Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
REVENUE
Commissions									$ 320,114	$ 329,668	$ 336,620
Investment Advisory Fee Revenue									353,671	314,349	320,746
Investment banking									126,211	115,353	78,215
Interest Income, Deposits with Financial Institutions									117,422	116,052	76,839
Interest									50,723	52,484	48,498
Principal transactions, net									30,094	14,461	23,273
Other									35,144	15,787	36,147
Total revenue	$ 295,881	$ 234,793	$ 250,935	$ 251,770	$ 243,254	$ 237,814	$ 242,556	$ 234,530	1,033,379	958,154	920,338
EXPENSES
Compensation and related expenses									657,714	607,192	602,138
Communications and technology									81,588	74,479	71,978
Occupancy and equipment costs									62,198	61,171	61,164
Clearing and exchange fees									21,962	22,985	23,545
Interest									45,687	46,396	28,354
Other									89,318	101,062	113,607
Total expenses	260,908	228,297	233,544	235,718	227,677	230,660	230,039	224,909	958,467	913,285	900,786
Income (loss) before income taxes from continuing operations	34,973	6,496	17,391	16,052	15,577	7,154	12,517	9,621	74,912	44,869	19,552
Current and Deferred Income Tax Expense (Benefit) from Continuing Operations									21,959	15,977	(2,134)
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent									52,953	28,892	21,686
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax									0	0	2,071
Discontinued Operation, Tax Effect of Discontinued Operation									0	0	941
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									0	0	1,130
Net income (loss) attributable to Oppenheimer Holdings Inc.	$ 25,435	$ 3,949	$ 12,375	$ 11,194	$ 8,261	$ 5,071	$ 8,855	$ 6,705	$ 52,953	$ 28,892	$ 22,816
Basic net income per share
Income (Loss) from Continuing Operations, Per Basic Share									$ 4.10	$ 2.18	$ 1.65
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share									0.00	0.00	0.07
Net income per share	$ 1.99	$ 0.31	$ 0.95	$ 0.86	$ 0.62	$ 0.38	$ 0.67	$ 0.51	4.10	2.18	1.72
Income (Loss) from Continuing Operations, Per Diluted Share									3.82	2.05	1.60
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share									0.00	0.00	0.07
Earnings Per Share, Diluted	1.83	0.29	0.89	0.81	0.59	0.36	0.63	0.48	3.82	2.05	$ 1.67
Dividends	$ 0.12	$ 0.12	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.11	$ 0.46	$ 0.44
Weighted average shares
Basic									12,904,397	13,248,876	13,246,423
Diluted									13,851,832	14,061,369	13,673,361
Retained Earnings [Member]
EXPENSES
Net income (loss) attributable to Oppenheimer Holdings Inc.									$ 52,953	$ 28,892	$ 22,816
Basic net income per share
Dividends									$ 0.46	$ 0.44	$ 0.44