Income Taxes - Additional Information (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Income Taxes [Line Items]
Unrecognized Tax Benefit, Reversal of Income Tax Interest Payable	$ 104,000
Profit (loss) before income taxes for foreign operations	$ (965,000)	$ 732,000	$ 4,300,000
Effective Income Tax Rate Reconciliation, Percent	56.00%	(16.70%)	70.60%
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount	$ 20,300,000
Unrecognized deferred tax liability related to earnings of foreign subsidiaries	2,300,000
Valuation allowance	$ 1,280,000	$ 126,000
Goodwill amortized period	15 years
Unrecognized tax benefits	$ 1,088,000	2,490,000	$ 1,583,000	$ 1,574,000
Unrecognized tax benefit that would impact tax rate	710,000,000,000	1,800,000
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	652,000	0	0
Income tax-related interest (benefit) expense		23,000
Income tax-related interest payable	1,000	106,000
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	$ 848,000	$ 0	$ 0
State and Local Jurisdiction | New York State | Minimum [Member]
Schedule Of Income Taxes [Line Items]
Income tax examination year	2008
State and Local Jurisdiction | New York State | Maximum [Member]
Schedule Of Income Taxes [Line Items]
Income tax examination year	2010
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	$ 1,100,000
Oppenheimer Investments Asia Ltd.
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	1,200,000
Valuation allowance	1,200,000
Oppenheimer Europe Ltd
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	$ 397,000