Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
ASSETS
Cash and cash equivalents	$ 99,044	$ 63,364	$ 47,311	$ 63,807
Deposits with clearing organizations	35,614	49,490
Receivable from brokers, dealers and clearing organizations	255,818	365,791
Receivable from customers, net of allowance	798,048	840,355
Income tax receivable	20,065	12,231
Securities purchased under agreements to resell	0	206,499
Securities owned	1,027,933	734,831
Notes receivable, net of accumulated amortization and allowance for uncollectibles	31,120	32,849
Office facilities, net of accumulated depreciation	28,321	28,285
Assets held for sale	11,748	99,881
Subordinated loan receivable	0	0
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Other assets	106,381	94,839
Deferred tax assets	0	0
Investment in subsidiaries	0	0
Intercompany receivables	0	0
Total assets	2,583,681	2,698,004
Liabilities
Drafts payable	31,414	48,011
Bank call loans	132,000	100,200
Payable to brokers, dealers and clearing organizations	154,168	164,546
Payable to customers	517,681	594,833
Securities sold under agreements to repurchase	528,113	651,445
Securities sold, but not yet purchased, at fair value	295,507	126,493
Liabilities held for sale	20,605	74,680
Accrued compensation	120,976	149,092
Accounts payable and other liabilities	105,770	108,637
Income tax payable	0	0
Senior secured notes	149,231	148,868
Subordinated indebtedness	0	0
Deferred tax liabilities	12,204	6,117
Intercompany payables	0	0
Total liabilities	2,067,669	2,172,922
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	513,496	518,058
Noncontrolling interest	2,516	7,024
Total stockholders' equity	516,012	525,082	529,777
Total liabilities and stockholders' equity	2,583,681	2,698,004
Allowance for credit losses	2,503	2,545
Amounts pledged	799,379	546,334
Net accumulated depreciation	109,278	104,812
Accumulated amortization	64,763	54,919
Accumulated allowance	8,037	8,444
Unamortized debt issuance expense	769	1,132
Deferred tax assets, gross	62,014	63,481
Eliminations [Member]
ASSETS
Cash and cash equivalents	0	0	0	0
Deposits with clearing organizations	0	0
Receivable from brokers, dealers and clearing organizations	0	0
Receivable from customers, net of allowance	0	0
Income tax receivable	(49,177)	(49,106)
Securities purchased under agreements to resell		0
Securities owned	0	0
Notes receivable, net of accumulated amortization and allowance for uncollectibles	0	0
Office facilities, net of accumulated depreciation	0	0
Assets held for sale	0	0
Subordinated loan receivable	(112,558)	(112,558)
Intangible assets	0	0
Goodwill	0	0
Other assets	0	0
Deferred tax assets	(38,628)	(41,103)
Investment in subsidiaries	(1,078,736)	(1,109,971)
Intercompany receivables	(74,046)	(73,372)
Total assets	(1,353,145)	(1,386,110)
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
Liabilities held for sale	0	0
Accrued compensation	0	0
Accounts payable and other liabilities	0	0
Income tax payable	(49,177)	(49,106)
Senior secured notes	0	0
Subordinated indebtedness	(112,558)	(112,558)
Deferred tax liabilities	(38,628)	(41,103)
Intercompany payables	(74,046)	(73,372)
Total liabilities	(274,409)	(276,139)
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	(1,078,736)	(1,109,971)
Noncontrolling interest	0	0
Total stockholders' equity	(1,078,736)	(1,109,971)
Total liabilities and stockholders' equity	(1,353,145)	(1,386,110)
Parent Company [Member]
ASSETS
Cash and cash equivalents	302	907	603	439
Deposits with clearing organizations	0	0
Receivable from brokers, dealers and clearing organizations	0	0
Receivable from customers, net of allowance	0	0
Income tax receivable	41,022	33,801
Securities purchased under agreements to resell		0
Securities owned	0	0
Notes receivable, net of accumulated amortization and allowance for uncollectibles	0	0
Office facilities, net of accumulated depreciation	0	0
