Regulatory requirements (Details) - USD ($)		9 Months Ended
	Oct. 10, 2024	Sep. 30, 2024
Regulatory Capital Requirements [Line Items]
Regulatory capital required to be maintained		$ 4,150,000
Subsequent Event
Regulatory Capital Requirements [Line Items]
Reduction in net capital	$ 113,000,000
Oppenheimer
Regulatory Capital Requirements [Line Items]
Required percentage of net capital to aggregate customer-related debit items (as a percent)		2.00%
Net capital		$ 487,500,000
Aggregate indebtedness (as a percent)		42.54%
Excess capital		$ 464,600,000
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
Regulatory Capital Requirements [Line Items]
Common Equity Tier 1 Ratio (as a percent)		94.00%
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)		128.00%
Total Capital Ratio Required (as a percent)		100.00%
Oppenheimer Investments Asia Ltd.
Regulatory Capital Requirements [Line Items]
Net capital		$ 3,400,000
Excess Liquid Capital under Hong Kong SFC Rules		3,000,000.0
Regulatory capital required to be maintained		$ 386,133