Cowen (COWN) 10-Q 8 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	6-May-14
Document and Entity Information [Abstract]	'	'
Entity Registrant Name	'Cowen Group, Inc.	'
Entity Central Index Key	'0001466538	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	115,387,089

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Financial Condition (USD $)	Mar. 31, 2014	Dec. 31, 2013
Assets	'	'
Cash and cash equivalents	$61,565,000	$54,720,000
Cash collateral pledged	11,269,000	10,907,000
Securities owned, at fair value	469,378,000	311,039,000
Receivable on derivative contracts, at fair value	50,076,000	10,075,000
Securities borrowed	1,319,938,000	927,773,000
Other investments	144,147,000	99,483,000
Receivable from brokers	56,946,000	66,980,000
Fees receivable, net of allowance	57,618,000	45,067,000
Due from related parties	28,812,000	26,910,000
Fixed assets, net of accumulated depreciation and amortization of $21,753 and $21,853, respectively	28,160,000	26,999,000
Goodwill	37,240,000	37,240,000
Intangible assets, net of accumulated amortization of $24,821 and $26,610, respectively	11,353,000	12,094,000
Other assets	26,691,000	17,561,000
Consolidated Funds	'	'
Cash and cash equivalents	1,825,000	2,048,000
Other Investments, Consolidated Funds	179,390,000	187,480,000
Other assets	689,000	5,624,000
Total Assets	2,485,097,000	1,842,000,000
Liabilities	'	'
Securities sold, not yet purchased, at fair value	139,347,000	130,954,000
Securities sold under agreement to repurchase	0	3,657,000
Payable for derivative contracts, at fair value	50,032,000	7,674,000
Securities loaned	1,310,903,000	918,577,000
Payable to brokers	151,109,000	75,420,000
Compensation payable	34,152,000	51,807,000
Short-term borrowings and other debt	6,384,000	2,564,000
Convertible debt	114,101,000	0
Fees payable	10,833,000	6,324,000
Due to related parties	408,000	382,000
Accounts Payable, Accrued Expenses and Other Liabilities	48,563,000	45,290,000
Consolidated Funds	'	'
Capital withdrawals payable	0	5,222,000
Accounts payable, accrued expenses and other liabilities	1,579,000	549,000
Total Liabilities	1,867,411,000	1,248,420,000
Commitments and Contingencies (Note 13)	'	'
Redeemable non-controlling interests	85,448,000	85,814,000
Stockholders' equity	'	'
Preferred stock, par value $0.01 per share; 10,000,000 shares authorized, no shares issued and outstanding	0	0
Additional paid-in capital	757,359,000	737,341,000
(Accumulated deficit) retained earnings	-173,403,000	-183,243,000
Accumulated other comprehensive income (loss)	537,000	592,000
Less: Class A common stock held in treasury, at cost, 17,136,430 and 15,873,549 shares as of March 31, 2014 and December 31, 2013, respectively.	-53,415,000	-48,084,000
Total Stockholders' Equity	532,238,000	507,766,000
Total Liabilities and Stockholders' Equity	2,485,097,000	1,842,000,000
Common Stock Class A	'	'
Stockholders' equity	'	'
Common stock	1,160,000	1,160,000
Less: Class A common stock held in treasury, at cost, 17,136,430 and 15,873,549 shares as of March 31, 2014 and December 31, 2013, respectively.	-53,415,000	-48,084,000
Common Stock Class B	'	'
Stockholders' equity	'	'
Common stock	$0	$0

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Financial Condition (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Assets	'	'
Fixed assets, accumulated depreciation and amortization (in dollars)	$21,753	$21,853
Intangible assets, accumulated amortization (in dollars)	$24,821	$26,610
Stockholders' equity	'	'
Preferred stock, par value (in dollars per share)	$0.01	$0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Treasury Stock, Shares	17,136,430	15,873,549
Common Stock Class A	'	'
Stockholders' equity	'	'
Treasury Stock, Shares	17,136,430	15,873,549
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	132,488,976	130,900,182
Common stock, shares outstanding	115,352,546	115,026,633
Common stock, restricted shares	380,122	482,522
Common Stock Class B	'	'
Stockholders' equity	'	'
Common stock, par value (in dollars per share)	$0.01	$0.01
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Revenues	'	'
Investment banking	$49,562	$17,166
Brokerage	32,830	26,600
Management fees	8,924	9,493
Incentive income	2,498	2,611
Interest and dividends	9,252	9,321
Reimbursement from affiliates	1,900	1,485
Other revenues	555	478
Consolidated Funds	'	'
Interest and dividends	486	12
Other revenues	670	75
Total revenues	106,677	67,241
Expenses	'	'
Employee compensation and benefits	67,561	44,223
Floor brokerage and trade execution	5,655	5,853
Interest and dividends	7,072	6,418
Professional, advisory and other fees	3,601	3,853
Service fees	2,142	2,577
Communications	3,246	3,739
Occupancy and equipment	6,397	5,719
Depreciation and amortization	2,380	2,553
Client services and business development	4,514	4,099
Other expenses	3,158	3,644
Consolidated Funds	'	'
Interest and dividends	110	0
Professional, advisory and other fees	134	396
Floor brokerage and trade execution	2	0
Other expenses	56	38
Total expenses	106,028	83,112
Other income (loss)	'	'
Net gains (losses) on securities, derivatives and other investments	11,354	11,807
Consolidated Funds	'	'
Net realized and unrealized gains (losses) on investments and other transactions	2,164	5,070
Net realized and unrealized gains (losses) on derivatives	-21	304
Net gains (losses) on foreign currency transactions	-40	-215
Total other income (loss)	13,457	16,966
Income (loss) before income taxes	14,106	1,095
Income tax expense (benefit)	79	176
Net income (loss)	14,027	919
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	4,187	3,495
Net income (loss) attributable to Cowen Group, Inc. stockholders	$9,840	($2,576)
Weighted average common shares outstanding:	'	'
Basic (in shares)	115,680	113,798
Diluted (in shares)	122,898	113,798
Earnings (loss) per share:	'	'
Earnings Per Share, Basic	$0.09	($0.02)
Earnings Per Share, Diluted	$0.08	($0.02)

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements of Comprehensive Income (Loss) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Statement of Comprehensive Income [Abstract]	'		'
Net income (loss)	$14,027		$919
Other comprehensive income (loss), net of tax:	'		'
Foreign currency translation	37	[1]	-4	[1]
Defined benefit pension plans:	'		'
Net gain/(loss) arising during the period	-92		-22
Amortization of prior service cost	0		5
Total defined benefit pension plan	-92	[1]	-17	[1]
Total other comprehensive income, net of tax	-55		-21
Comprehensive income (loss)	$13,972		$898
[1]	During the periods presented, the Company did not have material reclassifications out of other comprehensive income.

Condensed_Consolidated_Stateme4

Condensed Consolidated Statements of Changes in Equity (USD $)	Total		Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings/(Accumulated deficit)	Redeemable Non-controlling Interest
Balance at Dec. 31, 2012	$495,109,000		$1,135,000	($31,728,000)	$713,211,000	$356,000	($187,865,000)	$85,703,000
Common Stock, Shares, Outstanding at Dec. 31, 2012	'		112,447,892	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'		'	'	'	'	'	'
Net income (loss) attributable to Cowen Group, Inc. stockholders	-2,576,000		'	'	'	'	-2,576,000	'
Net income (loss) attributable to redeemable non-controlling interests	3,495,000		'	'	'	'	'	3,495,000
Defined benefit plans	-17,000	[1]	'	'	'	-17,000	'	'
Foreign currency translation	-4,000	[1]	'	'	'	-4,000	'	'
Capital contributions	'		'	'	'	'	'	801,000
Capital withdrawals	'		'	'	'	'	'	-8,968,000
Restricted stock awards issued, shares	'		844,734	'	'	'	'	'
Common stock issued upon acquisition (See Note 2)	6,297,000		25,000	'	6,272,000	'	'	'
Common stock issued upon acquisition (See Note 2), shares	'		2,514,468	'	'	'	'	'
Purchase of treasury stock, at cost	-412,000		'	-412,000	'	'	'	'
Purchase of treasury stock, at cost, shares	'		'	-155,295	'	'	'	'
Amortization of share based compensation	4,752,000		'	'	4,752,000	'	'	'
Balance at Mar. 31, 2013	503,149,000		1,160,000	-32,140,000	724,235,000	335,000	-190,441,000	81,031,000
Common Stock, Shares, Outstanding at Mar. 31, 2013	'		115,651,799	'	'	'	'	'
Balance at Dec. 31, 2013	507,766,000		1,160,000	-48,084,000	737,341,000	592,000	-183,243,000	85,814,000
Common Stock, Shares, Outstanding at Dec. 31, 2013	'		115,026,633	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'		'	'	'	'	'	'
Net income (loss) attributable to Cowen Group, Inc. stockholders	9,840,000		'	'	'	'	9,840,000	'
Net income (loss) attributable to redeemable non-controlling interests	4,187,000		'	'	'	'	'	4,187,000
Defined benefit plans	-92,000	[1]	'	'	'	-92,000	'	'
Foreign currency translation	37,000	[1]	'	'	'	37,000	'	'
Capital contributions	'		'	'	'	'	'	6,007,000
Capital withdrawals	'		'	'	'	'	'	-10,560,000
Restricted stock awards issued, shares	'		1,588,794	'	'	'	'	'
Warrants issued	15,218,000		'	'	15,218,000	'	'	'
Purchase of treasury stock, at cost	-5,331,000		'	-5,331,000	'	'	'	'
Purchase of treasury stock, at cost, shares	'		'	-1,262,881	'	'	'	'
Amortization of share based compensation	4,800,000		'	'	4,800,000	'	'	'
Balance at Mar. 31, 2014	$532,238,000		$1,160,000	($53,415,000)	$757,359,000	$537,000	($173,403,000)	$85,448,000
Common Stock, Shares, Outstanding at Mar. 31, 2014	'		115,352,546	'	'	'	'	'
[1]	During the periods presented, the Company did not have material reclassifications out of other comprehensive income.

Condensed_Consolidated_Stateme5

Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Cash flows from operating activities:	'	'
Net income (loss)	$14,027,000	$919,000
Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities:	'	'
Depreciation and amortization	2,380,000	2,553,000
Amortization of Debt Discount	311,000	0
Share-based compensation	4,800,000	4,752,000
Deferred rent obligations	179,000	-4,159,000
Net loss on disposal of fixed assets	218,000	97,000
Purchases of securities owned, at fair value	-1,086,631,000	-1,280,090,000
Proceeds from sales of securities owned, at fair value	928,377,000	1,454,999,000
Proceeds from sales of securities sold, not yet purchased, at fair value	367,854,000	697,603,000
Payments to cover securities sold, not yet purchased, at fair value	-328,177,000	-646,438,000
Net (gains) losses on securities, derivatives and other investments	-12,171,000	-11,558,000
Consolidated Funds	'	'
Purchases of securities owned, at fair value	0	-78,792,000
Proceeds from sales of securities owned, at fair value	0	82,320,000
Purchases of other investments	-6,007,000	-973,000
Proceeds from sales of other investments	17,011,000	18,352,000
Receivable on derivative contracts, at fair value	-4,290,000	1,590,000
Payable for derivative contracts, at fair value	6,648,000	3,101,000
Net realized and unrealized (gains) losses on investments and other transactions	-2,913,000	-6,675,000
(Increase) decrease in operating assets:	'	'
Cash acquired upon transaction	0	10,747,000
Cash collateral pledged	-362,000	137,000
Securities owned, at fair value, held at broker dealer	-692,000	-11,616,000
Securities borrowed	-392,165,000	-51,623,000
Receivable from brokers	10,034,000	19,284,000
Fees receivable, net of allowance	-12,551,000	-1,644,000
Due from related parties	-1,902,000	1,478,000
Other assets	-5,308,000	-5,296,000
Consolidated Funds	'	'
Cash and cash equivalents	223,000	-261,000
Other assets	4,935,000	-6,407,000
Increase (decrease) in operating liabilities:	'	'
Securities sold, not yet purchased, at fair value, held at broker dealer	-29,354,000	-11,680,000
Securities loaned	392,326,000	48,895,000
Payable to brokers	75,689,000	-100,082,000
Compensation payable	-19,667,000	-46,014,000
Fees payable	4,509,000	-1,829,000
Due to related parties	26,000	-44,000
Accounts payable, accrued expenses and other liabilities	3,028,000	3,212,000
Consolidated Funds	'	'
Accounts payable, accrued expenses and other liabilities	1,030,000	-112,000
Net cash provided by / (used in) operating activities	-68,585,000	84,746,000
Cash flows from investing activities:	'	'
Purchases of other investments	-46,528,000	-5,161,000
Payments for Hedge, Investing Activities	-35,710,000	0
Proceeds from sales of other investments	11,603,000	15,534,000
Purchase of fixed assets	-4,279,000	-237,000
Net cash provided by / (used in) investing activities	-74,914,000	10,136,000
Cash flows from financing activities:	'	'
Securities sold under agreement to repurchase	-3,657,000	-136,704,000
Proceeds from issuance of convertible debt	149,500,000	0
Deferred debt issuance cost	-3,643,000	0
Cash convertible warrant transaction	15,218,000	0
Borrowings on short-term borrowings and other debt	6,217,000	2,044,000
Repayments on short-term borrowings and other debt	-1,137,000	-797,000
Purchase of treasury stock	-3,411,000	-235,000
Cash paid to acquire net assets (contingent payable)	-76,000	0
Capital withdrawals to non-controlling interests in operating entities	-3,500,000	-432,000
Consolidated Funds	'	'
Capital contributions by non-controlling interests in Consolidated Funds	6,007,000	300,000
Capital withdrawals to non-controlling interests in Consolidated Funds	-11,174,000	-5,645,000
Net cash provided by / (used in) financing activities	150,344,000	-141,469,000
Change in cash and cash equivalents	6,845,000	-46,587,000
Cash and cash equivalents at beginning of period	54,720,000	83,538,000
Cash and cash equivalents at end of period	61,565,000	36,951,000
Supplemental information	'	'
Non compete agreements and covenants with limiting conditions acquired (see Note 2)	'	460,000
Common stock issuance upon close of acquisition (see Note 2)	'	6,297,000
Purchase of treasury stock, at cost, through net settlement (see Note 21)	1,919,000	177,000
Discount on debt	$35,710,000	'

Organization_and_Business

Organization and Business	3 Months Ended
	Mar. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization and Business	'
	Organization and Business
	Cowen Group, Inc., a Delaware corporation formed in 2009, is a diversified financial services firm and, together with its consolidated subsidiaries (collectively, “Cowen,” “Cowen Group” or the “Company”), provides alternative investment management, investment banking, research, market-making and sales and trading and securities lending services through its two business segments: alternative investment and broker-dealer. Ramius, the Company's alternative investment segment, includes hedge funds, replication products, liquid alternative risk premia products, customized solutions, mutual funds, managed futures funds, fund of funds, real estate and healthcare royalty funds. Cowen's broker-dealer segment offers research, brokerage and investment banking services to companies and institutional investor clients primarily in the healthcare, technology, media and telecommunications, consumer, aerospace and defense, industrials, real estate investment trusts ("REITs"), clean technology, energy, metals and mining, transportation, chemicals and agriculture sectors.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2014
Business Combinations [Abstract]	'
Acquisitions	'
	Acquisitions
	On March 11, 2013, the Company completed its acquisition of all of the outstanding interests in Dahlman Rose & Company, LLC ("Dahlman"), a privately-held investment bank specializing in the energy, metals and mining, transportation, chemicals and agriculture sectors. This acquisition was an all-stock transaction. In the aggregate, the purchase price, assets acquired and liabilities assumed were not significant and the near term impact to the Company and its consolidated results of operations and cash flows is not expected to be significant. Dahlman was subsequently renamed to Cowen Securities LLC ("Cowen Securities"). Following the acquisition, the Cowen Securities broker-dealer ceased operations and its business was fully integrated into Cowen and Company.
	The acquisition was accounted for under the acquisition method of accounting in accordance with accounting principles generally accepted in the United States of America ("US GAAP"). As such, results of operations for the Cowen Securities are included in the accompanying condensed consolidated statements of operations since the date of the acquisition, and the assets acquired, liabilities assumed and the resulting goodwill were recorded at their fair values within their respective line items on the accompanying condensed consolidated statement of financial condition. The goodwill is fully deductible for tax purposes.

Significant_Accounting_Policie

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Significant Accounting Policies	'
	Significant Accounting Policies
	These unaudited condensed consolidated financial statements and related notes have been prepared in accordance with US GAAP and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) related to interim financial statements. Results for interim periods should not be considered indicative of results for any other interim period or for the full year. These financial statements should be read in conjunction with the audited consolidated financial statements as of December 31, 2013 and 2012 and for the years ended December 31, 2013, 2012, and 2011, included in the Form 10-K of Cowen Group as filed with the SEC on March 3, 2014. The financial information contained herein is unaudited; however, management believes all adjustments have been made that are necessary for a fair presentation of the results for the interim periods. The year-end condensed balance sheet data was derived from audited financial statements, but does not include all disclosures required by US GAAP. All material intercompany transactions and balances have been eliminated in consolidation. Certain fund entities that are consolidated in these condensed consolidated financial statements, as further discussed below, are not subject to these consolidation provisions with respect to their own investments pursuant to their specialized accounting.
	The Company serves as the managing member/general partner and/or investment manager to affiliated fund entities which it sponsors and manages. Funds in which the Company has a controlling financial interest are consolidated with the Company pursuant to US GAAP as described below. Consequently, the Company's condensed consolidated financial statements reflect the assets, liabilities, income and expenses of these funds on a gross basis. The ownership interests in these funds that are not owned by the Company are reflected as redeemable non-controlling interests in consolidated subsidiaries in the accompanying condensed consolidated financial statements. The management fees and incentive income earned by the Company from these funds are eliminated in consolidation.
	b.	Principles of consolidation
	The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting operating entity ("VOE") or a variable interest entity ("VIE") under US GAAP.
	Voting Operating Entities—VOEs are entities in which (i) the total equity investment at risk is sufficient to enable the entity to finance its activities independently and (ii) the equity holders at risk have the obligation to absorb losses, the right to receive residual returns and the right to direct the activities of the entity that most significantly impact the entity's economic performance. VOEs are consolidated in accordance with US GAAP.
	Under US GAAP, the usual condition for a controlling financial interest in a VOE is ownership of a majority voting interest. Accordingly, the Company consolidates VOEs in which it owns a majority of the entity's voting shares or units. US GAAP also provides that a general partner of a limited partnership (or a managing member, in the case of a limited liability company) is presumed to control the partnership, and thus should consolidate it, unless a simple majority of the limited partners has the right to remove the general partner without cause or to terminate the partnership. In accordance with these standards, the Company presently consolidates four entities deemed to be VOEs for which it acts as the general partner and investment manager.
	As of and during the period ended March 31, 2014 the Company consolidated the following funds: Ramius Enterprise LP (“Enterprise LP”) and Ramius Merger Fund LLC (the "Merger Fund") (collectively the "2014 Consolidated Funds"). As of December 31, 2013 and during the quarter ended March 31, 2013, the Company consolidated the following funds: Enterprise LP, Ramius Multi‑Strategy Master FOF LP (“Multi‑Strat Master FOF”), Ramius Vintage Multi‑Strategy Master FOF LP (“Vintage Master FOF”), Ramius Levered Multi‑Strategy FOF LP (“Levered FOF”), and the Merger Fund (collectively the "2013 Consolidated Funds"). As of December 31, 2013, Levered FOF, Multi-Strat Master FOF and Vintage Master FOF, all of which are investment companies managed by Ramius Alternative Solutions LLC, were fully liquidated. RTS Global 3X LP was consolidated up through March 31, 2013 when it was liquidated. Collectively, the 2013 Consolidated Funds and the 2014 Consolidated Funds are referred to as the "Consolidated Funds".
	As of March 31, 2014, the Company also consolidated two investment companies; RCG Linkem II LLC, formed to make an investment in a wireless broadband communication provider in Italy and Ramius Co-Investment II LLC, which was formed to make an investment in a biomedical company that develops innovative gene therapies for severe genetic disorders. Ramius Co-Investment I LLC, formed for the same purpose as Ramius Co-Investment II LLC, was consolidated as of December 31, 2013 but was deconsolidated during the quarter ended March 31, 2014 when Ramius Co-Investment I LLC was liquidated. The Company determined that RCG Linkem II, LLC, Ramius Co-Investment I LLC (up until the first quarter of 2014) and Ramius Co-Investment II LLC are VOE's due to its controlling equity interests held through the managing member and/or affiliates and control exercised by the managing member who is not subject to substantive removal rights.
	Variable Interest Entities—VIEs are entities that lack one or more of the characteristics of a VOE. In accordance with US GAAP, an enterprise must consolidate all VIEs of which it is the primary beneficiary. Under the US GAAP consolidation model for VIEs, an enterprise that (1) has the power to direct the activities of a VIE that most significantly impacts the VIE's economic performance, and (2) has an obligation to absorb losses or the right to receive benefits from the VIE that could potentially be significant to the VIE, is considered to be the primary beneficiary of the VIE and thus is required to consolidate it.
	However, the FASB has deferred the application of the revised consolidation model for VIEs that meet the following conditions: (a) the entity has all the attributes of an investment company as defined under AICPA Audit and Accounting Guide, Investment Companies, or does not have all the attributes of an investment company but is an entity for which it is acceptable based on industry practice to apply measurement principles that are consistent with investment companies, (b) the reporting entity does not have explicit or implicit obligations to fund any losses of the entity that could potentially be significant to the entity, and (c) the entity is not a securitization entity, asset-backed financing entity or an entity that was formerly considered a qualifying special-purpose entity. The Company's involvement with its funds is such that all three of the above conditions are met for substantially all of the funds managed by the Company. Where the VIEs have qualified for the deferral, the analysis is based on previous consolidation rules. These rules require an analysis to (a) determine whether an entity in which the Company holds a variable interest is a variable interest entity and (b) whether the Company's involvement, through holding interests directly or indirectly in the entity or contractually through other variable interests (e.g., management and performance related fees), would be expected to absorb a majority of the VIE's expected losses, receive a majority of the VIEs expected residual returns, or both. If these conditions are met, the Company is considered to be the primary beneficiary of the VIE and thus is required to consolidate it.
	The Company reconsiders whether it is the primary beneficiary of a VIE by performing a periodic qualitative and/or quantitative analysis of the VIE that includes a review of, among other things, its capital structure, contractual agreements between the Company and the VIE, the economic interests that create or absorb variability, related party relationships and the design of the VIE. As of March 31, 2014 and December 31, 2013, the Company consolidates three VIEs. As of March 31, 2014 and December 31, 2013, the total net assets of the consolidated VIEs are $2.9 million and $8.2 million, respectively. The VIEs act as managing members/general partners and/or investment managers to affiliated fund entities which they sponsor and/or manage. The VIEs are financed through their operations and/or loan agreements with the Company.
	As of March 31, 2014 and December 31, 2013, the Company holds a variable interest in Ramius Enterprise Master Fund Ltd (“Enterprise Master”) through one of its Consolidated Funds, Enterprise LP and the Company holds a variable interest in Ramius Merger Master Fund Ltd through one of its Consolidated Funds, Merger Fund, (the “Unconsolidated Master Funds”). Investment companies, which account for their investments under the specialized industry accounting guidance for investment companies prescribed under US GAAP, are not subject to the consolidation provisions for their investments. Therefore, the Company has not consolidated the Unconsolidated Master Funds.
	In the ordinary course of business, the Company also sponsors various other entities that it has determined to be VIEs. These VIEs are primarily funds and real estate entities for which the Company serves as the general partner, managing member and/or investment manager with decision-making rights.
	The Company does not consolidate any of these funds or real estate entities that are VIEs as it has concluded that it is not the primary beneficiary in each instance. Fund investors are entitled to all of the economics of these VIEs with the exception of the management fee and incentive income, if any, earned by the Company. The Company's involvement with funds and real estate entities that are unconsolidated VIEs is limited to providing investment management services in exchange for management fees and incentive income. Although the Company may advance amounts and pay certain expenses on behalf of the funds and real estate entities that it considers to be VIEs, it does not provide, nor is it required to provide, any type of substantive financial support to these entities outside of regular investment management services. (See Note 5 for additional disclosures on VIEs)
	Equity Method Investments—For operating entities over which the Company exercises significant influence but which do not meet the requirements for consolidation as outlined above, the Company uses the equity method of accounting. The Company's investments in equity method investees are recorded in other investments in the condensed consolidated statements of financial condition. The Company's share of earnings or losses from equity method investees is included in net gains (losses) on securities, derivatives and other investments in the condensed consolidated statements of operations.
	The Company evaluates for impairment its equity method investments whenever events or changes in circumstances indicate that the carrying amounts of such investments may not be recoverable. The difference between the carrying value of the equity method investment and its estimated fair value is recognized as an impairment charge when the loss in value is deemed other than temporary.
	Other—If the Company does not consolidate an entity, apply the equity method of accounting or account for an investment under the cost method, the Company accounts for all securities which are bought and held principally for the purpose of selling them in the near term as trading securities in accordance with US GAAP, at fair value with unrealized gains (losses) resulting from changes in fair value reflected within net gains (losses) on securities, derivatives and other investments in the condensed consolidated statements of operations.
	Retention of Specialized Accounting—The Consolidated Funds are investment companies and apply specialized industry accounting for investment companies. The Company has retained this specialized accounting for these funds pursuant to US GAAP. The Company reports its investments on the condensed consolidated statements of financial condition at their estimated fair value, with unrealized gains (losses) resulting from changes in fair value reflected within net realized and unrealized gains (losses) on investments and other transactions. Accordingly, the accompanying condensed consolidated financial statements reflect different accounting policies for investments depending on whether or not they are held through a consolidated investment company. In addition, the Company's broker-dealer subsidiaries, Cowen and Company, LLC (“Cowen and Company”), ATM Execution LLC ("ATM Execution"), ATM USA, LLC ("ATM USA"), and Cowen Equity Finance LP ("Cowen Equity Finance"), apply the specialized industry accounting for brokers and dealers in securities also prescribed under US GAAP. The Company also retains specialized accounting in consolidation.
	c.	Use of estimates
	The preparation of the accompanying condensed consolidated financial statements in conformity with US GAAP requires the management of the Company to make estimates and assumptions that affect the fair value of securities and other investments, the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the accompanying condensed consolidated financial statements, the accounting for goodwill and identifiable intangible assets and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates. Certain reclassifications have been made to prior period amounts in order to conform with current period presentation.
	d.	Valuation of investments and derivative contracts
	US GAAP establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (level 1 measurements) and the lowest priority to unobservable inputs (level 3 measurements). The three levels of the fair value hierarchy are as follows:
	Level 1 Inputs that reflect unadjusted quoted prices in active markets for identical assets or liabilities that the Company has
	the ability to access at the measurement date;
	Level 2     Inputs other than quoted prices that are observable for the asset or liability either directly or indirectly, including
	inputs in markets that are not considered to be active; and
	Level 3 Fair value is determined based on pricing inputs that are unobservable and includes situations where there is little,
	if any, market activity for the asset or liability. The determination of fair value for assets and liabilities in this
	category requires significant management judgment or estimation.
	Inputs are used in applying the various valuation techniques and broadly refer to the assumptions that market participants use to make valuation decisions, including assumptions about risk. Inputs may include price information, volatility statistics, specific and broad credit data, liquidity statistics, and other factors. A financial instrument's level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. However, the determination of what constitutes “observable” requires significant judgment by the Company. The Company considers observable data to be that market data which is readily available, regularly distributed or updated, reliable and verifiable, not proprietary, and provided by independent sources that are actively involved in the relevant market. The categorization of a financial instrument within the hierarchy is based upon the pricing transparency of the instrument and does not necessarily correspond to the Company's perceived risk of that instrument.
	The Company and its operating subsidiaries act as the manager for the Consolidated Funds. Both the Company and the Consolidated Funds hold certain investments which are valued by the Company, acting as the investment manager. The fair value of these investments is generally estimated based on proprietary models developed by the Company, which include discounted cash flow analysis, public market comparables, and other techniques and may be based, at least in part, on independently sourced market information. The material estimates and assumptions used in these models include the timing and expected amount of cash flows, the appropriateness of discount rates used, and, in some cases, the ability to execute, timing of, and estimated proceeds from expected financings. Significant judgment and estimation goes into the selection of an appropriate valuation methodology as well as the assumptions used in these models, and the timing and actual values realized with respect to investments could be materially different from values derived based on the use of those estimates. The valuation methodologies applied impact the reported value of the Company's investments and the investments held by the Consolidated Funds in the condensed consolidated financial statements. Certain of the Company's investments are relatively illiquid or thinly traded and may not be immediately liquidated on demand if needed. Fair values assigned to these investments may differ significantly from the fair values that would have been used had a ready market for the investments existed and such differences could be material.
	The Company primarily uses the “market approach” to value its financial instruments measured at fair value. In determining an instrument's level within the hierarchy, the Company categorizes the Company's financial instruments into three categories: securities, derivative contracts and other investments. To the extent applicable, each of these categories can further be divided between those held long or sold short.
	Securities—Securities whose values are based on quoted market prices in active markets for identical assets, and are therefore classified in level 1 of the fair value hierarchy, include active listed equities, certain U.S. government and sovereign obligations, ETF's and certain money market securities. The Company does not adjust the quoted price for such instruments, even in situations where the Company holds a large position and a sale could reasonably impact the quoted price.
	Certain positions for which trading activity may not be readily visible, consisting primarily of convertible debt, corporate debt and loans, are stated at fair value and classified within level 2. The estimated fair values assigned by management are determined in good faith and are based on available information considering, trading activity, broker quotes, quotations provided by published pricing services, counterparties and other market participants, and pricing models using quoted inputs, and do not necessarily represent the amounts which might ultimately be realized. As level 2 investments include positions that are not always traded in active markets and/or are subject to transfer restrictions, valuations may be adjusted to reflect illiquidity and/or non-transferability.
	Derivative contracts—Derivative contracts can be exchange-traded or privately negotiated over-the-counter (“OTC”). Exchange-traded derivatives, such as futures contracts and exchange-traded option contracts, are typically classified within level 1 or level 2 of the fair value hierarchy depending on whether or not they are deemed to be actively traded. OTC derivatives, such as generic forwards, swaps and options, have inputs which can generally be corroborated by market data and are therefore classified within level 2. OTC derivatives, such as swaps, options and warrants where market data is not readily available or observable are classified as level 3.
	Other investments—Other investments consist primarily of portfolio funds, real estate investments and equity method investments, which are valued as follows:
	i.	Portfolio funds—Portfolio funds (“Portfolio Funds”) include interests in funds and investment companies managed by the Company or its affiliates. The Company follows US GAAP regarding fair value measurements and disclosures relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The guidance permits, as a practical expedient, an entity holding investments in certain entities that either are investment companies as defined by the AICPA Audit and Accounting Guide, Investment Companies, or have attributes similar to an investment company, and calculate net asset value per share or its equivalent for which the fair value is not readily determinable, to measure the fair value of such investments on the basis of that NAV per share, or its equivalent, without adjustment.
	The Company categorizes its investments in Portfolio Funds within the fair value hierarchy dependent on its ability to redeem the investment. If the Company has the ability to redeem its investment at NAV at the measurement date or within the near term, the Portfolio Fund is categorized as a level 2 investment within the fair value hierarchy. If the Company does not know when it will have the ability to redeem its investment or cannot do so in the near term, the Portfolio Fund is categorized as a level 3 investment within the fair value hierarchy. See Notes 5 and 6 for further details of the Company's investments in Portfolio Funds.
	ii.	Real estate investments—Real estate debt and equity investments are valued at fair value. The fair value of real estate investments are estimated based on the price that would be received to sell an asset in an orderly transaction between marketplace participants at the measurement date. Real estate investments without a public market are valued based on assumptions and valuation techniques used by the Company. Such valuation techniques may include discounted cash flow analysis, prevailing market capitalization rates or earnings multiples applied to earnings from the investment, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties, consideration of the amount that currently would be required to replace the asset, as adjusted for obsolescence, as well as independent external appraisals. In general, the Company considers several valuation techniques when measuring the fair value of a real estate investment. However, in certain circumstances, a single valuation technique may be appropriate. Real estate investments are reviewed on a quarterly basis by the Company for significant changes at the property level or a significant change in the overall market which would impact the value of the real estate investment resulting in unrealized appreciation or depreciation.
	The Company also reflects its real estate equity investments net of investment level financing. Valuation adjustments attributable to underlying financing arrangements are considered in the real estate equity valuation based on amounts at which the financing liabilities could be transferred to market participants at the measurement date.
	Real estate and capital markets are cyclical in nature. Property and investment values are affected by, among other things, the availability of capital, occupancy rates, rental rates and interest and inflation rates. In addition, the Company invests in real estate and real estate related investments for which no liquid market exists. The market prices for such investments may be volatile and may not be readily ascertainable. Amounts ultimately realized by the Company from investments sold may differ from the fair values presented, and the differences could be material.
	The Company's real estate investments are typically categorized as a level 3 investment within the fair value hierarchy as management uses significant unobservable inputs in determining their estimated fair value.
	See Notes 5 and 6 for further information regarding the Company's investments, including equity method investments, and fair value measurements.
	e.	Securities borrowed and securities loaned
	Securities borrowed and securities loaned are carried at the amounts of cash collateral advanced or received on a gross basis. The related rebates are recorded in the statement of operations as interest income and interest expense. Securities borrowed transactions require the Company to deposit cash collateral with the lender. With respect to securities loaned, the Company receives cash collateral from the borrower. The initial collateral advanced or received approximates or is greater than the market value of securities borrowed or loaned. The Company monitors the market value of securities borrowed and loaned on a daily basis, with additional collateral obtained or returned, as necessary. Securities borrowed and loaned may also result in credit exposures for the Company in an event that the counterparties are unable to fulfill their contractual obligations. The Company minimizes its credit risk by continuously monitoring  its credit exposure and collateral values by demanding additional or returning excess collateral in accordance with the netting provisions available in the master securities lending contracts in place with the counterparties.
	Fees and interest received or paid are recorded in interest and dividend income and interest expense, respectively, on an accrual basis. In cases where the fair value basis of accounting is elected, any resulting change in fair value is reported in trading revenues. Accrued interest income and expense are recorded in the same manner as under the accrual method. At March 31, 2014 and December 31, 2013, the Company does not have any securities lending transactions for which fair value basis of accounting was elected.
	f.	Securities purchased under agreements to resell and securities sold under agreements to repurchase
	The Company uses securities purchased under agreements to resell and securities sold under agreements to repurchase (“Repurchase Agreements”) as part of its liquidity management activities and to support its trading and risk management activities. In particular, securities purchased and sold under Repurchase Agreements are used for short-term liquidity purposes. As of December 31, 2013, Repurchase Agreements are secured predominantly by liquid corporate credit and/or government issued securities. The use of Repurchase Agreements will fluctuate with the Company's need to fund short term credit or obtain competitive short term credit financing. The Company's securities sold under agreements to repurchase were transacted pursuant to agreements with one counterparty as of December 31, 2013. The Company does not hold any repurchase agreements as of March 31, 2014.
	Collateral is valued daily and the Company and its counterparties may adjust the collateral or require additional collateral to be deposited when appropriate. Collateral held by counterparties may be sold or re-hypothecated by such counterparties, subject to certain limitations sometimes imposed by the Company and in accordance with the master netting agreements in place with the counterparty. Collateralized Repurchase Agreements may result in credit exposure in the event the counterparties to the transactions are unable to fulfill their contractual obligations. The Company minimizes the credit risk associated with this activity by monitoring credit exposure and collateral values, and by requiring additional collateral to be promptly deposited with or returned to the Company when deemed necessary.
	g.    Debt
	Long-term debt is carried at the principal amount borrowed net of any discount/premium. The discount is accreted to interest expense using the effective interest method over the remaining life of the underlying debt obligations. Accrued but unpaid coupon interest is included in accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition.
	h.    Deferred rent
	Deferred rent primarily consists of step rent, allowances from landlords and valuing the Company's lease properties in accordance with US GAAP. Step rent represents the difference between actual operating lease payments due and straight-line rent expense, which is recorded by the Company over the term of the lease, including the build-out period. This amount is recorded as deferred rent in the early years of the lease, when cash payments are generally lower than straight-line rent expense, and reduced in the later years of the lease when payments begin to exceed the straight-line expense. Landlord allowances are generally comprised of amounts received and/or promised to the Company by landlords and may be received in the form of cash or free rent. These allowances are part of the negotiated terms of the lease. The Company records a receivable from the landlord and a deferred rent liability when the allowances are earned. This deferred rent is amortized into income (through lower rent expense) over the term (including the pre-opening build-out period) of the applicable lease, and the receivable is reduced as amounts are received from the landlord. Liabilities resulting from valuing the Company's leased properties acquired through business combinations are quantified by comparing the current fair value of the leased space to the current rental payments on the date of acquisition. Deferred rent, included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition, as of March 31, 2014 and December 31, 2013 is $14.1 million and $14.6 million, respectively.

