Regulatory Requirements	12 Months Ended
Dec. 31, 2015
Brokers and Dealers [Abstract]
Regulatory Requirements	Regulatory Requirements As registered broker-dealers, Cowen and Company, ATM Execution, Cowen Prime and Cowen Prime Trading are subject to the SEC's Uniform Net Capital Rule 15c3-1 (the “Rule”), which requires the maintenance of minimum net capital. Under the alternative method permitted by the Rule, Cowen and Company's minimum net capital requirement, as defined, is $1.0 million. Under the alternative method ATM Execution, Cowen Prime and Cowen Prime Trading are required to maintain minimum net capital, as defined, equal to $250,000. The broker-dealers are not permitted to withdraw equity if certain minimum net capital requirements are not met. As of December 31, 2015, Cowen and Company had total net capital of approximately $50.8 million, which was approximately $49.8 million in excess of its minimum net capital requirement of $1.0 million. As of December 31, 2015, ATM Execution had total net capital of approximately $4.1 million, which was approximately $3.8 million in excess of its minimum net capital requirement of $250,000. As of December 31, 2015, Cowen Prime had total net capital of approximately $17.9 million, which was approximately $17.6 million in excess of its minimum net capital requirement of $250,000. Cowen Prime Trading had total net capital of approximately $3.6 million, which was approximately $3.3 million in excess of its minimum net capital requirement of $250,000. Cowen and Company, ATM Execution, Cowen Prime and Cowen Prime Trading claim exemption from the provisions of Rule 15c3-3 under the Securities Exchange Act of 1934 as their activities are limited to those set forth in the conditions for exemption appearing in paragraph (k)(2)(ii) of the Rule. Proprietary accounts of broker-dealers (“PAB”) held at the clearing broker are considered allowable assets for net capital purposes, pursuant to agreements between Cowen and Company, ATM Execution, Cowen Prime and Cowen Prime Trading and the clearing brokers, which require, among other things, that the clearing brokers performs computations for PAB and segregates certain balances on behalf of Cowen and Company, ATM Execution, Cowen Prime and Cowen Prime Trading, if applicable. Ramius UK Ltd. ("Ramius UK") and Cowen International Limited ("CIL") are subject to the capital requirements of the Financial Conduct Authority (“FCA”) of the UK. Financial Resources, as defined, must exceed the requirement of the FCA. As of December 31, 2015, Ramius UK's Financial Resources of $0.28 million exceeded its minimum requirement of $0.05 million by $0.23 million. As of December 31, 2015, CIL's Financial Resources of $3.2 million exceeded its minimum requirement of $2.1 million by $1.1 million. During the second quarter of 2015, the Company decided to cease regulated activities carried out by Cowen and Company (Asia) Limited (“Cowen Asia”). On November 27, 2015, the Securities and Futures Commission (“SFC”) of Hong Kong revoked the license. As of December 31, 2015, Cowen Asia was no longer subject to the financial resources requirements of the SFC in Hong Kong. Cowen’s Luxembourg reinsurance companies, Vianden RCG Re SCA (“Vianden”) and Hollenfels, are subject to minimum net capital requirements as required by relevant European Commission directives and local regulatory rules in Luxembourg. As of December 31, 2015, Vianden and Hollenfels had total regulatory capital of approximately $64.0 million and $77.4 million, respectively, which was approximately $58.2 million and $73.4 million in excess of the total minimum net capital requirement of $6.6 million and $4.0 million, respectively. Based on minimum capital and surplus requirements pursuant to the laws of the state of New York that apply to captive insurance companies, RCG Insurance Company, Cowen’s captive insurance company incorporated and licensed in the state of New York, was required to maintain capital and surplus of approximately$0.3 million as of December 31, 2015. RCG Insurance Company’s capital and surplus as of December 31, 2015 totaled approximately $22 million.

Regulatory Requirements

As registered broker-dealers, Cowen and Company, ATM Execution, Cowen Prime and Cowen Prime Trading are subject to the SEC's Uniform Net Capital Rule 15c3-1 (the “Rule”), which requires the maintenance of minimum net capital. Under the alternative method permitted by the Rule, Cowen and Company's minimum net capital requirement, as defined, is $1.0 million. Under the alternative method ATM Execution, Cowen Prime and Cowen Prime Trading are required to maintain minimum net capital, as defined, equal to $250,000. The broker-dealers are not permitted to withdraw equity if certain minimum net capital requirements are not met. As of December 31, 2015, Cowen and Company had total net capital of approximately $50.8 million, which was approximately $49.8 million in excess of its minimum net capital requirement of $1.0 million. As of December 31, 2015, ATM Execution had total net capital of approximately $4.1 million, which was approximately $3.8 million in excess of its minimum net capital requirement of $250,000. As of December 31, 2015, Cowen Prime had total net capital of approximately $17.9 million, which was approximately $17.6 million in excess of its minimum net capital requirement of $250,000. Cowen Prime Trading had total net capital of approximately $3.6 million, which was approximately $3.3 million in excess of its minimum net capital requirement of $250,000.

Cowen and Company, ATM Execution, Cowen Prime and Cowen Prime Trading claim exemption from the provisions of Rule 15c3-3 under the Securities Exchange Act of 1934 as their activities are limited to those set forth in the conditions for exemption appearing in paragraph (k)(2)(ii) of the Rule.

Proprietary accounts of broker-dealers (“PAB”) held at the clearing broker are considered allowable assets for net capital purposes, pursuant to agreements between Cowen and Company, ATM Execution, Cowen Prime and Cowen Prime Trading and the clearing brokers, which require, among other things, that the clearing brokers performs computations for PAB and segregates certain balances on behalf of Cowen and Company, ATM Execution, Cowen Prime and Cowen Prime Trading, if applicable.

Ramius UK Ltd. ("Ramius UK") and Cowen International Limited ("CIL") are subject to the capital requirements of the Financial Conduct Authority (“FCA”) of the UK. Financial Resources, as defined, must exceed the requirement of the FCA. As of December 31, 2015, Ramius UK's Financial Resources of $0.28 million exceeded its minimum requirement of $0.05 million by $0.23 million. As of December 31, 2015, CIL's Financial Resources of $3.2 million exceeded its minimum requirement of $2.1 million by $1.1 million.

During the second quarter of 2015, the Company decided to cease regulated activities carried out by Cowen and Company (Asia) Limited (“Cowen Asia”). On November 27, 2015, the Securities and Futures Commission (“SFC”) of Hong Kong revoked the license. As of December 31, 2015, Cowen Asia was no longer subject to the financial resources requirements of the SFC in Hong Kong.

Cowen’s Luxembourg reinsurance companies, Vianden RCG Re SCA (“Vianden”) and Hollenfels, are subject to minimum net capital requirements as required by relevant European Commission directives and local regulatory rules in Luxembourg. As of December 31, 2015, Vianden and Hollenfels had total regulatory capital of approximately $64.0 million and $77.4 million, respectively, which was approximately $58.2 million and $73.4 million in excess of the total minimum net capital requirement of $6.6 million and $4.0 million, respectively.

Based on minimum capital and surplus requirements pursuant to the laws of the state of New York that apply to captive insurance companies, RCG Insurance Company, Cowen’s captive insurance company incorporated and licensed in the state of New York, was required to maintain capital and surplus of approximately$0.3 million as of December 31, 2015. RCG Insurance Company’s capital and surplus as of December 31, 2015 totaled approximately $22 million.