,440
Securities sold, but not yet purchased, at fair value	184,649	92,510
Accrued compensation	102,668	165,134
Accounts payable and other liabilities	161,542	102,724
Income tax payable	25,761	26,505
Senior secured notes	0	0
Subordinated indebtedness	112,558	112,558
Deferred tax liabilities, net of deferred tax assets of $62,254 ($68,622 in 2014)	42,301	41,309
Intercompany payables	13,135	10,950
Total liabilities	2,230,335	2,243,320
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	531,984	528,308
Noncontrolling interest	6,490	6,088
Total stockholders' equity	538,474	534,396
Total liabilities and stockholders' equity	$ 2,768,809	$ 2,777,716