Cowen (COWN) 10-Q 3 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-34516
Entity Registrant Name	Cowen Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-0423711
Entity Address, Address Line One	599 Lexington Avenue
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10022
City Area Code	646
Local Phone Number	562-1010
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		26,866,951
Entity Central Index Key	0001466538
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Common Stock Class A | The Nasdaq Global Market
Entity Information [Line Items]
Title of 12(b) Security	Class A Common Stock, par value $0.01 per share
Trading Symbol	COWN
Security Exchange Name	NASDAQ
2033 Notes | The Nasdaq Global Market
Entity Information [Line Items]
Title of 12(b) Security	7.75% Senior Notes due 2033
Trading Symbol	COWNL
Security Exchange Name	NASDAQ

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($)		Mar. 31, 2021	Dec. 31, 2020
Assets
Cash and cash equivalents		$ 1,147,531,000	$ 645,169,000
Cash collateral pledged		110,303,000	110,743,000
Segregated cash		168,942,000	185,141,000
Securities owned, at fair value ($2,042,776 and $1,218,947 were pledged to various parties)		3,156,100,000	2,001,602,000
Securities Purchased under Agreements to Resell		0	191,000
Receivable on derivative contracts, at fair value		95,536,000	51,482,000
Securities borrowed		1,996,757,000	1,908,187,000
Other investments ($151,933 and $133,454 at fair value, respectively)		366,783,000	255,027,000
Deposits with clearing organizations, brokers and banks		82,078,000	104,952,000
Receivable from brokers, dealers and clearing organizations, net of allowance of $640 and $885, respectively		1,920,753,000	1,729,744,000
Receivable from customers, net of allowance of $758 and $530, respectively		199,668,000	103,963,000
Fees receivable, net of allowance of $2,982 and $3,348, respectively		208,898,000	160,349,000
Due from related parties		20,921,000	21,068,000
Fixed assets, net of accumulated depreciation and amortization of $42,681 and $40,670, respectively		31,424,000	33,023,000
Operating lease right-of-use assets		77,268,000	78,241,000
Goodwill		147,084,000	147,084,000
Intangible assets, net of accumulated amortization of $27,073 and $37,884, respectively		28,116,000	24,403,000
Deferred tax asset, net		1,757,000	9,030,000
Other assets		76,921,000	54,884,000
Consolidated Funds
Cash and cash equivalents, Consolidated Funds		935,000	417,000
Securities owned, at fair value		8,940,000	10,622,000
Other Investments, Consolidated Funds		100,035,000	192,670,000
Other assets, Consolidated Funds		46,000	207,000
Total Assets		9,946,796,000	7,828,199,000
Liabilities
Securities sold, not yet purchased, at fair value		931,082,000	728,115,000
Securities Sold under Agreements to Repurchase		2,546,000	5,036,000
Payable for derivative contracts, at fair value		52,125,000	76,160,000
Securities Loaned		3,083,945,000	2,476,414,000
Payables to brokers, dealers and clearing organizations		488,471,000	415,143,000
Payable to customers		2,657,600,000	1,680,326,000
Commission management payable		139,621,000	116,987,000
Compensation payable		361,793,000	373,339,000
Operating lease liabilities		81,400,000	82,735,000
Notes payable and other debt	[1]	542,519,000	383,067,000
Convertible debt	[2]	81,682,000	80,808,000
Fees payable		42,915,000	43,833,000
Due to related parties		99,000	51,000
Accounts payable, accrued expenses and other liabilities		240,790,000	196,479,000
Consolidated Funds
Due to related parties		9,000	7,000
Accounts payable, accrued expenses and other liabilities		219,000	578,000
Total Liabilities		8,706,816,000	6,659,078,000
Commitments and Contingencies
Redeemable non-controlling interests in consolidated subsidiaries and funds		0	0
Stockholders' equity
Additional paid-in capital		1,151,377,000	1,130,138,000
(Accumulated deficit) retained earnings		328,930,000	185,901,000
Accumulated other comprehensive income (loss)		(3,000)	(7,000)
Less: Class A common stock held in treasury, at cost, 23,375,473 and 22,619,863 shares as of March 31, 2021 and December 31, 2020, respectively.		(373,800,000)	(346,900,000)
Cowen Inc. Stockholders' Equity		1,106,865,000	969,497,000
Nonredeemable non-controlling interests		133,115,000	199,624,000
Permanent Equity		1,239,980,000	1,169,121,000
Total Liabilities and Stockholders' Equity		9,946,796,000	7,828,199,000
Portfolio Funds
Assets
Other investments ($151,933 and $133,454 at fair value, respectively)	[3]	151,933,000	133,454,000
Consolidated Funds
Other Investments, Consolidated Funds	[3]	100,035,000	192,670,000
Convertible Preferred Stock
Stockholders' equity
Preferred stock		1,000	1,000
Common Stock Class A
Stockholders' equity
Common stock		334,000	334,000
Less: Class A common stock held in treasury, at cost, 23,375,473 and 22,619,863 shares as of March 31, 2021 and December 31, 2020, respectively.		(373,774,000)	(346,870,000)
Common Stock Class B
Stockholders' equity
Common stock		$ 0	$ 0
[1]	The carrying amount of the notes payable and other debt includes an unamortized discount and unamortized premium of $1.5 million and $0.3 million as of March 31, 2021, respectively and unamortized premium of $0.4 million as of December 31, 2020
[2]	The carrying amount of the convertible debt includes an unamortized discount of $5.8 million and $6.7 million as of March 31, 2021 and December 31, 2020, respectively.
[3]	In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.

