Regulatory Requirements (Details)	3 Months Ended
	Mar. 31, 2022 USD ($)
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	$ 250,000
Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	$ 1,500,000
Minimum net capital required, percent	2.00%
Net capital	$ 406,557,000
Net capital requirement under alternative method	9,343,000
Excess capital	397,214,000
ATM Execution LLC
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital	7,880,000
Net capital requirement under alternative method	250,000
Excess capital	7,630,000
Westminster Research
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital	19,521,000
Net capital requirement under alternative method	250,000
Excess capital	19,271,000
Cowen Financial Products LLC
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital	36,658,000
Net capital requirement under alternative method	20,000,000
Excess capital	16,658,000
Cowen and Company (Asia) Limited
Regulatory Requirements for Broker-Dealers [Line Items]
Financial resources	2,045,000	[1]
Financial resources requirement	383,000	[1]
Excess financial resources	1,662,000	[1]
RCG Insurance Company
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	300,000
Net capital	6,000,000
Options Clearing Corporation | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	$ 2,000,000
Minimum net capital required, percent	2.00%
U.K. Financial Services Authority | Cowen International Limited
Regulatory Requirements for Broker-Dealers [Line Items]
Financial resources	$ 51,109,000	[1]
Financial resources requirement	25,735,000	[1]
Excess financial resources	25,374,000	[1]
U.K. Financial Services Authority | Cowen Execution Services Ltd
Regulatory Requirements for Broker-Dealers [Line Items]
Financial resources	17,900,000	[1]
Financial resources requirement	5,075,000	[1]
Excess financial resources	12,825,000	[1]
Minimum | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Required net capital under commodity exchange act	45,000
Special Reserve Accounts | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	51,800,000
PAB Reserve Bank Accounts | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	$ 71,700,000

[1] The equivalent of Net Capital under FCA rules is referred as “capital resources” and under SFC rules is referred as “net liquid capital.” The equivalent of Minimum Net Capital Requirement under FCA rules is referred as “minimum capital resources requirement and under SFC rules is referred as “net liquid capital requirement."