Regulatory requirements (Details)	6 Months Ended
	Jun. 30, 2024 USD ($)
Regulatory Capital Requirements [Line Items]
Regulatory capital required to be maintained	$ 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	$ 460,700,000
Aggregate indebtedness (as a percent)	43.90%
Excess capital	$ 439,700,000
Freedom
Regulatory Capital Requirements [Line Items]
Net capital	$ 3,900,000
Aggregate indebtedness (as a percent)	6.67%
Freedom maintain net capital equal to the greater	$ 100,000
Net capital in excess of minimum required	$ 3,800,000
Oppenheimer Europe Ltd
Regulatory Capital Requirements [Line Items]
Common Equity Tier 1 Ratio (as a percent)	127.00%
Common Equity Tier 1 Ratio Required (as a percent)	56.00%
Tier 1 Capital Ratio Required (as a percent)	75.00%
Total Capital Ratio (as a percent)	171.00%
Total Capital Ratio Required (as a percent)	100.00%
Oppenheimer Investments Asia Ltd.
Regulatory Capital Requirements [Line Items]
Net capital	$ 3,600,000
Excess Liquid Capital under Hong Kong SFC Rules	3,200,000
Regulatory capital required to be maintained	$ 384,170