Consolidated Statements of Fi_2

Consolidated Statements of Financial Condition (Parenthetical) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Assets
Security Owned and Pledged as Collateral, Fair Value	$ 2,042,776,000	$ 1,218,947,000
Allowance for receivable from brokers	640,000	885,000
Allowance for receivable from customers	758,000	530,000
Allowance for fees receivable	2,982,000	3,348,000
Fixed assets, accumulated depreciation and amortization (in dollars)	42,681,000	40,670,000
Intangible assets, accumulated amortization (in dollars)	$ 27,073,000	$ 37,884,000
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	120,750	120,750
Preferred Stock, Liquidation Preference, Value	$ 120,750,000	$ 120,750,000
Common stock, shares authorized	125,000,000
Portfolio Funds
Assets
Investment Owned, at Fair Value	$ 151,933,000	$ 133,454,000
Common Stock Class A
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	62,500,000	62,500,000
Common stock, shares issued	50,227,804	49,465,491
Common stock, shares outstanding	26,852,331	26,845,628
Treasury Stock, Shares	23,375,473	22,619,863
Common Stock Class A | Restricted Stock
Stockholders' equity
Common stock, shares outstanding	292,968	334,230
Common Stock Class B
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	62,500,000	62,500,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues
Investment banking	$ 304,834	$ 105,028
Brokerage	173,737	141,377
Securities principal transactions, net	63,965	(31,045)
Portfolio fund principal transactions, net	15,403	(2,818)
Carried interest allocations	96,769	(11,544)
Gross Investment Income, Operating	176,137	(45,407)
Management fees	25,742	11,604
Incentive income	2,258	0
Interest and dividends	59,388	42,077
Reimbursement from affiliates	288	261
Insurance and reinsurance premiums	7,117	10,471
Other revenues	8,169	1,321
Consolidated Funds
Principal transactions, net, Consolidated Funds	(3,349)	(73,143)
Interest and dividends	2	2,525
Other revenues	0	609
Total revenues	754,323	196,723
Interest and dividends expense	57,641	38,792
Total net revenues	696,682	157,931
Expenses
Employee compensation and benefits	388,196	124,428
Brokerage and trade execution costs	45,656	32,886
Underwriting expenses	6,915	3,640
Professional, advisory and other fees	15,460	11,039
Service fees	5,731	6,837
Communications	9,267	8,176
Occupancy and equipment	9,540	9,530
Depreciation and amortization	4,354	5,442
Client services and business development	6,848	11,803
Insurance and reinsurance claims, commissions and amortization of deferred acquisition costs	6,455	10,430
Other expenses	3,457	4,228
Consolidated Funds
Interest and dividends	0	1,252
Professional, advisory and other fees	110	990
Brokerage and trade execution costs	0	20
Other expenses	161	452
Total expenses	502,150	231,153
Other income (loss)
Net gains (losses) on other investments	12,645	(62)
Bargain Purchase Gain, net of tax	3,855	0
Gain/(loss) on debt extinguishment	(4,538)	0
Total other income (loss)	11,962	(62)
Income (loss) before income taxes	206,494	(73,284)
Income tax expense (benefit)	54,428	(1,173)
Net income (loss)	152,066	(72,111)
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	4,562	(62,188)
Net income (loss) attributable to Cowen Inc.	147,504	(9,923)
Preferred stock dividends	1,698	1,698
Net income (loss) attributable to Cowen Inc. common stockholders	$ 145,806	$ (11,621)
Weighted average common shares outstanding:
Basic (in shares)	27,359	28,598
Diluted (in shares)	33,565	28,598
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 5.33	$ (0.41)
Earnings Per Share, Diluted (in dollars per share)	$ 4.34	$ (0.41)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 152,066	$ (72,111)
Other comprehensive income (loss), net of tax:
Foreign currency translation	4	0
Total other comprehensive income (loss), net of tax	4	0
Comprehensive income (loss)	152,070	(72,111)
Net Income (Loss) Attributable to Noncontrolling Interest	4,562	(62,188)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 147,508	$ (9,923)

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings/(Accumulated deficit)	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings/(Accumulated deficit)	Nonredeemable Noncontrolling Interests [Member]	Permanent Equity [Member]	Permanent Equity [Member]Cumulative Effect, Period of Adoption, Adjustment	Common Stock Class A	Common Stock Class ARetained Earnings/(Accumulated deficit)	Preferred Stock	Convertible Preferred StockRetained Earnings/(Accumulated deficit)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Stockholders' Equity	$ 809,855
Stockholders' Equity Attributable to Noncontrolling Interest								$ 94,320
Common stock											$ 334
Common stock, shares outstanding, start at Dec. 31, 2019											28,610,357
Balance, start at Dec. 31, 2019		$ (10)	$ (10)	$ 284,301	$ 1,110,635	$ (5)	$ (16,809)		$ 904,175	$ (10)			$ 1
Preferred stock, shares outstanding, start at Dec. 31, 2019													120,750
Redeemable Non-controlling Interest, start at Dec. 31, 2019	391,275
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to Cowen Inc.	(9,923)						(9,923)		(9,923)
Net income (loss) attributable to non-controlling interest in consolidated subsidiaries and funds, Non-Reedemable								(1,198)	(1,198)
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	(60,990)
Foreign currency translation	0
Capital contributions	118,866							88,682	88,682
Capital withdrawals	(131,150)							(43,563)	(43,563)
Restricted stock awards issued, shares											591,763
Purchase of treasury stock, at cost, shares											(1,615,265)
Purchase of treasury stock, at cost	(20,891)			(20,891)					(20,891)
Common stock issued during period, shares, acquisitions											41,262
Common stock issued during period, value, acquisitions	618				618				618		$ 0
Preferred dividends paid	(1,698)								(1,698)					$ (1,698)
Dividends, Cash	(1,429)								(1,429)			$ (1,429)
Amortization of share based awards	8,281				8,281				8,281
Common stock, shares outstanding, end at Mar. 31, 2020											27,628,117
Balance, end at Mar. 31, 2020				305,192	1,119,534	(5)	(29,869)		923,044				$ 1
Preferred stock, shares outstanding, end at Mar. 31, 2020													120,750
Redeemable Non-controlling Interest, end at Mar. 31, 2020	318,001
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Stockholders' Equity	784,803
Stockholders' Equity Attributable to Noncontrolling Interest								138,241
Common stock											$ 334
Total Stockholders' Equity	969,497
Stockholders' Equity Attributable to Noncontrolling Interest	199,624							199,624
Common stock											$ 334
Common stock, shares outstanding, start at Dec. 31, 2020											26,845,628
Balance, start at Dec. 31, 2020	1,169,121			346,870	1,130,138	(7)	185,901		1,169,121				$ 1
Preferred stock, shares outstanding, start at Dec. 31, 2020													120,750
Redeemable Non-controlling Interest, start at Dec. 31, 2020	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to Cowen Inc.	147,504						147,504		147,504
Net income (loss) attributable to non-controlling interest in consolidated subsidiaries and funds, Non-Reedemable								4,562	4,562
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	0
Foreign currency translation	4					4			4
Capital contributions	0							22,515	22,515
Capital withdrawals	0							(18,773)	(18,773)
Noncontrolling Interest, Decrease from Deconsolidation	0							74,813	74,813
Restricted stock awards issued, shares											705,512
Purchase of treasury stock, at cost, shares											(755,610)
Purchase of treasury stock, at cost	(26,904)			(26,904)					(26,904)
Common stock issued during period, shares, acquisitions											56,801
Common stock issued during period, value, acquisitions	2,202				2,202				2,202		$ 0
Preferred dividends paid	(1,698)								(1,698)					$ (1,698)
Dividends, Cash	(2,777)								(2,777)			$ (2,777)
Amortization of share based awards	19,037				19,037				19,037
Common stock, shares outstanding, end at Mar. 31, 2021											26,852,331
Balance, end at Mar. 31, 2021	1,239,980			$ 373,774	$ 1,151,377	$ (3)	$ 328,930		$ 1,239,980				$ 1
Preferred stock, shares outstanding, end at Mar. 31, 2021													120,750
Redeemable Non-controlling Interest, end at Mar. 31, 2021	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total Stockholders' Equity	1,106,865
Stockholders' Equity Attributable to Noncontrolling Interest	$ 133,115							$ 133,115
Common stock											$ 334