Cash_collateral_pledged

Cash collateral pledged	3 Months Ended
	Mar. 31, 2014
Cash and Cash Equivalents [Abstract]	'
Cash collateral pledged	'
	Cash collateral pledged
	As of March 31, 2014 and December 31, 2013, the Company pledged cash collateral in the amount of $11.3 million and $10.9 million, respectively, which relates to letters of credit issued to the landlords of the Company's premises in New York City, Boston and San Francisco (see Note 14).

Investments_of_Operating_Entit

Investments of Operating Entities and Consolidated Funds	3 Months Ended
	Mar. 31, 2014
Investments, Debt and Equity Securities [Abstract]	'
Investments of Operating Entities and Consolidated Funds	'
	Investments of Operating Entities and Consolidated Funds
	a.	Operating Entities
	Securities owned, at fair value
	Securities owned, at fair value are held by the Company and are considered held for trading. Substantially all equity securities are pledged to the clearing broker under terms which permit the clearing broker to sell or re-pledge the securities to others subject to certain limitations.
	As of March 31, 2014 and December 31, 2013, securities owned, at fair value consisted of the following:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	U.S. Government securities (a)	$	9			$	9
	Preferred stock	324				324
	Common stocks	270,349				176,939
	Convertible bonds (b)	11,564				5,958
	Corporate bonds (c)	167,349				121,372
	Warrants and rights	4,265				5,912
	Mutual funds	15,518				525
		$	469,378			$	311,039
	(a)	As of March 31, 2014, the maturity was April 2016 with an interest rate of 5.95%. As of December 31, 2013, the maturity was April 2016 with an interest rate of 5.95%.
	(b)	As of March 31, 2014, maturities ranged from June 2014 to November 2014 and interest rates ranged between 4.00% to 10.00%. As of December 31, 2013, maturities ranged from May 2014 to October 2014 and interest rates ranged between 5.00% to 10.00% .
	(c)	As of March 31, 2014, maturities ranged from September 2014 to February 2046 and interest rates ranged between 4.74% and 12.25%. As of December 31, 2013, maturities ranged from January 2014 to February 2046 and interest rates ranged between 3.38% and 11.75%.
	Receivable on and Payable for derivative contracts, at fair value
	The Company's direct involvement with derivative financial instruments includes futures, currency forwards, equity swaps, options and warrants and rights. Open equity positions in futures transactions are recorded as receivables from and payables to broker-dealers or clearing brokers, as applicable. The Company's derivatives trading activities exposes the Company to certain risks, such as price and interest rate fluctuations, volatility risk, credit risk, counterparty risk, foreign currency movements and changes in the liquidity of markets.
	On the date of issuance of the Company's cash convertible unsecured senior notes ("Convertible Notes") (see Note 14), the Company recognized the embedded cash conversion option at $35.7 million which is included in payable for derivative contracts in the accompanying condensed consolidated statement of financial condition. Also, on the date of issuance of the Convertible Notes, the Company entered into a separate cash convertible note hedge transaction (the "Hedge Transaction") with a counterparty (the “Option Counterparty”) whereby, the Company purchased a cash settled option contract with terms identical to the conversion option embedded in the Convertible Notes and simultaneously sold an equity settled warrant with a higher strike price. The Hedge Transaction is expected to reduce the Company’s exposure to potential cash payments in excess of the principal amount of converted notes that the Company may be required to make upon conversion of the Convertible Notes. The Hedge Transaction is included in receivable on derivative contracts in the accompanying condensed consolidated statement of financial condition. On the date of issuance of the Convertible Notes, the Company paid a premium of $35.7 million for the option under the Hedge Transaction and received a premium of $15.2 million for the equity settled warrant transaction, for a net cost of $20.5 million. Aside from the initial premium paid, we will not be required to make any cash payments under the Hedge Transaction and could be entitled to receive an amount of cash from the Option Counterparty generally equal to the amount by which the market price per share of common stock exceeds the strike price of the Hedge Transaction during the relevant valuation period. The warrants cover 28,048,786 shares of the Company's Class A common stock and have an initial exercise price of $7.18 per share. The warrants expire over a period of 80 trading days beginning on November 14, 2018. The warrant transaction could have a dilutive effect to the extent that the market value per share of the Company’s Class A common stock exceeds the applicable strike price of the warrants.
	The Company's long and short exposure to derivatives is as follows:
	Receivable on derivative contracts	As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	Commodity Future	$	53			$	285
	Cross Rate	10				22
	Equity Swap	8				70
	Options (a)	50,005				9,698
		$	50,076			$	10,075
	(a) As of March 31, 2014 and December 31, 2013, the Company had 62,479 and 71,129 contracts held, respectively.
	Payable for derivative contracts	As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	Futures	$	62			$	275
	Currency forwards	28				301
	Equity and credit default swaps	735				525
	Options (a)	49,207				6,573
		$	50,032			$	7,674
	(a) As of March 31, 2014 and December 31, 2013, the Company had 27,745 and 38,221 contracts held, respectively.
	The following tables present the gross and net derivative positions and the related offsetting amount, as of March 31, 2014 and December 31, 2013.
	As of March 31, 2014
		Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
						(a)
		(dollars in thousands)
	Receivable on derivative contracts, at fair value	$	50,076			$	—			$	50,076	$	—	$	—
	Payable for derivative contracts, at fair value	50,032				—				50,032		—		—
	As of December 31, 2013
		Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
						(a)
		(dollars in thousands)
	Receivable on derivative contracts, at fair value	$	10,075			$	—			$	10,075	$	10,075	$	—
	Payable for derivative contracts, at fair value	7,674				—				7,674		7,674		$	—
	(a)	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
	(b)	Includes the amount of collateral held or posted.
	The realized and unrealized gains/(losses) related to derivatives trading activities for the three months ended March 31, 2014 and 2013, were $(1.8) million and $(5.2) million, respectively, and are included in other income in the accompanying condensed consolidated statements of operations.
	Pursuant to the various derivatives transactions discussed above, the Company is required to post collateral for its obligations or potential obligations. As of March 31, 2014 and December 31, 2013, collateral consisting of $18.1 million and $10.0 million of cash, respectively, is included in receivable from brokers on the accompanying condensed consolidated statements of financial condition. As of March 31, 2014 and December 31, 2013 all derivative contracts were with multiple major financial institutions.
	Other investments
	As of March 31, 2014 and December 31, 2013, other investments consisted of the following:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	(1) Portfolio Funds, at fair value	$	79,440			$	71,051
	(2) Real estate investments, at fair value	42,283				2,088
	(3) Equity method investments	22,034				25,966
	(4) Lehman claims, at fair value	390				378
	$	144,147			$	99,483
-1	Portfolio Funds, at fair value
The Portfolio Funds, at fair value as of March 31, 2014 and December 31, 2013, included the following:
	As of March 31, 2014				As of December 31, 2013
	(dollars in thousands)
HealthCare Royalty Partners (a)(*)	$	10,784			$	9,741
HealthCare Royalty Partners II (a)(*)	6,140				4,961
Orchard Square Partners Credit Fund LP (b)(*)	13,828				12,674
Starboard Value and Opportunity Fund LP (c)(*)	18,439				17,495
Formation 8 Partners Fund I (d)	6,083				2,788
RCG LV Park Lane LLC (e)	706				678
RCGL 12E13th LLC (f)	584				558
RCG Longview Debt Fund V, L.P. (f)	11,856				11,979
Other private investment (g)	7,785				7,772
Other affiliated funds (h)(*)	3,235				2,405
	$	79,440			$	71,051
* These portfolio funds are affiliates of the Company.
The Company has no unfunded commitments regarding the portfolio funds held by the Company except as noted in Note 13.
(a)	HealthCare Royalty Partners, L.P. and HealthCare Royalty Partners II, L.P. are private equity funds and therefore distributions will be made when cash flows are received from the underlying investments, typically on a quarterly basis.
(b)	Orchard Square Partners Credit Fund LP (formerly known as Ramius Global Credit Fund LP) has a quarterly redemption policy with a 60 day notice period and a 4% penalty on redemptions of investments of less than a year in duration.
(c)	Starboard Value and Opportunity Fund LP permits quarterly withdrawals upon 90 days notice.
(d)	Formation 8 Partners Fund I is a private equity fund which invests in equity of early stage and growth transformational information and energy technology companies. Distributions will be made when the underlying investments are liquidated.
(e)	RCG LV Park Lane LLC  is a single purpose entity formed to participate in a joint venture which acquired, at a discount, the mortgage notes on a portfolio of multifamily real estate properties located in Birmingham, Alabama.  RCG LV Park Lane LLC is a private equity structure and therefore distributions will be made when the underlying investments are liquidated.
(f)	RCGL 12E13th LLC and RCG Longview Debt Fund V, L.P. are real estate private equity structures and therefore distributions will be made when the underlying investments are liquidated.
(g)	Other private investment represents the Company's closed end investment in a portfolio fund that invests in a wireless broadband communication provider in Italy.
(h)	The majority of these funds are affiliates of the Company or are managed by the Company and the investors can redeem from these funds as investments are liquidated.
-2	Real estate investments, at fair value
Real estate investments as of March 31, 2014 and December 31, 2013 are carried at fair value and include real estate equity investments held by RCG RE Manager, LLC (“RE Manager”), a real estate operating subsidiary of the Company, of $2.3 million and $2.1 million, respectively. Additionally, during March 2014, the Company invested $40 million (which approximates fair value at March 31, 2014) in two real estate mortgage loan participation agreements, with a related party, earning interest at LIBOR plus 6%, which include put/call options exercisable within 90 days.
-3	Equity method investments
Equity method investments include investments held by the Company in several operating companies whose operations primarily include the day to day management of a number of real estate funds, including the portfolio management and administrative services related to the acquisition, disposition, and active monitoring of the real estate funds' underlying debt and equity investments. The Company's ownership interests in these equity method investments range from 20% to 55%. The Company holds a majority of the outstanding ownership interest (i.e., more than 50%) in three of these entities: RCG Longview Debt Fund IV Management, LLC, RCG Longview Debt Fund IV Partners, LLC and RCG Longview Partners II, LLC. The operating agreements that govern the management of day-to-day operations and affairs of each of these three entities stipulate that certain decisions require support and approval from other members in addition to the support and approval of the Company. As a result, all operating decisions made in these three entities require the support of both the Company and an affirmative vote of a majority of the other managing members who are not affiliates of the Company. As the Company does not possess control over any of these entities, the presumption of consolidation has been overcome pursuant to current accounting standards and the Company accounts for these investments under the equity method of accounting. Also included in equity method investments is the investment in (a) HealthCare Royalty Partners General Partners (b) an investment in the CBOE (Chicago Board Options Exchange) Stock Exchange LLC representing a 9.5% stake in the exchange service provider for which the Company exercises significant influence over through representation on the CBOE Board of Directors, and (c) Starboard Value (and certain related parties) which serves as an operating company whose operations primarily include the day to day management (including portfolio management) of a deep value small cap hedge fund and related managed accounts.
The following table summarizes equity method investments held by the Company:
	As of March 31, 2014				As of December 31, 2013
	(dollars in thousands)
RCG Longview Debt Fund IV Management, LLC	$	495			$	1,533
RCG Longview Debt Fund V Partners, LLC	1,672				1,497
HealthCare Royalty GP, LLC	879				794
HealthCare Royalty GP II, LLC	1,040				840
HealthCare Royalty GP III, LLC	47				47
CBOE Stock Exchange, LLC	1,283				1,351
Starboard Value LP	10,019				14,263
RCG Longview Partners, LLC	2,692				1,839
RCG Urban American, LLC	346				316
RCG Urban American Management, LLC	274				238
RCG Longview Equity Management, LLC	106				292
Urban American Real Estate Fund II, LLC	2,047				1,785
RCG Kennedy House, LLC	483				502
Other	651				669
	$	22,034			$	25,966
As of March 31, 2014 and December 31, 2013, the Company's share of losses in its equity method investment in RCG Longview Partners II, LLC has exceeded the carrying amount recorded in this investee. These amounts are included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition. RCG Longview Partners II, LLC, as general partner to a real estate fund, has reversed previously recorded incentive income allocations and has recorded a current clawback obligation to the limited partners in the fund. This obligation is due to a change in unrealized value of the fund on which there have previously been distributed carried interest realizations; however, the settlement of a potential obligation is not due until the end of the life of the respective fund. As the Company is obligated to return previous distributions it received from RCG Longview Partners II, LLC, it has continued to record its share of gains/losses in the investee including reflecting its share of the clawback obligation in the amount of $6.2 million.
The Company's income (loss) from equity method investments was $6.5 million and $4.2 million for the three months ended March 31, 2014 and 2013, respectively, and is included in net gains (losses) on securities, derivatives and other investments on the accompanying condensed consolidated statements of operations. In addition, the Company recorded no impairment charges in relation to its equity method investments for the three months ended March 31, 2014 and 2013, respectively.
-4	Lehman Claims, at fair value
Lehman Brothers International (Europe) (“LBIE”), through certain affiliates, was a prime broker to the Company, and the Company held cash and cash equivalent balances with LBIE. On September 15, 2008, LBIE was placed into administration (the “Administration”) in the United Kingdom and, as a result, the assets held by the Company in its LBIE accounts were frozen at LBIE. The assets which the Company believed were held at LBIE at the time of Administration (the “Total Net Equity Claim”) consisted of $1.0 million, which the Company believed would represent an unsecured claim against LBIE. On November 2, 2012, the Company executed a Claims Determination Deed with respect to this claim.  By entering into this deed, the Company and LBIE reached agreement on the amount of the Company's unsecured claim, which was agreed to be approximately $0.9 million.  As a result of entering into this deed, the Company is entitled to participate in dividends to unsecured creditors of LBIE. At the end of November 2012 the Company received its first dividend in an amount equal to 25.2% of its agreed claim, or approximately $0.2 million, at the end of June 2013 the Company received its second dividend in an amount equal to 43.3% of its agreed claim, or approximately $0.4 million, and at the end of November 2013 the Company received its third dividend in an amount equal to 23.7% of its agreed claim, or approximately $0.2 million. The total amounts received to date in respect of the Company’s unsecured claim against LBIE are approximately $0.9 million, representing 92.2% of its agreed claim. On February 28, 2014, LBIE announced that the fourth interim distribution would be paid on or around April 30, 2014. The dividend rate will be 7.8% of the agreed claim amount, or approximately $0.1 million, bringing the total cumulative distributions received to 100% of the agreed claim amount. LBIE also indicated that no further distributions will be possible until such time as matters concerning how the surplus remaining in the estate will be distributed are resolved. Accordingly, the Company does not know the timing with respect to future dividends to unsecured creditors or the ultimate value that will be received, with respect to its claim. The claim described above does not include claims held by the Company against LBIE through its investment in Enterprise Master discussed in Note 5b(2).
Given the fact that LBIE has made multiple distributions to unsecured creditors and the increased trading levels for unsecured claims of LBIE, the Company decided to record the estimated fair value of the Total Net Equity Claim at 132.5% and 131.5% as of March 31, 2014 and December 31, 2013, respectively, which represented management's best estimate at the respective dates of the value that ultimately may be recovered with respect to the Total Net Equity Claim (the “Estimated Recoverable Lehman Claim”). The Estimated Recoverable Lehman Claim was recorded at estimated fair value considering a number of factors including the status of the assets under U.K. insolvency laws and the trading levels of LBIE unsecured debt. In determining the estimated value of the Total Net Equity Claim, the Company was required to use considerable judgment and is based on the facts currently available. As additional information on the LBIE proceeding becomes available, the Company may need to adjust the valuation of the Estimated Recoverable Lehman Claim. The actual recovery that may ultimately be received by the Company with respect to the pending LBIE claim is not known and could be different from the estimated value assigned by the Company. (See Note 5b(2)).
Securities sold, not yet purchased, at fair value
Securities sold, not yet purchased, at fair value represent obligations of the Company to deliver a specified security at a contracted price and, thereby, create a liability to purchase that security at prevailing prices. The Company's liability for securities to be delivered is measured at their fair value as of the date of the condensed consolidated financial statements. However, these transactions result in off-balance sheet risk, as the Company's ultimate cost to satisfy the delivery of securities sold, not yet purchased, at fair value may exceed the amount reflected in the accompanying condensed consolidated statements of financial condition. Substantially all equity securities and options are pledged to the clearing broker under terms which permit the clearing broker to sell or re-pledge the securities to others subject to certain limitations. As of March 31, 2014 and December 31, 2013, securities sold, not yet purchased, at fair value consisted of the following:
	As of March 31, 2014				As of December 31, 2013
	(dollars in thousands)
Common stocks	$	139,290			$	130,899
Corporate bonds (a)	57				55
	$	139,347			$	130,954
(a)	As of March 31, 2014 and December 31, 2013, the maturity was January 2026 with an interest rate of 5.55%.
Securities purchased under agreements to resell and securities sold under agreements to repurchase
The Company held no securities purchased under agreements to resell or securities sold under agreements to repurchase as of March 31, 2014. The following table represents the Company's securities sold under agreements to repurchase as of December 31, 2013:
	As of December 31, 2013
	(dollars in thousands)
Securities sold under agreements to repurchase
Agreements with Royal Bank of Canada bearing interest of 1.75% due June 2015 to November 2015	$	3,657
	$	3,657
The following tables present the gross and net repurchase agreements and the related offsetting amount, as of December 31, 2013.
As of December 31, 2013
	Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
					(a)
	(dollars in thousands)
Securities sold under agreements to repurchase	$	3,657			$	—			$	3,657	$	3,657	$	—
(a)	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
(b)	Includes the amount of collateral held or posted.
For all of the Company's holdings of repurchase agreements as of December 31, 2013, the repurchase dates were open and the agreement could be terminated by either party at any time. The agreements rolls over on a day-to-day basis.
Transactions involving the purchase or sale of securities under repurchase/resell agreements are carried at their contract value, which approximates fair value, and are accounted for as collateralized financings. In connection with these financings, as of December 31, 2013, the Company had pledged collateral of $4.6 million (consisting of corporate bonds), which is included in securities owned, at fair value in the accompanying condensed consolidated statements of financial condition.
Securities lending and borrowing transactions
As of March 31, 2014 and December 31, 2013, the Company has loaned to brokers and dealers, securities having a market value of $1.3 billion and $881.7 million, respectively.  In addition, the Company has borrowed from brokers and dealers, securities having a market value of $1.3 billion and $892.8 million as of March 31, 2014 and December 31, 2013, respectively.
The following tables present the contractual gross and net securities borrowing and lending agreements and the related offsetting amount, as of March 31, 2014 and December 31, 2013.
As of March 31, 2014
	Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
					(a)
	(dollars in thousands)
Securities borrowed	$	1,319,938			$	—			$	1,319,938	$	1,319,938	$	—
Securities loaned	1,310,903				—				1,310,903		1,310,903		—
As of December 31, 2013
	Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
					(a)
	(dollars in thousands)
Securities borrowed	$	927,773			$	—			$	927,773	$	927,773	$	—
Securities loaned	918,577				—				918,577		918,577		—
(a)	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
(b)	Includes the amount of cash collateral held/posted.
Variable Interest Entities
The total assets and liabilities of the variable interest entities for which the Company has concluded that it holds a variable interest, but for which it is not the primary beneficiary, are $2.0 billion and $247.5 million as of March 31, 2014 and $1.7 billion and $242.5 million as of December 31, 2013, respectively. In addition, the maximum exposure relating to these variable interest entities as of March 31, 2014 was $180.6 million, and as of December 31, 2013 was $193.9 million, all of which is included in other investments, at fair value in the Company's condensed consolidated statements of financial condition. The exposure to loss primarily relates to the Consolidated Feeder Funds' investment in their Unconsolidated Master Funds as of March 31, 2014 and December 31, 2013.
b.	Consolidated Funds
Other investments, at fair value
As of March 31, 2014 and December 31, 2013 other investments, at fair value, held by the Consolidated Funds are comprised of:
	As of March 31, 2014				As of December 31, 2013
	(dollars in thousands)
(1) Portfolio Funds	$	175,614			$	182,638
(2) Lehman claims	3,776				4,842
	$	179,390			$	187,480
-1	Investments in Portfolio Funds, at fair value
As of March 31, 2014 and December 31, 2013, investments in Portfolio Funds, at fair value, included the following:
	As of March 31, 2014				As of December 31, 2013
	(dollars in thousands)
Investments of Enterprise LP	$	143,059			$	155,530
Investments of Merger Fund	32,555				26,963
Investments of consolidated fund of funds	—				145
	$	175,614			$	182,638
Consolidated investments of Enterprise LP
Enterprise LP operates under a “master-feeder” structure, whereby Enterprise Master's shareholders are Enterprise LP and RCG II Intermediate Fund, L.P. The consolidated investments in Portfolio Funds include Enterprise LP's investment of $143.1 million and $155.5 million in Enterprise Master as of March 31, 2014 and December 31, 2013, respectively. On May 12, 2010, the Company announced its intention to close Enterprise Master. Prior to this announcement, strategies utilized by Enterprise Master included merger arbitrage and activist investing, investments in distressed securities, convertible hedging, capital structure arbitrage, equity market neutral, investments in private placements of convertible securities, proprietary mortgages, structured credit investments, investments in mortgage backed securities and other structured finance products, investments in real estate and real property interests, structured private placements and other relative value strategies. Enterprise Master had broad investment powers and maximum flexibility in seeking to achieve its investment objective. Enterprise Master was permitted to invest in equity securities, debt instruments, options, futures, swaps, credit default swaps and other derivatives. Enterprise Master has been selling, and will continue to sell, its positions and return capital to its investors. There are no unfunded commitments at Enterprise LP.
Consolidated investments of Merger Fund
The Merger Fund operates under a “master-feeder” structure, whereby Ramius Merger Master Ltd's ("Merger Master") shareholders are Merger Fund and Ramius Merger Fund Ltd. The consolidated investments in Portfolio Funds include Merger Fund's investment of $32.6 million and $27.0 million in Merger Master as of March 31, 2014 and December 31, 2013, respectively. The Merger Master’s investment objective is to achieve consistent absolute returns while emphasizing the preservation of investor capital. The Merger Master seeks to achieve these objectives by taking a fundamental, research-driven approach to investing, primarily in the securities of issuers engaged in, or subject to, announced (or unannounced but otherwise anticipated) extraordinary corporate transactions, which may include, but are not limited to, mergers, acquisitions, leveraged buyouts, tender offers, hostile takeover bids, sale processes, exchange offers, and recapitalizations. Merger Master invests in the securities of one or more issuers engaged in or subject to such extraordinary corporate transactions. Merger Master typically seeks to derive a profit by realizing the price differential, or “spread,” between the market price of securities purchased or sold short and the market price or value of securities realized in connection with the completion or termination of the extraordinary corporate transaction, or in connection with the adjustment of market prices in anticipation thereof, while seeking to minimize the market risk associated with the aforementioned investment activities. Merger Master will, depending on markets conditions, generally focus the majority of its investment program on announced transactions. If the investment manager of Merger Master considers it necessary, it may either alone or as part of a group, also initiate shareholder actions seeking to maximize value. Such shareholder actions may include, but are not limited to, re-orienting management’s focus or initiating the sale of the company (or one or more of its divisions) to a third party. There are no unfunded commitments at Merger Fund.
Investment of a consolidated fund of funds investment company
The investment of the consolidated fund of fund investment company was $0.1 million as of December 31, 2013, which was the remaining investment of Vintage Master FOF that was transferred to a third party during the three months ended March 31, 2014. Vintage Master FOF's investment objective was to allocate its capital among portfolio managers that invest through investment pools or managed accounts thereby forming concentrated investments in high conviction managers designed to achieve attractive risk adjusted returns with moderate relative volatility. The investment held at December 31, 2013 was a hedged equity strategy held in an externally managed portfolio fund. The hedged equity strategy focused on equity strategies with some directional market exposure. The strategy attempted to profit from market efficiencies and direction. There are no fund of fund investment companies consolidated as of March 31, 2014.
-2	Lehman Claims, at fair value
With respect to the aforementioned Lehman claims, the Total Net Equity Claim of Enterprise Master based on the value of assets at the time of Lehman's insolvency held directly by Enterprise Master and through Enterprise Master's ownership interest in affiliated funds consisted of $24.3 million. Included in this claim were assets with a value of $9.5 million at the time LBIE entered Administration that were returned to Enterprise Master and its affiliated funds in June 2010. Enterprise Master and its affiliated funds sold the returned assets for an aggregate $10.7 million, and distributed this amount to Enterprise Master's investors in July 2010. In December 2011, Enterprise Master received an aggregate of approximately $2.4 million relating to securities, interest and dividends earned with respect to securities held by LBIE on behalf of Enterprise Master and its affiliated funds. A distribution of $2.9 million occurred in February of 2012. On November 2, 2012, Enterprise Master executed a Claims Determination Deed with respect to the unsecured portion of its direct claim against LBIE.  By entering into this deed, Enterprise Master and LBIE reached agreement on the amount of Enterprise Master's unsecured claim, which was agreed to be approximately $1.3 million.  As a result of entering into this deed, Enterprise Master was entitled to participate in dividends to unsecured creditors of LBIE and at the end of November 2012 Enterprise Master received its first dividend in an amount equal to 25.2% of its agreed claim, or approximately $0.3 million. In February 2013, Enterprise Master sold its unsecured claim, including the amount received in connection with the first dividend, for $1.3 million, or par. Enterprise Master distributed the proceeds of the sale to the Company in March 2013. Of the original remaining net equity claim, $10.6 million represented claims to trust assets that the Company believes were held by LBIE through Lehman Brothers, Inc. (“LBI”). LBIE made a corresponding claim for these assets and other trust assets held at LBI by LBIE on behalf of other prime brokerage clients pursuant to an omnibus customer claim (the “LBIE Omnibus Customer Claim”). LBIE was only going to be able to return trust assets held at LBI to Enterprise Master once LBIE received a distribution from LBI in respect of the LBIE Omnibus Customer Claim. In February 2013, LBIE, Lehman Brothers Holdings, Inc. and LBI announced that they entered into two separate agreements settling all intercompany claims between LBI on the one part, and LBHI and LBIE on the other part. The settlement agreements were subject to the approval by the U.S. Bankruptcy Judge in the LBI Securities Investor Protection Act (SIPA) proceeding and, in the case of the agreement between LBI and LBIE, an order of the English High Court. The U.S. Banking Judge approved the settlement agreement in April 2013 and the English High Court issued an order approving the settlement in May 2013. The settlements allowed the trustee appointed under SIPA (the “SIPA Trustee”) to proceed with plans to allocate and distribute sufficient cash and securities to LBI's customer claimants, including LBIE with respect to the LBIE Omnibus Customer Claim, to enable the SIPA Trustee to satisfy valid customer claims in full. In March 2013, LBIE made a consensual proposal to the clients holding trust assets pursuant to the LBIE Omnibus Customer Claim to facilitate the return of the amounts recovered from LBI with respect to the LBIE Omnibus Customer Claim. Under the consensual proposal, LBIE indicated that it intended to liquidate any securities received from LBI with respect to the LBIE Omnibus Customer Claim and then allocate the value received from LBI among all of the LBIE clients who had trust assets held at LBI under the LBIE Omnibus Customer Claim. In allocating the amounts received from LBI, LBIE indicated that it intended to allow clients to determine their entitlements on a portfolio basis based on the higher of (i) the market value of the portfolio as of September 19, 2008 or (ii) the market value of the portfolio together with accrued income thereon as of November 30, 2012 (the “Best Claim”). LBIE's purpose in seeking a consensual arrangement with its clients relating to the liquidation and allocation described above was to ensure that a distribution could be made without having to seek UK court direction on these issues, which would otherwise have substantially delayed any distribution. On April 2, 2013, LBIE announced that the consensual proposal had been accepted by a sufficient number of clients to satisfy the acceptance threshold and would therefore become effective. The settlement agreement between LBI and LBIE also became effective and LBIE announced in June 2013 that it had recovered the majority of the cash and securities from LBI and that it had liquidated approximately 90% of the aggregate value of securities received or to be received from LBI and that it intended to make its first distribution to trust asset claimants at the end of September 2013. On September 26, 2013, LBIE announced that it had made a first interim distribution to trust claimants of 100% of the claimant's Best Claim amount. As previously announced by LBIE, LBIE has requested guidance from the US Internal Revenue Service ("IRS") with regard to the character and source of the settlement payments. In order to balance LBIE's objective of making a significant distribution to claimants with the requirement to pay the appropriate US withholding tax in respect of distributions, as an interim solution LBIE deposited 30% of the gross distribution to claimants with the IRS as a reserve, except with respect to claimants who provided LBIE with a validly executed Form W-9. Once the appropriate US withholding tax treatment of the distributions is finally determined by the IRS, LBIE expects to be in a position to promptly receive back funds and release any excess reserves back to the appropriate claimants. On April 25, 2015, LBIE disclosed that it intends to make a distribution to trust claimants with June 12, 2014 as the proposed distribution date. The proposed distribution would be to release excess reserves back to the appropriate claimants. The amount to be released has not yet been publicly disclosed. The amount of the distribution received by Enterprise Master on September 26, 2013 was $14.9 million, with $1 million reserved by LBIE in respect of the withholding described above. On January 30, 2014, LBIE made a second distribution to trust claimants of 6% of the claimant’s Best Claim amount. LBIE has also requested guidance from the IRS with respect to the character and source of this settlement payment and as an interim solution the withholding agent has reserved 30% of the distribution amount paid, except with respect to claimants who provided LBIE with a validly executed Form W-9. As of March 31, 2014, after giving effect to the receipt of the distribution described above, the Company is valuing Enterprise Master's remaining trust asset claim at 101.5% of its Best Claim, or $0.2 million. After giving effect to all of these distributions, the remaining Net Equity Claim for Enterprise Master held directly and through its ownership interest in affiliated funds was $5.8 million as of March 31, 2014. Of the $5.8 million current valuation of Enterprise Master's claim, $3.8 million was attributable to Enterprise LP based on its ownership percentage in Enterprise Master at the time of the Administration.
In addition to Enterprise Master's claims against LBIE, LBI was a prime broker to Enterprise Master and Enterprise Master held cash balances of $4.9 million at LBI. These are not part of the LBIE Omnibus Customer Claim. On September 19, 2008, LBI was placed in a Securities Investor Protection Corporation (“SIPC”) liquidation proceeding after the filing for bankruptcy of its parent Lehman Brothers Holdings, Inc. The settlement agreements between LBI, LBHI and LBIE discussed above have permitted the trustee appointed under the Securities Investor Protection Act (the “SIPA Trustee”) to make distributions to LBI customers and the SIPA Trustee announced that it expected to be able to make 100% distributions to its customers. In July 2013, Enterprise Master received a distribution of $4.9 million from LBI in respect of this claim.
The remaining components of the LBIE claims included within the $5.8 million value as of March 31, 2014 consist of several components valued as follows: (a) the trust assets that the Company was informed were within the control of LBIE and were expected to be returned in the relatively near term were valued at market less a 1% discount that corresponds to the fee to be charged under the Claim Resolution Agreement (“CRA”) and (b) the foreign denominated trust assets that are not within the control of LBIE (which the Company does not believe are held through LBI), were valued at $4.4 million, which represents the market value of those assets less a 1% discount that corresponds to the fee charged under the CRA, which represented the Company's estimate of potential recovery rates. The estimated final recoverable amount by Enterprise Master may differ from the actual recoverable amount of the pending LBIE and LBI claims, and the differences may be significant.
As a result of Enterprise Master and certain of the funds managed by the Company having assets held at LBIE frozen in their LBIE prime brokerage account and the degree of uncertainty as to the status of those assets and the process and prospects of the return of those assets, Enterprise Master and the funds managed by the Company decided that only the investors who were invested at the time of the Administration should participate in any profit or loss relating to the Estimated Recoverable Lehman Claim. As a result, Enterprise Master and certain of the funds managed by the Company with assets held at LBIE granted a 100% participation in the Estimated Recoverable Lehman Claims to Special Purpose Vehicles (the “SPVs” or “Lehman Segregated Funds”) incorporated under the laws of the Cayman Islands on September 29, 2008, whose shares were distributed to each of their investor funds. Fully redeeming investors of Enterprise LP will not be paid out on the balance invested in the SPV until the claim with LBIE is settled and assets are returned by LBIE.
Indirect Concentration of the Underlying Investments Held by Consolidated Funds
From time to time, through its investments in the Consolidated Funds, the Company may indirectly maintain exposure to a particular issue or issuer (both long and/or short) which may account for 5% or more of the Consolidated Funds' net assets (on an aggregated basis). Based on information that is available to the Company as of March 31, 2014 and December 31, 2013, the Company assessed whether or not its Consolidated Funds had interests in an issuer for which the Company's pro-rata share exceeds 5% of the Consolidated Funds' net assets (on an aggregated basis). There were no indirect concentrations that exceed 5% of the Consolidated Funds' net assets held by the Company as of March 31, 2014 or December 31, 2013.
Underlying Investments of Unconsolidated Funds Held by Consolidated Funds
Enterprise Master and Merger Master
Enterprise LP's investment in Enterprise Master represents Enterprise LP's proportionate share of Enterprise Master's net assets; as a result, the investment balances of Enterprise Master reflected below may exceed the net investment which Enterprise LP has recorded. Merger Fund's investment in Merger Master represents Merger Fund's proportionate share of Merger Master's net assets; as a result, the investment balances of Merger Master reflected below may exceed the net investment which Merger Fund has recorded.The following tables present summarized investment information for the underlying investments and derivatives held by Enterprise Master and Merger Master as of March 31, 2014 and December 31, 2013:
Securities owned by Enterprise Master, at fair value
	As of March 31, 2014				As of December 31, 2013
	(dollars in thousands)
Bank debt	$	5			$	5
Common stock	2,527				2,677
Preferred stock	973				973
Private equity	409				406
Restricted stock	124				124
Rights	2,531				2,528
Trade claims	128				128
	$	6,697			$	6,841
Derivative contracts, at fair value, owned by Enterprise Master, net
	As of March 31, 2014				As of December 31, 2013
Description	(dollars in thousands)
Currency forwards	$	6			$	(21	)
	$	6			$	(21	)
Portfolio Funds, owned by Enterprise Master, at fair value
			As of March 31, 2014				As of December 31, 2013
	Strategy		(dollars in thousands)
RCG Longview Equity Fund, LP*	Real Estate		$	8,949			$	8,470
RCG Longview II, LP*	Real Estate		825				800
RCG Longview Debt Fund IV, LP*	Real Estate		15,308				17,641
RCG Longview, LP*	Real Estate		467				319
RCG Soundview, LLC*	Real Estate		442				442
RCG Urban American Real Estate Fund, L.P.*	Real Estate		2,003				1,812
RCG International Sarl*	Multi-Strategy		1,693				1,795
RCG Special Opportunities Fund, Ltd*	Multi-Strategy		82,692				82,119
RCG Endeavour, LLC*	Multi-Strategy		5				6
RCG Energy, LLC *	Energy		2,866				2,842
RCG Renergys, LLC*	Energy		1				1
Other Private Investments	Various		13,254				12,952
Real Estate Investments	Real Estate		16,947				15,024
			$	145,452			$	144,223
*	Affiliates of the Company.
Merger Master
Securities owned by Merger Master, at fair value
	As of March 31, 2014				As of December 31, 2013
	(dollars in thousands)
Common stocks	$	63,734			$	33,901
Corporate bond (a)	11,328				14,444
Options	434				200
	$	75,496			$	48,545
(a)	As of March 31, 2014, maturities ranged from April 2016 to June 2019 and interest rates ranged between 8.50% and 10.88%. As of December 31, 2013, maturities ranged from April 2016 to October 2020 and interest rates ranged between 7.00% and 10.88%.
Securities sold, not yet purchased, by Merger Master, at fair value
As of March 31, 2014 and December 31, 2013, Merger Master held common stock, sold not yet purchased, of $32.5 million and $19.5 million, respectively.
Derivative contracts, at fair value, owned by Merger Master, net
	As of March 31, 2014				As of December 31, 2013
Description	(dollars in thousands)
Currency forwards	$	(4	)		$	(10	)
Options	(155		)		(54		)
Cross rate	(84		)		(92		)
	$	(243	)		$	(156	)