Assets held for sale	0	0
Subordinated loan receivable	0	0
Intangible assets	0	0
Goodwill	0	0
Other assets	128	69
Deferred tax assets	100	317
Investment in subsidiaries	584,576	577,320
Intercompany receivables	45,174	60,187
Total assets	671,302	672,601
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
Liabilities held for sale	0	0
Accrued compensation	0	0
Accounts payable and other liabilities	6,135	3,235
Income tax payable	2,440	2,440
Senior secured notes	149,231	148,868
Subordinated indebtedness	0	0
Deferred tax liabilities	0	0
Intercompany payables	0	0
Total liabilities	157,806	154,543
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	513,496	518,058
Noncontrolling interest	0	0
Total stockholders' equity	513,496	518,058
Total liabilities and stockholders' equity	671,302	672,601
Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	30,379	2,586	1,377	1,557
Deposits with clearing organizations	0	0
Receivable from brokers, dealers and clearing organizations	0	0
Receivable from customers, net of allowance	0	0
Income tax receivable	28,220	27,536
Securities purchased under agreements to resell		0
Securities owned	1,269	1,183
Notes receivable, net of accumulated amortization and allowance for uncollectibles	0	0
Office facilities, net of accumulated depreciation	21,803	20,793
Assets held for sale	0	0
Subordinated loan receivable	112,558	112,558
Intangible assets	0	0
Goodwill	0	0
Other assets	2,503	3,224
Deferred tax assets	309	330
Investment in subsidiaries	494,160	532,651
Intercompany receivables	28,872	13,185
Total assets	720,073	714,046
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
Liabilities held for sale	0	0
Accrued compensation	0	0
Accounts payable and other liabilities	34,191	35,812
Income tax payable	22,189	22,189
Senior secured notes	0	0
Subordinated indebtedness	0	0
Deferred tax liabilities	10	0
Intercompany payables	62,205	62,204
Total liabilities	118,595	120,205
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	601,478	593,841
Noncontrolling interest	0	0
Total stockholders' equity	601,478	593,841
Total liabilities and stockholders' equity	720,073	714,046
Non-Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	68,363	59,871	$ 45,331	$ 61,811
Deposits with clearing organizations	35,614	49,490
Receivable from brokers, dealers and clearing organizations	255,818	365,791
Receivable from customers, net of allowance	798,048	840,355
Income tax receivable	0	0
Securities purchased under agreements to resell		206,499
Securities owned	1,026,664	733,648
Notes receivable, net of accumulated amortization and allowance for uncollectibles	31,120	32,849
Office facilities, net of accumulated depreciation	6,518	7,492
Assets held for sale	11,748	99,881
Subordinated loan receivable	0	0
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Other assets	103,750	91,546
Deferred tax assets	38,219	40,456
Investment in subsidiaries	0	0
Intercompany receivables	0	0
Total assets	2,545,451	2,697,467
Liabilities
Drafts payable	31,414	48,011
Bank call loans	132,000	100,200
Payable to brokers, dealers and clearing organizations	154,168	164,546
Payable to customers	517,681	594,833
Securities sold under agreements to repurchase	528,113	651,445
Securities sold, but not yet purchased, at fair value	295,507	126,493
Liabilities held for sale	20,605	74,680
Accrued compensation	120,976	149,092
Accounts payable and other liabilities	65,444	69,590
Income tax payable	24,548	24,477
Senior secured notes	0	0
Subordinated indebtedness	112,558	112,558
Deferred tax liabilities	50,822	47,220
Intercompany payables	11,841	11,168
Total liabilities	2,065,677	2,174,313
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	477,258	516,130
Noncontrolling interest	2,516	7,024
Total stockholders' equity	479,774	523,154
Total liabilities and stockholders' equity	$ 2,545,451	$ 2,697,467