Income taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Income Taxes [Line Items]
Profit (loss) before income taxes for foreign operations	$ 1,200,000	$ 1,500,000	$ 4,900,000
Effective income tax (as a percent)	29.20%	27.20%	29.30%
Valuation allowance	$ 6,153,000	$ 5,059,000
Goodwill amortized period		15 years
Unrecognized tax benefits	343,000	$ 212,000	$ 1,079,000	$ 1,079,000
Unrecognized tax benefit that would impact tax rate	271,000	167,000
Unrecognized tax benefits released	200,000
Unrecognized tax benefits, penalties and interest tax expense	164,000	227,000	$ 87,000
Income tax-related interest payable	41,000	$ 205,000
Oppenheimer Israel (OPCO) Ltd.
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	3,200,000
Oppenheimer Europe Ltd
Schedule Of Income Taxes [Line Items]
Valuation allowance	$ 3,500,000