Fair_Value_Measurements_for_Op

Fair Value Measurements for Operating Entities and Consolidated Funds	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements for Operating Entities and Consolidated Funds	'
	Fair Value Measurements for Operating Entities and Consolidated Funds
	The following table presents the assets and liabilities that are measured at fair value on a recurring basis on the accompanying condensed consolidated statements of financial condition by caption and by level within the valuation hierarchy as of March 31, 2014 and December 31, 2013:
	Operating Entities
		Assets at Fair Value as of March 31, 2014
		Level 1		Level 2				Level 3			Total
				(dollars in thousands)
	Securities owned and derivatives
	US Government securities	$	9	$	—			$	—		$	9
	Preferred stock	—		—				324			324
	Common stocks	258,824		2,242				9,283			270,349
	Convertible bonds	—		9,614				1,950			11,564
	Corporate bonds	—		167,349				—			167,349
	Warrants and rights	997		—				3,268			4,265
	Mutual funds	15,518		—				—			15,518
	Receivable on derivative contracts, at fair value
	Futures	53		—				—			53
	Currency forwards	—		10				—			10
	Equity swaps	—		8				—			8
	Options	7,149		—				42,856			50,005
	Other investments
	Portfolio Funds	—		20,857				58,583			79,440
	Real estate investments	—		—				42,283			42,283
	Lehman claim	—		—				390			390
		$	282,550	$	200,080			$	158,937		$	641,567
		Liabilities at Fair Value as of March 31, 2014
		Level 1		Level 2				Level 3			Total
		(dollars in thousands)
	Securities sold, not yet purchased and derivatives
	Common stocks	$	139,290	$	—			$	—		$	139,290
	Corporate bonds	—		57				—			57
	Payable for derivative contracts, at fair value
	Futures	62		—				—			62
	Currency forwards	—		28				—			28
	Equity and credit default swaps	—		735				—			735
	Options	6,351		—				42,856			49,207
	Accounts payable, accrued expenses and other liabilities
	Contingent consideration liability (a)	$	—	$	—			$	6,861		$	6,861
		$	145,703	$	820			$	49,717		$	196,240
	(a) In accordance with the terms of purchase agreements from acquisitions that closed during 2012, the Company is required to pay to certain sellers a portion of future net profits of the acquired businesses, if certain revenue targets are achieved over the period through October 2016. The Company estimated the contingent consideration using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts can range from $3.5 million to $13.0 million.
		Assets at Fair Value as of December 31, 2013
		Level 1		Level 2				Level 3			Total
				(dollars in thousands)
	Securities owned and derivatives
	US Government securities	$	9	$	—			$	—		$	9
	Preferred stock	—		—				324			324
	Common stocks	171,277		2,103				3,559			176,939
	Convertible bonds	—		4,008				1,950			5,958
	Corporate bonds	—		121,372				—			121,372
	Warrants and rights	107		—				5,805			5,912
	Mutual funds	525		—				—			525
	Receivable on derivative contracts, at fair value
	Futures	285		—				—			285
	Currency forwards	—		22				—			22
	Equity swaps	—		70				—			70
	Options	9,698		—				—			9,698
	Other investments
	Portfolio Funds	—		19,402				51,649			71,051
	Real estate investments	—		—				2,088			2,088
	Lehman claim	—		—				378			378
		$	181,901	$	146,977			$	65,753		$	394,631
		Liabilities at Fair Value as of December 31, 2013
		Level 1		Level 2				Level 3			Total
		(dollars in thousands)
Securities sold, not yet purchased and derivatives
Common stocks	$	130,899	$	—			$	—		$	130,899
Corporate bonds	—		55				—			55
Payable for derivative contracts, at fair value
Futures	275		—				—			275
Currency forwards	—		301				—			301
Equity swaps	—		525				—			525
Options	6,573		—				—			6,573
Accounts payable, accrued expenses and other liabilities
Contingent consideration liability	—		—				6,937			6,937
	$	137,747	$	881			$	6,937		$	145,565
Consolidated Funds' investments
	Assets at Fair Value as of March 31, 2014
	Level 1		Level 2				Level 3			Total
			(dollars in thousands)
Other investments
Portfolio Funds	$	—	$	32,555			$	143,059		$	175,614
Lehman claims	—		—				3,776			3,776
	$	—	$	32,555			$	146,835		$	179,390
	Assets at Fair Value as of December 31, 2013
	Level 1		Level 2				Level 3			Total
			(dollars in thousands)
Other investments
Portfolio Funds	—		26,964				155,674			182,638
Lehman claims	—		—				4,842			4,842
	$	—	$	26,964			$	160,516		$	187,480
The following table includes a rollforward of the amounts for the three months ended March 31, 2014 and 2013, for financial instruments classified within level 3. The classification of a financial instrument within level 3 is based upon the significance of the unobservable inputs to the overall fair value measurement.
	Three Months Ended March 31, 2014
	Balance at December 31, 2013		Transfers in					Transfers out			Purchases/(covers)			(Sales)/shorts				Realized gains (losses)				Unrealized gains or losses				Balance at March 31, 2014
	(dollars in thousands)
Operating Entities
Preferred stock	$	324	$	—				$	—		$	—		$	—			$	—			$	—			$	324
Common stocks	3,559		—					—			—			—				—				5,724				9,283
Convertible bonds	1,950		—					—			—			—				—				—				1,950
Options, asset	—		—					—			35,710			—				—				7,146				42,856
Options, liability	—		—					—			35,710			—				—				7,146				42,856
Warrants and Rights, asset	5,805		—			—		—			—			(1,328		)		—				(1,209		)		3,268
Portfolio Funds	51,649		—					—			4,385			(1,242		)		180				3,611				58,583
Real estate	2,088		—					—			40,000			(27		)		—				222				42,283
Lehman claim	378		—					—			—			—				—				12				390
Contingent consideration liability	6,937		—					—			(76		)	—				—				—				6,861
Consolidated Funds
Portfolio Funds	155,674		—					—			—			(15,944		)		—				3,329				143,059
Lehman claim	4,842		—					—			—			(980		)		—				(86		)		3,776
	Three Months Ended March 31, 2013
	Balance at December 31, 2012		Transfers in					Transfers out				Purchases/(covers)			(Sales)/shorts				Realized gains (losses)				Unrealized gains or losses				Balance at March 31, 2013
	(dollars in thousands)
Operating Entities
Preferred stock	$	2,332	$	—				$	—			$	—		$	—			$	—			$	—			$	2,332
Common stocks	2,549		—					—				—			(265		)		260				(266		)		2,278
Corporate Bond	515		—					—				2,735			(3,346		)		(914		)		1,010				—
Warrants and Rights, asset	1,713		290			(a)		—				166			(110		)		—				1,184				3,243
Warrants and Rights, liability	3		—					—				—			—				—				—				3
Portfolio Funds	25,670		—					—				3,590			(3,876		)		8				167				25,559
Real estate	1,864		—					—				—			—				—				11				1,875
Lehman claim	706		—					—				—			—				—				(46		)		660
Contingent consideration liability	8,116		—					—				—			—				—				—				8,116
Consolidated Funds
Portfolio Funds	182,920		—					—				—			(7,031		)		222				2,246				178,357
Lehman claim	14,124		—					—				—			(1,449		)		1,360				1,105				15,140
(a) The security was acquired through an acquisition (See Note 2).
All realized and unrealized gains (losses) in the table above are reflected in other income (loss) in the accompanying condensed consolidated statements of operations.
Certain assets and liabilities are measured at fair value on a nonrecurring basis and therefore are not included in the tables above.
The Company recognizes all transfers and the related unrealized gain (loss) at the beginning of the reporting period.
Transfers between level 1 and 2 generally relate to whether the principal market for the security becomes active or inactive. Transfers between level 2 and 3 generally relate to whether significant relevant observable inputs are available for the fair value measurements or due to change in liquidity restrictions for the investments.
During the three months ended March 31, 2014 and 2013, there were no transfers between level 1 and level 2 assets and liabilities.
The following table includes quantitative information as of March 31, 2014 for financial instruments classified within level 3. The table below quantifies information about the significant unobservable inputs used in the fair value measurement of the Company's level 3 financial instruments.
	Quantitative Information about Level 3 Fair Value Measurements
	Fair Value at March 31, 2014		Valuation techniques		Unobservable Inputs		Range
Level 3 Assets
Common and preferred stocks	$	9,198	Discounted cash flows, market multiples, recent transactions, bid levels, and comparable transactions		Market multiples		2x to 3x
Warrants and rights, net	3,268		Model based		Volatility		20% to 100% (weighted average 36%)
Options	42,856		Option pricing models, credit valuation adjustment, debt valuation adjustment		Volatility Credit spreads		30% to 45% 600bps - 750 bps
Other level 3 assets (a)	250,450
Total level 3 assets	305,772
Level 3 Liabilities
Options	42,856		Option pricing models, credit valuation adjustment, debt valuation adjustment		Volatility Credit spreads		30% to 45% 600bps - 750 bps
Contingent consideration	6,861		Discounted cash flows		Projected cash flow and discount rate		0% to 9%
Total level 3 liabilities	$	49,717
(a)	Quantitative disclosures of unobservable inputs and assumptions are not required for investments for which NAV per share is used as a practical expedient to determine fair value, as their redemption features rather than observability of inputs cause them to be classified as a level 3 type asset within the fair value hierarchy. In addition, the fair value of the Consolidated Funds' investments are determined based on net asset value and therefore quantitative disclosures are not included in the table above. The quantitative disclosures also exclude financial instruments for which the determination of fair value is based on prices from prior transactions.
The Company has established valuation policies and procedures and an internal control infrastructure over its fair value measurement of financial instruments which includes ongoing oversight by the valuation committee as well as periodic audits performed by the Company's internal audit group. The valuation committee is comprised of senior management, including non-investment professionals, who are responsible for overseeing and monitoring the pricing of the Company's investments, including the review of the results of the independent price verification process, approval of new trading asset classes and use of applicable pricing models and approaches.
The US GAAP fair value leveling hierarchy is designated and monitored on an ongoing basis. In determining the designation, the Company takes into consideration a number of factors including the observability of inputs, liquidity of the investment and the significance of a particular input to the fair value measurement. Designations, models, pricing vendors, third party valuation providers and inputs used to derive fair market value are subject to review by the valuation committee and the internal audit group. The Company reviews its valuation policy guidelines on an ongoing basis and may adjust them in light of, improved valuation metrics and models, the availability of reliable inputs and information, and prevailing market conditions. The Company reviews a daily profit and loss report, as well as other periodic reports, and analyzes material changes from period-to-period in the valuation of its investments as part of its control procedures. The Company also performs back testing on a regular basis by comparing prices observed in executed transactions to previous valuations.
The fair market value for level 3 securities may be highly sensitive to the use of industry standard models, unobservable inputs and subjective assumptions. The degree of fair market value sensitivity is also contingent upon the subjective weight given to specific inputs and valuation metrics. The Company holds various equity and debt instruments where different weight may be applied to industry standard models representing standard valuation metrics such as: discounted cash flows, market multiples, comparative transactions, capital rates, recovery rates and timing, and bid levels. Generally, changes in the weights ascribed to the various valuation metrics and the significant unobservable inputs in isolation may result in significantly lower or higher fair value measurements. Volatility levels for warrants and options are not readily observable and subject to interpretation. Changes in capital rates, discount rates and replacement costs could significantly increase or decrease the valuation of the real estate investments. The interrelationship between unobservable inputs may vary significantly amongst level 3 securities as they are generally highly idiosyncratic. Significant increases (decreases) in any of those inputs in isolation can result in a significantly lower (higher) fair value measurement.

Receivables_from_and_Payable_t

Receivables from and Payable to Brokers	3 Months Ended
	Mar. 31, 2014
Brokers and Dealers [Abstract]	'
Receivables from and Payable to Brokers	'
	Receivables from and Payable to Brokers
	Receivables from and payable to brokers includes cash held at the clearing brokers, amounts receivable or payable for unsettled transactions, monies borrowed and proceeds from short sales (including commissions and fees related to securities transactions) equal to the fair value of securities sold, not yet purchased, which are restricted until the Company purchases the securities sold short. Pursuant to the master netting agreements the Company entered into with its brokers, these balances are presented net (assets less liabilities) across balances with the same broker. As of March 31, 2014 and December 31, 2013, receivable from brokers was $56.9 million and $67.0 million, respectively. Payable to brokers was $151.1 million and $75.4 million as of March 31, 2014 and December 31, 2013, respectively. The Company's receivables from and payable to brokers balances are held at multiple financial institutions.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill Disclosure	'
	Goodwill
	In accordance with US GAAP, the Company tests goodwill for impairment on an annual basis or at an interim period if events or changed circumstances would more likely than not reduce the fair value of a reporting unit below its carrying amount. Under US GAAP, the Company first assesses the qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amounts as a basis for determining if it is necessary to perform the two-step approach. Periodically estimating the fair value of a reporting unit requires significant judgment and often involves the use of significant estimates and assumptions. These estimates and assumptions could have a significant effect on whether or not an impairment charge is recorded and the magnitude of such a charge.
	As a result of the Company's acquisition of Dahlman, during the first quarter of 2013, the Company recognized goodwill in the amount of $8.7 million within the broker dealer reporting unit (See Note 2).
	No impairment charges for goodwill were recognized during the three months ended March 31, 2014 and 2013, respectively.

Redeemable_NonControlling_Inte

Redeemable Non-Controlling Interests in Consolidated Subsidiaries	3 Months Ended
	Mar. 31, 2014
Noncontrolling Interest [Abstract]	'
Redeemable Non-Controlling Interests in Consolidated Subsidiaries	'
	Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds
	Redeemable non-controlling interests in consolidated subsidiaries and funds and the related net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds are comprised as follows:
		As of March 31, 2014		As of December 31, 2013
		(dollars in thousands)
	Redeemable non-controlling interests in consolidated subsidiaries and funds
	Operating companies	$	10,840	$	12,009
	Consolidated funds	74,608		73,805
		$	85,448	$	85,814
		Three Months Ended March 31,
		2014		2013
		(dollars in thousands)
	Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds
	Operating companies	$	3,439	$	1,795
	Consolidated funds	748		1,700
		$	4,187	$	3,495

ShareBased_Compensation_and_Em

Share-Based Compensation and Employee Ownership Plans	3 Months Ended
	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Share-Based Compensation and Employee Ownership Plans	'
	Share-Based and Deferred Compensation and Employee Ownership Plans
	The Company issues share based compensation under the 2006 Equity and Incentive Plan, the 2007 Equity and Incentive Plan (both established prior to the November 2009 transaction between Ramius and Cowen) and the Cowen Group, Inc. 2010 Equity and Incentive Plan (collectively, the “Equity Plans”). The Equity Plans permit the grant of options, restricted shares, restricted stock units, stock appreciation rights ("SAR's") and other equity based awards to the Company's employees, consultants and directors for up to 17,725,000 shares of common stock plus any approved additional shares in accordance with the Equity Plans. Stock options granted generally vest over two-to-five-year periods and expire seven years from the date of grant. Restricted shares and restricted share units issued may be immediately vested or may generally vest over a two-to-five-year period. SAR's vest and expire after 5 years from grant date. As of March 31, 2014, there were approximately 1.6 million shares available for future issuance under the Equity Plans.
	Under the 2010 Equity Plan, the Company awarded $29.0 million of deferred cash awards to its employees in the first quarter of 2014. These awards vest over a period of five years and accrue interest between 0.70% to 0.75% per year. As of March 31, 2014, the Company had unrecognized compensation expense related to deferred cash awards of $49.8 million.
	The Company measures compensation cost for share based awards according to the equity method. In accordance with the expense recognition provisions of those standards, the Company amortizes unearned compensation associated with share based awards on a straight-line basis over the vesting period of the option or award. In relation to awards under the Equity Plans, the Company recognized expense of $4.8 million, for the three months ended March 31, 2014 and 2013, respectively. The income tax effect recognized for the Equity Plans was a benefit of $1.0 million and $2.0 million for the three months ended March 31, 2014 and 2013, respectively; however, these benefits were offset by a valuation allowance.
	Stock Options and Stock Appreciation Rights
	The Company values options and SAR's on grant date using the Black-Scholes option valuation model which requires the Company to make assumptions regarding the expected term, volatility, risk-free rate and dividend yield:
	Expected term.    Expected term represents the period of time that awards granted are expected to be outstanding. The Company elected to use the "simplified" calculation method, as applicable to companies that lack extensive historical data. The mid-point between the vesting date and the contractual expiration date is used as the expected term under this method.
	Expected volatility.    The Company bases its expected volatility on its own stock price history.
	Risk free rate.    The risk-free rate for periods within the expected term of the award is based on the interest rate of a traded zero-coupon U.S. Treasury bond with a term equal to the awards' expected term on the date of grant.
	Dividend yield.    The Company has not paid and does not expect to pay dividends in the foreseeable future. Accordingly, the assumed dividend yield is zero.
	The following table summarizes the Company's stock option activity for the three months ended March 31, 2014:
		Shares Subject		Weighted Average		Weighted Average	Aggregate Intrinsic
		to Option		Exercise Price/Share		Remaining Term	Value(1)
						(in years)	(dollars in thousands)
	Balance outstanding at December 31, 2013	300,006		$	7.19	2.4	$	—
	Options granted	—		—		—	—
	Options acquired	—		—		—	—
	Options expired	—		—		—	—
	Balance outstanding at March 31, 2014	300,006		$	7.19	2.16	$	—
	Options exercisable at March 31, 2014	300,006		$	7.19	2.16	$	—
	-1	Based on the Company's closing stock price of $4.41 on March 31, 2014 and $3.91 on December 31, 2013.
	As of March 31, 2014, the unrecognized compensation expense related to the Company's grant of stock options was insignificant.
	The following table summarizes the Company's SAR's for the three months ended March 31, 2014:
		Shares Subject		Weighted Average		Weighted Average	Aggregate Intrinsic
		to Option		Exercise Price/Share		Remaining Term	Value(1)
						(in years)	(dollars in thousands)
	Balance outstanding at December 31, 2013	400,000		$	2.9	4.21	$	608
	SAR's granted	—		—		—	—
	SAR's acquired	—		—		—	—
	SAR's expired	—		—		—	—
	Balance outstanding at March 31, 2014	400,000		2.9		3.96	$	864
	SAR's exercisable at March 31, 2014	—		$	—	—
	-1	Based on the Company's closing stock price of $4.41 on March 31, 2014 and $3.91 on December 31, 2013.
	As of March 31, 2014 and December 31, 2013, the unrecognized compensation expense related to the Company's grant of SAR's was $0.3 million , respectively.
	Restricted Shares and Restricted Stock Units Granted to Employees
	Restricted shares and restricted stock units are referred to collectively as restricted stock. The following table summarizes the Company's restricted share and restricted stock unit activity for the three months ended March 31, 2014:
		Nonvested Restricted Shares and Restricted Stock Units		Weighted-Average
				Grant Date
				Fair Value
	Balance outstanding at December 31, 2013	13,551,544		$	3.37
	Granted (1)	7,694,398		3.78
	Vested	(1,652,652	)	2.84
	Canceled	—		—
	Forfeited	(57,251	)	3.21
	Balance outstanding at March 31, 2014	19,536,039		$	3.58
	(1) On January 16, 2014, the Company awarded 1,220,750 performance linked restricted stock units to employees of the Company. The awards will vest on June 10, 2019 and will be earned only to the extent that the Company attains specified performance goals relating its volume-weighted average share price and the aggregate net income for the years from 2014 to 2018. The actual number of RSUs ultimately earned could vary from zero, if performance goals are not met, to as much as 100% of the targeted award. Each RSU is equal to the one share of the Company’s Class A common stock. Compensation expense is recognized to the extent that it is probable that the Company will attain the performance goals.
	The fair value of restricted stock is determined based on the number of shares granted and the quoted price of the Company's common stock on the date of grant.
	As of March 31, 2014, there was $51.2 million of unrecognized compensation expense related to the Company's grant of nonvested restricted shares and restricted stock units to employees. Unrecognized compensation expense related to nonvested restricted shares and restricted stock units granted to employees is expected to be recognized over a weighted-average period of 2.03 years.
	Restricted Shares and Restricted Stock Units Granted to Non-employee Board Members
	There were no restricted stock units awarded during the three months ended March 31, 2014. Vested awards of 102,400 were delivered during the three months ended March 31, 2014. As of March 31, 2014 there were 380,122 restricted stock units outstanding.

Defined_Benefit_Plans

Defined Benefit Plans	3 Months Ended
	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]	'
Defined Benefit Plans	'
	Defined Benefit Plan
	The amounts contained in the following table relate to the Company's defined benefit plan for the three months ended March 31, 2014 and 2013:
		Three Months Ended March 31,
		2014			2013
		(dollars in thousands)
	Components of net periodic benefit cost included in employee compensation and benefits
	Service cost	$	—		$	—
	Interest cost	33			51
	Expected return on plan assets	(66		)	(63		)
	Amortization of (loss) / gain	—			—
	Amortization of prior service cost	—			5
	Effect of curtailment	—			—
	Effect of special termination benefits	—			—
	Effect of settlement	—			—
	Net periodic benefit cost	$	(33	)	$	(7	)

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The taxable results of the Company’s U.S. operations are included in the consolidated income tax returns of Cowen Group, Inc. as well as stand-alone state and local tax returns. The Company has subsidiaries that are resident in foreign countries where tax filings have to be submitted on a stand‑alone basis. These subsidiaries are subject to tax in their respective countries and the Company is responsible for and, thus, reports all taxes incurred by these subsidiaries. The countries where the Company owns subsidiaries that file tax returns are United Kingdom, Luxembourg, Gibraltar, and Hong Kong.
	The Company calculates its U.S. tax provision using the estimated annual effective tax rate methodology. The tax expense or benefit caused by an unusual or infrequent item is recorded in the quarter in which it occurs. The Company uses the discrete methodology to calculate its income tax provision for its foreign subsidiaries. Based on these methodologies, the Company’s effective income tax rate was (0.56)% and 16.07% for the three months ended March 31, 2014 and 2013, respectively. During the three months ended March 31, 2014, the unusual or infrequent items whose tax impacts were recorded discretely primarily related to the amortization of Convertible Notes and the tax provisions of the Company’s foreign subsidiaries.
	For the three months ended March 31, 2014 and 2013, the effective tax rate differs from the statutory rate of 35% primarily due to a change in the Company's valuation allowance, stock compensation and other nondeductible expenses.
	The Company records deferred tax assets and liabilities for the future tax benefit or expense that will result from differences between the carrying value of its assets for income tax purposes and for financial reporting purposes, as well as for operating or capital loss and tax credit carryovers. A valuation allowance is recorded to bring the net deferred tax assets to a level that, in management's view, is more likely than not to be realized in the foreseeable future. This level will be estimated based on a number of factors, especially the amount of net deferred tax assets of the Company that are actually expected to be realized, for tax purposes, in the foreseeable future. As of March 31, 2014, the Company recorded a valuation allowance against substantially all of its net deferred tax assets.
	The Company is subject to examination by the United States Internal Revenue Service, the United Kingdom Inland Revenue Service as well as state, local and foreign tax authorities in jurisdictions where the Company has significant business operations, such as New York. Currently, the Company is under audit by New York State for the 2009 tax year. Management is not expecting a material tax liability from this audit.
	The Company intends to permanently reinvest the capital and accumulated earnings of its foreign subsidiaries in the respective subsidiary, but remits the current earnings of its foreign subsidiaries to the United States to the extent permissible under local regulatory rules. The undistributed earnings of the Company’s foreign subsidiaries totaled $1.5 million and $2.3 million as of March 31, 2014 and March 31, 2013, respectively, and the tax liability that would arise if these earnings were remitted to the United States would be approximately $0.2 million and $0.3 million, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	Lease Obligations
	The Company has entered into non-cancellable leases for office space and equipment. These leases contain rent escalation clauses. The Company records rent expense on a straight-line basis over the lease term, including any rent holiday periods. Rent expense was $4.2 million and $3.7 million for the three months ended March 31, 2014 and 2013, respectively.
	As of March 31, 2014, future minimum annual lease and service payments for the Company were as follows:
		Equipment Leases (a)		Service Payments		Facility Leases (b)
		(dollars in thousands)
	2014	$	2,181	$	9,036	$	13,848
	2015	2,603		7,667		17,789
	2016	2,284		3,367		14,698
	2017	2,198		2,714		11,587
	2018	2,198		2,609		11,296
	Thereafter	813		22		41,601
		$	12,277	$	25,415	$	110,819
	(a)	Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 14 for further information on the capital lease minimum payments which are included in the table.
	(b)	The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $0.3 million and $0.3 million for the three months ended March 31, 2014 and 2013.
	Clawback Obligations
	For financial reporting purposes, the general partners have recorded a liability for potential clawback obligations to the limited partners of a real estate fund, due to changes in the unrealized value of the fund's remaining investments and where the fund's general partner has previously received carried interest distributions. The actual clawback liability, however, does not become realized until the end of the fund's life. The fund is currently in winding-down mode and as of both March 31, 2014 and December 31, 2013, the clawback obligations were both $6.2 million.
	The Company serves as the general partner/managing member and/or investment manager to various affiliated and sponsored funds. As such, the Company is contingently liable for obligations for those entities. These amounts are not included above as the Company believes that the assets in these funds are sufficient to discharge any liabilities.
	Unfunded Commitments
	As of March 31, 2014, the Company had unfunded commitments of $13.8 million pertaining to capital commitments in four real estate investments held by the Company, all of which pertain to related party investments. Such commitments can be called at any time, subject to advance notice. The Company, as a limited partner of the HealthCare Royalty Partners funds and also as a member of HealthCare Royalty Partners General Partner, has committed to invest $42.4 million in the Healthcare Royalty Partners funds which are managed by Healthcare Royalty Management. This commitment is expected to be called over a two to five year period. The Company will make its pro-rata investment in the HealthCare Royalty Partners funds along with the other limited partners. Through March 31, 2014, the Company has funded $31.7 million towards these commitments. In April 2013, the Company committed $1.0 million to Starboard Leaders Fund LP, which may increase or decrease over time dependent on the performance of the fund, and, as of March 31, 2014, has funded $0.6 million towards this commitment. As of March 31, 2014, the Company has an unfunded commitment to Formation 8 Partners Fund I LP of $5.0 million. The remaining capital commitment is expected to be called over a four year period.
	Litigation
	In the ordinary course of business, the Company and its affiliates and subsidiaries and current and former officers, directors and employees (the "Company and Related Parties") are named as defendants in, or as parties to, various legal actions and proceedings. Certain of these actions and proceedings assert claims or seek relief in connection with alleged violations of securities, banking, anti-fraud, anti-money laundering, employment and other statutory and common laws. Certain of these actual or threatened legal actions and proceedings include claims for substantial or indeterminate compensatory or punitive damages, or for injunctive relief.
	In the ordinary course of business, the Company and Related Parties are also subject to governmental and regulatory examinations, information gathering requests (both formal and informal), certain of which may result in adverse judgments, settlements, fines, penalties, injunctions or other relief. Certain affiliates and subsidiaries of the Company are investment banks, registered broker-dealers, futures commission merchants, investment advisers or other regulated entities and, in those capacities, are subject to regulation by various U.S., state and foreign securities, commodity futures and other regulators. In connection with formal and informal inquiries by these regulators, the Company and such affiliates and subsidiaries receive requests, and orders seeking documents and other information in connection with various aspects of their regulated activities.
	Due to the global scope of the Company's operations, and its presence in countries around the world, the Company and Related Parties may be subject to litigation, and governmental and regulatory examinations, information gathering requests, investigations and proceedings (both formal and informal), in multiple jurisdictions with legal and regulatory regimes that may differ substantially, and present substantially different risks, from those the Company and Related Parties are subject to in the United States.
	The Company seeks to resolve all litigation and regulatory matters in the manner management believes is in the best interests of the Company and its shareholders, and contests liability, allegations of wrongdoing and, where applicable, the amount of damages or scope of any penalties or other relief sought as appropriate in each pending matter.
	In accordance with the US GAAP, the Company establishes reserves for contingencies when the Company believes that it is probable that a loss has been incurred and the amount of loss can be reasonably estimated. The Company discloses a contingency if there is at least a reasonable possibility that a loss may have been incurred and there is no reserve for the loss because the conditions above are not met. The Company's disclosure includes an estimate of the reasonably possible loss or range of loss for those matters, for which an estimate can be made. Neither a reserve nor disclosure is required for losses that are deemed remote.
	The Company appropriately reserves for certain matters where, in the opinion of management, the likelihood of liability is probable and the extent of such liability is reasonably estimable. Such amounts are included within accounts payable, accrued expenses and other liabilities in the condensed consolidated statements of financial condition. Estimates, by their nature, are based on judgment and currently available information and involve a variety of factors, including, but not limited to, the type and nature of the litigation, claim or proceeding, the progress of the matter, the advice of legal counsel, the Company's defenses and its experience in similar cases or proceedings as well as its assessment of matters, including settlements, involving other defendants in similar or related cases or proceedings. The Company may increase or decrease its legal reserves in the future, on a matter-by-matter basis, to account for developments in such matters. The Company accrues legal fees as incurred.
	There have been no developments with respect to the Company’s legal proceedings that occurred during the three months ended March 31, 2014.

