Income taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Income Taxes [Line Items]
Income (loss) before income taxes for foreign operations	$ 1,200	$ 4,800	$ 7,700
Effective income tax (as a percent)	32.60%	35.30%	29.50%
Effective income tax rate, non-deductible regulatory settlement		$ 13,000
Net change in total valuation allowance	$ 1,700
Unrecognized tax benefits	1,258	1,236	$ 1,072	$ 343
Unrecognized tax benefit that would impact tax rate	994	977
Additions for tax positions of prior years	217	224	729
Settlements with taxing authorities	59	60	0
Unrecognized tax benefits, penalties and interest tax expense	3	107	$ 173
Income tax-related interest payable	325	$ 322
State and Local Jurisdiction
Schedule Of Income Taxes [Line Items]
Additions for tax positions of prior years	200
Settlements with taxing authorities	200
Oppenheimer Israel (OPCO) Ltd.
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	1,900
Oppenheimer Europe Ltd
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	$ 10,600