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ / shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income (loss)	$ 152,066	$ (72,111)
Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities:
Bargain Purchase Gain, net of tax	3,855	0
Depreciation and amortization	4,354	5,442
Amortization of debt issuance costs	480	334
Amortization of debt discount (premium)	776	1,109
Noncash lease expense	(362)	(1,200)
Gain (Loss) on Extinguishment of Debt	3,890	0
Share-based compensation	19,037	8,281
Change in deferred taxes	5,913	(1,682)
Contingent Liability adjustment	(614)	0
Purchases of securities owned, at fair value	(269,073)	(749,807)
Proceeds from sales of securities owned, at fair value	271,314	845,779
Proceeds from sales of securities sold, not yet purchased, at fair value	63,511	416,453
Payments to cover securities sold, not yet purchased, at fair value	(58,346)	(334,068)
Proceeds from other investments	16,995	15,693
Investment income (loss) principal transactions, net	(158,833)	38,039
Consolidated Funds
Purchases of securities owned, at fair value	0	(1,024,733)
Proceeds from sales of securities owned, at fair value	2,687	991,096
Purchases of other investments	0	(1,240)
Proceeds from other investments	14,130	6,669
Investment Income (loss) principal transactions, net	3,143	74,071
(Increase) decrease in operating assets:
Securities owned, at fair value, held at broker-dealer	(1,112,154)	713,313
Receivable on derivative contracts, at fair value	(44,054)	(20,889)
Securities borrowed	(88,570)	(216,989)
Deposits with clearing organizations, brokers and banks	22,874	(40,193)
Receivable from brokers, dealers and clearing organizations	(191,009)	(91,622)
Receivable from customers, net of allowance	(95,705)	(87,362)
Fees receivable, net of allowance	(46,170)	(30,723)
Due from related parties	440	1,947
Other assets	(9,344)	(6,919)
Consolidated Funds
Cash and cash equivalents	(6,138)	(8,847)
Receivable on derivative contracts, at fair value	(2,917)	(11,459)
Receivable from brokers	0	5,296
Other assets	13	(94)
Increase (decrease) in operating liabilities:
Securities sold, not yet purchased, at fair value, held at broker dealer	187,749	15,925
Securities sold under agreement to repurchase	(2,490)	34,176
Payable for derivative contracts, at fair value	(24,035)	11,624
Securities loaned	607,531	(604,072)
Payable to brokers, dealers and clearing organizations	73,328	59,078
Payable to customers	977,274	58,590
Commission management payable	22,634	41,068
Compensation payable	(17,809)	(156,333)
Fees payable	(918)	(378)
Due to related parties	48	0
Accounts payable, accrued expenses and other liabilities	41,793	23,974
Consolidated Funds
Contributions received in advance	0	150
Payable to brokers	0	399
Payable for derivative contracts, at fair value	0	13,297
Due To Related Parties, Consolidated Funds	0	(581)
Accounts payable, accrued expenses and other liabilities	(359)	382
Net Cash Provided by (Used in) Operating Activities	359,225	(79,117)
Cash flows from investing activities:
Securities purchased under agreement to resell	191	0
Purchases of other investments	(29,117)	(17,650)
Purchase of business (see note 3)	2,109	0
Proceeds from sales of other investments	31,267	12,059
Purchase of fixed assets and intangibles	(1,643)	(2,485)
Net Cash Provided by (Used in) Investing Activities	2,807	(8,076)
Cash flows from financing activities:
Deferred Debt Issuance Costs	6,467	0
Borrowings on notes and other debt	301,490	62,812
Repayments on notes and other debt	(139,737)	(933)
Purchase of treasury stock	$ (20,629)	$ (18,018)
Cash dividends paid	$ (2,313)	$ (1,168)
Preferred dividends paid	$ (1,698)	$ (1,698)
Contingent liability payment	(10,698)	(782)
Capital contributions by non-controlling interests in operating entities	3,498	286
Capital withdrawals to non-controlling interests in operating entities	(2,348)	(462)
Consolidated Funds
Capital contributions by non-controlling interests in Consolidated Funds	19,017	207,263
Capital withdrawals to non-controlling interests in Consolidated Funds	(16,424)	(166,238)
Net Cash Provided by (Used in) Financing Activities	123,691	81,062
Change in cash and cash equivalents	485,723	(6,131)
Total cash beginning of period	941,053	415,014
Cash and cash equivalents	1,147,531	270,079
Cash collateral pledged	110,303	7,538
Segregated cash	168,942	131,266
Total cash at end of period	1,426,776	408,883
Supplemental information
Cash paid during the year for interest	65,259	29,560
Cash paid during the year for taxes	8,087	950
Purchase of treasury stock, at cost, through net settlement	6,245	2,825
Dividends, Preferred Stock, Cash	(1,698)	(1,698)
Dividends, Cash	2,777	1,429
Net assets (liabilities) acquired upon acquisition (net of cash)	3,107	0
Decrease in noncontrolling interest due to deconsolidation of entity	74,813	0
Common stock issuance upon close of acquisition	$ 2,202	$ 618

