Regulatory Requirements	12 Months Ended
Dec. 31, 2011
Regulatory Requirements [Abstract]
Regulatory Requirements	Regulatory Requirements As registered broker‑dealers, Cowen and Company and Cowen Capital LLC (formerly known as LaBranche Capital, LLC) 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. Cowen Capital LLC is required to maintain minimum net capital, as defined, at an equivalent to the greater of $1.0 million or 2% of aggregate indebtedness, as defined. The broker-dealers are not permitted to withdraw equity if certain minimum net capital requirements are not met. As of December 31, 2011, Cowen and Company had total net capital of approximately $64.9 million, which was approximately $63.9 million in excess of its minimum net capital requirement of $1 million. As of December 31, 2011, Cowen Capital, LLC had total net capital of approximately $11.9 million, which exceeded minimum requirements by $10.9 million. Cowen and Company is exempt 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 introducing brokers (“PAIB”) held at the clearing broker are considered allowable assets for net capital purposes, pursuant to agreements between Cowen and Company and the clearing broker, which require, among other things, that the clearing broker performs computations for PAIB and segregates certain balances on behalf of Cowen and Company, if applicable. Ramius UK Ltd. (“Ramius UK”) and Cowen International Limited (“CIL”) are subject to the capital requirements of the Financial Services Authority (“FSA”) of the UK. Financial Resources, as defined, must exceed the total Financial Resources requirement of the FSA. As of December 31, 2011, Ramius UK's Financial Resources of $0.6 million exceeded its minimum requirement of $0.5 million by $0.1 million. As of December 31, 2011, CIL's Financial Resources of $5.4 million exceeded its minimum requirement of $2.3 million by $3.1 million. Cowen and Company (Asia) Limited (“CCAL”) (formerly known as Cowen Latitude Advisors Limited) is subject to the financial resources requirements of the Securities and Futures Commission (“SFC”) of Hong Kong. Financial Resources, as defined, must exceed the Total Financial Resources requirement of the SFC. As of December 31, 2011, CCAL's Financial Resources of $1.4 million exceeded the minimum requirement of $0.4 million by $1.0 million. As a registered broker dealer in the United Kingdom, CITL (formerly known as LaBranche Structured Products Europe Limited) is subject to the capital adequacy and capital resources as managed and monitored in accordance with the regulatory capital requirements of the FSA in the United Kingdom. In calculating regulatory capital, CITL's capital consists wholly of Tier 1 capital. Tier 1 capital is the core measure of a company's financial strength from a regulator's point of view. It consists of the type of financial capital considered the most reliable and liquid, primarily Shareholder's Equity. As of December 31, 2011, Tier 1 capital, as defined, was $32.8 million which exceeded the total variable capital requirement by $27.8 million. As a registered corporation under the Hong Kong Securities and Futures Ordinance, CSPH (formerly known as LaBranche Structured Products Hong Kong Limited) is subject to the capital requirements of the Hong Kong Securities and Futures (Financial Resources) Rules (“FRR”). The minimum paid-up share capital requirement is HKD 5,000,000 ($0.6 million as of December 31, 2011) and the minimum liquid capital requirement is the higher of HKD 3,000,000 ($0.4 million as of December 31, 2011) and the variable required liquid capital as defined in the FRR. The Company monitors its compliance with the requirements of the FRR on a daily basis. As of December 31, 2011, CSPH's liquid capital, as defined, was $2.2 million, which exceeded its minimum requirements by $1.8 million.

Regulatory Requirements

As registered broker‑dealers, Cowen and Company and Cowen Capital LLC (formerly known as LaBranche Capital, LLC) 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. Cowen Capital LLC is required to maintain minimum net capital, as defined, at an equivalent to the greater of $1.0 million or 2% of aggregate indebtedness, as defined. The broker-dealers are not permitted to withdraw equity if certain minimum net capital requirements are not met. As of December 31, 2011, Cowen and Company had total net capital of approximately $64.9 million, which was approximately $63.9 million in excess of its minimum net capital requirement of $1 million. As of December 31, 2011, Cowen Capital, LLC had total net capital of approximately $11.9 million, which exceeded minimum requirements by $10.9 million.

Cowen and Company is exempt 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 introducing brokers (“PAIB”) held at the clearing broker are considered allowable assets for net capital purposes, pursuant to agreements between Cowen and Company and the clearing broker, which require, among other things, that the clearing broker performs computations for PAIB and segregates certain balances on behalf of Cowen and Company, if applicable.

Ramius UK Ltd. (“Ramius UK”) and Cowen International Limited (“CIL”) are subject to the capital requirements of the Financial Services Authority (“FSA”) of the UK. Financial Resources, as defined, must exceed the total Financial Resources requirement of the FSA. As of December 31, 2011, Ramius UK's Financial Resources of $0.6 million exceeded its minimum requirement of $0.5 million by $0.1 million. As of December 31, 2011, CIL's Financial Resources of $5.4 million exceeded its minimum requirement of $2.3 million by $3.1 million.

Cowen and Company (Asia) Limited (“CCAL”) (formerly known as Cowen Latitude Advisors Limited) is subject to the financial resources requirements of the Securities and Futures Commission (“SFC”) of Hong Kong. Financial Resources, as defined, must exceed the Total Financial Resources requirement of the SFC. As of December 31, 2011, CCAL's Financial Resources of $1.4 million exceeded the minimum requirement of $0.4 million by $1.0 million.

As a registered broker dealer in the United Kingdom, CITL (formerly known as LaBranche Structured Products Europe Limited) is subject to the capital adequacy and capital resources as managed and monitored in accordance with the regulatory capital requirements of the FSA in the United Kingdom. In calculating regulatory capital, CITL's capital consists wholly of Tier 1 capital. Tier 1 capital is the core measure of a company's financial strength from a regulator's point of view. It consists of the type of financial capital considered the most reliable and liquid, primarily Shareholder's Equity. As of December 31, 2011, Tier 1 capital, as defined, was $32.8 million which exceeded the total variable capital requirement by $27.8 million.

As a registered corporation under the Hong Kong Securities and Futures Ordinance, CSPH (formerly known as LaBranche Structured Products Hong Kong Limited) is subject to the capital requirements of the Hong Kong Securities and Futures (Financial Resources) Rules (“FRR”). The minimum paid-up share capital requirement is HKD 5,000,000 ($0.6 million as of December 31, 2011) and the minimum liquid capital requirement is the higher of HKD 3,000,000 ($0.4 million as of December 31, 2011) and the variable required liquid capital as defined in the FRR. The Company monitors its compliance with the requirements of the FRR on a daily basis. As of December 31, 2011, CSPH's liquid capital, as defined, was $2.2 million, which exceeded its minimum requirements by $1.8 million.