Regulatory Requirements - Additional Information (Detail) (USD $)	9 Months Ended	3 Months Ended
	Sep. 30, 2014 Oppenheimer [Member]	Sep. 30, 2014 Freedom [Member]	Sep. 30, 2014 Oppenheimer Investments Asia [Member]	Sep. 30, 2014 Oppenheimer Europe Ltd [Member] Basel Three New Requirements [Member]
Regulatory Capital Requirements [Line Items]
Required percentage of net capital to aggregate customer-related debit items	2.00%
Initial capital	$ 157,900,000	$ 4,800,000	$ 3,100,000
Actual percentage of net capital to aggregate customer-related debit items	11.80%
Excess capital	131,200,000
Freedom maintain net capital equal to the greater		250,000
Aggregate indebtedness		6.67%
Net capital in excess of minimum required		4,500,000	2,700,000
Cash and securities segregated for regulatory and other purposes		18,300,000
Initial required capital			$ 386,000
Common equity Tier 1 capital ratio				8.93%
Common equity Tier 1 required				4.50%
Tier 1 capital ratio				8.93%
Tier 1 capital ratio required				6.00%
Total capital ratio				10.38%
Total capital ratio required				8.00%