Organization and Business

Organization and Business	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business	Organization and Business Cowen Inc., a Delaware corporation formed in 2009, is a diversified financial services firm that, together with its consolidated subsidiaries (collectively, "Cowen" or the "Company"), provides investment banking, research, sales and trading, prime brokerage, global clearing, securities financing, commission management services and investment management through its two business segments: the Operating Company ("Op Co") and the Asset Company ("Asset Co"). The Op Co segment consists of four divisions: the Investment Banking division, the Markets division, the Research division and the Cowen Investment Management ("CIM") division. The Company refers to the Investment Banking division, the Markets division and the Research division combined as its investment banking businesses. Op Co's investment banking businesses offer advisory and global capital markets origination, domain knowledge-driven research, sales and trading platforms for institutional investors, global clearing, commission management services and also a comprehensive suite of prime brokerage service. Sectors covered by Op Co's investment banking business include healthcare, technology, media and telecommunications, consumer, industrials, technology enabled services, and energy. Op Co’s CIM division includes advisers to investment funds (including private equity structures and privately placed hedge funds) and registered funds. The Company has also invested capital in its insurance and reinsurance businesses.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies a. Basis of presentation These unaudited condensed consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America ("US GAAP") as promulgated by the Financial Accounting Standards Board ("FASB") through Accounting Standards Codification (the "Accounting Standards") as the source of authoritative accounting principles in the preparation of financial statements, and include the accounts of the Company, its operating and other subsidiaries, and entities in which the Company has a controlling financial interest or a general partner interest. All material intercompany transactions and balances have been eliminated on consolidation. Certain investment funds that are consolidated in these accompanying condensed consolidated financial statements, as further discussed below, are not subject to the consolidation provisions with respect to their own controlled investments pursuant to specialized industry accounting. The accompanying condensed financial statements should be read in conjunction with the Company’s financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020 (the "2020 Form 10-K"). Certain footnote disclosures included in the 2020 Form 10-K have been condensed or omitted from the accompanying condensed financial statements as they are not required for interim reporting under US GAAP or are insignificant to the interim reporting period. During the first quarter of 2021, the Company changed the presentation of certain income streams on its condensed consolidated statements of operations by moving the income streams from Other income - net gains (losses) on securities, derivatives and other investments to Revenues. Additionally, the Company moved proprietary trading gains and losses generated by the Company’s broker dealer entities from Brokerage revenue to Investment income (loss) – securities principal transactions, net. The specified presentation changes included the following: From To Income Streams Other income - net gains (losses) on securities, derivatives and other investments Investment income (loss) – securities principal transactions, net proprietary trading gains and losses generated outside of the Company’s broker-dealer entities Other income - net gains (losses) on securities, derivatives and other investments Investment income (loss) – portfolio fund principal transactions, net gains and losses from portfolio funds Other income - net gains (losses) on securities, derivatives and other investments Investment income (loss) – carried interest allocations carried interest allocations Other income - net gains (losses) on securities, derivatives and other investments Other revenue net gains and losses on foreign currency transactions Brokerage revenue Investment income (loss) – securities principal transactions, net proprietary trading gains and losses generated by the Company’s broker-dealer entities Other income – Consolidated Funds – net realized and unrealized gains (losses) on investments and other transactions and other income – Consolidated Funds – net realized and unrealized gains (losses) on derivatives Consolidated Funds – principal transactions, net proprietary trading gains and losses generated from the Consolidated Funds Other income – Consolidated Funds – net gains (losses) on foreign currency transactions Consolidated Funds – other revenue net gains and losses on foreign currency transactions generated by the Consolidated Funds The Company believes that these presentation changes provide a better representation of the Company’s operating results as it is used by management to monitor the Company’s financial performance and is consistent with industry practice. The changes in presentation have no impact on net income and prior period amounts have been recast to reflect such changes in presentation. b. Principles of consolidation The Company consolidates all entities that it controls through a majority voting interest or otherwise, including those investment funds in which the Company either directly or indirectly has a controlling financial interest. In addition, the Company consolidates all variable interest entities for which it is the primary beneficiary. The Company consolidates two and three investment funds for which it acts as the managing member/general partner and investment manager as of March 31, 2021 and December 31, 2020, respectively. At March 31, 2021, the Company consolidated the following investment funds: Ramius Enterprise LP (“Enterprise LP”) and Cowen Private Investments LP ("Cowen Private"). At December 31, 2020, the Company consolidated the following investment funds: Enterprise LP, Cowen Private, and Cowen Sustainable Investments I LP ("CSI I LP"). These funds are referred to as each a "Consolidated Fund" and collectively the "Consolidated Funds". During the first quarter of 2021, the Company deconsolidated CSI I LP due the Company's portion being diluted through a capital equalization event. During the second quarter of 2020, the Company deconsolidated Ramius Merger Fund LLC (the "Merger Fund") and UCITS Fund ("UCITS Fund") due to a partial redemption of the Company’s direct portfolio fund investment in Merger Fund and a partial termination of the notional value of UCITS Fund units referenced in a total return swap with a third party. The Company continues to hold a direct retained portfolio fund investment in the Merger Fund and CSI I LP and continues to have economic exposure to the returns of UCITS Fund through a total return swap with a third party. Merger Fund, CSI I LP and UCITS Fund continue to be related parties of the Company after deconsolidation. CSI I Golden Holdco LP ("Golden HoldCo") and CSI I Prodigy Holdco LP ("Prodigy HoldCo") were consolidated through November 2020 when the Company raised additional capital within the sustainable investing strategy that diluted the Company's direct and indirect ownership. As a result, the Company's direct and indirect ownership in Golden Holdco and Prodigy Holdco is no longer expected to be significant to either entity and the entities were deconsolidated. 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, (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 and (iii) voting rights of equity holders are proportionate to their obligation to absorb losses or the right to receive returns. Under US GAAP consolidation requirements, the usual condition for a controlling financial interest in a VOE is ownership of a majority voting interest. Accordingly, the Company consolidates all VOEs in which it owns a majority of the entity's voting shares or units. 