Income Taxes - Additional Information (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Income Taxes [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 87,000	$ 113,000
Profit (loss) before income taxes for foreign operations	$ (4,900,000)	$ 4,000,000	$ 8,500,000
Effective Income Tax Rate Reconciliation, Percent	29.30%	35.60%	(10.80%)
Effective Income Tax Reconciliation, impact of the TCJA Tax Reform	$ 0	$ 0	$ 9,013,000
Valuation allowance	4,368,000	$ 3,204,000
Goodwill amortized period		15 years
Unrecognized tax benefits	1,079,000	$ 1,079,000	1,079,000	$ 1,088,000
Unrecognized tax benefit that would impact tax rate	853,000,000,000	853,000
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	9,000
Income tax-related interest payable	432,000	345,000
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	$ 0	$ 0	$ 0
State and Local Jurisdiction | New York State | Minimum [Member]
Schedule Of Income Taxes [Line Items]
Income tax examination year	2011
State and Local Jurisdiction | New York State | Maximum [Member]
Schedule Of Income Taxes [Line Items]
Income tax examination year	2014
State and Local Jurisdiction | New York City | Minimum [Member]
Schedule Of Income Taxes [Line Items]
Income tax examination year	2009
State and Local Jurisdiction | New York City | Maximum [Member]
Schedule Of Income Taxes [Line Items]
Income tax examination year	2012
Oppenheimer Israel (OPCO) Ltd.
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	$ 2,900,000
Oppenheimer Europe [Member]
Schedule Of Income Taxes [Line Items]
Valuation allowance	$ 700,000