Income Taxes - Additional Information (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Income Taxes [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 227,000	$ 87,000
Profit (loss) before income taxes for foreign operations	$ 1,500,000	$ 4,900,000	$ 4,000,000.0
Effective Income Tax Rate Reconciliation, Percent	27.20%	29.30%	35.60%
Valuation allowance	$ 5,059,000	$ 4,368,000
Goodwill amortized period		15 years
Unrecognized tax benefits	212,000	$ 1,079,000	$ 1,079,000	$ 1,079,000
Unrecognized tax benefit that would impact tax rate	167,000	853,000
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	0
Income tax-related interest payable	205,000	432,000
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	1,079,000	$ 0	$ 0
Unrecognized Tax Benefits Amount Released	1,100,000
Oppenheimer Israel (OPCO) Ltd.
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	3,200,000
Oppenheimer Europe [Member]
Schedule Of Income Taxes [Line Items]
Valuation allowance	$ 3,400,000