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. The Company determines whether it is the primary beneficiary of a VIE upon its initial involvement with the VIE and reassesses whether it is the primary beneficiary on an ongoing basis as long as it has any continuing involvement with the 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, 2021, the total assets and total liabilities of the consolidated VIEs were $243.3 million and $8.0 million, respectively. As of December 31, 2020, the total assets and total liabilities of the consolidated VIEs were $325.5 million and $10.1 million, respectively. The deconsolidation of one Consolidated Fund decreased the overall VIEs net assets. The VIEs act as investment managers and/or investment companies that may be managed by the Company or the Company may have equity interest in those investment companies. The VIEs are financed through their operations and/or loan agreements with the Company. In the ordinary course of business, the Company also sponsors various other entities that it has determined to be VIEs. These VIEs are primarily investment funds for which the Company serves as the general partner, managing member and/or investment manager with decision-making rights. The Company does not consolidate the real estate funds that are VIEs due to the Company's conclusion that it is not the primary beneficiary of these funds in each instance. Investment 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 has equity interests in the funds as both a general partner and a limited partner. In these instances the Company has concluded that the variable interests are not potentially significant to the VIE. Although the Company may advance amounts and pay certain expenses on behalf of the investment funds 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 6 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 accompanying 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 other investments in the accompanying condensed consolidated statements of operations. The Company evaluates its equity method investments for impairment 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 or apply the equity method of accounting, the Company accounts for such entities (primarily, all securities of such entity which are bought and held principally for the purpose of selling them in the near term as trading securities), at fair value with unrealized gains (losses) resulting from changes in fair value reflected within Investment income (loss) - Securities principal transactions, net or Investment income (loss) - portfolio fund investment income (loss) in the accompanying condensed consolidated statements of operations. Retention of Specialized Accounting —The Consolidated Funds and certain other consolidated companies are investment companies and apply specialized industry accounting. The Company reports its investments on the consolidated statements of financial condition at their estimated fair value, with unrealized gains (losses) resulting from changes in fair value reflected within Consolidated Funds - Principal transactions, net in the accompanying condensed consolidated statements of operations. 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. Certain portfolio fund investments qualify as equity method investments and are investment companies that apply specialized industry accounting. In applying equity method accounting guidance, the Company retains the specialized accounting of the investees and 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 Investment Income - portfolio fund principal transactions, net in the accompanying condensed consolidated statements of operations. In addition, the Company's broker-dealer subsidiaries, Cowen and Company, LLC ("Cowen and Company"), Westminster Research Associates LLC ("Westminster"), Cowen Execution Services Limited ("Cowen Execution Ltd"), ATM Execution LLC ("ATM Execution"), Cowen International Limited ("Cowen International Ltd"), and Cowen Prime Services LLC ("Cowen Prime") apply the specialized industry accounting for brokers and dealers in securities, which the Company retains upon 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, and the disclosure of contingent assets and liabilities at the date of the accompanying condensed consolidated financial statements, as well as 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. d. Allowance for credit losses The Company measures the allowance for credit losses in accordance with adopted ASC Topic 326, Financial Instruments – Credit Losses (“ASC 326”), which. ASC 326 impacts the prescribes the impairment model for certain financial assets measured at amortized cost by requiring a current expected credit loss ("CECL") methodology to estimate expected credit losses over the entire life of the financial asset, recorded at inception or purchase. Under the accounting update guidance, the Company has the ability to determine there are no expected credit losses in certain circumstances (e.g., based on collateral arrangements or based on the credit quality of the borrower or issuer). The Company applies the guidance in ASC 326 to securities borrowed and fees and other receivables carried at amortized cost (including, but not limited to, receivables related to securities transactions, corporate finance and syndicate receivables, management fees and incentive fees receivable). The allowance for credit losses is based on the Company's expectation of the collectability of financial instruments carried at amortized cost, including securities borrowed and fees and other receivables utilizing the CECL framework. The Company considers factors such as historical experience, credit quality, age of balances and current and future economic conditions that may affect the Company’s expectation of the collectability in determining the allowance for credit losses. The Company’s expectation is that the credit risk associated with fees and other receivables is not significant until they are 90 days past due based on the contractual arrangement and expectation of collection in accordance with industry standards. For securities borrowed, the Company applies a practical expedient to measure the allowance for credit losses based on the fair value of the collateral. If the fair value of the collateral held exceeds the amortized cost and the borrower is expected to continue to replenish the collateral as needed, the Company will not recognize an allowance. If the fair value of collateral is less than amortized cost and the borrower is expected to continue to replenish the collateral as needed, the Company applies the CECL model, utilizing a probability and loss given default methodology, only to the extent of the shortfall between the fair value of the collateral and amortized cost. The credit loss expense related to the allowance for credit losses as well as any recoveries of amounts previously charged is reflected in other expenses in the accompanying condensed consolidated statements of operations. e. 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. Inputs reflect unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. 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 based on their proportional rights of the underlying portfolio company, and 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 impact 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. The Company has the option to measure certain financial assets and financial liabilities at fair value with changes in fair value recognized in earnings each period. The election is made on an instrument by instrument basis at initial recognition of an asset or liability or upon an event that gives rise to a new basis of accounting for that instrument. The Company has elected the fair value option for certain of its investments held by its operating companies. This option has been elected because the Company believes that it is consistent with the manner in which the business is managed, as well as the way that financial instruments in other parts of the business are recorded. Securities —Securities with values based on quoted market prices in active markets for identical assets are classified within level 1 of the fair value hierarchy. These securities primarily include active listed equities, certain U.S. government and sovereign obligations, Exchange Traded Funds ("ETFs"), mutual funds and certain money market securities. Certain positions for which trading activity may not be readily visible, consisting primarily of convertible debt, corporate debt and loans and restricted equities, are stated at fair value and classified within level 2 of the fair value hierarchy. 