Convertible_Debt_and_Short_Ter

Convertible Debt and Short Term Borrowings	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Debt Disclosure [Text Block]	'
	Debt and Short Term Borrowings
	As of March 31, 2014 and December 31, 2013, the Company's outstanding debt was as follows:
		As of March 31, 2014			As of December 31, 2013
		(dollars in thousands)
	Convertible debt	$	114,101		$	—
	Note payable	1,428			41
	Capital lease obligations	4,956			2,523
		$	120,485		$	2,564
	Convertible Debt
	On March 10, 2014, the Company issued $149.5 million of 3.0% cash convertible senior notes ("Convertible Notes"). The Convertible Notes are due on March 15, 2019 unless earlier repurchased by the Company or converted by the holder into cash in accordance with their terms prior to such date. The interest on the Convertible Notes is payable semi-annually on March 15 and September 15 of each year. The Convertible Notes are senior unsecured obligations and rank senior in right of payments to other obligations. The Convertible Notes may be converted into cash, upon the occurance of certain events, whereby a holder will receive, per $1,000 principal amount of notes being converted, an amount equal to the sum of principal amount outstanding and the conversion amount based on the current conversion price (the "Conversion Option"). The Convertible Notes were issued with an initial conversion price of $5.33 per share.
	The Company accrued interest expense of $0.2 million for the three months ended March 31, 2014. The initial unamortized discount on the Convertible Notes was $35.7 million and is shown net in convertible debt in the accompanying condensed consolidated statements of financial condition. Amortization on the discount for the three months ended March 31, 2014, included within interest expense in the accompanying condensed consolidated statements of operations, was $0.3 million based on an effective interest rate of 8.89%. The Convertible Notes are classified as Level 2 valuations. As of March 31, 2014 the estimated fair value of the Convertible Notes, which includes the conversion option, was $160.9 million, which is based on the last quoted price of the Convertible Notes on March 31, 2014. The carrying amount of the debt as of March 31, 2014 was $114.1 million net of the unamortized discount of $35.4 million. The Company capitalized the debt issuance costs in the amount of $3.6 million, which is included in other assets in the accompanying condensed consolidated statements of financial condition, and will be amortized over the life of the Convertible Notes. As of March 31, 2014, the Company is in compliance with all covenants included in the indenture governing the Convertible Notes.
	Of the net proceeds from the sale of the Convertible Notes, approximately $20.5 million was applied to pay the net cost of a cash convertible note hedge and warrant transaction which increases the effective conversion price to $7.18 (See Note 5), and approximately $0.3 million was applied to repurchase shares of Cowen Class A common stock. The remainder of the net proceeds will be used for general corporate purposes.
	Note Payable
	During January 2014, the Company borrowed $2.0 million to fund insurance premium payments. This note bears interest at 1.55% and is due on December 1, 2014, with monthly payment requirements of $0.2 million. As of March 31, 2014, the outstanding balance on this note payable was $1.4 million. Interest expense for the three months ended March 31, 2014 was insignificant.
	Capital Lease Obligations
	The Company entered into several capital leases for computer equipment during the fourth quarter of 2010 and one in January 2014. These leases amount to $7.6 million and are recorded in fixed assets and as capital lease obligations, which are included in short-term borrowings and other debt in the accompanying condensed consolidated statements of financial condition, and have lease terms that range from 48 to 60 months and interest rates that range from 0.60% to 6.03%. As of March 31, 2014, the remaining balance on these capital leases was $5.0 million. Interest expense was $0.1 million and $0.1 million for the three months ended March 31, 2014 and 2013, respectively.
	Annual scheduled maturities of debt and minimum payments for debt outstanding as of March 31, 2014, is as follows:
		Convertible Debt			Notes payable			Capital Lease
								Obligation
		(dollars in thousands)
	2014	$	2,284		$	1,448		$	1,236
	2015	4,411			—			1,343
	2016	4,411			—			1,025
	2017	4,411			—			938
	2018	4,411			—			938
	Thereafter	151,688			—			79
	Subtotal	171,616			1,448			5,559
	Less: Amount representing interest (a)	(57,515		)	(20		)	(603		)
	Total	$	114,101		$	1,428		$	4,956
	(a)	Amount necessary to reduce net minimum payments to present value calculated at the Company's implicit rate at inception. This amount also includes the unamortized discount on the convertible debt.
	Letters of Credit
	As of March 31, 2014, the Company has the following six irrevocable letters of credit related to leased office space, for which there is cash collateral pledged, which the Company pays a fee on the stated amount of the letter of credit.
	Location		Amount			Maturity
			(dollars in thousands)
	San Francisco		$	82		May-14
	Boston		$	382		Mar-15
	New York		$	1,191		Sep-14
	New York		$	6,746		Dec-14
	New York		$	1,000		Feb-15
	New York		$	1,861		Jun-14
	To the extent any letter of credit is drawn upon, interest will be assessed at the prime commercial lending rate. As of March 31, 2014 and December 31, 2013, there were no amounts due related to these letters of credit.

Treasury_Stock

Treasury Stock	3 Months Ended
	Mar. 31, 2014
Equity [Abstract]	'
Treasury Stock	'
	Treasury stock
	Treasury stock of $53.4 million as of March 31, 2014, compared to $48.1 million as of December 31, 2013, resulted from $1.9 million acquired through repurchases of shares to cover employee minimum tax withholding obligations related to stock compensation vesting events under the Company's Equity Plan or other similar transactions and $3.4 million purchased in connection with a share repurchase program.
	The following represents the activity relating to the treasury stock held by the Company during the three months ended March 31, 2014:
		Treasury stock shares	Cost		Average cost
			(dollars in thousands)		per share
	Balance outstanding at December 31, 2013	15,873,549	$	48,084	$	3.03
	Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions	452,809	1,920		4.24
	Purchase of treasury stock	810,072	3,411		4.21
	Balance outstanding at March 31, 2014	17,136,430	$	53,415	$	3.12

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss) (Notes)	3 Months Ended
	Mar. 31, 2014
Accumulated Other Comprehensive Income / (Loss) [Abstract]	'
Accumulated other comprehensive income (loss)	'
	Accumulated other comprehensive income (loss)
	Accumulated other comprehensive income includes the after tax change in unrealized gains and losses on foreign currency translation adjustments and net gain (loss) and amortization of prior service costs related to the Company's defined benefit plans.
		Foreign currency translation (a)			Defined benefit plans (a)			Total
		(dollars in thousands)
	Balance at December 31, 2013	248			344			592
	Net change	37			(92		)	(55		)
	Balance at March 31, 2014	$	285		$	252		$	537
		Foreign currency translation (a)			Defined benefit plans (a)			Total
		(dollars in thousands)
	Balance at December 31, 2012	$	258		$	98		$	356
	Net change	(4		)	(17		)	(21		)
	Balance at March 31, 2013	$	254		$	81		$	335
	(a) During the periods presented, the Company did not have material reclassifications out of other comprehensive income.

Earnings_Per_Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	Earnings Per Share
	The Company calculates its basic and diluted earnings per share in accordance with US GAAP. Basic earnings per common share is calculated by dividing net income attributable to the Company's stockholders by the weighted average number of common shares outstanding for the period. As of March 31, 2014, there were 115,352,546 shares outstanding. The Company has included 380,122 fully vested, unissued restricted stock units in its calculation of basic earnings per share.
	Diluted earnings per common share are calculated by adjusting the weighted average outstanding shares to assume conversion of all potentially dilutive nonvested restricted stock and stock options. The Company uses the treasury stock method to reflect the potential dilutive effect of the unvested restricted shares, restricted stock units, unexercised stock options, warrants and SAR's. In calculating the number of dilutive shares outstanding, the shares of common stock underlying unvested restricted shares and restricted stock units are assumed to have been delivered, and options and warrants are assumed to have been exercised, on the grant date. The assumed proceeds from the assumed vesting, delivery and exercising were calculated as the sum of (a) the amount of compensation cost attributed to future services and not yet recognized and (b) the amount of tax benefit that would be credited to additional paid-in capital assuming vesting and delivery of the restricted stock. The tax benefit is the amount resulting from a tax deduction for compensation in excess of compensation expense recognized for financial statement reporting purposes. All outstanding stock options and warrants were not included in the computation of diluted net income (loss) per common share for the three months ended March 31, 2014 and 2013, respectively, as their inclusion would have been anti-dilutive.
	The computation of earnings per share is as follows:
		Three Months Ended March 31,
		2014		2013
	Net income (loss)	$	14,027	$	919
	Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	4,187		3,495
	Net income (loss) attributable to Cowen Group, Inc. stockholders	9,840		(2,576		)
	Shares for basic and diluted calculations:
	Weighted average shares used in basic computation	115,680		113,798
	Warrants	—		—
	Stock options	—		—
	Stock appreciation rights	54		—
	Restricted stock	7,164		—
	Weighted average shares used in diluted computation	122,898		113,798
	Earnings (loss) per share:
	Basic	$	0.09	$	(0.02	)
	Diluted	$	0.08	$	(0.02	)

Segment_Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Segment Reporting	'
	Segment Reporting
	The Company conducts its operations through two segments: the alternative investment segment and the broker‑dealer segment. These activities are conducted primarily in the United States and substantially all of its revenues are generated domestically. The performance measure for these segments is Economic Income (Loss), which management uses to evaluate the financial performance of and make operating decisions for the segments including determining appropriate compensation levels.
	In general, Economic Income (Loss) is a pre-tax measure that (i) eliminates the impact of consolidation for consolidated funds and (ii) excludes certain other acquisition-related and/or reorganization expenses (See Note 2). In addition, Economic Income (Loss) revenues include investment income that represents the income the Company has earned in investing its own capital, including realized and unrealized gains and losses, interest and dividends, net of associated investment related expenses. For US GAAP purposes, these items are included in each of their respective line items. Economic Income (Loss) revenues also include management fees, incentive income and investment income earned through the Company's investment as a general partner in certain real estate entities and the Company's investment in the activist business. For US GAAP purposes, all of these items are recorded in other income (loss). In addition, Economic Income (Loss) expenses are reduced by reimbursement from affiliates, which for US GAAP purposes is presented gross as part of revenue.
	As further stated below, one major difference between Economic Income (Loss) and US GAAP net income (loss) is that Economic Income (Loss) presents the segments' results of operations without the impact resulting from the full consolidation of any of the Consolidated Funds. Consolidation of these funds results in including in income the pro rata share of the income or loss attributable to other owners of such entities which is reflected in net income (loss) attributable to redeemable non-controlling interest in consolidated subsidiaries in the accompanying condensed consolidated statements of operations. This pro rata share has no effect on the overall financial performance for the alternative investment segment, as ultimately, this income or loss is not income or loss for the alternative investment segment itself. Included in Economic Income (Loss) is the actual pro rata share of the income or loss attributable to the Company as an investor in such entities, which is relevant in management making operating decisions and evaluating financial performance.
	The following tables set forth operating results for the Company's alternative investment and broker dealer segments and related adjustments necessary to reconcile the Company's Economic Income (Loss) measure to arrive at the Company's consolidated US GAAP net income (loss):
		Three Months Ended March 31, 2014
											Adjustments
		Alternative			Broker-Dealer (1)			Total Economic Income/(Loss)			Funds			Other				US GAAP
		Investment									Consolidation			Adjustments
		(dollars in thousands)
	Revenues
	Investment banking	$	—		$	49,562		$	49,562		$	—		$	—			$	49,562
	Brokerage	—			34,349			34,349			—			(1,519		)	(e)	32,830
	Management fees	14,089			—			14,089			(234		)	(4,931		)	(a)	8,924
	Incentive income	4,726			—			4,726			—			(2,228		)	(a)	2,498
	Investment Income	8,328			(156		)	8,172			—			(8,172		)	(c)	—
	Interest and dividends	—			—			—			—			9,252			(c)	9,252
	Reimbursement from affiliates	—			—			—			(80		)	1,980			(b)	1,900
	Other revenue	(43		)	(102		)	(145		)	—			700			(c)	555
	Consolidated Funds revenues	—			—			—			1,156			—				1,156
	Total revenues	27,100			83,653			110,753			842			(4,918		)		106,677
	Expenses
	Employee compensation and benefits	13,387			53,570			66,957			—			604				67,561
	Non-compensation expenses—Fixed	8,894			13,921			22,815			—			(22,815		)	(c)(d)	—
	Non-compensation expenses—Variable	749			8,688			9,437			—			(9,437		)	(c)(d)	—
	Non-compensation expenses	—			—			—			—			31,093			(c)(d)	31,093
	Interest and dividends	609			34			643			—			6,429			(c)	7,072
	Reimbursement from affiliates	(1,726		)	—			(1,726		)	—			1,726			(b)	—
	Consolidated Funds expenses	—			—			—			302			—				302
	Total expenses	21,913			76,213			98,126			302			7,600				106,028
	Other income (loss)
	Net gains (losses) on securities, derivatives and other investments	—			—			—			—			11,354			(c)	11,354
	Consolidated Funds net gains (losses)	—			—			—			207			1,896				2,103
	Total other income (loss)	—			—			—			207			13,250				13,457
	Income (loss) before income taxes and non-controlling interests	5,187			7,440			12,627			747			732				14,106
	Income taxes expense / (benefit)	—			—			—			—			79			(b)	79
	Economic Income (Loss) / Net income (loss) before non-controlling interests	5,187			7,440			12,627			747			653				14,027
	(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	(2,625		)	—			(2,625		)	(747		)	(815		)		(4,187		)
	Economic Income (Loss) / Net Income (loss) attributable to Cowen Group, Inc. stockholders	$	2,562		$	7,440		$	10,002		$	—		$	(162	)		$	9,840
	(1) For the three months ended March 31, 2014, the Company has reflected a minimal amount of investment income and related compensation expense within the broker-dealer segment.
		Three Months Ended March 31, 2013
											Adjustments
		Alternative			Broker-Dealer (1)			Total Economic Income/(Loss)			Funds			Other				US GAAP
		Investment									Consolidation			Adjustments
		(dollars in thousands)
	Revenues
	Investment banking	$	—		$	17,166		$	17,166		$	—		$	—			$	17,166
	Brokerage	—			28,017			28,017			—			(1,417		)	(e)	26,600
	Management fees	14,144			—			14,144			(311		)	(4,340		)	(a)	9,493
	Incentive income	5,126			—			5,126			—			(2,515		)	(a)	2,611
	Investment Income	8,304			2,568			10,872			—			(10,872		)	(c)	—
	Interest and dividends	—			—			—			—			9,321			(c)	9,321
	Reimbursement from affiliates	—			—			—			65			1,420			(b)	1,485
	Other revenue	113			(553		)	(440		)	—			918			(c)	478
	Consolidated Funds revenues	—			—			—			87			—				87
	Total revenues	27,687			47,198			74,885			(159		)	(7,485		)		67,241
	Expenses
	Employee compensation and benefits	13,638			30,608			44,246			—			(23		)		44,223
	Non-compensation expenses—Fixed	9,138			13,265			22,403			—			(22,403		)	(c)(d)	—
	Non-compensation expenses—Variable	1,006			7,720			8,726			—			(8,726		)	(c)(d)	—
	Non-compensation expenses	—			—			—			—			32,037			(c)(d)	32,037
	Interest and dividends	81			43			124			—			6,294			(c)	6,418
	Reimbursement from affiliates	(1,420		)	—			(1,420		)	—			1,420			(b)	—
Consolidated Funds expenses	—			—			—			434			—				434
Total expenses	22,443			51,636			74,079			434			8,599				83,112
Other income (loss)
Net gains (losses) on securities, derivatives and other investments	—			—			—			—			11,807			(c)	11,807
Consolidated Funds net gains (losses)	—			—			—			2,293			2,866				5,159
Total other income (loss)	—			—			—			2,293			14,673				16,966
Income (loss) before income taxes and non-controlling interests	5,244			(4,438		)	806			1,700			(1,411		)		1,095
Income taxes expense / (benefit)	—			—			—			—			176			(b)	176
Economic Income (Loss) / Net income (loss) before non-controlling interests	5,244			(4,438		)	806			1,700			(1,587		)		919
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	(2,075		)	—			(2,075		)	(1,700		)	280				(3,495		)
Economic Income (Loss) / Net Income (loss) attributable to Cowen Group, Inc. stockholders	$	3,169		$	(4,438	)	$	(1,269	)	$	—		$	(1,307	)		$	(2,576	)
(1) For the three months ended March 31, 2013, the Company has reflected $2.3 million of investment income and related compensation expense of $0.8 million within the broker-dealer segment in proportion to its capital.
The following is a summary of the adjustments made to US GAAP net income (loss) for the segment to arrive at
Economic Income (Loss):
Funds Consolidation: The impacts of consolidation and the related elimination entries of the Consolidated Funds are not included in Economic Income (Loss). Adjustments to reconcile to US GAAP net income (loss) include elimination of incentive income and management fees earned from the Consolidated Funds and addition of fund expenses excluding management fees paid, fund revenues and investment income (loss).
Other Adjustments:
(a)     Economic Income (Loss) recognizes revenues (i) net of distribution fees paid to agents and (ii) our proportionate share
of management and incentive fees of certain real estate operating entities and the activist business.
(b)    Economic Income (Loss) excludes income taxes as management does not consider this item when evaluating the
performance of the segment. Also, reimbursement from affiliates is shown as a reduction of Economic Income
expenses, but is included as a part of revenues under US GAAP.
(c)     Economic Income (Loss) recognizes Company income from proprietary trading net of related expenses.
(d)     Economic Income (Loss) recognizes the Company's proportionate share of expenses for certain real estate and other
operating entities for which the investments are recorded under the equity method of accounting for investments.
(e)    Economic Income (Loss) recognizes stock borrow/loan activity and other brokerage dividends as brokerage revenue.
For the three months ended March 31, 2014 and 2013, there was no one fund or other customer which represented more than 10% of the Company's total revenues.

Regulatory_Requirements

Regulatory Requirements	3 Months Ended
	Mar. 31, 2014
Brokers and Dealers [Abstract]	'
Regulatory Requirements	'
	Regulatory Requirements
	As registered broker-dealers, Cowen and Company, ATM Execution (formerly known as Cowen Capital LLC), ATM USA, and Cowen Equity Finance 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, ATM USA and Cowen Equity Finance are each 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 March 31, 2014, Cowen and Company had total net capital of approximately $47.1 million, which was approximately $46.1 million in excess of its minimum net capital requirement of $1.0 million. As of March 31, 2014, ATM Execution had total net capital of approximately $3.3 million, which was approximately $3.0 million in excess of its minimum net capital requirement of $250,000. As of March 31, 2014, ATM USA had total net capital of approximately $0.9 million, which was approximately $0.6 million in excess of its minimum net capital requirement of $250,000. As of March 31, 2014, Cowen Equity Finance had total net capital of approximately $10.7 million which was approximately $10.4 million in excess of its minimum net capital requirement of $250,000.
	Cowen and Company and ATM Execution are 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. Similarly, ATM USA and Cowen Equity Finance are exempt from the provisions of Rule 15c3-3 under (k)(2)(i).
	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 ATM Execution 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 and ATM Execution, 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 March 31, 2014, Ramius UK's Financial Resources of $0.37 million exceeded its minimum requirement of $0.12 million by $0.25 million. As of March 31, 2014, CIL's Financial Resources of $4.4 million exceeded its minimum requirement of $2.2 million by $2.2 million.
	Cowen and Company (Asia) Limited (“CCAL”) 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 March 31, 2014, CCAL's Financial Resources of $0.9 million exceeded the minimum requirement of $0.4 million by $0.5 million.

Related_Party_Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2014
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	Related Party Transactions
	The Company and its affiliated entities are the managing member, general partner and/or investment manager to the Company's alternative asset management products, HealthCare Royalty Management, LLC, and the HealthCare Royalty Partners funds, and certain managed accounts. Management fees and incentive income are primarily earned from affiliated entities. Fees receivable primarily represents the management fees and incentive income owed to the Company from these related funds and certain affiliated managed accounts. As of March 31, 2014 and December 31, 2013, $15.1 million and $18.9 million, respectively, included in fees receivable are earned from related parties.
	The Company may, at its discretion, reimburse certain fees charged to the funds that it manages to avoid duplication of fees when such funds have an underlying investment in another affiliated investment fund. For the three months ended March 31, 2014 and 2013, the Company reimbursed the funds it manages $0.5 million and $0.5 million, respectively, which were recorded net in management fees and incentive income in the accompanying condensed consolidated statements of operations. As of March 31, 2014 and December 31, 2013, related amounts still payable were $1.4 million and $1.7 million, respectively, and were reflected in fees payable in the accompanying condensed consolidated statements of financial condition.
	The Company may also make loans to employees or other affiliates, excluding executive officers of the Company. These loans are interest bearing and settle pursuant to the agreed-upon terms with such employees or affiliates and are included in due from related parties in the condensed consolidated statements of financial condition. As of March 31, 2014 and December 31, 2013, loans to employees of $10.6 million and $6.0 million, respectively, were included in due from related parties on the condensed consolidated statements of financial condition. Of these amounts $7.8 million and $3.8 million, respectively, are related to forgivable loans. These forgivable loans provide for a cash payment up-front to employees, with the amount due back to the Company forgiven over a vesting period.  An employee that voluntarily ceases employment, or is terminated with cause, is generally required to pay back to the Company any unvested forgivable loans granted to them.  The forgivable loans are recorded as an asset to the Company on the date of grant and payment, and then amortized to compensation expense on a straight-line basis over the vesting period.  The vesting period on forgivable loans is generally one to three years. The Company recorded compensation expense of $0.8 million and $0.4 million, for the three months ended March 31, 2014 and 2013, respectively. This expense is included in employee compensation and benefits in the condensed consolidated statement of operations. For the three months ended March 31, 2014, and 2013, the interest income was insignificant for all loans and advances. The remaining balance included in due from related parties primarily relates to amounts due to the Company from affiliated funds and real estate entities due to expenses paid on their behalf.
	In April 2011, the Company entered into a credit agreement with Starboard Value LP (see Note 5), whereby the Company can loan up to $3.0 million to Starboard Value LP at an interest rate of LIBOR plus 3.75% (payable quarterly) with a maturity of March 30, 2014. As of March 31, 2014, the loan was fully repaid. As of December 31, 2013, $1.5 million is included in due from related parties in the accompanying consolidated statement of financial condition. For the three months ended March 31, 2014, and 2013, interest charged for this loan was insignificant.
	Included in due to related parties is approximately $0.4 million and $0.4 million as of March 31, 2014 and December 31, 2013, respectively, related to a subordination agreement with an investor in certain real estate funds. This total is based on a hypothetical liquidation of the real estate funds as of the balance sheet date.
	During March 2014, the Company entered into real estate loan participation agreements amounting to $40 million with a related party (See Note 5).

Guarantees_and_OffBalance_Shee

Guarantees and Off-Balance Sheet Arrangements	3 Months Ended
	Mar. 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 condensed 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 condensed 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 condensed 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 Cowen Securities (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 March 31, 2014 was $2.5 million.
	Off-Balance Sheet Arrangements
	The Company has no material off-balance sheet arrangements as of March 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.

