Supplemental Guarantor Condensed Consolidated Financial Statements - Condensed Consolidating Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 98,778	$ 135,366	$ 86,810	$ 70,329
Cash and securities segregated for regulatory and other purposes	37,164	33,000
Deposits with clearing organizations	24,576	25,954
Receivable from brokers and clearing organizations	290,955	479,699
Receivable from customers, net of allowance for credit losses of $2,239	881,514	817,941
Income tax receivable	13,980	451
Securities purchased under agreements to resell
Securities owned, including amounts pledged of $391,900, at fair value	848,329	759,742
Notes receivable, net	45,030	47,324
Office facilities, net	30,938	28,332
Deferred tax assets, net	1,780	16,340
Intangible assets, net	31,700	31,700
Goodwill	137,889	137,889
Other	186,534	164,282
Total assets	2,629,167	2,678,020
Liabilities
Drafts payable	44,927	56,586
Bank call loans	204,000	128,300
Payable to brokers and clearing organizations	215,612	204,218
Payable to customers	607,034	692,378
Securities sold under agreements to repurchase	544,136	392,391
Securities sold, but not yet purchased, at fair value	63,046	173,450
Accrued compensation	97,887	150,434
Accounts payable and other liabilities	148,617	180,262
Senior secured notes	195,000	195,000
Excess of fair value of acquired assets over cost
Total liabilities	2,120,259	2,173,019
Stockholders' equity attributable to Oppenheimer Holdings Inc.	504,417	500,740	501,060
Noncontrolling interest	4,491	4,261
Stockholders' equity	508,908	505,001	507,167
Total Liabilities and Equity	2,629,167	2,678,020
Parent [Member]
ASSETS
Cash and cash equivalents	40	35	667	2,555
Income tax receivable	15,094	13,207
Securities purchased under agreements to resell
Deferred tax assets, net		(143)
Other	3,332	3,418
Investment in subsidiaries	514,028	506,679
Intercompany receivables	177,650	178,743
Total assets	710,144	701,939
Liabilities
Accounts payable and other liabilities	8,287	3,759
Income tax payable	2,440	2,440
Senior secured notes	195,000	195,000
Excess of fair value of acquired assets over cost
Total liabilities	205,727	201,199
Stockholders' equity attributable to Oppenheimer Holdings Inc.	504,417	500,740
Stockholders' equity	504,417	500,740
Total Liabilities and Equity	710,144	701,939
Guarantor subsidiaries [Member]
ASSETS
Cash and cash equivalents	31,394	40,658	32,200	11,882
Income tax receivable	31,100	30,568
Securities purchased under agreements to resell
Securities owned, including amounts pledged of $391,900, at fair value	2,574	2,459
Subordinated loan receivable	112,558	112,558
Office facilities, net	17,626	15,547
Deferred tax assets, net	309	309
Other	25,276	1,437
Investment in subsidiaries	875,266	880,609
Intercompany receivables	(70,560)	(114,449)
Total assets	1,025,543	969,696
Liabilities
Accounts payable and other liabilities	60,255	43,350
Income tax payable	22,189	22,189
Deferred tax liabilities, net		(943)
Excess of fair value of acquired assets over cost
Intercompany payables	65,875	36,605
Total liabilities	148,319	101,201
Stockholders' equity attributable to Oppenheimer Holdings Inc.	877,224	868,495
Stockholders' equity	877,224	868,495
Total Liabilities and Equity	1,025,543	969,696
Non-guarantor Subsidiaries [Member]
ASSETS
Cash and cash equivalents	67,344	94,673	53,943	55,892
Cash and securities segregated for regulatory and other purposes	37,164	33,000
Deposits with clearing organizations	24,576	25,954
Receivable from brokers and clearing organizations	290,955	479,699
Receivable from customers, net of allowance for credit losses of $2,239	881,514	817,941
Income tax receivable	(684)	(450)
Securities purchased under agreements to resell
Securities owned, including amounts pledged of $391,900, at fair value	845,755	757,283
Notes receivable, net	45,030	47,324
Office facilities, net	13,312	12,785
Deferred tax assets, net	36,595	52,350
Intangible assets, net	31,700	31,700
Goodwill	137,889	137,889
Other	157,926	159,427
Investment in subsidiaries	(182,562)	(195,045)
Intercompany receivables	(41,213)	(27,686)
Total assets	2,345,301	2,426,844
Liabilities
Drafts payable	44,927	56,586
Bank call loans	204,000	128,300
Payable to brokers and clearing organizations	215,612	204,218
Payable to customers	607,034	692,378
Securities sold under agreements to repurchase	544,136	392,391
Securities sold, but not yet purchased, at fair value	63,046	173,450
Accrued compensation	97,887	150,434
Accounts payable and other liabilities	80,567	133,646
Income tax payable	5,296	18,687
Subordinated indebtedness	112,558	112,558
Deferred tax liabilities, net	36,728	36,677
Excess of fair value of acquired assets over cost
Total liabilities	2,011,791	2,099,325
Stockholders' equity attributable to Oppenheimer Holdings Inc.	329,019	323,258
Noncontrolling interest	4,491	4,261
Stockholders' equity	333,510	327,519
Total Liabilities and Equity	2,345,301	2,426,844
Eliminations [Member]
ASSETS
Income tax receivable	(31,530)	(42,874)
Securities purchased under agreements to resell
Subordinated loan receivable	(112,558)	(112,558)
Deferred tax assets, net	(35,124)	(36,176)
Investment in subsidiaries	(1,206,732)	(1,192,243)
Intercompany receivables	(65,877)	(36,608)
Total assets	(1,451,821)	(1,420,459)
Liabilities
Accounts payable and other liabilities	(492)	(493)
Income tax payable	(29,925)	(43,316)
Subordinated indebtedness	(112,558)	(112,558)
Deferred tax liabilities, net	(36,728)	(35,734)
Excess of fair value of acquired assets over cost
Intercompany payables	(65,875)	(36,605)
Total liabilities	(245,578)	(228,706)
Stockholders' equity attributable to Oppenheimer Holdings Inc.	(1,206,243)	(1,191,753)
Stockholders' equity	(1,206,243)	(1,191,753)
Total Liabilities and Equity	$ (1,451,821)	$ (1,420,459)