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, are classified as level 2 when their inputs can be corroborated by market data. OTC derivatives, such as swaps and options, with significant inputs that cannot be corroborated by readily available or observable market data are classified as level 3. Other Investments —Other investments consist primarily of portfolio funds, real estate investments, carried interest and equity method investments, which are valued as follows: i. Portfolio Funds— Portfolio funds include interests in private investment partnerships, foreign investment companies and other collective investment vehicles which may be managed by the Company or its affiliates. The Company applies the practical expedient provided by the US GAAP fair value measurements and disclosures guidance relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The practical expedient permits an entity holding investments in certain entities that either are investment companies or have attributes similar to an investment company, and calculate NAV 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. Investments which are valued using NAV per share as a practical expedient are not categorized within the fair value hierarchy. ii. Carried Interest— For the private equity and debt fund products the Company offers, the Company is allocated incentive income by the investment funds based on the extent by which the investment funds performance exceeds predetermined thresholds. Carried interest allocations are generally structured from a legal standpoint as an allocation of capital in the Company’s capital account. The Company accounts for carried interest allocations by applying an equity ownership model. Accordingly, the Company accrues performance allocations quarterly based on the fair value of the underlying investments assuming hypothetical liquidation at book value. iii. 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 applies the equity method of accounting. The Company's investments in equity method investees are recorded in other investments in the accompanying 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 other investments in the accompanying condensed consolidated statements of operations. See Notes 6 and 7 for further information regarding the Company's investments, including equity method investments and fair value measurements. f. Offsetting of derivative contracts To reduce credit exposures on derivatives, the Company may enter into master netting agreements with counterparties that permit the Company the right, in the event of a default by a counterparty, to offset the counterparty’s rights and obligations under the agreement and to liquidate and offset any collateral against any net amount owed by the counterparty. Derivatives are reported on a net-by-counterparty basis (i.e., the net payable or receivable for derivative assets and liabilities for a given counterparty) in the condensed consolidated statements of financial condition when a legal right of offset exists under an enforceable netting agreement. Additionally, derivatives are reported net of cash collateral received and posted under enforceable credit support agreements in the condensed consolidated statements of financial position, provided a legal right of offset exists. See Notes 6 for further information about offsetting of derivative financial instruments. g. Receivable from and payable to brokers Receivable from brokers, dealers, and clearing organizations includes amounts receivable for securities failed to deliver by the Company to a purchaser by the settlement date, amounts receivable from broker-dealers and clearing organizations, commissions receivable from broker-dealers, and interest receivable from securities financing arrangements and are reported net of an allowance for credit losses. Payable to brokers, dealers and clearing organizations includes amounts payable for securities failed to receive by the Company from a seller by the settlement date, amounts payable to broker-dealers and clearing organizations for unsettled trades, interest payable for securities financing arrangements, and payables of deposits held in proprietary account of brokers and dealers. Pursuant to the master netting agreements the Company has entered into with its brokers, dealers and clearing organizations, receivables and payables arising from unsettled trade are presented net (assets less liabilities) across balances with the same counterparty. The Company's receivable from and payable to brokers, dealers and clearing organizations balances are held at multiple financial institutions. h. Receivable from and payable to customers Receivable from customers includes amounts owed by customers on cash and margin transactions, recorded on a settlement-date basis and prepaid research, net of allowance for credit losses. For prepaid research, a prepaid research asset is established for research and related services disbursed in advance of anticipated client commission volumes. Payable to customers primarily consists of amounts owed to customers relating to securities transactions not completed on settlement date, recorded on a settlement-date basis on the statement of financial condition, and other miscellaneous customer payables. Securities owned by customers, including those that collateralize margin, are not reflected as assets of the Company on the statement of financial condition. The Company holds these securities with the intention of settlement against customer orders and are held as collateral for customer receivables. i. Fees receivable Fees related to security transactions are reported net of an allowance for credit losses. Management and incentive fees are earned as the managing member, general partner and/or investment manager to the Company's investment funds and are recognized in accordance with appropriate revenue recognition guidance (see Note 2n). j. Securities financing arrangements 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 accompanying condensed consolidated statements of operations as interest and dividends income and interest and dividends expense. Securities borrowed transactions require the Company to deposit cash collateral with the lender. With respect to securities loaned, the Company receives cash or securities as collateral from the borrower. When the Company receives securities as collateral, and has concluded it (i) is the transferor and (ii) can pledge the securities to third parties, the Company recognizes the securities received as collateral at fair value in Securities owned, at fair value with the corresponding obligation to return the securities received as collateral at fair value in Securities sold, not yet purchased, at fair value. Securities received as collateral are not recognized when the Company either (i) is not the transferor or (ii) cannot pledge the securities to third parties. 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. See Note 2d for further information. Fees and interest received or paid are recorded in interest and dividends income and interest and dividends expense, respectively, on an accrual basis in the accompanying condensed consolidated statements of operations. In cases where the fair value basis of accounting is elected, any resulting change in fair value would be reported in Investment Income - Securities principal transactions, net in the accompanying condensed consolidated statements of operations. Accrued interest income and expense are recorded in receivable from brokers, dealers and clearing organizations and payable to brokers, dealers and clearing organizations, respectively, on an accrual basis in the accompanying condensed consolidated statements of financial condition. At March 31, 2021 and December 31, 2020, the Company did not have any securities lending transactions for which fair value basis of accounting was elected. k. Securities sold under agreements to repurchase Securities purchased under agreement to resell and securities sold under agreements to repurchase ("repurchase agreements") are accounted for as collateralized financing transactions and are recorded at their contracted resale or repurchase amoun