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	Subsequent Events
	The Company has evaluated events through May 8, 2014 which is the date the condensed consolidated financial statements were available to be issued and has determined that there were no additional subsequent events requiring adjustment or disclosure in the consolidated financial statements.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Basis of presentation	'
	These unaudited condensed consolidated financial statements and related notes have been prepared in accordance with US GAAP and the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) related to interim financial statements. Results for interim periods should not be considered indicative of results for any other interim period or for the full year. These financial statements should be read in conjunction with the audited consolidated financial statements as of December 31, 2013 and 2012 and for the years ended December 31, 2013, 2012, and 2011, included in the Form 10-K of Cowen Group as filed with the SEC on March 3, 2014. The financial information contained herein is unaudited; however, management believes all adjustments have been made that are necessary for a fair presentation of the results for the interim periods. The year-end condensed balance sheet data was derived from audited financial statements, but does not include all disclosures required by US GAAP. All material intercompany transactions and balances have been eliminated in consolidation. Certain fund entities that are consolidated in these condensed consolidated financial statements, as further discussed below, are not subject to these consolidation provisions with respect to their own investments pursuant to their specialized accounting.
	The Company serves as the managing member/general partner and/or investment manager to affiliated fund entities which it sponsors and manages. Funds in which the Company has a controlling financial interest are consolidated with the Company pursuant to US GAAP as described below. Consequently, the Company's condensed consolidated financial statements reflect the assets, liabilities, income and expenses of these funds on a gross basis. The ownership interests in these funds that are not owned by the Company are reflected as redeemable non-controlling interests in consolidated subsidiaries in the accompanying condensed consolidated financial statements. The management fees and incentive income earned by the Company from these funds are eliminated in consolidation.
Principles of consolidation	'
	Principles of consolidation
	The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting operating entity ("VOE") or a variable interest entity ("VIE") under US GAAP.
	Voting Operating Entities—VOEs are entities in which (i) the total equity investment at risk is sufficient to enable the entity to finance its activities independently and (ii) the equity holders at risk have the obligation to absorb losses, the right to receive residual returns and the right to direct the activities of the entity that most significantly impact the entity's economic performance. VOEs are consolidated in accordance with US GAAP.
	Under US GAAP, the usual condition for a controlling financial interest in a VOE is ownership of a majority voting interest. Accordingly, the Company consolidates VOEs in which it owns a majority of the entity's voting shares or units. US GAAP also provides that a general partner of a limited partnership (or a managing member, in the case of a limited liability company) is presumed to control the partnership, and thus should consolidate it, unless a simple majority of the limited partners has the right to remove the general partner without cause or to terminate the partnership. In accordance with these standards, the Company presently consolidates four entities deemed to be VOEs for which it acts as the general partner and investment manager.
	As of and during the period ended March 31, 2014 the Company consolidated the following funds: Ramius Enterprise LP (“Enterprise LP”) and Ramius Merger Fund LLC (the "Merger Fund") (collectively the "2014 Consolidated Funds"). As of December 31, 2013 and during the quarter ended March 31, 2013, the Company consolidated the following funds: Enterprise LP, Ramius Multi‑Strategy Master FOF LP (“Multi‑Strat Master FOF”), Ramius Vintage Multi‑Strategy Master FOF LP (“Vintage Master FOF”), Ramius Levered Multi‑Strategy FOF LP (“Levered FOF”), and the Merger Fund (collectively the "2013 Consolidated Funds"). As of December 31, 2013, Levered FOF, Multi-Strat Master FOF and Vintage Master FOF, all of which are investment companies managed by Ramius Alternative Solutions LLC, were fully liquidated. RTS Global 3X LP was consolidated up through March 31, 2013 when it was liquidated. Collectively, the 2013 Consolidated Funds and the 2014 Consolidated Funds are referred to as the "Consolidated Funds".
	As of March 31, 2014, the Company also consolidated two investment companies; RCG Linkem II LLC, formed to make an investment in a wireless broadband communication provider in Italy and Ramius Co-Investment II LLC, which was formed to make an investment in a biomedical company that develops innovative gene therapies for severe genetic disorders. Ramius Co-Investment I LLC, formed for the same purpose as Ramius Co-Investment II LLC, was consolidated as of December 31, 2013 but was deconsolidated during the quarter ended March 31, 2014 when Ramius Co-Investment I LLC was liquidated. The Company determined that RCG Linkem II, LLC, Ramius Co-Investment I LLC (up until the first quarter of 2014) and Ramius Co-Investment II LLC are VOE's due to its controlling equity interests held through the managing member and/or affiliates and control exercised by the managing member who is not subject to substantive removal rights.
	Variable Interest Entities—VIEs are entities that lack one or more of the characteristics of a VOE. In accordance with US GAAP, an enterprise must consolidate all VIEs of which it is the primary beneficiary. Under the US GAAP consolidation model for VIEs, an enterprise that (1) has the power to direct the activities of a VIE that most significantly impacts the VIE's economic performance, and (2) has an obligation to absorb losses or the right to receive benefits from the VIE that could potentially be significant to the VIE, is considered to be the primary beneficiary of the VIE and thus is required to consolidate it.
	However, the FASB has deferred the application of the revised consolidation model for VIEs that meet the following conditions: (a) the entity has all the attributes of an investment company as defined under AICPA Audit and Accounting Guide, Investment Companies, or does not have all the attributes of an investment company but is an entity for which it is acceptable based on industry practice to apply measurement principles that are consistent with investment companies, (b) the reporting entity does not have explicit or implicit obligations to fund any losses of the entity that could potentially be significant to the entity, and (c) the entity is not a securitization entity, asset-backed financing entity or an entity that was formerly considered a qualifying special-purpose entity. The Company's involvement with its funds is such that all three of the above conditions are met for substantially all of the funds managed by the Company. Where the VIEs have qualified for the deferral, the analysis is based on previous consolidation rules. These rules require an analysis to (a) determine whether an entity in which the Company holds a variable interest is a variable interest entity and (b) whether the Company's involvement, through holding interests directly or indirectly in the entity or contractually through other variable interests (e.g., management and performance related fees), would be expected to absorb a majority of the VIE's expected losses, receive a majority of the VIEs expected residual returns, or both. If these conditions are met, the Company is considered to be the primary beneficiary of the VIE and thus is required to consolidate it.
	The Company reconsiders whether it is the primary beneficiary of a VIE by performing a periodic qualitative and/or quantitative analysis of the VIE that includes a review of, among other things, its capital structure, contractual agreements between the Company and the VIE, the economic interests that create or absorb variability, related party relationships and the design of the VIE. As of March 31, 2014 and December 31, 2013, the Company consolidates three VIEs. As of March 31, 2014 and December 31, 2013, the total net assets of the consolidated VIEs are $2.9 million and $8.2 million, respectively. The VIEs act as managing members/general partners and/or investment managers to affiliated fund entities which they sponsor and/or manage. The VIEs are financed through their operations and/or loan agreements with the Company.
	As of March 31, 2014 and December 31, 2013, the Company holds a variable interest in Ramius Enterprise Master Fund Ltd (“Enterprise Master”) through one of its Consolidated Funds, Enterprise LP and the Company holds a variable interest in Ramius Merger Master Fund Ltd through one of its Consolidated Funds, Merger Fund, (the “Unconsolidated Master Funds”). Investment companies, which account for their investments under the specialized industry accounting guidance for investment companies prescribed under US GAAP, are not subject to the consolidation provisions for their investments. Therefore, the Company has not consolidated the Unconsolidated Master Funds.
	In the ordinary course of business, the Company also sponsors various other entities that it has determined to be VIEs. These VIEs are primarily funds and real estate entities for which the Company serves as the general partner, managing member and/or investment manager with decision-making rights.
	The Company does not consolidate any of these funds or real estate entities that are VIEs as it has concluded that it is not the primary beneficiary in each instance. Fund investors are entitled to all of the economics of these VIEs with the exception of the management fee and incentive income, if any, earned by the Company. The Company's involvement with funds and real estate entities that are unconsolidated VIEs is limited to providing investment management services in exchange for management fees and incentive income. Although the Company may advance amounts and pay certain expenses on behalf of the funds and real estate entities that it considers to be VIEs, it does not provide, nor is it required to provide, any type of substantive financial support to these entities outside of regular investment management services. (See Note 5 for additional disclosures on VIEs)
	Equity Method Investments—For operating entities over which the Company exercises significant influence but which do not meet the requirements for consolidation as outlined above, the Company uses the equity method of accounting. The Company's investments in equity method investees are recorded in other investments in the condensed consolidated statements of financial condition. The Company's share of earnings or losses from equity method investees is included in net gains (losses) on securities, derivatives and other investments in the condensed consolidated statements of operations.
	The Company evaluates for impairment its equity method investments whenever events or changes in circumstances indicate that the carrying amounts of such investments may not be recoverable. The difference between the carrying value of the equity method investment and its estimated fair value is recognized as an impairment charge when the loss in value is deemed other than temporary.
	Other—If the Company does not consolidate an entity, apply the equity method of accounting or account for an investment under the cost method, the Company accounts for all securities which are bought and held principally for the purpose of selling them in the near term as trading securities in accordance with US GAAP, at fair value with unrealized gains (losses) resulting from changes in fair value reflected within net gains (losses) on securities, derivatives and other investments in the condensed consolidated statements of operations.
	Retention of Specialized Accounting—The Consolidated Funds are investment companies and apply specialized industry accounting for investment companies. The Company has retained this specialized accounting for these funds pursuant to US GAAP. The Company reports its investments on the condensed consolidated statements of financial condition at their estimated fair value, with unrealized gains (losses) resulting from changes in fair value reflected within net realized and unrealized gains (losses) on investments and other transactions. Accordingly, the accompanying condensed consolidated financial statements reflect different accounting policies for investments depending on whether or not they are held through a consolidated investment company. In addition, the Company's broker-dealer subsidiaries, Cowen and Company, LLC (“Cowen and Company”), ATM Execution LLC ("ATM Execution"), ATM USA, LLC ("ATM USA"), and Cowen Equity Finance LP ("Cowen Equity Finance"), apply the specialized industry accounting for brokers and dealers in securities also prescribed under US GAAP. The Company also retains specialized accounting in consolidation.
Use of estimates	'
	Use of estimates
	The preparation of the accompanying condensed consolidated financial statements in conformity with US GAAP requires the management of the Company to make estimates and assumptions that affect the fair value of securities and other investments, the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the accompanying condensed consolidated financial statements, the accounting for goodwill and identifiable intangible assets and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates. Certain reclassifications have been made to prior period amounts in order to conform with current period presentation.
Valuation of investments and derivative contracts	'
	Valuation of investments and derivative contracts
	US GAAP establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (level 1 measurements) and the lowest priority to unobservable inputs (level 3 measurements). The three levels of the fair value hierarchy are as follows:
	Level 1 Inputs that reflect unadjusted quoted prices in active markets for identical assets or liabilities that the Company has
	the ability to access at the measurement date;
	Level 2     Inputs other than quoted prices that are observable for the asset or liability either directly or indirectly, including
	inputs in markets that are not considered to be active; and
	Level 3 Fair value is determined based on pricing inputs that are unobservable and includes situations where there is little,
	if any, market activity for the asset or liability. The determination of fair value for assets and liabilities in this
	category requires significant management judgment or estimation.
	Inputs are used in applying the various valuation techniques and broadly refer to the assumptions that market participants use to make valuation decisions, including assumptions about risk. Inputs may include price information, volatility statistics, specific and broad credit data, liquidity statistics, and other factors. A financial instrument's level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. However, the determination of what constitutes “observable” requires significant judgment by the Company. The Company considers observable data to be that market data which is readily available, regularly distributed or updated, reliable and verifiable, not proprietary, and provided by independent sources that are actively involved in the relevant market. The categorization of a financial instrument within the hierarchy is based upon the pricing transparency of the instrument and does not necessarily correspond to the Company's perceived risk of that instrument.
	The Company and its operating subsidiaries act as the manager for the Consolidated Funds. Both the Company and the Consolidated Funds hold certain investments which are valued by the Company, acting as the investment manager. The fair value of these investments is generally estimated based on proprietary models developed by the Company, which include discounted cash flow analysis, public market comparables, and other techniques and may be based, at least in part, on independently sourced market information. The material estimates and assumptions used in these models include the timing and expected amount of cash flows, the appropriateness of discount rates used, and, in some cases, the ability to execute, timing of, and estimated proceeds from expected financings. Significant judgment and estimation goes into the selection of an appropriate valuation methodology as well as the assumptions used in these models, and the timing and actual values realized with respect to investments could be materially different from values derived based on the use of those estimates. The valuation methodologies applied impact the reported value of the Company's investments and the investments held by the Consolidated Funds in the condensed consolidated financial statements. Certain of the Company's investments are relatively illiquid or thinly traded and may not be immediately liquidated on demand if needed. Fair values assigned to these investments may differ significantly from the fair values that would have been used had a ready market for the investments existed and such differences could be material.
	The Company primarily uses the “market approach” to value its financial instruments measured at fair value. In determining an instrument's level within the hierarchy, the Company categorizes the Company's financial instruments into three categories: securities, derivative contracts and other investments. To the extent applicable, each of these categories can further be divided between those held long or sold short.
	Securities—Securities whose values are based on quoted market prices in active markets for identical assets, and are therefore classified in level 1 of the fair value hierarchy, include active listed equities, certain U.S. government and sovereign obligations, ETF's and certain money market securities. The Company does not adjust the quoted price for such instruments, even in situations where the Company holds a large position and a sale could reasonably impact the quoted price.
	Certain positions for which trading activity may not be readily visible, consisting primarily of convertible debt, corporate debt and loans, are stated at fair value and classified within level 2. The estimated fair values assigned by management are determined in good faith and are based on available information considering, trading activity, broker quotes, quotations provided by published pricing services, counterparties and other market participants, and pricing models using quoted inputs, and do not necessarily represent the amounts which might ultimately be realized. As level 2 investments include positions that are not always traded in active markets and/or are subject to transfer restrictions, valuations may be adjusted to reflect illiquidity and/or non-transferability.
	Derivative contracts—Derivative contracts can be exchange-traded or privately negotiated over-the-counter (“OTC”). Exchange-traded derivatives, such as futures contracts and exchange-traded option contracts, are typically classified within level 1 or level 2 of the fair value hierarchy depending on whether or not they are deemed to be actively traded. OTC derivatives, such as generic forwards, swaps and options, have inputs which can generally be corroborated by market data and are therefore classified within level 2. OTC derivatives, such as swaps, options and warrants where market data is not readily available or observable are classified as level 3.
	Other investments—Other investments consist primarily of portfolio funds, real estate investments and equity method investments, which are valued as follows:
	i.	Portfolio funds—Portfolio funds (“Portfolio Funds”) include interests in funds and investment companies managed by the Company or its affiliates. The Company follows US GAAP regarding fair value measurements and disclosures relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The guidance permits, as a practical expedient, an entity holding investments in certain entities that either are investment companies as defined by the AICPA Audit and Accounting Guide, Investment Companies, or have attributes similar to an investment company, and calculate net asset value per share or its equivalent for which the fair value is not readily determinable, to measure the fair value of such investments on the basis of that NAV per share, or its equivalent, without adjustment.
	The Company categorizes its investments in Portfolio Funds within the fair value hierarchy dependent on its ability to redeem the investment. If the Company has the ability to redeem its investment at NAV at the measurement date or within the near term, the Portfolio Fund is categorized as a level 2 investment within the fair value hierarchy. If the Company does not know when it will have the ability to redeem its investment or cannot do so in the near term, the Portfolio Fund is categorized as a level 3 investment within the fair value hierarchy. See Notes 5 and 6 for further details of the Company's investments in Portfolio Funds.
	ii.	Real estate investments—Real estate debt and equity investments are valued at fair value. The fair value of real estate investments are estimated based on the price that would be received to sell an asset in an orderly transaction between marketplace participants at the measurement date. Real estate investments without a public market are valued based on assumptions and valuation techniques used by the Company. Such valuation techniques may include discounted cash flow analysis, prevailing market capitalization rates or earnings multiples applied to earnings from the investment, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties, consideration of the amount that currently would be required to replace the asset, as adjusted for obsolescence, as well as independent external appraisals. In general, the Company considers several valuation techniques when measuring the fair value of a real estate investment. However, in certain circumstances, a single valuation technique may be appropriate. Real estate investments are reviewed on a quarterly basis by the Company for significant changes at the property level or a significant change in the overall market which would impact the value of the real estate investment resulting in unrealized appreciation or depreciation.
	The Company also reflects its real estate equity investments net of investment level financing. Valuation adjustments attributable to underlying financing arrangements are considered in the real estate equity valuation based on amounts at which the financing liabilities could be transferred to market participants at the measurement date.
	Real estate and capital markets are cyclical in nature. Property and investment values are affected by, among other things, the availability of capital, occupancy rates, rental rates and interest and inflation rates. In addition, the Company invests in real estate and real estate related investments for which no liquid market exists. The market prices for such investments may be volatile and may not be readily ascertainable. Amounts ultimately realized by the Company from investments sold may differ from the fair values presented, and the differences could be material.
	The Company's real estate investments are typically categorized as a level 3 investment within the fair value hierarchy as management uses significant unobservable inputs in determining their estimated fair value.
	See Notes 5 and 6 for further information regarding the Company's investments, including equity method investments, and fair value measurements.
Securities borrowed and securities loaned and repurchase agreements	'
	Securities borrowed and securities loaned
	Securities borrowed and securities loaned are carried at the amounts of cash collateral advanced or received on a gross basis. The related rebates are recorded in the statement of operations as interest income and interest expense. Securities borrowed transactions require the Company to deposit cash collateral with the lender. With respect to securities loaned, the Company receives cash collateral from the borrower. The initial collateral advanced or received approximates or is greater than the market value of securities borrowed or loaned. The Company monitors the market value of securities borrowed and loaned on a daily basis, with additional collateral obtained or returned, as necessary. Securities borrowed and loaned may also result in credit exposures for the Company in an event that the counterparties are unable to fulfill their contractual obligations. The Company minimizes its credit risk by continuously monitoring  its credit exposure and collateral values by demanding additional or returning excess collateral in accordance with the netting provisions available in the master securities lending contracts in place with the counterparties.
	Fees and interest received or paid are recorded in interest and dividend income and interest expense, respectively, on an accrual basis. In cases where the fair value basis of accounting is elected, any resulting change in fair value is reported in trading revenues. Accrued interest income and expense are recorded in the same manner as under the accrual method. At March 31, 2014 and December 31, 2013, the Company does not have any securities lending transactions for which fair value basis of accounting was elected.
Repurchase and Resale Agreements	'
	Securities purchased under agreements to resell and securities sold under agreements to repurchase
	The Company uses securities purchased under agreements to resell and securities sold under agreements to repurchase (“Repurchase Agreements”) as part of its liquidity management activities and to support its trading and risk management activities. In particular, securities purchased and sold under Repurchase Agreements are used for short-term liquidity purposes. As of December 31, 2013, Repurchase Agreements are secured predominantly by liquid corporate credit and/or government issued securities. The use of Repurchase Agreements will fluctuate with the Company's need to fund short term credit or obtain competitive short term credit financing. The Company's securities sold under agreements to repurchase were transacted pursuant to agreements with one counterparty as of December 31, 2013. The Company does not hold any repurchase agreements as of March 31, 2014.
	Collateral is valued daily and the Company and its counterparties may adjust the collateral or require additional collateral to be deposited when appropriate. Collateral held by counterparties may be sold or re-hypothecated by such counterparties, subject to certain limitations sometimes imposed by the Company and in accordance with the master netting agreements in place with the counterparty. Collateralized Repurchase Agreements may result in credit exposure in the event the counterparties to the transactions are unable to fulfill their contractual obligations. The Company minimizes the credit risk associated with this activity by monitoring credit exposure and collateral values, and by requiring additional collateral to be promptly deposited with or returned to the Company when deemed necessary.
Debt	'
	Long-term debt is carried at the principal amount borrowed net of any discount/premium. The discount is accreted to interest expense using the effective interest method over the remaining life of the underlying debt obligations. Accrued but unpaid coupon interest is included in accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition.
Deferred rent	'
	Deferred rent
	Deferred rent primarily consists of step rent, allowances from landlords and valuing the Company's lease properties in accordance with US GAAP. Step rent represents the difference between actual operating lease payments due and straight-line rent expense, which is recorded by the Company over the term of the lease, including the build-out period. This amount is recorded as deferred rent in the early years of the lease, when cash payments are generally lower than straight-line rent expense, and reduced in the later years of the lease when payments begin to exceed the straight-line expense. Landlord allowances are generally comprised of amounts received and/or promised to the Company by landlords and may be received in the form of cash or free rent. These allowances are part of the negotiated terms of the lease. The Company records a receivable from the landlord and a deferred rent liability when the allowances are earned. This deferred rent is amortized into income (through lower rent expense) over the term (including the pre-opening build-out period) of the applicable lease, and the receivable is reduced as amounts are received from the landlord. Liabilities resulting from valuing the Company's leased properties acquired through business combinations are quantified by comparing the current fair value of the leased space to the current rental payments on the date of acquisition. Deferred rent, included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition, as of March 31, 2014 and December 31, 2013 is $14.1 million and $14.6 million, respectively.
New accounting pronouncements	'
	eferred rent primarily consists of step rent, allowances from landlords and valuing the Company's lease properties in accordance with US GAAP. Step rent represents the difference between actual operating lease payments due and straight-line rent expense, which is recorded by the Company over the term of the lease, including the build-out period. This amount is recorded as deferred rent in the early years of the lease, when cash payments are generally lower than straight-line rent expense, and reduced in the later years of the lease when payments begin to exceed the straight-line expense. Landlord allowances are generally comprised of amounts received and/or promised to the Company by landlords and may be received in the form of cash or free rent. These allowances are part of the negotiated terms of the lease. The Company records a receivable from the landlord and a deferred rent liability when the allowances are earned. This deferred rent is amortized into income (through lower rent expense) over the term (including the pre-opening build-out period) of the applicable lease, and the receivable is reduced as amounts are received from the landlord. Liabilities resulting from valuing the Company's leased properties acquired through business combinations are quantified by comparing the current fair value of the leased space to the current rental payments on the date of acquisition. Deferred rent, included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition, as of March 31, 2014 and December 31, 2013 is $14.1 million and $14.6 million, respectively.
Income Tax	'
	The taxable results of the Company’s U.S. operations are included in the consolidated income tax returns of Cowen Group, Inc. as well as stand-alone state and local tax returns. The Company has subsidiaries that are resident in foreign countries where tax filings have to be submitted on a stand‑alone basis. These subsidiaries are subject to tax in their respective countries and the Company is responsible for and, thus, reports all taxes incurred by these subsidiaries. The countries where the Company owns subsidiaries that file tax returns are United Kingdom, Luxembourg, Gibraltar, and Hong Kong.
Earnings Per Share	'
	Diluted earnings per common share are calculated by adjusting the weighted average outstanding shares to assume conversion of all potentially dilutive nonvested restricted stock and stock options. The Company uses the treasury stock method to reflect the potential dilutive effect of the unvested restricted shares, restricted stock units, unexercised stock options, warrants and SAR's. In calculating the number of dilutive shares outstanding, the shares of common stock underlying unvested restricted shares and restricted stock units are assumed to have been delivered, and options and warrants are assumed to have been exercised, on the grant date. The assumed proceeds from the assumed vesting, delivery and exercising were calculated as the sum of (a) the amount of compensation cost attributed to future services and not yet recognized and (b) the amount of tax benefit that would be credited to additional paid-in capital assuming vesting and delivery of the restricted stock. The tax benefit is the amount resulting from a tax deduction for compensation in excess of compensation expense recognized for financial statement reporting purposes. All outstanding stock options and warrants were not included in the computation of diluted net income (loss) per common share for the three months ended March 31, 2014 and 2013, respectively, as their inclusion would have been anti-dilutive.
Segment Reporting	'
	The performance measure for these segments is Economic Income (Loss), which management uses to evaluate the financial performance of and make operating decisions for the segments including determining appropriate compensation levels.
	In general, Economic Income (Loss) is a pre-tax measure that (i) eliminates the impact of consolidation for consolidated funds and (ii) excludes certain other acquisition-related and/or reorganization expenses (See Note 2). In addition, Economic Income (Loss) revenues include investment income that represents the income the Company has earned in investing its own capital, including realized and unrealized gains and losses, interest and dividends, net of associated investment related expenses. For US GAAP purposes, these items are included in each of their respective line items. Economic Income (Loss) revenues also include management fees, incentive income and investment income earned through the Company's investment as a general partner in certain real estate entities and the Company's investment in the activist business. For US GAAP purposes, all of these items are recorded in other income (loss). In addition, Economic Income (Loss) expenses are reduced by reimbursement from affiliates, which for US GAAP purposes is presented gross as part of revenue.
	As further stated below, one major difference between Economic Income (Loss) and US GAAP net income (loss) is that Economic Income (Loss) presents the segments' results of operations without the impact resulting from the full consolidation of any of the Consolidated Funds. Consolidation of these funds results in including in income the pro rata share of the income or loss attributable to other owners of such entities which is reflected in net income (loss) attributable to redeemable non-controlling interest in consolidated subsidiaries in the accompanying condensed consolidated statements of operations. This pro rata share has no effect on the overall financial performance for the alternative investment segment, as ultimately, this income or loss is not income or loss for the alternative investment segment itself. Included in Economic Income (Loss) is the actual pro rata share of the income or loss attributable to the Company as an investor in such entities, which is relevant in management making operating decisions and evaluating financial performance.

Investments_of_Operating_Entit1

Investments of Operating Entities and Consolidated Funds (Tables)	3 Months Ended
	Mar. 31, 2014
Investment Holdings [Line Items]	'
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	'
	As of March 31, 2014 and December 31, 2013, securities owned, at fair value consisted of the following:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	U.S. Government securities (a)	$	9			$	9
	Preferred stock	324				324
	Common stocks	270,349				176,939
	Convertible bonds (b)	11,564				5,958
	Corporate bonds (c)	167,349				121,372
	Warrants and rights	4,265				5,912
	Mutual funds	15,518				525
		$	469,378			$	311,039
	(a)	As of March 31, 2014, the maturity was April 2016 with an interest rate of 5.95%. As of December 31, 2013, the maturity was April 2016 with an interest rate of 5.95%.
	(b)	As of March 31, 2014, maturities ranged from June 2014 to November 2014 and interest rates ranged between 4.00% to 10.00%. As of December 31, 2013, maturities ranged from May 2014 to October 2014 and interest rates ranged between 5.00% to 10.00% .
	(c)	As of March 31, 2014, maturities ranged from September 2014 to February 2046 and interest rates ranged between 4.74% and 12.25%. As of December 31, 2013, maturities ranged from January 2014 to February 2046 and interest rates ranged between 3.38% and 11.75%.
Schedule of Derivative Instruments	'
	The Company's long and short exposure to derivatives is as follows:
	Receivable on derivative contracts	As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	Commodity Future	$	53			$	285
	Cross Rate	10				22
	Equity Swap	8				70
	Options (a)	50,005				9,698
		$	50,076			$	10,075
	(a) As of March 31, 2014 and December 31, 2013, the Company had 62,479 and 71,129 contracts held, respectively.
	Payable for derivative contracts	As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	Futures	$	62			$	275
	Currency forwards	28				301
	Equity and credit default swaps	735				525
	Options (a)	49,207				6,573
		$	50,032			$	7,674
	(a) As of March 31, 2014 and December 31, 2013, the Company had 27,745 and 38,221 contracts held, respectively.
	The following tables present the gross and net derivative positions and the related offsetting amount, as of March 31, 2014 and December 31, 2013.
	As of March 31, 2014
		Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
						(a)
		(dollars in thousands)
	Receivable on derivative contracts, at fair value	$	50,076			$	—			$	50,076	$	—	$	—
	Payable for derivative contracts, at fair value	50,032				—				50,032		—		—
	As of December 31, 2013
		Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
						(a)
		(dollars in thousands)
	Receivable on derivative contracts, at fair value	$	10,075			$	—			$	10,075	$	10,075	$	—
	Payable for derivative contracts, at fair value	7,674				—				7,674		7,674		$	—
	(a)	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
	(b)	Includes the amount of collateral held or posted.
Schedule of Other Investments	'
	As of March 31, 2014 and December 31, 2013, other investments consisted of the following:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	(1) Portfolio Funds, at fair value	$	79,440			$	71,051
	(2) Real estate investments, at fair value	42,283				2,088
	(3) Equity method investments	22,034				25,966
	(4) Lehman claims, at fair value	390				378
		$	144,147			$	99,483
Schedule of Other Investments, Portfolio Funds	'
	The Portfolio Funds, at fair value as of March 31, 2014 and December 31, 2013, included the following:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	HealthCare Royalty Partners (a)(*)	$	10,784			$	9,741
	HealthCare Royalty Partners II (a)(*)	6,140				4,961
	Orchard Square Partners Credit Fund LP (b)(*)	13,828				12,674
	Starboard Value and Opportunity Fund LP (c)(*)	18,439				17,495
	Formation 8 Partners Fund I (d)	6,083				2,788
	RCG LV Park Lane LLC (e)	706				678
	RCGL 12E13th LLC (f)	584				558
	RCG Longview Debt Fund V, L.P. (f)	11,856				11,979
	Other private investment (g)	7,785				7,772
	Other affiliated funds (h)(*)	3,235				2,405
		$	79,440			$	71,051
	* These portfolio funds are affiliates of the Company.
	The Company has no unfunded commitments regarding the portfolio funds held by the Company except as noted in Note 13.
	(a)	HealthCare Royalty Partners, L.P. and HealthCare Royalty Partners II, L.P. are private equity funds and therefore distributions will be made when cash flows are received from the underlying investments, typically on a quarterly basis.
	(b)	Orchard Square Partners Credit Fund LP (formerly known as Ramius Global Credit Fund LP) has a quarterly redemption policy with a 60 day notice period and a 4% penalty on redemptions of investments of less than a year in duration.
	(c)	Starboard Value and Opportunity Fund LP permits quarterly withdrawals upon 90 days notice.
	(d)	Formation 8 Partners Fund I is a private equity fund which invests in equity of early stage and growth transformational information and energy technology companies. Distributions will be made when the underlying investments are liquidated.
	(e)	RCG LV Park Lane LLC  is a single purpose entity formed to participate in a joint venture which acquired, at a discount, the mortgage notes on a portfolio of multifamily real estate properties located in Birmingham, Alabama.  RCG LV Park Lane LLC is a private equity structure and therefore distributions will be made when the underlying investments are liquidated.
	(f)	RCGL 12E13th LLC and RCG Longview Debt Fund V, L.P. are real estate private equity structures and therefore distributions will be made when the underlying investments are liquidated.
	(g)	Other private investment represents the Company's closed end investment in a portfolio fund that invests in a wireless broadband communication provider in Italy.
	(h)	The majority of these funds are affiliates of the Company or are managed by the Company and the investors can redeem from these funds as investments are liquidated.
Schedule of Equity Method Investments	'
	The following table summarizes equity method investments held by the Company:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	RCG Longview Debt Fund IV Management, LLC	$	495			$	1,533
	RCG Longview Debt Fund V Partners, LLC	1,672				1,497
	HealthCare Royalty GP, LLC	879				794
	HealthCare Royalty GP II, LLC	1,040				840
	HealthCare Royalty GP III, LLC	47				47
	CBOE Stock Exchange, LLC	1,283				1,351
	Starboard Value LP	10,019				14,263
	RCG Longview Partners, LLC	2,692				1,839
	RCG Urban American, LLC	346				316
	RCG Urban American Management, LLC	274				238
	RCG Longview Equity Management, LLC	106				292
	Urban American Real Estate Fund II, LLC	2,047				1,785
	RCG Kennedy House, LLC	483				502
	Other	651				669
		$	22,034			$	25,966
Investments Sold, Not yet Purchased	'
	As of March 31, 2014 and December 31, 2013, securities sold, not yet purchased, at fair value consisted of the following:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	Common stocks	$	139,290			$	130,899
	Corporate bonds (a)	57				55
		$	139,347			$	130,954
	(a)	As of March 31, 2014 and December 31, 2013, the maturity was January 2026 with an interest rate of 5.55%
Schedule of Securities Financing Transactions	'
	The following table represents the Company's securities sold under agreements to repurchase as of December 31, 2013:
		As of December 31, 2013
		(dollars in thousands)
	Securities sold under agreements to repurchase
	Agreements with Royal Bank of Canada bearing interest of 1.75% due June 2015 to November 2015	$	3,657
		$	3,657
	The following tables present the gross and net repurchase agreements and the related offsetting amount, as of December 31, 2013.
	As of December 31, 2013
		Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
						(a)
		(dollars in thousands)
	Securities sold under agreements to repurchase	$	3,657			$	—			$	3,657	$	3,657	$	—
	(a)	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
	(b)	Includes the amount of collateral held or posted.
Securities Borrowed and Securities Loaned Disclosure [Text Block]	'
	The following tables present the contractual gross and net securities borrowing and lending agreements and the related offsetting amount, as of March 31, 2014 and December 31, 2013.
	As of March 31, 2014
		Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
						(a)
		(dollars in thousands)
	Securities borrowed	$	1,319,938			$	—			$	1,319,938	$	1,319,938	$	—
	Securities loaned	1,310,903				—				1,310,903		1,310,903		—
	As of December 31, 2013
		Gross amounts recognized				Gross amounts offset on the Condensed Consolidated Statements of Financial Condition				Net amounts included on the Condensed Consolidated Statements of Financial Condition		Amounts not offset on the condensed consolidated balance sheet but eligible for offsetting upon counterparty default (b)		Net amounts
						(a)
		(dollars in thousands)
	Securities borrowed	$	927,773			$	—			$	927,773	$	927,773	$	—
	Securities loaned	918,577				—				918,577		918,577		—
	(a)	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
	(b)	Includes the amount of cash collateral held/posted.
Consolidated Funds	'
Investment Holdings [Line Items]	'
Schedule of Other Investments	'
	As of March 31, 2014 and December 31, 2013 other investments, at fair value, held by the Consolidated Funds are comprised of:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	(1) Portfolio Funds	$	175,614			$	182,638
	(2) Lehman claims	3,776				4,842
		$	179,390			$	187,480
Schedule of Other Investments, Portfolio Funds	'
	As of March 31, 2014 and December 31, 2013, investments in Portfolio Funds, at fair value, included the following:
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	Investments of Enterprise LP	$	143,059			$	155,530
	Investments of Merger Fund	32,555				26,963
	Investments of consolidated fund of funds	—				145
		$	175,614			$	182,638
Enterprise Master	'
Investment Holdings [Line Items]	'
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	'
	Securities owned by Enterprise Master, at fair value
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	Bank debt	$	5			$	5
	Common stock	2,527				2,677
	Preferred stock	973				973
	Private equity	409				406
	Restricted stock	124				124
	Rights	2,531				2,528
	Trade claims	128				128
		$	6,697			$	6,841
Schedule of Derivative Instruments	'
	Derivative contracts, at fair value, owned by Enterprise Master, net
		As of March 31, 2014				As of December 31, 2013
	Description	(dollars in thousands)
	Currency forwards	$	6			$	(21	)
		$	6			$	(21	)
Schedule of Other Investments, Portfolio Funds	'
	Portfolio Funds, owned by Enterprise Master, at fair value
				As of March 31, 2014				As of December 31, 2013
		Strategy		(dollars in thousands)
	RCG Longview Equity Fund, LP*	Real Estate		$	8,949			$	8,470
	RCG Longview II, LP*	Real Estate		825				800
	RCG Longview Debt Fund IV, LP*	Real Estate		15,308				17,641
	RCG Longview, LP*	Real Estate		467				319
	RCG Soundview, LLC*	Real Estate		442				442
	RCG Urban American Real Estate Fund, L.P.*	Real Estate		2,003				1,812
	RCG International Sarl*	Multi-Strategy		1,693				1,795
	RCG Special Opportunities Fund, Ltd*	Multi-Strategy		82,692				82,119
	RCG Endeavour, LLC*	Multi-Strategy		5				6
	RCG Energy, LLC *	Energy		2,866				2,842
	RCG Renergys, LLC*	Energy		1				1
	Other Private Investments	Various		13,254				12,952
	Real Estate Investments	Real Estate		16,947				15,024
				$	145,452			$	144,223
	*	Affiliates of the Company.
Merger Master	'
Investment Holdings [Line Items]	'
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	'
	Securities owned by Merger Master, at fair value
		As of March 31, 2014				As of December 31, 2013
		(dollars in thousands)
	Common stocks	$	63,734			$	33,901
	Corporate bond (a)	11,328				14,444
	Options	434				200
		$	75,496			$	48,545
	(a)	As of March 31, 2014, maturities ranged from April 2016 to June 2019 and interest rates ranged between 8.50% and 10.88%. As of December 31, 2013, maturities ranged from April 2016 to October 2020 and interest rates ranged between 7.00% and 10.88%.
Schedule of Derivative Instruments	'
	Derivative contracts, at fair value, owned by Merger Master, net
		As of March 31, 2014				As of December 31, 2013
	Description	(dollars in thousands)
	Currency forwards	$	(4	)		$	(10	)
	Options	(155		)		(54		)
	Cross rate	(84		)		(92		)
		$	(243	)		$	(156	)

