Guarantees and Off-Balance Sheet Arrangements	12 Months Ended
Dec. 31, 2014
Guarantees and Off Balance Sheet Arrangements [Abstract]
Guarantees and Off-Balance Sheet Arrangements	Guarantees and Off-Balance Sheet Arrangements Guarantees US GAAP requires the Company to disclose information about its obligations under certain guarantee arrangements. Those standards define guarantees as contracts and indemnification agreements that contingently require a guarantor to make payments to the guaranteed party based on changes in an underlying security (such as an interest or foreign exchange rate, security or commodity price, an index or the occurrence or nonoccurrence of a specified event) related to an asset, liability or equity security of a guaranteed party. Those standards also define guarantees as contracts that contingently require the guarantor to make payments to the guaranteed party based on another entity's failure to perform under an agreement as well as indirect guarantees of the indebtedness of others. In the normal course of its operations, the Company enters into contracts that contain a variety of representations and warranties and which provide general indemnifications. The Company's maximum exposure under these arrangements is unknown as this would involve future claims that may be made against the Company that have not yet occurred. However, based on experience, the Company expects the risk of loss to be remote. The Company indemnifies and guarantees certain service providers, such as clearing and custody agents, trustees and administrators, against specified potential losses in connection with their acting as an agent of, or providing services to, the Company or its affiliates. The Company also indemnifies some clients against potential losses incurred in the event specified third-party service providers, including sub-custodians and third-party brokers, improperly execute transactions. The maximum potential amount of future payments that the Company could be required to make under these indemnifications cannot be estimated. However, the Company believes that it is unlikely it will have to make significant payments under these arrangements and has not recorded any contingent liability in the consolidated financial statements for these indemnifications. The Company is a member of various securities exchanges. Under the standard membership agreements, members are required to guarantee the performance of other members and, accordingly, if another member becomes unable to satisfy its obligations to the exchange, all other members would be required to meet the shortfall. The Company's liability under these arrangements is not quantifiable and could exceed the cash and securities it has posted as collateral. However, management believes that the potential for the Company to be required to make payments under these arrangements is remote. Accordingly, no contingent liability is recorded in the accompanying consolidated statements of financial condition for these arrangements. The Company also provides representations and warranties to counterparties in connection with a variety of commercial transactions and occasionally indemnifies them against potential losses caused by the breach of those representations and warranties. The Company may also provide standard indemnifications to some counterparties to protect them in the event additional taxes are owed or payments are withheld, due either to a change in or adverse application of certain tax laws. These indemnifications generally are standard contractual terms and are entered into in the normal course of business. The maximum potential amount of future payments that the Company could be required to make under these indemnifications cannot be estimated. However, the Company believes it is unlikely it will have to make material payments under these arrangements and has not recorded any contingent liability in the accompanying consolidated financial statements for these indemnifications. Through the Company's securities lending program (see Note 5(a)), the Company can borrow and lend customers' securities, via custodial and non-custodial arrangements, to third parties. As part of this program, the Company provides a guarantee in an aggregate amount of $150.0 million to counterparties of the securities lending agreements, which protects the lender against the failure of the third-party borrower to return the lent securities in the event the Company did not obtain sufficient collateral. To minimize its liability under these indemnification agreements, the Company obtains cash collateral with a value exceeding 100% of the market value of the securities on loan from the borrower. Collateral is marked to market daily to assure that collateralization is adequate. Additional collateral is called from the borrower if a shortfall exists, or collateral may be released to the borrower in the event of overcollateralization. If a borrower defaults, the Company would use the collateral held to purchase replacement securities in the market or to credit the lending customer with the cash equivalent thereof. In conjunction with the acquisition of Dahlman (See Note 2) the Company has agreed to guarantee loans which were issued to employees of Cowen Securities by a third-party bank prior to the acquisition that closed in March 2013. The value of these loans at December 31, 2014 was $0.2 million. Off-Balance Sheet Arrangements The Company has no material off-balance sheet arrangements as of December 31, 2014 and December 31, 2013. However, through indemnification provisions in the clearing agreement, customer activities may expose the Company to off-balance-sheet credit risk. Pursuant to the clearing agreement, the Company is required to reimburse the Company's clearing broker, without limit, for any losses incurred due to a counterparty's failure to satisfy its contractual obligations. However, these transactions are collateralized by the underlying security, thereby reducing the associated risk to changes in the market value of the security through the settlement date. In addition, during the normal course of business, the Company has exposure to a number of risks including market risk, currency risk, credit risk, operational risk, liquidity risk and legal risk. As part of the Company's risk management process, these risks are monitored on a regular basis throughout the course of the year.