Acquisition

Acquisition	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Acquisitions	Acquisition Malta Holdings On February 26, 2021 (the "Malta Holdings Acquisition Date"), the Company, through its indirect wholly owned subsidiary, Cowen Malta Holdings Ltd. (“Malta Holdings”), completed the acquisition of all of the outstanding equity interest of Axeria Insurance Limited (the “Acquisition"), an insurance company organized under the laws of Malta whose principal business activity is to provide insurance coverage to third parties (See Note 14). Axeria Insurance Limited was renamed Cowen Insurance Company Ltd (“Cowen Insurance Co”) upon acquisition. The Acquisition was completed for a combination of cash and deferred consideration. In the aggregate, the purchase price, assets acquired, and liabilities assumed were not significant and near-term impact to the Company and its consolidated results of operations and cash flows is not expected to be significant. The aggregate estimated purchase price of the Acquisition was $12.7 million. On the Malta Holdings Acquisition Date, the Company paid upfront consideration of $12.5 million, with additional deferred consideration of $0.2 million. The deferred consideration liability is included within accounts payable, accrued expenses and other liabilities on the consolidated statements of financial condition. The Acquisition was accounted for under the acquisition method of accounting in accordance with US GAAP. As such, the results of operations of the business acquired is included in the accompanying condensed consolidated statements of operations since the date of the Acquisition and the assets acquired, liabilities assumed recorded at their fair values within their respective line items on the accompanying condensed consolidated statement of financial condition. The Company has recognized a bargain purchase gain of $5.2 million related to the Acquisition and is shown net of associated tax of $1.3 million in the consolidated statement of operations. The bargain purchase gain is primarily driven by the recognition of the customer relationships intangible asset and a contractual discount on the closing equity balance at the Malta Holdings Acquisition Date. Additionally, following the Acquisition, the business acquired is included in the Cowen Investment Management reporting unit within the Operating Company segment. The table below summarizes the preliminary purchase price allocation of net tangible and intangible assets acquired and liabilities assumed as of February 26, 2021: (dollars in thousands) Cash $ 14,844 Securities owned, at fair value 1,571 Fixed assets 30 Intangible assets 4,794 Other assets 12,828 Compensation payable (17) Other liabilities (16,099) Total net identifiable assets acquired and liabilities assumed 17,951 Bargain purchase gain (5,216) Total estimated purchase price $ 12,735 As of the Malta Holdings Acquisition Date, the estimated fair value of the Company's intangible assets, which are primarily broker relationships, was $4.6 million and had a weighted average useful life of 10 years. The licenses of $0.2 million has indefinite life. Amortization expense for the three months ended March 31, 2021 was insignificant. As of March 31, 2021, the estimated amortization expense related to these intangible assets in future periods is as follows: (dollars in thousands) 2021 $ 343 2022 458 2023 458 2024 458 2025 458 Thereafter 2,365 $ 4,540

Cash Collateral Pledged

Cash Collateral Pledged	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash Collateral Pledged	Cash Collateral Pledged As of March 31, 2021 and December 31, 2020, the Company pledged cash collateral in the amount of $3.5 million and $4.0 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. The Company also has pledged cash collateral for reinsurance agreements which amounted to $106.8 million, as of March 31, 2021, and $106.8 million, as of December 31, 2020, which are expected to be released periodically as per the terms of the reinsurance policy between June 30, 2021 and March 31, 2024 (see Notes 14 and 18). As of March 31, 2021 , the Company has the following irrevocable letters of credit, rela ted 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) New York $ 215 April 2022 New York $ 1,424 October 2022 New York $ 1,252 November 2021 Boston $ 194 March 2028 San Francisco $ 458 October 2025 $ 3,543 To the extent any letter of credit is drawn upon, interest will be assessed at the prime commercial lending rate. As of March 31, 2021 and December 31, 2020 ther e were no amounts due related to these letters of credit.

Segregated Cash

Segregated Cash	3 Months Ended
	Mar. 31, 2021
Segregated Cash [Abstract]
Segregated Cash	Segregated CashAs of March 31, 2021 and December 31, 2020, cash segregated in compliance with federal regulations and other restricted deposits of $168.9 million and $185.1 million, respectively, consisted of cash deposited in Special Reserve Bank Accounts for the exclusive benefit of customers under SEC Rule 15c3-3 and cash deposited in Special Reserve Bank Accounts for the exclusive benefit of Proprietary Accounts of Broker-Dealers ("PAB") under SEC Rule 15c3-3