Fair_Value_Measurements_for_Op1

Fair Value Measurements for Operating Entities and Consolidated Funds (Tables)	3 Months Ended
	Mar. 31, 2014
Fair Value Disclosures [Abstract]	'
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	'
	The following table presents the assets and liabilities that are measured at fair value on a recurring basis on the accompanying condensed consolidated statements of financial condition by caption and by level within the valuation hierarchy as of March 31, 2014 and December 31, 2013:
	Operating Entities
		Assets at Fair Value as of March 31, 2014
		Level 1		Level 2				Level 3			Total
				(dollars in thousands)
	Securities owned and derivatives
	US Government securities	$	9	$	—			$	—		$	9
	Preferred stock	—		—				324			324
	Common stocks	258,824		2,242				9,283			270,349
	Convertible bonds	—		9,614				1,950			11,564
	Corporate bonds	—		167,349				—			167,349
	Warrants and rights	997		—				3,268			4,265
	Mutual funds	15,518		—				—			15,518
	Receivable on derivative contracts, at fair value
	Futures	53		—				—			53
	Currency forwards	—		10				—			10
	Equity swaps	—		8				—			8
	Options	7,149		—				42,856			50,005
	Other investments
	Portfolio Funds	—		20,857				58,583			79,440
	Real estate investments	—		—				42,283			42,283
	Lehman claim	—		—				390			390
		$	282,550	$	200,080			$	158,937		$	641,567
		Liabilities at Fair Value as of March 31, 2014
		Level 1		Level 2				Level 3			Total
		(dollars in thousands)
	Securities sold, not yet purchased and derivatives
	Common stocks	$	139,290	$	—			$	—		$	139,290
	Corporate bonds	—		57				—			57
	Payable for derivative contracts, at fair value
	Futures	62		—				—			62
	Currency forwards	—		28				—			28
	Equity and credit default swaps	—		735				—			735
	Options	6,351		—				42,856			49,207
	Accounts payable, accrued expenses and other liabilities
	Contingent consideration liability (a)	$	—	$	—			$	6,861		$	6,861
		$	145,703	$	820			$	49,717		$	196,240
	(a) In accordance with the terms of purchase agreements from acquisitions that closed during 2012, the Company is required to pay to certain sellers a portion of future net profits of the acquired businesses, if certain revenue targets are achieved over the period through October 2016. The Company estimated the contingent consideration using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts can range from $3.5 million to $13.0 million.
		Assets at Fair Value as of December 31, 2013
		Level 1		Level 2				Level 3			Total
				(dollars in thousands)
	Securities owned and derivatives
	US Government securities	$	9	$	—			$	—		$	9
	Preferred stock	—		—				324			324
	Common stocks	171,277		2,103				3,559			176,939
	Convertible bonds	—		4,008				1,950			5,958
	Corporate bonds	—		121,372				—			121,372
	Warrants and rights	107		—				5,805			5,912
	Mutual funds	525		—				—			525
	Receivable on derivative contracts, at fair value
	Futures	285		—				—			285
	Currency forwards	—		22				—			22
	Equity swaps	—		70				—			70
	Options	9,698		—				—			9,698
	Other investments
	Portfolio Funds	—		19,402				51,649			71,051
	Real estate investments	—		—				2,088			2,088
	Lehman claim	—		—				378			378
		$	181,901	$	146,977			$	65,753		$	394,631
		Liabilities at Fair Value as of December 31, 2013
		Level 1		Level 2				Level 3			Total
		(dollars in thousands)
	Securities sold, not yet purchased and derivatives
Common stocks	$	130,899	$	—			$	—		$	130,899
Corporate bonds	—		55				—			55
Payable for derivative contracts, at fair value
Futures	275		—				—			275
Currency forwards	—		301				—			301
Equity swaps	—		525				—			525
Options	6,573		—				—			6,573
Accounts payable, accrued expenses and other liabilities
Contingent consideration liability	—		—				6,937			6,937
	$	137,747	$	881			$	6,937		$	145,565
Consolidated Funds' investments
	Assets at Fair Value as of March 31, 2014
	Level 1		Level 2				Level 3			Total
			(dollars in thousands)
Other investments
Portfolio Funds	$	—	$	32,555			$	143,059		$	175,614
Lehman claims	—		—				3,776			3,776
	$	—	$	32,555			$	146,835		$	179,390
	Assets at Fair Value as of December 31, 2013
	Level 1		Level 2				Level 3			Total
			(dollars in thousands)
Other investments
Portfolio Funds	—		26,964				155,674			182,638
Lehman claims	—		—				4,842			4,842
	$	—	$	26,964			$	160,516		$	187,480
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	'
	The following table includes a rollforward of the amounts for the three months ended March 31, 2014 and 2013, for financial instruments classified within level 3. The classification of a financial instrument within level 3 is based upon the significance of the unobservable inputs to the overall fair value measurement.
		Three Months Ended March 31, 2014
		Balance at December 31, 2013		Transfers in					Transfers out			Purchases/(covers)			(Sales)/shorts				Realized gains (losses)				Unrealized gains or losses				Balance at March 31, 2014
		(dollars in thousands)
	Operating Entities
	Preferred stock	$	324	$	—				$	—		$	—		$	—			$	—			$	—			$	324
	Common stocks	3,559		—					—			—			—				—				5,724				9,283
	Convertible bonds	1,950		—					—			—			—				—				—				1,950
	Options, asset	—		—					—			35,710			—				—				7,146				42,856
	Options, liability	—		—					—			35,710			—				—				7,146				42,856
	Warrants and Rights, asset	5,805		—			—		—			—			(1,328		)		—				(1,209		)		3,268
	Portfolio Funds	51,649		—					—			4,385			(1,242		)		180				3,611				58,583
	Real estate	2,088		—					—			40,000			(27		)		—				222				42,283
	Lehman claim	378		—					—			—			—				—				12				390
	Contingent consideration liability	6,937		—					—			(76		)	—				—				—				6,861
	Consolidated Funds
	Portfolio Funds	155,674		—					—			—			(15,944		)		—				3,329				143,059
	Lehman claim	4,842		—					—			—			(980		)		—				(86		)		3,776
		Three Months Ended March 31, 2013
		Balance at December 31, 2012		Transfers in					Transfers out				Purchases/(covers)			(Sales)/shorts				Realized gains (losses)				Unrealized gains or losses				Balance at March 31, 2013
		(dollars in thousands)
	Operating Entities
	Preferred stock	$	2,332	$	—				$	—			$	—		$	—			$	—			$	—			$	2,332
	Common stocks	2,549		—					—				—			(265		)		260				(266		)		2,278
	Corporate Bond	515		—					—				2,735			(3,346		)		(914		)		1,010				—
	Warrants and Rights, asset	1,713		290			(a)		—				166			(110		)		—				1,184				3,243
	Warrants and Rights, liability	3		—					—				—			—				—				—				3
	Portfolio Funds	25,670		—					—				3,590			(3,876		)		8				167				25,559
	Real estate	1,864		—					—				—			—				—				11				1,875
	Lehman claim	706		—					—				—			—				—				(46		)		660
	Contingent consideration liability	8,116		—					—				—			—				—				—				8,116
	Consolidated Funds
	Portfolio Funds	182,920		—					—				—			(7,031		)		222				2,246				178,357
	Lehman claim	14,124		—					—				—			(1,449		)		1,360				1,105				15,140
	(a) The security was acquired through an acquisition (See Note 2).
Fair Value Inputs, Assets, Quantitative Information	'
	The following table includes quantitative information as of March 31, 2014 for financial instruments classified within level 3. The table below quantifies information about the significant unobservable inputs used in the fair value measurement of the Company's level 3 financial instruments.
		Quantitative Information about Level 3 Fair Value Measurements
		Fair Value at March 31, 2014		Valuation techniques		Unobservable Inputs		Range
	Level 3 Assets
	Common and preferred stocks	$	9,198	Discounted cash flows, market multiples, recent transactions, bid levels, and comparable transactions		Market multiples		2x to 3x
	Warrants and rights, net	3,268		Model based		Volatility		20% to 100% (weighted average 36%)
	Options	42,856		Option pricing models, credit valuation adjustment, debt valuation adjustment		Volatility Credit spreads		30% to 45% 600bps - 750 bps
	Other level 3 assets (a)	250,450
	Total level 3 assets	305,772
	Level 3 Liabilities
	Options	42,856		Option pricing models, credit valuation adjustment, debt valuation adjustment		Volatility Credit spreads		30% to 45% 600bps - 750 bps
	Contingent consideration	6,861		Discounted cash flows		Projected cash flow and discount rate		0% to 9%
	Total level 3 liabilities	$	49,717
	(a)	Quantitative disclosures of unobservable inputs and assumptions are not required for investments for which NAV per share is used as a practical expedient to determine fair value, as their redemption features rather than observability of inputs cause them to be classified as a level 3 type asset within the fair value hierarchy. In addition, the fair value of the Consolidated Funds' investments are determined based on net asset value and therefore quantitative disclosures are not included in the table above. The quantitative disclosures also exclude financial instruments for which the determination of fair value is based on prices from prior transactions.

Redeemable_NonControlling_Inte1

Redeemable Non-Controlling Interests in Consolidated Subsidiaries (Tables)	3 Months Ended
	Mar. 31, 2014
Noncontrolling Interest [Abstract]	'
Redeemable non-controlling interests in consolidated subsidiaries	'
	Redeemable non-controlling interests in consolidated subsidiaries and funds and the related net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds are comprised as follows:
		As of March 31, 2014		As of December 31, 2013
		(dollars in thousands)
	Redeemable non-controlling interests in consolidated subsidiaries and funds
	Operating companies	$	10,840	$	12,009
	Consolidated funds	74,608		73,805
		$	85,448	$	85,814
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries	'
		Three Months Ended March 31,
		2014		2013
		(dollars in thousands)
	Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds
	Operating companies	$	3,439	$	1,795
	Consolidated funds	748		1,700
		$	4,187	$	3,495

ShareBased_Compensation_and_Em1

Share-Based Compensation and Employee Ownership Plans (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Schedule of Share-based Compensation, Stock Options, Activity	'
	The following table summarizes the Company's stock option activity for the three months ended March 31, 2014:
		Shares Subject		Weighted Average		Weighted Average	Aggregate Intrinsic
		to Option		Exercise Price/Share		Remaining Term	Value(1)
						(in years)	(dollars in thousands)
	Balance outstanding at December 31, 2013	300,006		$	7.19	2.4	$	—
	Options granted	—		—		—	—
	Options acquired	—		—		—	—
	Options expired	—		—		—	—
	Balance outstanding at March 31, 2014	300,006		$	7.19	2.16	$	—
	Options exercisable at March 31, 2014	300,006		$	7.19	2.16	$	—
	-1	Based on the Company's closing stock price of $4.41 on March 31, 2014 and $3.91 on December 31, 2013.
Schedule of Share-based Compensation, Stock Appreciation Rights, Activity	'
	As of March 31, 2014, the unrecognized compensation expense related to the Company's grant of stock options was insignificant.
	The following table s
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity	'
	Restricted shares and restricted stock units are referred to collectively as restricted stock. The following table summarizes the Company's restricted share and restricted stock unit activity for the three months ended March 31, 2014:
		Nonvested Restricted Shares and Restricted Stock Units		Weighted-Average
				Grant Date
				Fair Value
	Balance outstanding at December 31, 2013	13,551,544		$	3.37
	Granted (1)	7,694,398		3.78
	Vested	(1,652,652	)	2.84
	Canceled	—		—
	Forfeited	(57,251	)	3.21
	Balance outstanding at March 31, 2014	19,536,039		$	3.58

Defined_Benefit_Plans_Tables

Defined Benefit Plans (Tables)	3 Months Ended
	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]	'
Schedule of Net Periodic Benefit Cost	'
	The amounts contained in the following table relate to the Company's defined benefit plan for the three months ended March 31, 2014 and 2013:
		Three Months Ended March 31,
		2014			2013
		(dollars in thousands)
	Components of net periodic benefit cost included in employee compensation and benefits
	Service cost	$	—		$	—
	Interest cost	33			51
	Expected return on plan assets	(66		)	(63		)
	Amortization of (loss) / gain	—			—
	Amortization of prior service cost	—			5
	Effect of curtailment	—			—
	Effect of special termination benefits	—			—
	Effect of settlement	—			—
	Net periodic benefit cost	$	(33	)	$	(7	)

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Future Minimum Annual Lease and Service Payments	'
	As of March 31, 2014, future minimum annual lease and service payments for the Company were as follows:
		Equipment Leases (a)		Service Payments		Facility Leases (b)
		(dollars in thousands)
	2014	$	2,181	$	9,036	$	13,848
	2015	2,603		7,667		17,789
	2016	2,284		3,367		14,698
	2017	2,198		2,714		11,587
	2018	2,198		2,609		11,296
	Thereafter	813		22		41,601
		$	12,277	$	25,415	$	110,819
	(a)	Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 14 for further information on the capital lease minimum payments which are included in the table.
	(b)	The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $0.3 million and $0.3 million for the three months ended March 31, 2014 and 2013.

Debt_Tables

Debt (Tables)	3 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Schedule of Debt and Capital Lease Obligations [Table Text Block]	'
	As of March 31, 2014 and December 31, 2013, the Company's outstanding debt was as follows:
		As of March 31, 2014			As of December 31, 2013
		(dollars in thousands)
	Convertible debt	$	114,101		$	—
	Note payable	1,428			41
	Capital lease obligations	4,956			2,523
		$	120,485		$	2,564
Schedule of Maturities of Debt and Future Minimum Lease Payments for Capital Leases [Table Text Block]	'
	Annual scheduled maturities of debt and minimum payments for debt outstanding as of March 31, 2014, is as follows:
		Convertible Debt			Notes payable			Capital Lease
								Obligation
		(dollars in thousands)
	2014	$	2,284		$	1,448		$	1,236
	2015	4,411			—			1,343
	2016	4,411			—			1,025
	2017	4,411			—			938
	2018	4,411			—			938
	Thereafter	151,688			—			79
	Subtotal	171,616			1,448			5,559
	Less: Amount representing interest (a)	(57,515		)	(20		)	(603		)
	Total	$	114,101		$	1,428		$	4,956
	(a)	Amount necessary to reduce net minimum payments to present value calculated at the Company's implicit rate at inception
Schedule of Line of Credit Facilities [Table Text Block]	'
	As of March 31, 2014, the Company has the following six irrevocable letters of credit related to leased office space, for which there is cash collateral pledged, which the Company pays a fee on the stated amount of the letter of credit.
	Location		Amount			Maturity
			(dollars in thousands)
	San Francisco		$	82		May-14
	Boston		$	382		Mar-15
	New York		$	1,191		Sep-14
	New York		$	6,746		Dec-14
	New York		$	1,000		Feb-15
	New York		$	1,861		Jun-14

Treasury_Stock_Tables

Treasury Stock (Tables)	3 Months Ended
	Mar. 31, 2014
Equity [Abstract]	'
Treasury Stock Activity	'
	The following represents the activity relating to the treasury stock held by the Company during the three months ended March 31, 2014:
		Treasury stock shares	Cost		Average cost
			(dollars in thousands)		per share
	Balance outstanding at December 31, 2013	15,873,549	$	48,084	$	3.03
	Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions	452,809	1,920		4.24
	Purchase of treasury stock	810,072	3,411		4.21
	Balance outstanding at March 31, 2014	17,136,430	$	53,415	$	3.12

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2014
Accumulated Other Comprehensive Income / (Loss) [Abstract]	'
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	'
		Foreign currency translation (a)			Defined benefit plans (a)			Total
		(dollars in thousands)
	Balance at December 31, 2013	248			344			592
	Net change	37			(92		)	(55		)
	Balance at March 31, 2014	$	285		$	252		$	537
		Foreign currency translation (a)			Defined benefit plans (a)			Total
		(dollars in thousands)
	Balance at December 31, 2012	$	258		$	98		$	356
	Net change	(4		)	(17		)	(21		)
	Balance at March 31, 2013	$	254		$	81		$	335
	(a) During the periods presented, the Company did not have material reclassifications out of other comprehensive income.

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share, Basic and Diluted	'
	The computation of earnings per share is as follows:
		Three Months Ended March 31,
		2014		2013
	Net income (loss)	$	14,027	$	919
	Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	4,187		3,495
	Net income (loss) attributable to Cowen Group, Inc. stockholders	9,840		(2,576		)
	Shares for basic and diluted calculations:
	Weighted average shares used in basic computation	115,680		113,798
	Warrants	—		—
	Stock options	—		—
	Stock appreciation rights	54		—
	Restricted stock	7,164		—
	Weighted average shares used in diluted computation	122,898		113,798
	Earnings (loss) per share:
	Basic	$	0.09	$	(0.02	)
	Diluted	$	0.08	$	(0.02	)

Segment_Reporting_Tables

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Segment Reporting Information, by Segment	'
	The following tables set forth operating results for the Company's alternative investment and broker dealer segments and related adjustments necessary to reconcile the Company's Economic Income (Loss) measure to arrive at the Company's consolidated US GAAP net income (loss):
		Three Months Ended March 31, 2014
											Adjustments
		Alternative			Broker-Dealer (1)			Total Economic Income/(Loss)			Funds			Other				US GAAP
		Investment									Consolidation			Adjustments
		(dollars in thousands)
	Revenues
	Investment banking	$	—		$	49,562		$	49,562		$	—		$	—			$	49,562
	Brokerage	—			34,349			34,349			—			(1,519		)	(e)	32,830
	Management fees	14,089			—			14,089			(234		)	(4,931		)	(a)	8,924
	Incentive income	4,726			—			4,726			—			(2,228		)	(a)	2,498
	Investment Income	8,328			(156		)	8,172			—			(8,172		)	(c)	—
	Interest and dividends	—			—			—			—			9,252			(c)	9,252
	Reimbursement from affiliates	—			—			—			(80		)	1,980			(b)	1,900
	Other revenue	(43		)	(102		)	(145		)	—			700			(c)	555
	Consolidated Funds revenues	—			—			—			1,156			—				1,156
	Total revenues	27,100			83,653			110,753			842			(4,918		)		106,677
	Expenses
	Employee compensation and benefits	13,387			53,570			66,957			—			604				67,561
	Non-compensation expenses—Fixed	8,894			13,921			22,815			—			(22,815		)	(c)(d)	—
	Non-compensation expenses—Variable	749			8,688			9,437			—			(9,437		)	(c)(d)	—
	Non-compensation expenses	—			—			—			—			31,093			(c)(d)	31,093
	Interest and dividends	609			34			643			—			6,429			(c)	7,072
	Reimbursement from affiliates	(1,726		)	—			(1,726		)	—			1,726			(b)	—
	Consolidated Funds expenses	—			—			—			302			—				302
	Total expenses	21,913			76,213			98,126			302			7,600				106,028
	Other income (loss)
	Net gains (losses) on securities, derivatives and other investments	—			—			—			—			11,354			(c)	11,354
	Consolidated Funds net gains (losses)	—			—			—			207			1,896				2,103
	Total other income (loss)	—			—			—			207			13,250				13,457
	Income (loss) before income taxes and non-controlling interests	5,187			7,440			12,627			747			732				14,106
	Income taxes expense / (benefit)	—			—			—			—			79			(b)	79
	Economic Income (Loss) / Net income (loss) before non-controlling interests	5,187			7,440			12,627			747			653				14,027
	(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	(2,625		)	—			(2,625		)	(747		)	(815		)		(4,187		)
	Economic Income (Loss) / Net Income (loss) attributable to Cowen Group, Inc. stockholders	$	2,562		$	7,440		$	10,002		$	—		$	(162	)		$	9,840
	(1) For the three months ended March 31, 2014, the Company has reflected a minimal amount of investment income and related compensation expense within the broker-dealer segment.
		Three Months Ended March 31, 2013
											Adjustments
		Alternative			Broker-Dealer (1)			Total Economic Income/(Loss)			Funds			Other				US GAAP
		Investment									Consolidation			Adjustments
		(dollars in thousands)
	Revenues
	Investment banking	$	—		$	17,166		$	17,166		$	—		$	—			$	17,166
	Brokerage	—			28,017			28,017			—			(1,417		)	(e)	26,600
	Management fees	14,144			—			14,144			(311		)	(4,340		)	(a)	9,493
	Incentive income	5,126			—			5,126			—			(2,515		)	(a)	2,611
	Investment Income	8,304			2,568			10,872			—			(10,872		)	(c)	—
	Interest and dividends	—			—			—			—			9,321			(c)	9,321
	Reimbursement from affiliates	—			—			—			65			1,420			(b)	1,485
	Other revenue	113			(553		)	(440		)	—			918			(c)	478
	Consolidated Funds revenues	—			—			—			87			—				87
	Total revenues	27,687			47,198			74,885			(159		)	(7,485		)		67,241
	Expenses
	Employee compensation and benefits	13,638			30,608			44,246			—			(23		)		44,223
	Non-compensation expenses—Fixed	9,138			13,265			22,403			—			(22,403		)	(c)(d)	—
	Non-compensation expenses—Variable	1,006			7,720			8,726			—			(8,726		)	(c)(d)	—
	Non-compensation expenses	—			—			—			—			32,037			(c)(d)	32,037
	Interest and dividends	81			43			124			—			6,294			(c)	6,418
	Reimbursement from affiliates	(1,420		)	—			(1,420		)	—			1,420			(b)	—
	Consolidated Funds expenses	—			—			—			434			—				434
	Total expenses	22,443			51,636			74,079			434			8,599				83,112
	Other income (loss)
	Net gains (losses) on securities, derivatives and other investments	—			—			—			—			11,807			(c)	11,807
Consolidated Funds net gains (losses)	—			—			—			2,293			2,866				5,159
Total other income (loss)	—			—			—			2,293			14,673				16,966
Income (loss) before income taxes and non-controlling interests	5,244			(4,438		)	806			1,700			(1,411		)		1,095
Income taxes expense / (benefit)	—			—			—			—			176			(b)	176
Economic Income (Loss) / Net income (loss) before non-controlling interests	5,244			(4,438		)	806			1,700			(1,587		)		919
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	(2,075		)	—			(2,075		)	(1,700		)	280				(3,495		)
Economic Income (Loss) / Net Income (loss) attributable to Cowen Group, Inc. stockholders	$	3,169		$	(4,438	)	$	(1,269	)	$	—		$	(1,307	)		$	(2,576	)
(1) For the three months ended March 31, 2013, the Company has reflected $2.3 million of investment income and related compensation expense of $0.8 million within the broker-dealer segment in proportion to its capital.
The following is a summary of the adjustments made to US GAAP net income (loss) for the segment to arrive at
Economic Income (Loss):
Funds Consolidation: The impacts of consolidation and the related elimination entries of the Consolidated Funds are not included in Economic Income (Loss). Adjustments to reconcile to US GAAP net income (loss) include elimination of incentive income and management fees earned from the Consolidated Funds and addition of fund expenses excluding management fees paid, fund revenues and investment income (loss).
Other Adjustments:
(a)     Economic Income (Loss) recognizes revenues (i) net of distribution fees paid to agents and (ii) our proportionate share
of management and incentive fees of certain real estate operating entities and the activist business.
(b)    Economic Income (Loss) excludes income taxes as management does not consider this item when evaluating the
performance of the segment. Also, reimbursement from affiliates is shown as a reduction of Economic Income
expenses, but is included as a part of revenues under US GAAP.
(c)     Economic Income (Loss) recognizes Company income from proprietary trading net of related expenses.
(d)     Economic Income (Loss) recognizes the Company's proportionate share of expenses for certain real estate and other
operating entities for which the investments are recorded under the equity method of accounting for investments.
(e)    Economic Income (Loss) recognizes stock borrow/loan activity and other brokerage dividends as brokerage revenue.

Organization_and_Business_Deta

Organization and Business (Details)	3 Months Ended
	Mar. 31, 2014
	segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Number of business segments	2

Significant_Accounting_Policie2

Significant Accounting Policies (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified	cowenfund
Organization [Line Items]	'	'
Number of funds, Consolidated	4	'
Deferred rent	$14.10	$14.60
Total net assets of consolidated VIEs	$2.90	$8.20
Investment Company	'	'
Organization [Line Items]	'	'
Number of funds, Consolidated	2	'

Cash_collateral_pledged_Detail

Cash collateral pledged (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Cash and Cash Equivalents [Abstract]	'	'
Cash collateral pledged	$11,269	$10,907

Investments_of_Operating_Entit2

Investments of Operating Entities and Consolidated Funds - Securities Owned at Fair Value (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	$469,378,000		$311,039,000
Other investments	144,147,000		99,483,000
Securities sold, not yet purchased, at fair value	139,347,000		130,954,000
US Government Securities	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Trading Securities, Debt	9,000	[1]	9,000	[1]
Debt securities, interest rate	5.95%		5.95%
Convertible Bonds	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Trading Securities, Debt	11,564,000	[2]	5,958,000	[2]
Convertible Bonds | Minimum	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities, interest rate	4.00%		5.00%
Convertible Bonds | Maximum	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities, interest rate	10.00%		10.00%
Common Stock	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Trading Securities, Equity	270,349,000		176,939,000
Preferred Stock	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Trading Securities, Equity	324,000		324,000
Warrants and Rights	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Trading Securities, Equity	4,265,000		5,912,000
Mutual Funds	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Trading Securities, Equity	15,518,000		525,000
Corporate Bonds	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Trading Securities, Debt	167,349,000	[3]	121,372,000	[3]
Corporate Bonds | Minimum	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities, interest rate	4.74%		3.38%
Corporate Bonds | Maximum	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities, interest rate	12.25%		11.75%
Enterprise Master	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	6,697,000		6,841,000
Derivative, Fair Value, Net	6,000		-21,000
Enterprise Master | Currency Forwards	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Derivative, Fair Value, Net	6,000		-21,000
Enterprise Master | Bank debt	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	5,000		5,000
Enterprise Master | Common Stock	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	2,527,000		2,677,000
Enterprise Master | Preferred Stock	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	973,000		973,000
Enterprise Master | Private Equity	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	409,000		406,000
Enterprise Master | Restricted Stock	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	124,000		124,000
Enterprise Master | Rights	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	2,531,000		2,528,000
Enterprise Master | Trade Claims	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	128,000		128,000
Merger Master	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	75,496,000		48,545,000
Derivative, Fair Value, Net	-243,000		-156,000
Merger Master | Currency Forwards	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Derivative, Fair Value, Net	-4,000		-10,000
Merger Master | Common Stock	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	63,734,000		33,901,000
Merger Master | Options	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	434,000		200,000
Derivative, Fair Value, Net	-155,000		-54,000
Merger Master | Corporate Bonds	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Securities owned, at fair value	11,328,000	[4]	14,444,000	[4]
Merger Master | Corporate Bonds | Minimum	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities, interest rate	8.50%		7.00%
Merger Master | Corporate Bonds | Maximum	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Debt securities, interest rate	10.88%		10.88%
Merger Master | Cross Rate	'		'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'		'
Derivative, Fair Value, Net	($84,000)		($92,000)
[1]	As of MarchB 31, 2014, the maturity was April 2016 with an interest rate of 5.95%. As of DecemberB 31, 2013, the maturity was April 2016 with an interest rate of 5.95%.
[2]	As of MarchB 31, 2014, maturities ranged from June 2014 to November 2014 and interest rates ranged between 4.00% to 10.00%. As of DecemberB 31, 2013, maturities ranged from May 2014 to October 2014 and interest rates ranged between 5.00% to 10.00% .
[3]	As of MarchB 31, 2014, maturities ranged from September 2014 to February 2046 and interest rates ranged between 4.74% and 12.25%. As of DecemberB 31, 2013, maturities ranged from January 2014 to February 2046 and interest rates ranged between 3.38% and 11.75%.
[4]	As of MarchB 31, 2014, maturities ranged from April 2016 to June 2019 and interest rates ranged between 8.50% and 10.88%. As of DecemberB 31, 2013, maturities ranged from April 2016 to October 2020 and interest rates ranged between 7.00% and 10.88%.

Investments_of_Operating_Entit3

Investments of Operating Entities and Consolidated Funds - Derivatives (Details) (USD $)

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 10, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 10, 2014

contract

contract

Futures

Futures

Forward Contracts

Forward Contracts

Cross Rate

Cross Rate

Equity Swaps

Equity Swaps

Options

Options

Put Option

Put Option

Other Income

Other Income

Derivative contracts, at fair value

Derivative contracts, at fair value

Merger Master

Merger Master

Convertible Debt

Receivables from Brokers-Dealers and Clearing Organizations

Receivables from Brokers-Dealers and Clearing Organizations

Derivative [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Fair Value, Net

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

($243,000)

($156,000)

'

Derivative Asset, Fair Value, Gross Asset

'

'

10,075,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Embedded cash conversion value

'

35,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Call Option, Fair Value

'

35,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Warrants issued

15,218,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cost of hedge transaction and warrant, net

'

20,500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Class of Warrant or Right, Number of Securities Called by Warrants or Rights

28,048,786

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Class of Warrant, Exercise Price of Warrants or Rights

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7.18

Derivative Assets

50,076,000

'

10,075,000

53,000

285,000

'

'

10,000

22,000

8,000

70,000

50,005,000

[1]

9,698,000

[1]

'

'

'

'

'

'

'

'

'

Derivative Asset, Fair Value, Amount Offset Against Collateral

0

[2]

'

0

[2]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Asset, Fair Value, Amount Not Offset Against Collateral

0

[3]

'

10,075,000

[3]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative asset, net of offset

0

'

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Liability, Fair Value, Gross Liability

'

'

7,674,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Asset, Number of Instruments Held

62,479

'

71,129

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative liabilities

50,032,000

'

7,674,000

62,000

275,000

28,000

301,000

'

'

735,000

525,000

'

'

49,207,000

[4]

6,573,000

[4]

'

'

'

'

'

'

'

Derivative Liability, Number of Instruments Held

27,745

'

38,221

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Realized and unrealized gains/(losses) related to derivatives trading activities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-1,800,000

-5,200,000

'

'

'

'

'

Collateral posted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

18,100,000

10,000,000

'

'

'

Derivative Liability, Fair Value, Amount Offset Against Collateral

0

[2]

'

0

[2]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Liability, Fair Value, Amount Not Offset Against Collateral

0

[3]

'

7,674,000

[3]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Liability, net of offset

$0

'

$0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Trading days for expiration

'80 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

[1]

As of MarchB 31, 2014 and DecemberB 31, 2013, the Company had 62,479 and 71,129 contracts held, respectively.

[2]

Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.

[3]

Includes the amount of collateral held or posted.

[4]

As of March 31, 2014 and DecemberB 31, 2013, the Company had 27,745 and 38,221 contracts held, respectively.

