Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$ 50,313	$ 63,807	$ 65,174	$ 98,294
Cash segregated for regulatory and other purposes	855	18,594
Deposits with clearing organizations	51,625	36,510
Receivable from brokers, dealers and clearing organizations	357,170	314,475
Receivable from customers, net of allowance for credit losses	905,387	864,189
Income tax receivable	4,287	4,240
Securities purchased under agreements to resell	104,301	251,606
Securities owned, including amounts pledged of $704,168 ($518,123 in 2014), at fair value	1,005,150	843,155
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $48,448 and $9,135, respectively ($42,211 and $8,606, respectively, in 2014)	35,086	34,932
Office facilities, net	27,938	29,589
Loans held for sale, at fair value	76,351	19,243
Mortgage servicing rights	29,220	30,140	29,115	28,879
Subordinated Loan Receivable	0	0
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Other assets	112,271	107,386
Deferred Tax Assets, Net	0	0
Investment in subsidiaries	0	0
Intercompany receivables	0	0
Total assets	2,929,543	2,787,455
Liabilities
Drafts payable	4,054	35,373
Bank call loans	177,500	59,400
Payable to brokers, dealers and clearing organizations	238,007	257,161
Payable to customers	654,241	652,256
Securities sold under agreements to repurchase	623,852	687,440
Securities sold, but not yet purchased, at fair value	220,667	92,510
Accrued compensation	121,980	165,134
Accounts payable and other liabilities	182,426	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 $64,085 ($68,622 in 2014)	18,182	13,097
Intercompany payables	0	0
Total liabilities	2,390,909	2,253,723
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	531,794	527,644
Noncontrolling interest	6,840	6,088
Total stockholders' equity	538,634	533,732	529,607
Total liabilities and stockholders' equity	2,929,543	2,787,455
Net accumulated depreciation	101,972	103,547
Notes Receivable, Accumulated Amortization	48,448	42,211
Notes Receivable, Allowance for Credit Losses	9,135	8,606
Allowance for credit losses	2,491	2,427
Amounts pledged	704,168	518,123
Eliminations [Member]
ASSETS
Cash and cash equivalents	0	0	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	(54,371)	(51,134)
Securities purchased under agreements to resell	0	0
Securities owned, including amounts pledged of $704,168 ($518,123 in 2014), at fair value	0	0
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $48,448 and $9,135, 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	(25,254)	(28,300)
Investment in subsidiaries	(1,121,817)	(1,109,833)
Intercompany receivables	(77,686)	(87,442)
Total assets	(1,391,686)	(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	(54,371)	(51,134)
Senior secured notes	0	0
Subordinated indebtedness	(112,558)	(112,558)
Deferred tax liabilities, net of deferred tax assets of $64,085 ($68,622 in 2014)	(25,254)	(28,300)
Intercompany payables	(77,686)	(87,442)
Total liabilities	(269,869)	(279,434)
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	(1,121,817)	(1,109,833)
Noncontrolling interest	0	0
Total stockholders' equity	(1,121,817)	(1,109,833)
Total liabilities and stockholders' equity	(1,391,686)	(1,389,267)
Parent Company [Member]
ASSETS
Cash and cash equivalents	29	439	1,198	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	31,083	28,070
Securities purchased under agreements to resell	0	0
Securities owned, including amounts pledged of $704,168 ($518,123 in 2014), at fair value	0	0
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $48,448 and $9,135, 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	1,475	1,686
Deferred Tax Assets, Net	6	18
Investment in subsidiaries	576,771	565,257
Intercompany receivables	77,686	87,442
Total assets	687,050	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	2,816	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 $64,085 ($68,622 in 2014)	0	0
Intercompany payables	0	0
Total liabilities	155,256	155,268
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	531,794	527,644
Noncontrolling interest	0	0
Total stockholders' equity	531,794	527,644
Total liabilities and stockholders' equity	687,050	682,912
Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	2,685	1,557	6,560	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	27,572	27,304
Securities purchased under agreements to resell	0	0
Securities owned, including amounts pledged of $704,168 ($518,123 in 2014), at fair value	4,630	5,806
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $48,448 and $9,135, respectively ($42,211 and $8,606, respectively, in 2014)	0	0
Office facilities, net	19,475	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	3,225	3,803
Deferred Tax Assets, Net	309	309
Investment in subsidiaries	545,046	544,576
Intercompany receivables	0	0
Total assets	715,500	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	35,768	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 $64,085 ($68,622 in 2014)	71	88
Intercompany payables	64,289	76,492
Total liabilities	122,317	134,569
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	593,183	581,525
Noncontrolling interest	0	0
Total stockholders' equity	593,183	581,525
Total liabilities and stockholders' equity	715,500	716,094
Non-Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	47,599	61,811	$ 57,416	$ 66,945
Cash segregated for regulatory and other purposes	855	18,594
Deposits with clearing organizations	51,625	36,510
Receivable from brokers, dealers and clearing organizations	357,170	314,475
Receivable from customers, net of allowance for credit losses	905,387	864,189
Income tax receivable	3	0
Securities purchased under agreements to resell	104,301	251,606
Securities owned, including amounts pledged of $704,168 ($518,123 in 2014), at fair value	1,000,520	837,349
Notes receivable, net of accumulated amortization and allowance for uncollectibles of $48,448 and $9,135, respectively ($42,211 and $8,606, respectively, in 2014)	35,086	34,932
Office facilities, net	8,463	9,408
Loans held for sale, at fair value	76,351	19,243
Mortgage servicing rights	29,220	30,140
Subordinated Loan Receivable	0	0
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Other assets	107,571	101,897
Deferred Tax Assets, Net	24,939	27,973
Investment in subsidiaries	0	0
Intercompany receivables	0	0
Total assets	2,918,679	2,777,716
Liabilities
Drafts payable	4,054	35,373
Bank call loans	177,500	59,400
Payable to brokers, dealers and clearing organizations	238,007	257,161
Payable to customers	654,241	652,256
Securities sold under agreements to repurchase	623,852	687,440
Securities sold, but not yet purchased, at fair value	220,667	92,510
Accrued compensation	121,980	165,134
Accounts payable and other liabilities	143,842	102,724
Income tax payable	29,742	26,505
Senior secured notes	0	0
Subordinated indebtedness	112,558	112,558
Deferred tax liabilities, net of deferred tax assets of $64,085 ($68,622 in 2014)	43,365	41,309
Intercompany payables	13,397	10,950
Total liabilities	2,383,205	2,243,320
Stockholders’ equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	528,634	528,308
Noncontrolling interest	6,840	6,088
Total stockholders' equity	535,474	534,396
Total liabilities and stockholders' equity	$ 2,918,679	$ 2,777,716