Regulatory Requirements - Additional Information (Narrative) (Details)	3 Months Ended
	Mar. 31, 2017 USD ($)
Oppenheimer
Regulatory Capital Requirements [Line Items]
Required percentage of net capital to aggregate customer-related debit items	2.00%
Net capital	$ 132,100,000
Actual percentage of net capital to aggregate customer-related debit items	12.33%
Excess capital	$ 110,700,000
Freedom
Regulatory Capital Requirements [Line Items]
Net capital	5,700,000
Freedom maintain net capital equal to the greater	$ 100,000
Aggregate indebtedness	6.67%
Net capital in excess of minimum required	$ 5,600,000
Oppenheimer Europe Ltd
Regulatory Capital Requirements [Line Items]
Common Equity Tier 1 Ratio	11.75%
Common Equity Tier 1 Ratio Required	4.50%
Tier 1 Capital Ratio	11.75%
Tier 1 Capital Ratio Required	6.00%
Total Capital Ratio	13.27%
Total Capital Ratio Required	8.00%
Oppenheimer Investments Asia Ltd.
Regulatory Capital Requirements [Line Items]
Net capital	$ 2,500,000
Net capital in excess of minimum required	2,100,000
Regulatory capital required to be maintained	$ 387,000