Investments_of_Operating_Entit4

Investments of Operating Entities and Consolidated Funds - Other Investments (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Investment Holdings [Line Items]	'	'
Other investments	$144,147,000	$99,483,000
Other Investments, Consolidated Funds	179,390,000	187,480,000
Real Estate Equity Investment	'	'
Investment Holdings [Line Items]	'	'
Other investments	42,283,000	2,088,000
Portfolio Funds, at fair value	'	'
Investment Holdings [Line Items]	'	'
Other investments	79,440,000	71,051,000
Other Investments, Consolidated Funds	175,614,000	182,638,000
Equity Method Investments	'	'
Investment Holdings [Line Items]	'	'
Other investments	22,034,000	25,966,000
Lehman claims, at fair value	'	'
Investment Holdings [Line Items]	'	'
Other investments	390,000	378,000
Other Investments, Consolidated Funds	3,776,000	4,842,000
RCG RE Manager, LLC | Real Estate Equity Investment	'	'
Investment Holdings [Line Items]	'	'
Other investments	2,300,000	2,100,000
Merger Fund | Portfolio Funds, at fair value	'	'
Investment Holdings [Line Items]	'	'
Other Investments, Consolidated Funds	32,555,000	26,963,000
Enterprise LP | Portfolio Funds, at fair value	'	'
Investment Holdings [Line Items]	'	'
Other Investments, Consolidated Funds	$143,059,000	$155,530,000

Investments_of_Operating_Entit5

Investments of Operating Entities and Consolidated Funds - Portfolio Funds (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Investment Holdings [Line Items]	'		'	'
Other Investments, Consolidated Funds	$179,390,000		'	$187,480,000
Other investments	144,147,000		'	99,483,000
Portfolio Funds	'		'	'
Investment Holdings [Line Items]	'		'	'
Other Investments, Consolidated Funds	175,614,000		'	182,638,000
Other investments	79,440,000		'	71,051,000
Portfolio Funds | Healthcare Royalty Partners | Affiliated Entity	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	10,784,000	[1],[2]	'	9,741,000	[1],[2]
Portfolio Funds | Healthcare Royalty Partners II | Affiliated Entity	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	6,140,000	[1],[2]	'	4,961,000	[1],[2]
Portfolio Funds | Orchard Square Partners Credit Fund LP | Affiliated Entity	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	13,828,000	[2],[3]	'	12,674,000	[2],[3]
Required notice period, redemption	'60 days		'60 days	'
Penalty on redemptions of less than one year	4.00%		4.00%	'
Portfolio Funds | Starboard Value and Opportunity Fund LP | Affiliated Entity	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	18,439,000	[2],[4]	'	17,495,000	[2],[4]
Required notice period, withdrawal	'90 days		'90 days	'
Portfolio Funds | Formation 8 Partners Fund I LP	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	6,083,000	[5]	'	2,788,000	[5]
Portfolio Funds | RCG LV Park Lane LLC	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	706,000	[6]	'	678,000	[6]
Portfolio Funds | RCGL 12E13th LLC	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	584,000	[7]	'	558,000	[7]
Portfolio Funds | RCGLongview Debt Fund V, L.P.	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	11,856,000	[7]	'	11,979,000	[7]
Portfolio Funds | Other Funds	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	7,785,000	[8]	'	7,772,000	[8]
Portfolio Funds | Other Funds | Affiliated Entity	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	3,235,000	[2],[9]	'	2,405,000	[2],[9]
Portfolio Funds | Enterprise Master	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	145,452,000		'	144,223,000
Portfolio Funds | Enterprise Master | RCG Longview Equity Fund, LP | Affiliated Entity | Real Estate Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	8,949,000	[10]	'	8,470,000	[10]
Portfolio Funds | Enterprise Master | RCG Longview II, LP | Affiliated Entity | Real Estate Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	825,000	[10]	'	800,000	[10]
Portfolio Funds | Enterprise Master | RCG Longview Debt Fund IV, LP | Affiliated Entity | Real Estate Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	15,308,000	[10]	'	17,641,000	[10]
Portfolio Funds | Enterprise Master | RCG Longview, LP | Affiliated Entity | Real Estate Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	467,000	[10]	'	319,000	[10]
Portfolio Funds | Enterprise Master | RCG Soundview, LLC | Affiliated Entity | Real Estate Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	442,000	[10]	'	442,000	[10]
Portfolio Funds | Enterprise Master | RCG Urban American Real Estate Fund, L.P. | Affiliated Entity | Real Estate Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	2,003,000	[10]	'	1,812,000	[10]
Portfolio Funds | Enterprise Master | RCG International Sarl | Affiliated Entity | Multi-strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	1,693,000	[10]	'	1,795,000	[10]
Portfolio Funds | Enterprise Master | RCG Special Opportunities Fund, Ltd | Affiliated Entity | Multi-strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	82,692,000	[10]	'	82,119,000	[10]
Portfolio Funds | Enterprise Master | RCG Endeavour, LLC | Affiliated Entity | Multi-strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	5,000	[10]	'	6,000	[10]
Portfolio Funds | Enterprise Master | RCG Energy, LLC | Affiliated Entity | Energy Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	2,866,000	[10]	'	2,842,000	[10]
Portfolio Funds | Enterprise Master | RCG Renergys, LLC | Affiliated Entity | Energy Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	1,000	[10]	'	1,000	[10]
Portfolio Funds | Enterprise Master | Other Private Investment | Various Strategies	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	13,254,000		'	12,952,000
Portfolio Funds | Enterprise Master | Real Estate Funds | Real Estate Strategy	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	16,947,000		'	15,024,000
Portfolio Funds | Enterprise LP	'		'	'
Investment Holdings [Line Items]	'		'	'
Other Investments, Consolidated Funds	143,059,000		'	155,530,000
Portfolio Funds | Merger Fund	'		'	'
Investment Holdings [Line Items]	'		'	'
Other Investments, Consolidated Funds	32,555,000		'	26,963,000
Portfolio Funds | Consolidated Fund of Funds [Member]	'		'	'
Investment Holdings [Line Items]	'		'	'
Other Investments, Consolidated Funds	0		'	145,000
Real Estate Equity Investment	'		'	'
Investment Holdings [Line Items]	'		'	'
Other investments	$42,283,000		'	$2,088,000
Derivative, Remaining Maturity	'90 days		'	'
[1]	HealthCare Royalty Partners, L.P. and HealthCare Royalty Partners II, L.P. are private equity funds and therefore distributions will be made when cash flows are received from the underlying investments, typically on a quarterly basis.
[2]	These portfolio funds are affiliates of the Company.
[3]	Orchard Square Partners Credit Fund LP (formerly known as Ramius Global Credit FundB LP) has a quarterly redemption policy with a 60 day notice period and a 4% penalty on redemptions of investments of less than a year in duration.
[4]	Starboard Value and Opportunity FundB LP permits quarterly withdrawals upon 90 days notice.
[5]	Formation 8 Partners Fund I is a private equity fund which invests in equity of early stage and growth transformational information and energy technology companies. Distributions will be made when the underlying investments are liquidated.
[6]	RCG LV Park Lane LLC is a single purpose entity formed to participate in a joint venture which acquired, at a discount, the mortgage notes on a portfolio of multifamily real estate properties located in Birmingham, Alabama. RCG LV Park Lane LLC is a private equity structure and therefore distributions will be made when the underlying investments are liquidated.
[7]	RCGL 12E13th LLC and RCG Longview Debt Fund V, L.P. are real estate private equity structures and therefore distributions will be made when the underlying investments are liquidated.
[8]	Other private investment represents the Company's closed end investment in a portfolio fund that invests in a wireless broadband communication provider in Italy.
[9]	The majority of these funds are affiliates of the Company or are managed by the Company and the investors can redeem from these funds as investments are liquidated.
[10]	Affiliates of the Company.

Investments_of_Operating_Entit6

Investments of Operating Entities and Consolidated Funds - Real Estate Investments (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Investment Holdings [Line Items]	'	'
Other investments	$144,147,000	$99,483,000
Real Estate Equity Investment	'	'
Investment Holdings [Line Items]	'	'
Other investments	42,283,000	2,088,000
Mortgage Loans on Real Estate	40,000,000	'
Interest rate basis spread	6.00%	'
RCG RE Manager, LLC | Real Estate Equity Investment	'	'
Investment Holdings [Line Items]	'	'
Other investments	$2,300,000	$2,100,000

Investments_of_Operating_Entit7

Investments of Operating Entities and Consolidated Funds - Equity Method Investments (Details) (USD $)

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

cowenfund

Net Gains (Losses) on Securities, Derivatives and Other Investments

Net Gains (Losses) on Securities, Derivatives and Other Investments

Clawback Obligation

Clawback Obligation

CBOE Stock Exchange, LLC

RCG Longview Partners II, LLC [Member]

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Equity Method Investments

Minimum

Maximum

Clawback Obligation

RCG Longview Debt Fund IV Management, LLC

RCG Longview Debt Fund IV Management, LLC

RCG Longview Debt Fund V Partners, LLC

RCG Longview Debt Fund V Partners, LLC

Healthcare Royalty GP, LLC

Healthcare Royalty GP, LLC

Healthcare Royalty GP II, LLC

Healthcare Royalty GP II, LLC

Healthcare Royalty GP III, LLC

Healthcare Royalty GP III, LLC

CBOE Stock Exchange, LLC

CBOE Stock Exchange, LLC

Starboard Value LP

Starboard Value LP

RCG Longview Partners, LLC

RCG Longview Partners, LLC

RCG Urban American, LLC

RCG Urban American, LLC

RCG Urban American Management, LLC

RCG Urban American Management, LLC

RCG Longview Equity Management, LLC

RCG Longview Equity Management, LLC

Urban American Real Estate Fund II, LLC

Urban American Real Estate Fund II, LLC

RCG Kennedy House, LLC

RCG Kennedy House, LLC

Equity Method Investee, Other

Equity Method Investee, Other

Schedule of Equity Method Investments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Income (Loss) from Equity Method Investments

'

'

$6,500,000

$4,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity Method Investment, Ownership Percentage

'

'

'

'

'

'

9.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

20.00%

55.00%

Equity Method Investment, Number of Entities that Parent Owns a Majority Interest

3

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other Commitment

'

'

'

'

6,200,000

6,200,000

'

6,200,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other investments

$144,147,000

$99,483,000

'

'

'

'

'

'

$22,034,000

$25,966,000

$495,000

$1,533,000

$1,672,000

$1,497,000

$879,000

$794,000

$1,040,000

$840,000

$47,000

$47,000

$1,283,000

$1,351,000

$10,019,000

$14,263,000

$2,692,000

$1,839,000

$346,000

$316,000

$274,000

$238,000

$106,000

$292,000

$2,047,000

$1,785,000

$483,000

$502,000

$651,000

$669,000

'

'

Investments_of_Operating_Entit8

Investments of Operating Entities and Consolidated Funds - Lehman Claims (Details) (USD $)

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Nov. 30, 2013

Jun. 30, 2013

Nov. 30, 2012

Nov. 02, 2012

Sep. 15, 2008

Apr. 30, 2014

Sep. 26, 2013

Feb. 29, 2012

Dec. 31, 2011

Jul. 31, 2010

Jun. 30, 2010

Mar. 31, 2014

Jan. 30, 2014

Feb. 28, 2013

Nov. 30, 2012

Nov. 02, 2012

Sep. 15, 2008

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Jul. 31, 2013

Mar. 31, 2014

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise Master

Enterprise LP

Subsequent Event

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Lehman claims, at fair value

Trust Assets

Foreign Denominated Assets

Cash

Cash

Lehman claims, at fair value

Investment Holdings [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Initial value

'

'

'

'

'

'

'

'

$1,000,000

'

'

'

'

'

'

'

'

'

'

'

$24,300,000

'

'

$4,900,000

$4,900,000

'

Unsecured claim

'

'

'

'

'

'

'

900,000

'

'

'

'

'

'

'

'

'

'

'

1,300,000

'

'

'

'

'

'

Percent of client's Best Claim

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

101.50%

'

'

'

'

'

'

'

'

'

'

Distribution percent withheld for tax

'

'

'

'

'

'

'

'

'

'

30.00%

'

'

'

'

'

30.00%

'

'

'

'

'

'

'

'

'

Value of Best Claim

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200,000

'

'

'

'

'

'

'

'

'

'

Dividend percent received

'

'

'

'

23.70%

43.30%

25.20%

'

'

7.80%

'

'

'

'

'

'

'

'

25.20%

'

'

'

'

'

'

'

Dividend amount received

'

'

'

'

200,000

400,000

200,000

'

'

'

'

'

'

'

'

'

'

'

300,000

'

'

'

'

'

'

'

Total Dividend Amount Received

'

'

900,000

'

'

'

'

'

'

100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total Dividend percent received

'

'

92.20%

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other Investments, Claim Settlement Sold

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,300,000

'

'

'

'

'

'

'

'

Assets returned

'

'

'

'

'

'

'

'

'

'

'

'

2,400,000

'

9,500,000

'

'

'

'

'

'

'

'

'

'

'

Proceeds from sale of returned assets

'

'

'

'

'

'

'

'

'

'

'

'

'

10,700,000

'

'

'

'

'

'

'

'

'

'

'

'

Distributions of proceeds from returned assets

'

'

'

'

'

'

'

'

'

'

14,900,000

2,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Tax Withholding on Distribution of Proceeds from Sale of Returned Assets

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other investments

144,147,000

99,483,000

390,000

378,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other Investments, claim to trust assets held by LBIE through Lehman Brothers

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

10,600,000

'

'

'

'

'

'

'

'

'

'

Percentage of securities liquidated at LBI

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

90.00%

'

'

'

'

'

'

'

'

'

'

Distributions of client's Best Claim

'

'

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

6.00%

'

'

'

'

'

'

'

'

'

Other Investments, initial claim current value

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,800,000

'

'

'

'

'

'

'

'

'

3,800,000

Claim Resolution Agreement fee

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1.00%

1.00%

'

'

'

Other Investments, not within control of LBIE

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$4,400,000

'

'

'

Recoverable claims assigned to variable interest entities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100.00%

'

'

'

'

'

'

'

'

'

'

Percentage of Net Equity Claim

'

'

132.50%

131.50%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Investments_of_Operating_Entit9

Investments of Operating Entities and Consolidated Funds - Securities Sold, Not Yet Purchased (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
Investments Sold, Not yet Purchased [Line Items]	'		'
Securities owned, at fair value	$469,378		$311,039
Securities sold, not yet purchased, at fair value	139,347		130,954
Merger Master	'		'
Investments Sold, Not yet Purchased [Line Items]	'		'
Securities owned, at fair value	75,496		48,545
Corporate Bonds	'		'
Investments Sold, Not yet Purchased [Line Items]	'		'
Securities sold, not yet purchased, at fair value	57	[1]	55	[1]
Securities sold, not yet purchased, interest rate	5.55%		5.55%
Common Stock	'		'
Investments Sold, Not yet Purchased [Line Items]	'		'
Securities sold, not yet purchased, at fair value	139,290		130,899
Common Stock | Merger Master	'		'
Investments Sold, Not yet Purchased [Line Items]	'		'
Securities sold, not yet purchased, at fair value	32,500		19,500
Options | Merger Master	'		'
Investments Sold, Not yet Purchased [Line Items]	'		'
Securities owned, at fair value	434		200
Corporate Bond Securities [Member] | Merger Master	'		'
Investments Sold, Not yet Purchased [Line Items]	'		'
Securities owned, at fair value	11,328	[2]	14,444	[2]
Common Stock | Merger Master	'		'
Investments Sold, Not yet Purchased [Line Items]	'		'
Securities owned, at fair value	$63,734		$33,901
[1]	As of MarchB 31, 2014 and DecemberB 31, 2013, the maturity was January 2026 with an interest rate of 5.55%
[2]	As of MarchB 31, 2014, maturities ranged from April 2016 to June 2019 and interest rates ranged between 8.50% and 10.88%. As of DecemberB 31, 2013, maturities ranged from April 2016 to October 2020 and interest rates ranged between 7.00% and 10.88%.

Recovered_Sheet1

Investments of Operating Entities and Consolidated Funds - Securities Purchased Under Agreements to Resell or Sold Under Agreements to Repurchase (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Assets Purchased Under Agreements to Resell or Sold under Agreements to Repurchase [Line Items]	'	'
Securities Sold under Agreements to Repurchase, Gross	'	$3,657,000
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral	'	0	[1]
Securities sold under agreements to repurchase	0	3,657,000
Securities Sold Under Agreements to Repurchase, Amounts not Offset	'	3,657,000	[2]
Securities sold under agreements to repurchase, net	'	0
Securities Owned at Fair Value	'	'
Assets Purchased Under Agreements to Resell or Sold under Agreements to Repurchase [Line Items]	'	'
Securities pledged by the Company as collateral	'	4,600,000
Maturity on Demand	'	'
Assets Purchased Under Agreements to Resell or Sold under Agreements to Repurchase [Line Items]	'	'
Securities sold under agreements to repurchase	'	3,657,000
Royal Bank of Canada | Maturity on Demand	'	'
Assets Purchased Under Agreements to Resell or Sold under Agreements to Repurchase [Line Items]	'	'
Interest rates on repurchase agreements	'	1.75%
Securities sold under agreements to repurchase	'	$3,657,000
[1]	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
[2]	Includes the amount of collateral held or posted.

Recovered_Sheet2

Investments of Operating Entities and Consolidated Funds - Securities Lending and Borrowing Transactions (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]	'		'
Securities Loaned, Fair Value	$1,300,000,000		$881,700,000
Securities Borrowed, Fair Value	1,300,000,000		892,800,000
Securities borrowed	1,319,938,000		927,773,000
Securities Borrowed, Amount Offset Against Collateral	0	[1]	0	[1]
Securities Borrowed	1,319,938,000		927,773,000
Securities Borrowed, Not Offset against Collateral	1,319,938,000	[2]	927,773,000	[2]
Securities Borrowed, net	0		0
Securities loaned	1,310,903,000		918,577,000
Securities Loaned, Amount Offset Against Collateral	0	[1]	0	[1]
Securities Loaned	1,310,903,000		918,577,000
Securities Loaned, Not Offset Against Collateral	1,310,903,000	[2]	918,577,000	[2]
Securities Loaned, net	$0		$0
[1]	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
[2]	Includes the amount of cash collateral held/posted.

Recovered_Sheet3

Investments of Operating Entities and Consolidated Funds - Variable Interest Entities (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]	'	'
Total assets of nonconsolidated variable interest entities	$2,000,000,000	$1,700,000,000
Total liabilities of nonconsolidated variable interest entities	247,500,000	242,500,000
Variable Interest Entity, Not Primary Beneficiary	'	'
Variable Interest Entity [Line Items]	'	'
Maximum exposure regarding nonconsolidated variable interest entities	$180,600,000	$193,900,000

Fair_Value_Measurements_for_Op2

Fair Value Measurements for Operating Entities and Consolidated Funds Assets and Liabilities at Fair Value on a Recurring Basis (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Securities sold, not yet purchased, at fair value	$139,347,000		$130,954,000
Fair Value, Measurements, Recurring | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	641,567,000		394,631,000
Financial Liabilities Fair Value Disclosure	196,240,000		145,565,000
Fair Value, Measurements, Recurring | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	282,550,000		181,901,000
Financial Liabilities Fair Value Disclosure	145,703,000		137,747,000
Fair Value, Measurements, Recurring | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	200,080,000		146,977,000
Financial Liabilities Fair Value Disclosure	820,000		881,000
Fair Value, Measurements, Recurring | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	158,937,000		65,753,000
Financial Liabilities Fair Value Disclosure	49,717,000		6,937,000
Fair Value, Measurements, Recurring | Common Stock | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	139,290,000		130,899,000
Fair Value, Measurements, Recurring | Common Stock | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	139,290,000		130,899,000
Fair Value, Measurements, Recurring | Common Stock | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Common Stock | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Corporate Bonds | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	57,000		55,000
Fair Value, Measurements, Recurring | Corporate Bonds | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Corporate Bonds | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	57,000		55,000
Fair Value, Measurements, Recurring | Corporate Bonds | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Contingent liability payable | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	6,861,000	[1]	6,937,000
Fair Value, Measurements, Recurring | Contingent liability payable | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0	[1]	0
Fair Value, Measurements, Recurring | Contingent liability payable | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0	[1]	0
Fair Value, Measurements, Recurring | Contingent liability payable | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	6,861,000	[1]	6,937,000
Fair Value, Measurements, Recurring | Futures | Derivative Liabilities | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	62,000		275,000
Fair Value, Measurements, Recurring | Futures | Derivative Liabilities | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	62,000		275,000
Fair Value, Measurements, Recurring | Futures | Derivative Liabilities | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Futures | Derivative Liabilities | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Forward Contracts | Derivative Liabilities | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	28,000		301,000
Fair Value, Measurements, Recurring | Forward Contracts | Derivative Liabilities | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Forward Contracts | Derivative Liabilities | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	28,000		301,000
Fair Value, Measurements, Recurring | Forward Contracts | Derivative Liabilities | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Equity Swaps | Derivative Liabilities | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	735,000		525,000
Fair Value, Measurements, Recurring | Equity Swaps | Derivative Liabilities | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Equity Swaps | Derivative Liabilities | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	735,000		525,000
Fair Value, Measurements, Recurring | Equity Swaps | Derivative Liabilities | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Options | Derivative Liabilities | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	49,207,000		6,573,000
Fair Value, Measurements, Recurring | Options | Derivative Liabilities | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	6,351,000		6,573,000
Fair Value, Measurements, Recurring | Options | Derivative Liabilities | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring | Options | Derivative Liabilities | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Financial Liabilities Fair Value Disclosure	42,856,000		0
Fair Value, Measurements, Recurring | US Government Securities | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	9,000		9,000
Fair Value, Measurements, Recurring | US Government Securities | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	9,000		9,000
Fair Value, Measurements, Recurring | US Government Securities | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | US Government Securities | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Preferred Stock | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	324,000		324,000
Fair Value, Measurements, Recurring | Preferred Stock | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Preferred Stock | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Preferred Stock | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	324,000		324,000
Fair Value, Measurements, Recurring | Common Stock | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	270,349,000		176,939,000
Fair Value, Measurements, Recurring | Common Stock | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	258,824,000		171,277,000
Fair Value, Measurements, Recurring | Common Stock | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	2,242,000		2,103,000
Fair Value, Measurements, Recurring | Common Stock | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	9,283,000		3,559,000
Fair Value, Measurements, Recurring | Convertible Bonds | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	11,564,000		5,958,000
Fair Value, Measurements, Recurring | Convertible Bonds | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Convertible Bonds | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	9,614,000		4,008,000
Fair Value, Measurements, Recurring | Convertible Bonds | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	1,950,000		1,950,000
Fair Value, Measurements, Recurring | Corporate Bonds | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	167,349,000		121,372,000
Fair Value, Measurements, Recurring | Corporate Bonds | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Corporate Bonds | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	167,349,000		121,372,000
Fair Value, Measurements, Recurring | Corporate Bonds | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Warrants and Rights | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	4,265,000		5,912,000
Fair Value, Measurements, Recurring | Warrants and Rights | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	997,000		107,000
Fair Value, Measurements, Recurring | Warrants and Rights | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Warrants and Rights | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	3,268,000		5,805,000
Fair Value, Measurements, Recurring | Mutual Funds | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	15,518,000		525,000
Fair Value, Measurements, Recurring | Mutual Funds | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	15,518,000		525,000
Fair Value, Measurements, Recurring | Mutual Funds | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Mutual Funds | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	53,000		285,000
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	53,000		285,000
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Derivative Assets | Forward Contracts | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	10,000		22,000
Fair Value, Measurements, Recurring | Derivative Assets | Forward Contracts | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Derivative Assets | Forward Contracts | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	10,000		22,000
Fair Value, Measurements, Recurring | Derivative Assets | Forward Contracts | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Derivative Assets | Equity Swaps | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	8,000		70,000
Fair Value, Measurements, Recurring | Derivative Assets | Equity Swaps | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Derivative Assets | Equity Swaps | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	8,000		70,000
Fair Value, Measurements, Recurring | Derivative Assets | Equity Swaps | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Derivative Assets | Options | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	50,005,000		9,698,000
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	7,149,000		9,698,000
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	42,856,000		0
Fair Value, Measurements, Recurring | Portfolio Funds, at fair value | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	79,440,000		71,051,000
Fair Value, Measurements, Recurring | Portfolio Funds, at fair value | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Portfolio Funds, at fair value | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	20,857,000		19,402,000
Fair Value, Measurements, Recurring | Portfolio Funds, at fair value | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	58,583,000		51,649,000
Fair Value, Measurements, Recurring | Real Estate Investments, at fair value | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	42,283,000		2,088,000
Fair Value, Measurements, Recurring | Real Estate Investments, at fair value | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Real Estate Investments, at fair value | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Real Estate Investments, at fair value | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	42,283,000		2,088,000
Fair Value, Measurements, Recurring | Lehman claims, at fair value | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	390,000		378,000
Fair Value, Measurements, Recurring | Lehman claims, at fair value | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Lehman claims, at fair value | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Fair Value, Measurements, Recurring | Lehman claims, at fair value | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	390,000		378,000
Consolidated Funds | Fair Value, Measurements, Recurring | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	179,390,000		187,480,000
Consolidated Funds | Fair Value, Measurements, Recurring | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Fair Value, Measurements, Recurring | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	32,555,000		26,964,000
Consolidated Funds | Fair Value, Measurements, Recurring | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	146,835,000		160,516,000
Consolidated Funds | Fair Value, Measurements, Recurring | Portfolio Funds, at fair value | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	175,614,000		182,638,000
Consolidated Funds | Fair Value, Measurements, Recurring | Portfolio Funds, at fair value | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Fair Value, Measurements, Recurring | Portfolio Funds, at fair value | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	32,555,000		26,964,000
Consolidated Funds | Fair Value, Measurements, Recurring | Portfolio Funds, at fair value | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	143,059,000		155,674,000
Consolidated Funds | Fair Value, Measurements, Recurring | Lehman claims, at fair value | Total Estimated Fair Value	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	3,776,000		4,842,000
Consolidated Funds | Fair Value, Measurements, Recurring | Lehman claims, at fair value | Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Fair Value, Measurements, Recurring | Lehman claims, at fair value | Level 2	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Fair Value, Measurements, Recurring | Lehman claims, at fair value | Level 3	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Assets, Fair Value Disclosure, Recurring	3,776,000		4,842,000
ATM Group and Cowen Equity Finance LP [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low	'		3,500,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	'		$13,000,000
[1]	In accordance with the terms of purchase agreements from acquisitions that closed during 2012, the Company is required to pay to certain sellers a portion of future net profits of the acquired businesses, if certain revenue targets are achieved over the period through October 2016. The Company estimated the contingent consideration using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts can range from $3.5 million to $13.0 million.

Fair_Value_Measurements_for_Op3

Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013		Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$305,772,000	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	49,717,000	'		'	'
Preferred Stock	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	324,000	2,332,000		324,000	2,332,000
Asset, Transfers In	0	0		'	'
Asset, Transfers Out	0	0		'	'
Purchases/(covers)	0	0		'	'
(Sales)/short buys	0	0		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	0		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	0	0		'	'
Common Stock	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	9,283,000	2,278,000		3,559,000	2,549,000
Asset, Transfers In	0	0		'	'
Asset, Transfers Out	0	0		'	'
Purchases/(covers)	0	0		'	'
(Sales)/short buys	0	-265,000		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	260,000		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	5,724,000	-266,000		'	'
Corporate Bonds	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	'	0		'	515,000
Asset, Transfers In	'	0		'	'
Asset, Transfers Out	'	0		'	'
Purchases/(covers)	'	2,735,000		'	'
(Sales)/short buys	'	-3,346,000		'	'
Asset, Realized Gain (Loss) Included in Earnings	'	-914,000		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	'	1,010,000		'	'
Call Options	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	42,856,000	'		0	'
Asset, Transfers In	0	'		'	'
Asset, Transfers Out	0	'		'	'
Purchases/(covers)	35,710,000	'		'	'
(Sales)/short buys	0	'		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	'		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	7,146,000	'		'	'
Put Option	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	42,856,000	'		0	'
Asset, Transfers In	0	'		'	'
Asset, Transfers Out	0	'		'	'
Purchases/(covers)	35,710,000	'		'	'
(Sales)/short buys	0	'		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	'		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	7,146,000	'		'	'
Convertible Bonds	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	1,950,000	'		1,950,000	'
Asset, Transfers In	0	'		'	'
Asset, Transfers Out	0	'		'	'
Purchases/(covers)	0	'		'	'
(Sales)/short buys	0	'		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	'		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	0	'		'	'
Warrants and Rights	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	3,268,000	3,243,000		5,805,000	1,713,000
Asset, Transfers In	0	290,000	[1]	'	'
Asset, Transfers Out	0	0		'	'
Purchases/(covers)	0	166,000		'	'
(Sales)/short buys	-1,328,000	-110,000		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	0		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	-1,209,000	1,184,000		'	'
Portfolio Funds, at fair value	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	58,583,000	25,559,000		51,649,000	25,670,000
Asset, Transfers In	0	0		'	'
Asset, Transfers Out	0	0		'	'
Purchases/(covers)	4,385,000	3,590,000		'	'
(Sales)/short buys	-1,242,000	-3,876,000		'	'
Asset, Realized Gain (Loss) Included in Earnings	180,000	8,000		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	3,611,000	167,000		'	'
Real Estate Investments, at fair value	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	42,283,000	1,875,000		2,088,000	1,864,000
Asset, Transfers In	0	0		'	'
Asset, Transfers Out	0	0		'	'
Purchases/(covers)	40,000,000	0		'	'
(Sales)/short buys	-27,000	0		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	0		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	222,000	11,000		'	'
Lehman claims, at fair value	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	390,000	660,000		378,000	706,000
Asset, Transfers In	0	0		'	'
Asset, Transfers Out	0	0		'	'
Purchases/(covers)	0	0		'	'
(Sales)/short buys	0	0		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	0		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	12,000	-46,000		'	'
Consolidated Funds | Portfolio Funds, at fair value	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	143,059,000	178,357,000		155,674,000	182,920,000
Asset, Transfers In	0	0		'	'
Asset, Transfers Out	0	0		'	'
Purchases/(covers)	0	0		'	'
(Sales)/short buys	-15,944,000	-7,031,000		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	222,000		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	3,329,000	2,246,000		'	'
Consolidated Funds | Lehman claims, at fair value	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	3,776,000	15,140,000		4,842,000	14,124,000
Asset, Transfers In	0	0		'	'
Asset, Transfers Out	0	0		'	'
Purchases/(covers)	0	0		'	'
(Sales)/short buys	-980,000	-1,449,000		'	'
Asset, Realized Gain (Loss) Included in Earnings	0	1,360,000		'	'
Asset, Unrealized Gain (Loss) Included in Earnings	-86,000	1,105,000		'	'
Warrants and Rights, sold not yet purchased	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	'	3,000		'	3,000
Liability, Transfers In	'	0		'	'
Liability, Transfers Out	'	0		'	'
Liability, Purchases	'	0		'	'
Liability, Sales	'	0		'	'
Liability, Realized Gain (Loss), Included in Earnings	'	0		'	'
Liability, Unrealized Gain (Loss) Included in Earnings	'	0		'	'
Contingent liability payable	'	'		'	'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]	'	'		'	'
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	6,861,000	8,116,000		6,937,000	8,116,000
Liability, Transfers In	0	0		'	'
Liability, Transfers Out	0	0		'	'
Liability, Purchases	-76,000	0		'	'
Liability, Sales	0	0		'	'
Liability, Realized Gain (Loss), Included in Earnings	0	0		'	'
Liability, Unrealized Gain (Loss) Included in Earnings	0	0		'	'
ATM Group and Cowen Equity Finance LP [Member]	'	'		'	'
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'	'		'	'
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low	'	'		$3,500,000	'
[1]	The security was acquired through an acquisition (See Note 2).

Fair_Value_Measurements_for_Op4

Fair Value Measurements for Operating Entities and Consolidated Funds Fair Value Inputs, Unobservable Inputs, Quantitative Information (Details) (USD $)

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

In Thousands, unless otherwise specified

Options

Options

Options

Contingent liability payable

Contingent liability payable

Contingent liability payable

Contingent liability payable

Contingent liability payable

Contingent liability payable

Other Investments [Member]

Options

Options

Options

Warrants and Rights

Warrants and Rights

Warrants and Rights

Warrants and Rights

Warrants and Rights

Warrants and Rights

Warrants and Rights

Common and Preferred Stock

Common and Preferred Stock

Common and Preferred Stock

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Level 3

Market Approach Valuation Technique

Market Approach Valuation Technique

Income Approach and Market Approach Valuation Techniques

Income Approach and Market Approach Valuation Techniques

Market Approach Valuation Technique

Market Approach Valuation Technique

Market Approach Valuation Technique

Market Approach Valuation Technique

Market Approach Valuation Technique

Income Approach and Market Approach Valuation Techniques

Income Approach and Market Approach Valuation Techniques

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value

$305,772

'

'

'

'

'

'

'

'

'

$250,450

$42,856

'

'

$3,268

$5,805

$3,243

$1,713

'

'

'

$9,198

'

'

DCF discount rate

'

'

'

'

'

'

'

'

0.00%

9.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Market multiple

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

3

Volatility

'

'

30.00%

45.00%

'

'

'

'

'

'

'

'

30.00%

45.00%

'

'

'

'

'

20.00%

100.00%

'

'

'

Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value

$49,717

$42,856

'

'

$6,861

$6,937

$8,116

$8,116

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fair Value Assumptions, Weighted Average Volatility Rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

36.00%

'

'

'

'

'

Fair Value Assumptions, Credit Spread

'

'

6.00%

7.50%

'

'

'

'

'

'

'

'

6.00%

7.50%

'

'

'

'

'

'

'

'

'

'

Receivables_from_and_Payable_t1

Receivables from and Payable to Brokers (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Brokers and Dealers [Abstract]	'	'
Receivable from brokers	$56,946	$66,980
Payable to brokers	$151,109	$75,420

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets Goodwill Details (Details) (Dahlman Rose & Company, LLC, USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2013
Dahlman Rose & Company, LLC	'
Goodwill [Line Items]	'
Goodwill, Other Changes	$8.70

Redeemable_NonControlling_Inte2

Redeemable Non-Controlling Interests in Consolidated Subsidiaries (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Noncontrolling Interest [Line Items]	'	'	'
Redeemable non-controlling interests in consolidated subsidiaries	$85,448	'	$85,814
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	4,187	3,495	'
Operating Entities	'	'	'
Noncontrolling Interest [Line Items]	'	'	'
Redeemable non-controlling interests in consolidated subsidiaries	10,840	'	12,009
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	3,439	1,795	'
Consolidated Funds	'	'	'
Noncontrolling Interest [Line Items]	'	'	'
Redeemable non-controlling interests in consolidated subsidiaries	74,608	'	73,805
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	$748	$1,700	'

ShareBased_Compensation_and_Em2

Share-Based Compensation and Employee Ownership Plans Narrative (Details) (Equity Plans, USD $)

3 Months Ended

3 Months Ended

3 Months Ended

In Millions, except Share data, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Employee Stock Option

Employee Stock Option

Employee Stock Option

Restricted Shares and Restricted Stock Units (RSUs)

Restricted Shares and Restricted Stock Units (RSUs)

Stock Appreciation Rights (SARs)

Stock Appreciation Rights (SARs)

Restricted Stock

Restricted Stock

Restricted Stock Units (RSUs)

Minimum

Maximum

Minimum

Maximum

Non-employee Director

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Unrecognized compensation expense

'

'

'

'

'

$51.20

'

$0.30

$0.30

'

'

'

Shares authorized under compensation plan, in shares

17,725,000

'

'

'

'

'

'

'

'

'

'

'

Stock compensation award, vesting period

'

'

'

'2 years

'5 years

'

'

'

'

'2 years

'5 years

'

Stock options, initial term

'

'

'7 years

'

'

'

'

'

'

'

'

'

SAR's, initial term

'

'

'

'

'

'

'

'5 years

'

'

'

'

Shares available for issuance under compensation plan, in shares

1,600,000

'

'

'

'

'

'

'

'

'

'

'

Stock-compensation expense recognized in connection with compensation plan

'

4.8

'

'

'

'

'

'

'

'

'

'

Tax benefit of stock-compensation expense recognized in connection with compensation plan

$1

$2

'

'

'

'

'

'

'

'

'

'

Vested, shares

'

'

'

'

'

1,652,652

'

0

'

'

'

102,400

Granted, shares

'

'

'

'

'

'

'

'

'

'

'

0

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number

'

'

'

'

'

19,536,039

13,551,544

400,000

400,000

'

'

380,122

ShareBased_Compensation_and_Em3

Share-Based Compensation and Employee Ownership Plans Deferred Compensation (Details) (Cowen Group, Inc. 2010 Equity and Incentive Plan, USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Deferred Cash Award	'
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]	'
Deferred cash awards granted	29
Deferred cash awards, unrecognized compensation expense	49.8
Maximum | Deferred Cash Award	'
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]	'
Deferred cash award, interest rate	0.75%
Minimum | Deferred Cash Award	'
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]	'
Deferred cash award, interest rate	0.70%
Deferred Cash Award	'
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]	'
Deferred cash awards, vesting period	'5 years

ShareBased_Compensation_and_Em4

Share-Based Compensation and Employee Ownership Plans Stock Options (Details) (USD $)	3 Months Ended		12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0.00%		'
Weighted Average Exercise Price/Share	'		'
Weighted average remaining term, options outstanding	'2 years 1 month 28 days		'2 years 4 months 24 days
Weighted average remaining term, options exercisable	'2 years 1 month 28 days		'
Aggregate Intrinsic Value	'		'
Closing stock price, in dollars per share	$4.41		$3.91
Equity Plans	'		'
Shares Subject to Option	'		'
Balance outstanding, beginning of period, shares	300,006		'
Options granted, shares	0		'
Options acquired, shares	0		'
Options expired, shares	0		'
Balance outstanding, end of period, shares	300,006		'
Options exercisable, shares	300,006		'
Weighted Average Exercise Price/Share	'		'
Balance outstanding, beginning of period, in dollars per share	$7.19		'
Options granted, in dollars per share	$0		'
Options acquired, in dollars per share	$0		'
Options expired, in dollars per share	$0		'
Balance outstanding, end of period, in dollars per share	$7.19		'
Options exercisable, in dollars per share	$7.19		'
Aggregate Intrinsic Value	'		'
Balance outstanding, beginning of period	$0	[1]	'
Balance outstanding, end of period	0	[1]	'
Options exercisable	$0	[1]	'
[1]	Based on the Company's closing stock price of $4.41 on MarchB 31, 2014 and $3.91 on DecemberB 31, 2013.