Guarantees and Off-Balance Sheet Arrangements

Guarantees

US GAAP requires the Company to disclose information about its obligations under certain guarantee arrangements. Those standards define guarantees as contracts and indemnification agreements that contingently require a guarantor to make payments to the guaranteed party based on changes in an underlying security (such as an interest or foreign exchange rate, security or commodity price, an index or the occurrence or nonoccurrence of a specified event) related to an asset, liability or equity security of a guaranteed party. Those standards also define guarantees as contracts that contingently require the guarantor to make payments to the guaranteed party based on another entity's failure to perform under an agreement as well as indirect guarantees of the indebtedness of others.

In the normal course of its operations, the Company enters into contracts that contain a variety of representations and warranties and which provide general indemnifications. The Company's maximum exposure under these arrangements is unknown as this would involve future claims that may be made against the Company that have not yet occurred. However, based on experience, the Company expects the risk of loss to be remote.

The Company indemnifies and guarantees certain service providers, such as clearing and custody agents, trustees and administrators, against specified potential losses in connection with their acting as an agent of, or providing services to, the Company or its affiliates. The Company also indemnifies some clients against potential losses incurred in the event specified third-party service providers, including sub-custodians and third-party brokers, improperly execute transactions. The maximum potential amount of future payments that the Company could be required to make under these indemnifications cannot be estimated. However, the Company believes that it is unlikely it will have to make significant payments under these arrangements and has not recorded any contingent liability in the consolidated financial statements for these indemnifications.

The Company is a member of various securities exchanges. Under the standard membership agreements, members are required to guarantee the performance of other members and, accordingly, if another member becomes unable to satisfy its obligations to the exchange, all other members would be required to meet the shortfall. The Company's liability under these arrangements is not quantifiable and could exceed the cash and securities it has posted as collateral. However, management believes that the potential for the Company to be required to make payments under these arrangements is remote. Accordingly, no contingent liability is recorded in the accompanying consolidated statements of financial condition for these arrangements.

The Company also provides representations and warranties to counterparties in connection with a variety of commercial transactions and occasionally indemnifies them against potential losses caused by the breach of those representations and warranties. The Company may also provide standard indemnifications to some counterparties to protect them in the event additional taxes are owed or payments are withheld, due either to a change in or adverse application of certain tax laws. These indemnifications generally are standard contractual terms and are entered into in the normal course of business. The maximum potential amount of future payments that the Company could be required to make under these indemnifications cannot be estimated. However, the Company believes it is unlikely it will have to make material payments under these arrangements and has not recorded any contingent liability in the accompanying consolidated financial statements for these indemnifications.

Through the Company's securities lending program (see Note 5(a)), the Company can borrow and lend customers' securities, via custodial and non-custodial arrangements, to third parties. As part of this program, the Company provides a guarantee in an aggregate amount of $150.0 million to counterparties of the securities lending agreements, which protects the lender against the failure of the third-party borrower to return the lent securities in the event the Company did not obtain sufficient collateral. To minimize its liability under these indemnification agreements, the Company obtains cash collateral with a value exceeding 100% of the market value of the securities on loan from the borrower. Collateral is marked to market daily to assure that collateralization is adequate. Additional collateral is called from the borrower if a shortfall exists, or collateral may be released to the borrower in the event of overcollateralization. If a borrower defaults, the Company would use the collateral held to purchase replacement securities in the market or to credit the lending customer with the cash equivalent thereof.

In conjunction with the acquisition of Dahlman (See Note 2) the Company has agreed to guarantee loans which were issued to employees of Cowen Securities by a third-party bank prior to the acquisition that closed in March 2013. The value of these loans at December 31, 2014 was $0.2 million.

Off-Balance Sheet Arrangements

The Company has no material off-balance sheet arrangements as of December 31, 2014 and December 31, 2013. However, through indemnification provisions in the clearing agreement, customer activities may expose the Company to off-balance-sheet credit risk. Pursuant to the clearing agreement, the Company is required to reimburse the Company's clearing broker, without limit, for any losses incurred due to a counterparty's failure to satisfy its contractual obligations. However, these transactions are collateralized by the underlying security, thereby reducing the associated risk to changes in the market value of the security through the settlement date.

In addition, during the normal course of business, the Company has exposure to a number of risks including market risk, currency risk, credit risk, operational risk, liquidity risk and legal risk. As part of the Company's risk management process, these risks are monitored on a regular basis throughout the course of the year.