Income taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule Of Income Taxes [Line Items]
Income (loss) before income taxes for foreign operations	$ 4,800	$ 7,700	$ 1,200
Effective income tax (as a percent)	35.30%	29.50%	29.20%
Net change in total valuation allowance	$ 3,400
Unrecognized tax benefits	1,236	$ 1,072	$ 343	$ 212
Additions for tax positions of prior years	224	729	343
Settlements with taxing authorities	(60)	0	(212)
Unrecognized tax benefit that would impact tax rate	977	847
Unrecognized tax benefits, penalties and interest tax expense	107	173	$ 164
Income tax-related interest payable	322	$ 214
Oppenheimer Israel (OPCO) Ltd.
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	2,000
Oppenheimer Europe Ltd
Schedule Of Income Taxes [Line Items]
Net operating loss carryforward	$ 8,600