ShareBased_Compensation_and_Em5

Share-Based Compensation and Employee Ownership Plans SARs (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Weighted Average Exercise Price/Share	'		'
Closing stock price, in dollars per share	$4.41		$3.91
Equity Plans	'		'
Weighted Average Exercise Price/Share	'		'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$0	[1]	'
Equity Plans | Stock Appreciation Rights (SARs)	'		'
Shares Subject to Option	'		'
Balance outstanding, beginning of period, shares	400,000		'
Granted, shares	0		'
Acquired, shares	0		'
Expired, shares	0		'
Balance outstanding, end of period, shares	400,000		400,000
Balance exercisable, shares	0		'
Weighted Average Exercise Price/Share	'		'
Balance outstanding, beginning of period, in dollars per share	$2.90		'
Granted, in dollars per share	$0		'
Acquired, in dollars per share	$0		'
Expired, in dollars per share	$0		'
Balance outstanding, end of period, in dollars per share	$2.90		$2.90
Balance exercisable, in dollars per share	$0		'
Weighted Average Remaining Term Outstanding	'3 years 11 months 16 days		'4 years 2 months 16 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	864,000	[1]	608,000	[1]
Unrecognized compensation expense	$300,000		$300,000
[1]	Based on the Company's closing stock price of $4.41 on MarchB 31, 2014 and $3.91 on DecemberB 31, 2013.

ShareBased_Compensation_and_Em6

Share-Based Compensation and Employee Ownership Plans Restricted Shares and Restricted Stock Units (Details) (Equity Plans, USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2014		Mar. 31, 2014
		Restricted Shares and Restricted Stock Units (RSUs)		Performance Shares [Member]
Nonvested Restricted Shares and Restricted Stock Units	'	'		'
Balance outstanding, beginning of period, shares	'	13,551,544		'
Granted, shares	'	7,694,398	[1]	1,220,750
Vested, shares	'	-1,652,652		'
Cancelled, shares	'	0		'
Forfeited, shares	'	-57,251		'
Balance outstanding, end of period, shares	'	19,536,039		'
Weighted-Average Grant Date Fair Value	'	'		'
Balance outstanding, beginning of period, in dollars per share	'	$3.37		'
Granted, in dollars per share	'	$3.78	[1]	'
Vested, in dollars per share	'	$2.84		'
Cancelled, in dollars per share	'	$0		'
Forfeited, in dollars per share	'	$3.21		'
Balance outstanding, end of period, in dollars per share	'	$3.58		'
Unrecognized compensation expense	'	$51.20		'
Weighted-average recognition period for unrecognized compensation expense	'	'2 years 0 months 11 days		'
Allocated Share-based Compensation Expense	$4.80	'		'
[1]	On January 16, 2014, the Company awarded 1,220,750 performance linked restricted stock units to employees of the Company. The awards will vest on June 10, 2019 and will be earned only to the extent that the Company attains specified performance goals relating its volume-weighted average share price and the aggregate net income for the years from 2014 to 2018. The actual number of RSUs ultimately earned could vary from zero, if performance goals are not met, to as much as 100% of the targeted award. Each RSU is equal to the one share of the Companybs Class A common stock.

Defined_Benefit_Plans_Defined_

Defined Benefit Plans Defined Benefit Plans Interim Disclosures (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Defined Benefit Plans Interim Disclosures [Abstract]	'	'
Service cost	$0	$0
Interest cost	33	51
Defined Benefit Plan, Expected Return on Plan Assets	66	63
Defined Benefit Plan, Amortization of Gains (Losses)	0	0
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0	5
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments	0	0
Effect of special termination benefits	0	0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements	0	0
Defined Benefit Plan, Net Periodic Benefit Cost	($33)	($7)

Income_Taxes_Unrecognized_Tax_

Income Taxes Unrecognized Tax Benefits (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Income Tax Disclosure [Abstract]	'	'
Undistributed Earnings of Foreign Subsidiaries	$1.50	$2.30
Tax Liabilities, Undistributed Foreign Earnings	$0.20	$0.30

Income_Taxes_Income_Tax_Rate_R

Income Taxes Income Tax Rate Reconciliation Interim Disclosure (Details)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Abstract]	'	'
Effective Income Tax Rate, Percent	-0.56%	16.07%
Statutory rate, Percent	35.00%	35.00%

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)

3 Months Ended

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Apr. 30, 2013

Mar. 31, 2014

Mar. 31, 2014

Affiliated Entity

Healthcare Royalty Partners

Starboard Leaders Fund LP

Formation 8 Partners Fund I LP

Equipment Leases

Service Payments

Facility Leases [Member]

Clawback Obligation [Member]

Clawback Obligation [Member]

Commitment to Invest

Commitment to Invest

Commitment to Invest

Commitment to Invest

Unfunded Commitments

Affiliated Entity

Affiliated Entity

Affiliated Entity

Healthcare Royalty Partners

Healthcare Royalty Partners

Starboard Leaders Fund LP

Formation 8 Partners Fund I LP

cowenfund

Affiliated Entity

Affiliated Entity

Affiliated Entity

Affiliated Entity

Minimum

Maximum

Lease Obligations

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net rent expense

$4,200,000

$3,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Future minimum annual lease and service payments

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual Obligation, Due in Remainder of Fiscal Year

'

'

'

'

'

'

2,181,000

[1]

9,036,000

13,848,000

[2]

'

'

'

'

'

'

'

Contractual Obligation, Due in Second Year

'

'

'

'

'

'

2,603,000

[1]

7,667,000

17,789,000

[2]

'

'

'

'

'

'

'

Contractual Obligation, Due in Third Year

'

'

'

'

'

'

2,284,000

[1]

3,367,000

14,698,000

[2]

'

'

'

'

'

'

'

Contractual Obligation, Due in Fourth Year

'

'

'

'

'

'

2,198,000

[1]

2,714,000

11,587,000

[2]

'

'

'

'

'

'

'

Contractual Obligation, Due in Fifth Year

'

'

'

'

'

'

2,198,000

[1]

2,609,000

11,296,000

[2]

'

'

'

'

'

'

'

Contractual Obligation, Due after Fifth Year

'

'

'

'

'

'

813,000

[1]

22,000

41,601,000

[2]

'

'

'

'

'

'

'

Future minimum annual lease and service payments

'

'

'

'

'

'

12,277,000

[1]

25,415,000

110,819,000

[2]

'

'

'

'

'

'

'

Sublease income related to operating leases

300,000

300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Contractual obligation

'

'

'

42,400,000

'

'

'

'

'

6,200,000

6,200,000

'

'

1,000,000

'

'

Number of real estate investments, in investments

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4

Expected call period

'

'

'

'

'

'

'

'

'

'

'

'2 years

'5 years

'

'

'

Funding toward commitments

'

'

'

31,700,000

600,000

'

'

'

'

'

'

'

'

'

'

'

Other commitments, unfunded amount

'

'

$13,800,000

'

'

$5,000,000

'

'

'

'

'

'

'

'

'

'

Term of capital commitment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'4 years

'

[1]

Equipment Leases include the Company's commitments relating to operating and capital leases. See NoteB 14 for further information on the capital lease minimum payments which are included in the table.

[2]

The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $0.3 million and $0.3 million for the three months ended MarchB 31, 2014 and 2013.

Convertible_Debt_and_Short_Ter1

Convertible Debt and Short Term Borrowings (Details) (USD $)

3 Months Ended

40 Months Ended

3 Months Ended

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Jan. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 10, 2014

Mar. 31, 2014

Jan. 30, 2014

letters_of_credit

Minimum

Maximum

Transaction [Domain]

Treasury Stock

Letter of Credit, NY Office, Expires June 2014 [Member]

Letter of Credit, NY Office, Expires February 2014 [Member]

Letter of Credit, NY Office, Expires December 2014 [Member]

Letter of Credit, NY Office, Expires September 2014 [Member]

Letter of Credit, Boston Office, Expires March 2015 [Member] [Member]

Letter of Credit, San Francisco Office, Expires May 2014 [Member]

Convertible Debt

Convertible Debt

Insurance Note

Insurance Note

Letter of Credit

Letter of Credit

Letter of Credit

Letter of Credit

Letter of Credit

Letter of Credit

Debt and Capital Lease Obligations [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of Letters of Credit

6

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Components of short-term borrowings and other debt

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Convertible debt

$114,101,000

'

'

$0

'

'

'

'

'

'

'

'

'

'

$114,101,000

'

'

'

Notes payable

1,428,000

'

'

41,000

'

'

'

'

'

'

'

'

'

'

'

'

1,428,000

2,000,000

Capital lease obligations

4,956,000

'

'

2,523,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt, Long-term and Short-term, Combined Amount

120,485,000

'

'

2,564,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Instrument, Unamortized Premium

'

'

'

'

'

'

'

'

'

'

'

'

'

'

35,400,000

'

'

'

Interest rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3.00%

'

1.55%

Debt Instrument, Face Amount

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

149,500,000

'

'

Interest on Convertible Debt, Net of Tax

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200,000

'

'

'

Principal amount of notes being converted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000

'

'

Debt Instrument, Convertible, Conversion Price

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$5.33

'

'

Discount on debt

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

35,700,000

'

'

Amortization of Debt Discount

311,000

0

'

'

'

'

'

'

'

'

'

'

'

'

300,000

'

'

'

Debt Instrument, Interest Rate, Effective Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

8.89%

'

'

Debt Instrument, Fair Value Disclosure

160,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Debt Issuance Cost

'

'

'

'

'

'

'

'

'

'

'

'

'

'

3,600,000

'

'

'

Cash convertible note hedge transaction

149,500,000

0

'

'

'

'

20,500,000

300,000

'

'

'

'

'

'

'

'

'

'

Class of Warrant, Exercise Price of Warrants or Rights

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7.18

'

'

Monthly payment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200,000

'

Capital Lease Obligations Incurred

'

'

7,600,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Lease Obligation, Initial Term

'

'

'

'

'48 months

'60 months

'

'

'

'

'

'

'

'

'

'

'

'

Capital leases, interest rate

'

'

'

'

0.60%

6.03%

'

'

'

'

'

'

'

'

'

'

'

'

Capital lease interest expense

100,000

100,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Letter of credit, borrowing capacity

'

'

'

'

'

'

'

'

1,861,000

1,000,000

6,746,000

1,191,000

382,000

82,000

'

'

'

'

Future minimum lease payments for capital lease obligations

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital leases, Future Minimum Payments Due, Remainder of Fiscal Year

1,236,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Leases, Future Minimum Payments Due in Two Years

1,343,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Leases, Future Minimum Payments Due in Three Years

1,025,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Leases, Future Minimum Payments Due in Four Years

938,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Leases, Future Minimum Payments Due in Five Years

938,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Leases, Future Minimum Payment Due Thereafter

79,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Subtotal

5,559,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Less: Amount representing interest

-603,000

[1]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital lease obligations

4,956,000

'

'

2,523,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Repayments on long-term and short-term borrowings

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Notes Payable, Repayments Due Remainder of Fiscal Year

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,284,000

'

1,448,000

'

Notes Payable, Repayments in Year Two

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4,411,000

'

0

'

Notes Payable, Repayments in Year Three

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4,411,000

'

0

'

Notes Payable, Repayments in Year Four

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4,411,000

'

0

'

Notes Payable, Repayments in Year Five

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4,411,000

'

0

'

Notes Payable, Repayments Due after Year Five

'

'

'

'

'

'

'

'

'

'

'

'

'

'

151,688,000

'

0

'

Subtotal

'

'

'

'

'

'

'

'

'

'

'

'

'

'

171,616,000

'

1,448,000

'

Less: Amount representing interest

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-57,515,000

[1]

'

-20,000

[1]

'

Notes payable

$1,428,000

'

'

$41,000

'

'

'

'

'

'

'

'

'

'

'

'

$1,428,000

$2,000,000

[1]

Amount necessary to reduce net minimum payments to present value calculated at the Company's implicit rate at inception

Treasury_Stock_Treasury_Stock_

Treasury Stock Treasury Stock Interim Disclosure (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Equity, Class of Stock [Line Items]	'	'	'
Treasury Stock, Value	$53,415	'	$48,084
Shares purchased for minimum tax withholding, cost	1,919	177	'
Treasury Stock, Shares	17,136,430	'	15,873,549
Treasury Stock	'	'	'
Equity, Class of Stock [Line Items]	'	'	'
Treasury Stock, Average Price Per Share	$3.12	'	$3.03
Shares Paid for Tax Withholding for Share Based Compensation	452,809	'	'
Shares purchased for minimum tax withholding, cost	1,920	'	'
Shares Paid for Tax Withholding for Share Based Compensation, Average Cost Per Share	$4.24	'	'
Treasury Stock, Shares, Acquired, Cost Method, Excluding Adjustments Related to Tax Withholding for Share-based Compensation	810,072	'	'
Purchase of treasury stock, cost	$3,411	'	'
Treasury Stock Acquired, Average Cost Per Share	$4.21	'	'

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013		Dec. 31, 2013		Dec. 31, 2012
Accumulated Other Comprehensive Income / (Loss) [Abstract]	'		'		'		'
Foreign Currency Translations	$285	[1]	$254	[1]	$248	[1]	$258	[1]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	37	[1]	-4	[1]	'		'
Defined Benefit Plans	252	[1]	81	[1]	344	[1]	98	[1]
Total defined benefit pension plan	92	[1]	17	[1]	'		'
Other Comprehensive Income (Loss), Net of Tax	-55		-21		'		'
Accumulated other comprehensive income (loss)	$537		$335		$592		$356
[1]	During the periods presented, the Company did not have material reclassifications out of other comprehensive income.

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Warrants and Rights

Warrants and Rights

Stock Options

Stock Options

Stock Appreciation Rights (SARs)

Stock Appreciation Rights (SARs)

Restricted Stock

Restricted Stock

Common Stock Class A

Common Stock Class A

Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares outstanding, shares

'

'

'

'

'

'

'

'

'

'

115,352,546

115,026,633

Common stock, restricted shares, shares

'

'

'

'

'

'

'

'

'

'

380,122

482,522

Computation of earnings per share:

'

'

'

'

'

'

'

'

'

'

'

'

Net income (loss)

$14,027,000

$919,000

'

'

'

'

'

'

'

'

'

'

Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds

4,187,000

3,495,000

'

'

'

'

'

'

'

'

'

'

Net income (loss) attributable to Cowen Group, Inc. stockholders

$9,840,000

($2,576,000)

'

'

'

'

'

'

'

'

'

'

Shares for basic and diluted calculations:

'

'

'

'

'

'

'

'

'

'

'

'

Weighted average shares used in basic computation, shares

115,680,000

113,798,000

'

'

'

'

'

'

'

'

'

'

Shares attributable to share-based payment awards, shares

'

'

0

0

0

0

54,000

0

7,164,000

0

'

'

Weighted average shares used in diluted computation, shares

122,898,000

113,798,000

'

'

'

'

'

'

'

'

'

'

Earnings (loss) per share:

'

'

'

'

'

'

'

'

'

'

'

'

Earnings Per Share, Basic

$0.09

($0.02)

'

'

'

'

'

'

'

'

'

'

Earnings Per Share, Diluted

$0.08

($0.02)

'

'

'

'

'

'

'

'

'

'

Segment_Reporting_Details

Segment Reporting (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
	customer		customer
	segment
Segment Reporting Information [Line Items]	'		'
Number of Operating Segments	2		'
Revenues	'		'
Investment banking	$49,562,000		$17,166,000
Brokerage	32,830,000		26,600,000
Management fees	8,924,000		9,493,000
Incentive income	2,498,000		2,611,000
Interest and dividends	9,252,000		9,321,000
Reimbursement from affiliates	1,900,000		1,485,000
Total revenues	106,677,000		67,241,000
Expenses	'		'
Employee compensation and benefits	67,561,000		44,223,000
Interest and dividends	7,072,000		6,418,000
Total expenses	106,028,000		83,112,000
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	11,354,000		11,807,000
Total other income (loss)	13,457,000		16,966,000
Income (loss) before income taxes and non-controlling interests	14,106,000		1,095,000
Income tax expense (benefit)	79,000		176,000
Economic income (loss)/ net income (loss) before non-controlling interests	14,027,000		919,000
Net income (loss) attributable to Cowen Group, Inc. stockholders	9,840,000		-2,576,000
Number of major customers	0		0
Reported Under U.S. GAAP	'		'
Revenues	'		'
Investment banking	49,562,000		17,166,000
Brokerage	32,830,000		26,600,000
Management fees	8,924,000		9,493,000
Incentive income	2,498,000		2,611,000
Investment Income	0		0
Interest and dividends	9,252,000		9,321,000
Reimbursement from affiliates	1,900,000		1,485,000
Other revenue	555,000		478,000
Total revenues	106,677,000		67,241,000
Expenses	'		'
Employee compensation and benefits	67,561,000		44,223,000
Interest and dividends	7,072,000		6,418,000
Non-compensation expenses - Fixed	0		0
Non-compensation expenses - Variable	0		0
Non-compensation expenses	31,093,000		32,037,000
Reimbursement from affiliates	0		0
Total expenses	106,028,000		83,112,000
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	11,354,000		11,807,000
Total other income (loss)	13,457,000		16,966,000
Income (loss) before income taxes and non-controlling interests	14,106,000		1,095,000
Income tax expense (benefit)	79,000		176,000
Economic income (loss)/ net income (loss) before non-controlling interests	14,027,000		919,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	-4,187,000		-3,495,000
Net income (loss) attributable to Cowen Group, Inc. stockholders	9,840,000		-2,576,000
Operating Segments | Reported Under Economic Income/(Loss)	'		'
Revenues	'		'
Investment banking	49,562,000		17,166,000
Brokerage	34,349,000		28,017,000
Management fees	14,089,000		14,144,000
Incentive income	4,726,000		5,126,000
Investment Income	8,172,000		10,872,000
Interest and dividends	0		0
Reimbursement from affiliates	0		0
Other revenue	-145,000		-440,000
Total revenues	110,753,000		74,885,000
Expenses	'		'
Employee compensation and benefits	66,957,000		44,246,000
Interest and dividends	643,000		124,000
Non-compensation expenses - Fixed	22,815,000		22,403,000
Non-compensation expenses - Variable	9,437,000		8,726,000
Non-compensation expenses	0		0
Reimbursement from affiliates	-1,726,000		-1,420,000
Total expenses	98,126,000		74,079,000
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	0		0
Total other income (loss)	0		0
Income (loss) before income taxes and non-controlling interests	12,627,000		806,000
Income tax expense (benefit)	0		0
Economic income (loss)/ net income (loss) before non-controlling interests	12,627,000		806,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	-2,625,000		-2,075,000
Net income (loss) attributable to Cowen Group, Inc. stockholders	10,002,000		-1,269,000
Alternative Investment | Reported Under Economic Income/(Loss)	'		'
Revenues	'		'
Investment banking	0		0
Brokerage	0		0
Management fees	14,089,000		14,144,000
Incentive income	4,726,000		5,126,000
Investment Income	8,328,000		8,304,000
Interest and dividends	0		0
Reimbursement from affiliates	0		0
Other revenue	-43,000		113,000
Total revenues	27,100,000		27,687,000
Expenses	'		'
Employee compensation and benefits	13,387,000		13,638,000
Interest and dividends	609,000		81,000
Non-compensation expenses - Fixed	8,894,000		9,138,000
Non-compensation expenses - Variable	749,000		1,006,000
Non-compensation expenses	0		0
Reimbursement from affiliates	-1,726,000		-1,420,000
Total expenses	21,913,000		22,443,000
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	0		0
Total other income (loss)	0		0
Income (loss) before income taxes and non-controlling interests	5,187,000		5,244,000
Income tax expense (benefit)	0		0
Economic income (loss)/ net income (loss) before non-controlling interests	5,187,000		5,244,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	-2,625,000		-2,075,000
Net income (loss) attributable to Cowen Group, Inc. stockholders	2,562,000		3,169,000
Broker-Dealer | Reported Under Economic Income/(Loss)	'		'
Revenues	'		'
Investment banking	49,562,000	[1]	17,166,000	[2]
Brokerage	34,349,000	[1]	28,017,000	[2]
Management fees	0	[1]	0	[2]
Incentive income	0	[1]	0	[2]
Investment Income	-156,000	[1]	2,568,000	[2]
Interest and dividends	0	[1]	0	[2]
Reimbursement from affiliates	0	[1]	0	[2]
Other revenue	-102,000	[1]	-553,000	[2]
Total revenues	83,653,000	[1]	47,198,000	[2]
Expenses	'		'
Employee compensation and benefits	53,570,000	[1]	30,608,000	[2]
Interest and dividends	34,000	[1]	43,000	[2]
Non-compensation expenses - Fixed	13,921,000	[1]	13,265,000	[2]
Non-compensation expenses - Variable	8,688,000	[1]	7,720,000	[2]
Non-compensation expenses	0	[1]	0	[2]
Reimbursement from affiliates	0	[1]	0	[2]
Total expenses	76,213,000	[1]	51,636,000	[2]
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	0	[1]	0	[2]
Total other income (loss)	0	[1]	0	[2]
Income (loss) before income taxes and non-controlling interests	7,440,000	[1]	-4,438,000	[2]
Income tax expense (benefit)	0	[1]	0	[2]
Economic income (loss)/ net income (loss) before non-controlling interests	7,440,000	[1]	-4,438,000	[2]
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	0	[1]	0	[2]
Net income (loss) attributable to Cowen Group, Inc. stockholders	7,440,000	[1]	-4,438,000	[2]
Investment Income from Entity's Capital	'		2,300,000
Compensation Expense Related to Investment of Entity's Capital	'		800,000
Significant Reconciling Items | Reconciliation from Economic Income/(Loss) to U.S. GAAP	'		'
Revenues	'		'
Investment banking	0		0
Brokerage	-1,519,000	[3]	-1,417,000	[3]
Management fees	-4,931,000	[4]	-4,340,000	[4]
Incentive income	-2,228,000	[4]	-2,515,000	[4]
Investment Income	-8,172,000	[5]	-10,872,000	[5]
Interest and dividends	9,252,000	[5]	9,321,000	[5]
Reimbursement from affiliates	1,980,000	[6]	1,420,000	[6]
Other revenue	700,000	[5]	918,000	[5]
Total revenues	-4,918,000		-7,485,000
Expenses	'		'
Employee compensation and benefits	604,000		-23,000
Interest and dividends	6,429,000	[5]	6,294,000	[5]
Non-compensation expenses - Fixed	-22,815,000	[5],[7]	-22,403,000	[5],[7]
Non-compensation expenses - Variable	-9,437,000	[5],[7]	-8,726,000	[5],[7]
Non-compensation expenses	31,093,000	[5],[7]	32,037,000	[5],[7]
Reimbursement from affiliates	1,726,000	[6]	1,420,000	[6]
Total expenses	7,600,000		8,599,000
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	11,354,000	[5]	11,807,000	[5]
Total other income (loss)	13,250,000		14,673,000
Income (loss) before income taxes and non-controlling interests	732,000		-1,411,000
Income tax expense (benefit)	79,000	[6]	176,000	[6]
Economic income (loss)/ net income (loss) before non-controlling interests	653,000		-1,587,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	-815,000		280,000
Net income (loss) attributable to Cowen Group, Inc. stockholders	-162,000		-1,307,000
Funds Consolidation | Reconciliation from Economic Income/(Loss) to U.S. GAAP	'		'
Revenues	'		'
Investment banking	0		0
Brokerage	0		0
Management fees	-234,000		-311,000
Incentive income	0		0
Investment Income	0		0
Interest and dividends	0		0
Reimbursement from affiliates	-80,000		65,000
Other revenue	0		0
Total revenues	842,000		-159,000
Expenses	'		'
Employee compensation and benefits	0		0
Interest and dividends	0		0
Non-compensation expenses - Fixed	0		0
Non-compensation expenses - Variable	0		0
Non-compensation expenses	0		0
Reimbursement from affiliates	0		0
Total expenses	302,000		434,000
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	0		0
Total other income (loss)	207,000		2,293,000
Income (loss) before income taxes and non-controlling interests	747,000		1,700,000
Income tax expense (benefit)	0		0
Economic income (loss)/ net income (loss) before non-controlling interests	747,000		1,700,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries	-747,000		-1,700,000
Net income (loss) attributable to Cowen Group, Inc. stockholders	0		0
Consolidated Funds | Reported Under U.S. GAAP	'		'
Revenues	'		'
Total revenues	1,156,000		87,000
Expenses	'		'
Total expenses	302,000		434,000
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	2,103,000		5,159,000
Consolidated Funds | Operating Segments | Reported Under Economic Income/(Loss)	'		'
Revenues	'		'
Total revenues	0		0
Expenses	'		'
Total expenses	0		0
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	0		0
Consolidated Funds | Alternative Investment | Reported Under Economic Income/(Loss)	'		'
Revenues	'		'
Total revenues	0		0
Expenses	'		'
Total expenses	0		0
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	0		0
Consolidated Funds | Broker-Dealer | Reported Under Economic Income/(Loss)	'		'
Revenues	'		'
Total revenues	0	[1]	0	[2]
Expenses	'		'
Total expenses	0	[1]	0	[2]
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	0	[1]	0	[2]
Consolidated Funds | Significant Reconciling Items | Reconciliation from Economic Income/(Loss) to U.S. GAAP	'		'
Revenues	'		'
Total revenues	0		0
Expenses	'		'
Total expenses	0		0
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	1,896,000		2,866,000
Consolidated Funds | Funds Consolidation | Reconciliation from Economic Income/(Loss) to U.S. GAAP	'		'
Revenues	'		'
Total revenues	1,156,000		87,000
Expenses	'		'
Total expenses	302,000		434,000
Other income (loss)	'		'
Net gain (losses) on securities, derivatives and other investments	$207,000		$2,293,000
[1]	For the three months ended MarchB 31, 2014, the Company has reflected a minimal amount of investment income and related compensation expense within the broker-dealer segment.
[2]	For the three months ended MarchB 31, 2013, the Company has reflected $2.3 million of investment income and related compensation expense of $0.8 million within the broker-dealer segment in proportion to its capital.
[3]	Economic Income (Loss) recognizes stock borrow/loan activity and other brokerage dividends as brokerage revenue.
[4]	Economic Income (Loss) recognizes revenues (i) net of distribution fees paid to agents and (ii) our proportionate share of management and incentive fees of certain real estate operating entities and the activist business.
[5]	Economic Income (Loss) recognizes Company income from proprietary trading net of related expenses.
[6]	Economic Income (Loss) excludes income taxes as management does not consider this item when evaluating the performance of the segment. Also, reimbursement from affiliates is shown as a reduction of Economic Income expenses, but is included as a part of revenues under US GAAP.
[7]	Economic Income (Loss) recognizes the Company's proportionate share of expenses for certain real estate and other operating entities for which the investments are recorded under the equity method of accounting for investments.

Regulatory_Requirements_Detail

Regulatory Requirements (Details) (USD $)	Mar. 31, 2014
Cowen and Company	'
Regulatory Requirements for Broker-Dealers [Line Items]	'
Net capital requirement under alternative method	$1,000,000
Net capital	47,100,000
Excess capital	46,100,000
ATM Execution	'
Regulatory Requirements for Broker-Dealers [Line Items]	'
Minimum net capital required	250,000
Net capital	3,300,000
Excess capital	3,000,000
ATM USA	'
Regulatory Requirements for Broker-Dealers [Line Items]	'
Minimum net capital required	250,000
Net capital	900,000
Excess capital	600,000
Cowen Equity Finance	'
Regulatory Requirements for Broker-Dealers [Line Items]	'
Minimum net capital required	250,000
Net capital	10,700,000
Excess capital	10,400,000
U.K. Financial Services Authority | Raimus U.K., Ltd.	'
Regulatory Requirements for Broker-Dealers [Line Items]	'
Financial resources	370,000
Financial resources requirement	120,000
Excess financial resources	250,000
U.K. Financial Services Authority | Cowen International Limited	'
Regulatory Requirements for Broker-Dealers [Line Items]	'
Financial resources	4,400,000
Financial resources requirement	2,200,000
Excess financial resources	2,200,000
H.K. Securities and Futures Commission | Cowen and Company (Asia) Limited	'
Regulatory Requirements for Broker-Dealers [Line Items]	'
Financial resources	900,000
Financial resources requirement	400,000
Excess financial resources	$500,000

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)

3 Months Ended

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2013

Apr. 30, 2011

Apr. 30, 2011

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Affiliated Entity

Affiliated Entity

Affiliated Entity

Affiliated Entity

Affiliated Entity

Affiliated Entity

Employees

Employees

Starboard Value LP

Starboard Value LP

Starboard Value LP

Investor

Investor

Real Estate Equity Investment

Employee Loans

Employee Loans

Management Fee and Incentive Income

Management Fee and Incentive Income

Fees Payable

Fees Payable

LIBOR

Minimum

Maximum

Related Party Transaction [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Fees receivable, net of allowance

$57,618,000

'

$45,067,000

$15,100,000

$18,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Reimbursement to affiliated funds

'

'

'

'

'

500,000

500,000

'

'

'

'

'

'

'

'

'

'

'

'

Fees payable to related parties

'

'

'

'

'

'

'

1,400,000

1,700,000

'

'

'

'

'

'

'

'

'

'

Due from employees

'

'

'

'

'

'

'

'

'

10,600,000

6,000,000

'

'

'

'

'

'

'

'

Forgivable Loan Balances

'

'

'

'

'

'

'

'

'

7,800,000

3,800,000

'

'

'

'

'

'

'

'

Forgivable Loans, Vesting Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'1 year

'3 years

Amortization on Forgivable Loans

800,000

400,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Credit agreement with related party, maximum loan amount

'

'

'

'

'

'

'

'

'

'

'

'

3,000,000

'

'

'

'

'

'

Credit agreement with related party, interest rate

'

'

'

'

'

'

'

'

'

'

'

'

'

3.75%

'

'

'

'

'

Credit agreement with related party, loan receivable

'

'

'

'

'

'

'

'

'

'

'

1,500,000

'

'

'

'

'

'

'

Due to Affiliate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

400,000

400,000

'

'

'

Mortgage Loans on Real Estate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$40,000,000

'

'

Guarantees_and_OffBalance_Shee1

Guarantees and Off-Balance Sheet Arrangements (Details) (USD $)	Mar. 31, 2014
Securities Lending	'
Guaranty loans	$150,000,000
Employee Loans	'
Guaranty loans	$2,500,000