Regulatory requirements (Details)	12 Months Ended
	Dec. 31, 2024 USD ($)
Regulatory Capital Requirements [Line Items]
Minimum capital required	$ 4,150,000
Oppenheimer
Regulatory Capital Requirements [Line Items]
Required percentage of net capital to aggregate customer-related debit items (as a percent)	2.00%
Net capital	$ 381,400,000
Aggregate indebtedness (as a percent)	32.48%
Excess capital	$ 357,900,000
Freedom
Regulatory Capital Requirements [Line Items]
Net capital	$ 3,800,000
Aggregate indebtedness (as a percent)	6.67%
Freedom maintain net capital equal to the greater	$ 100,000
Net capital in excess of minimum required	$ 3,700,000
Oppenheimer Europe Ltd | Basel Three New Requirements
Regulatory Capital Requirements [Line Items]
Common Equity Tier 1 ratio (as a percent)	182.00%
Common Equity Tier 1 ratio required (as a percent)	56.00%
Tier 1 Capital ratio (as a percent)	182.00%
Tier 1 Capital ratio required (as a percent)	75.00%
Total Capital ratio (as a percent)	243.00%
Total Capital ratio required (as a percent)	100.00%
Oppenheimer Investments Asia Ltd.
Regulatory Capital Requirements [Line Items]
Regulatory capital	$ 3,300,000
Excess Liquid Capital under Hong Kong SFC rules	2,900,000
Regulatory capital required to be maintained	$ 386,200