Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
ASSETS
Cash and cash equivalents	$ 107,537	$ 63,364	$ 50,313	$ 50,313	$ 63,807
Deposits with clearing organizations	42,910	49,490
Receivable from brokers, dealers and clearing organizations	315,308	365,791
Receivable from customers, net of allowance	780,670	840,355
Income tax receivable	17,534	12,231
Securities purchased under agreements to resell	0	206,499
Securities owned	951,906	734,831
Notes receivable, net of accumulated amortization and allowance for uncollectibles	33,012	32,849
Office facilities, net of accumulated depreciation	27,880	28,285
Assets held for sale	21,764	99,881
Subordinated loan receivable	0	0
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Other assets	107,619	94,839
Deferred tax assets	0	0
Investment in subsidiaries	0	0
Intercompany receivables	0	0
Total assets	2,575,729	2,698,004
Liabilities
Drafts payable	26,759	48,011
Bank call loans	151,900	100,200
Payable to brokers, dealers and clearing organizations	172,362	164,546
Payable to customers	596,441	594,833
Securities sold under agreements to repurchase	432,912	651,445
Securities sold, but not yet purchased, at fair value	259,032	126,493
Liabilities held for sale	36,490	74,680
Accrued compensation	108,097	149,092
Accounts payable and other liabilities	110,367	108,637
Income tax payable	0	0
Senior secured notes	149,110	148,868
Subordinated indebtedness	0	0
Deferred tax liabilities	10,147	6,117
Intercompany payables	0	0
Total liabilities	2,053,617	2,172,922
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	513,912	518,058
Noncontrolling interest	8,200	7,024
Total stockholders' equity	522,112	525,082	$ 538,634
Total liabilities and stockholders' equity	2,575,729	2,698,004
Allowance for credit losses	2,543	2,545
Amounts pledged	657,527	546,334
Net accumulated depreciation	107,810	104,812
Accumulated amortization	61,671	54,919
Accumulated allowance	8,062	8,444
Unamortized debt issuance expense	890	1,132
Deferred tax assets, gross	61,198	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	(49,506)	(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	(39,504)	(41,103)
Investment in subsidiaries	(1,105,584)	(1,109,971)
Intercompany receivables	(75,291)	(73,372)
Total assets	(1,382,443)	(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	(49,506)	(49,106)
Senior secured notes	0	0
Subordinated indebtedness	(112,558)	(112,558)
Deferred tax liabilities	(39,504)	(41,103)
Intercompany payables	(75,291)	(73,372)
Total liabilities	(276,859)	(276,139)
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	(1,105,584)	(1,109,971)
Noncontrolling interest	0	0
Total stockholders' equity	(1,105,584)	(1,109,971)
Total liabilities and stockholders' equity	(1,382,443)	(1,386,110)
Parent Company [Member]
ASSETS
Cash and cash equivalents	606	907		29	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	39,056	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	100	69
Deferred tax assets	48	317
Investment in subsidiaries	582,743	577,320
Intercompany receivables	45,929	60,187
Total assets	668,482	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	3,020	3,235
Income tax payable	2,440	2,440
Senior secured notes	149,110	148,868
Subordinated indebtedness	0	0
Deferred tax liabilities	0	0
Intercompany payables	0	0
Total liabilities	154,570	154,543
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	513,912	518,058
Noncontrolling interest	0	0
Total stockholders' equity	513,912	518,058
Total liabilities and stockholders' equity	668,482	672,601
Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	525	2,586		2,685	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	27,984	27,536
Securities purchased under agreements to resell		0
Securities owned	1,261	1,183
Notes receivable, net of accumulated amortization and allowance for uncollectibles	0	0
Office facilities, net of accumulated depreciation	21,274	20,793
Assets held for sale	0	0
Subordinated loan receivable	112,558	112,558
Intangible assets	0	0
Goodwill	0	0
Other assets	2,502	3,224
Deferred tax assets	309	330
Investment in subsidiaries	522,841	532,651
Intercompany receivables	29,362	13,185
Total assets	718,616	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	35,089	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	62,204	62,204
Total liabilities	119,492	120,205
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	599,124	593,841
Noncontrolling interest	0	0
Total stockholders' equity	599,124	593,841
Total liabilities and stockholders' equity	718,616	714,046
Non-Guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	106,406	59,871		$ 47,599	$ 61,811
Deposits with clearing organizations	42,910	49,490
Receivable from brokers, dealers and clearing organizations	315,308	365,791
Receivable from customers, net of allowance	780,670	840,355
Income tax receivable	0	0
Securities purchased under agreements to resell		206,499
Securities owned	950,645	733,648
Notes receivable, net of accumulated amortization and allowance for uncollectibles	33,012	32,849
Office facilities, net of accumulated depreciation	6,606	7,492
Assets held for sale	21,764	99,881
Subordinated loan receivable	0	0
Intangible assets	31,700	31,700
Goodwill	137,889	137,889
Other assets	105,017	91,546
Deferred tax assets	39,147	40,456
Investment in subsidiaries	0	0
Intercompany receivables	0	0
Total assets	2,571,074	2,697,467
Liabilities
Drafts payable	26,759	48,011
Bank call loans	151,900	100,200
Payable to brokers, dealers and clearing organizations	172,362	164,546
Payable to customers	596,441	594,833
Securities sold under agreements to repurchase	432,912	651,445
Securities sold, but not yet purchased, at fair value	259,032	126,493
Liabilities held for sale	36,490	74,680
Accrued compensation	108,097	149,092
Accounts payable and other liabilities	72,258	69,590
Income tax payable	24,877	24,477
Senior secured notes	0	0
Subordinated indebtedness	112,558	112,558
Deferred tax liabilities	49,641	47,220
Intercompany payables	13,087	11,168
Total liabilities	2,056,414	2,174,313
Stockholders' equity
Stockholders' equity attributable to Oppenheimer Holdings Inc.	506,460	516,130
Noncontrolling interest	8,200	7,024
Total stockholders' equity	514,660	523,154
Total liabilities and stockholders' equity	$ 2,571,074	$ 2,697,467