Investments of Operating Entiti

Investments of Operating Entities and Consolidated Funds	3 Months Ended
	Mar. 31, 2021
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, which are not part of the Company's self-clearing securities finance activities, are pledged to external clearing brokers under terms which permit the external clearing broker to sell or re-pledge the securities to others subject to certain limitations. As of March 31, 2021 and December 31, 2020, securities owned, at fair value consisted of the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Common stock $ 2,934,604 $ 1,770,301 Preferred stock 66,853 69,358 Warrants and rights 30,961 27,701 Government bonds 19,671 19,721 Corporate bonds 81,460 86,503 Convertible bonds 3,137 6,040 Term loan (*) 12,424 12,623 Trade claims (*) 5,905 8,713 Private investments 1,085 642 $ 3,156,100 $ 2,001,602 (*) The Company has elected the fair value option for securities owned, at fair value with a fair value of $5.9 million and $8.8 million, respectively, at March 31, 2021 and December 31, 2020. Receivable on and Payable for derivative contracts, at fair value The Company predominantly enters into derivative transactions to satisfy client needs and to manage its own exposure to market and credit risks resulting from its trading activities. The Company’s direct exposure to derivative financial instruments includes futures, currency forwards, equity swaps, credit default swaps and options.. The Company's derivatives trading activities expose 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. The Company's long and short exposure to derivatives is as follows: Receivable on derivative contracts As of March 31, 2021 As of December 31, 2020 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Currency forwards $ 132,960 $ 384 $ 4,902 $ 15 Swaps $ 1,746,919 142,266 $ 944,544 64,634 Options other (a) 163,622 42,124 371,188 49,102 Netting - swaps (b) (89,238) (62,269) $ 95,536 $ 51,482 Payable for derivative contracts As of March 31, 2021 As of December 31, 2020 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Currency forwards $ 1,990 $ 16 $ 123,346 $ 3,067 Swaps $ 1,603,710 82,391 $ 896,863 43,560 Options other (a) 130,627 31,524 198,320 66,566 Netting - swap (b) (61,806) (37,033) $ 52,125 $ 76,160 (a) Includes the volume of contracts for index, equity, commodity future and cash conversion options. (b) Derivatives are reported on a net basis, by counterparty, when a legal right of offset exists under an enforceable netting agreement as well as net of cash collateral received or posted under enforceable credit support agreements. See Note 2f for further information on offsetting of derivative financial instruments. The following tables present the gross and net derivative positions and the related offsetting amount, as of March 31, 2021 and December 31, 2020. This table does not include the impact of over-collateralization. Gross amounts offset on the Condensed Consolidated Statements of Financial Condition (a) Net amounts included on the Condensed Consolidated Statements of Financial Condition Gross amounts not offset in the Condensed Consolidated Statements of Financial Condition Gross amounts recognized Financial instruments (a) Cash Collateral pledged (a) Net amounts (dollars in thousands) As of March 31, 2021 Receivable on derivative contracts, at fair value $ 184,774 $ 89,238 $ 95,536 $ 2,694 $ 48,448 $ 44,394 Payable for derivative contracts, at fair value 113,931 61,806 52,125 2,694 1,124 48,307 As of December 31, 2020 Receivable on derivative contracts, at fair value $ 113,751 $ 62,269 $ 51,482 $ 691 $ 169 $ 50,622 Payable for derivative contracts, at fair value 113,193 37,033 76,160 691 3,174 72,295 (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. The realized and unrealized gains/(losses) related to derivatives trading activities were $35.5 million and $28.8 million for the three months ended March 31, 2021 and 2020, respectively, and are included in Investment income - Securities principal transactions, net in the accompanying condensed consolidated statements of operations. The net gains (losses) on derivative contracts in the table above are one of a number of activities comprising the Company's business activities and are calculated before consideration of economic hedging transactions, which generally offset the net gains (losses) included above. Pursuant to the various derivatives transactions discussed above, except for exchange traded derivatives and c ertain options, the Company is required to post/receive collateral. These amounts are recognized in receivable from brokers, dealers and clearing organizations and payable to brokers, dealers and clearing organizations respectively. As of March 31, 2021 and December 31, 2020, all derivative contracts were with major financial institutions. Other investments As of March 31, 2021 and December 31, 2020, other investments included the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Portfolio funds, at fair value (1) $ 151,933 $ 133,454 Carried interest (2) 180,352 82,892 Equity method investments (3) 34,498 38,681 $ 366,783 $ 255,027 (1) Portfolio funds, at fair value The portfolio funds, at fair value as of March 31, 2021 and December 31, 2020, included the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Starboard Value and Opportunity Fund LP (c)(*) $ 46,008 $ 42,519 Formation8 Partners Fund I, L.P. (f) 33,408 31,894 Cowen Healthcare Investments II LP (i) (*) 26,733 26,186 Lagunita Biosciences, LLC (d) 3,785 3,850 Eclipse Ventures Fund I, L.P. (b) 4,804 4,457 HealthCare Royalty Partners II LP (a)(*) 1,605 1,588 HealthCare Royalty Partners LP (a)(*) 1,035 1,072 Starboard Leaders Fund LP (e)(*) 2,328 2,020 Eclipse SPV I, LP (j)(*) 1,809 1,708 Ramius Merger Fund LLC (m)(*) 2,252 2,197 TriArtisan ES Partners LLC (k)(*) 1,848 1,657 Cowen Healthcare Investments III LP (i)(*) 7,717 5,714 TriArtisan PFC Partners LLC (l)(*) 760 691 Starboard Value and Opportunity Fund Ltd (c) (*) 2,556 2,364 Eclipse Ventures Fund II, L.P. (b) 1,910 1,733 Eclipse Continuity Fund I, L.P. (b) 1,252 1,101 Cowen Sustainable Investments I LP (i)(*) 9,299 — Difesa Partners, LP (h) 985 848 BDC Fund I Coinvest 1, L.P. (n) 1,250 1,250 Other private investment (o)(*) 311 326 Other affiliated funds (p)(*) 278 279 $ 151,933 $ 133,454 * 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 17. (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) Each of Eclipse Ventures Fund I, L.P., Eclipse Ventures Fund II, L.P. and Eclipse Continuity Fund I, L.P. are venture capital funds which invests in early stage and growth stage hardware companies. Distributions will be made when the underlying investments are liquidated. (c) Starboard Value and Opportunity Fund LP and Starboard Value and Opportunity Fund Ltd permits quarterly withdrawals upon 90 days' notice. (d) Lagunita Biosciences, LLC, is a healthcare investment company that creates and grows early stage companies to commercialize impactful translational science that addresses significant clinical needs, is a private equity structure and therefore distributions will be made when the underlying investments are liquidated. (e) Starboard Leaders Fund LP does not permit withdrawals, but instead allows terminations with respect to capital commitments upon 30 days' prior written notice at any time following the first anniversary of an investor's initial capital contribution. (f) Formation8 Partners Fund I, L.P. is a private equity fund which invests in early stage and growth transformational information and energy technology companies. Distributions will be made when the underlying investments are liquidated. (g) RCG Longview Debt Fund V, L.P. is a real estate private equity structures. The timing of distributions depends on the nature of the underlying investments and therefore will be made either quarterly or when the underlying investments are liquidated. (h) Difesa Partners, LP permits semi-annual withdrawals occurring on or after the anniversary of initial contribution upon 90 days written notice. (i) Cowen Healthcare Investments II LP, Cowen Healthcare Investments III LP and Cowen Sustainable Investments I LP are private equity funds. Distributions are made from the fund when cash flows or securities are received from the underlying investments. Investors do not have redemption rights. (j) Eclipse SPV I, L.P. is a co-investment vehicle organized to invest in a private company focused on software-driven automation projects. Distributions will be made when the underlying investments are liquidated. (k) TriArtisan ES Partners LLC is a co-investment vehicle organized to invest in a privately held nuclear services company. Distributions will be made when the underlying investment is liquidated. (l) TriArtisan PFC Partners LLC is a co-investment vehicle organized to invest in a privately held casual dining restaurant chain. Distributions will be made when the underlying investment in liquidated. (m) Ramius Merger Fund LLC permits monthly withdrawals on 45 days prior notice. (n) BDC Fund I Coinvest 1, L.P. is a private equity fund focused on investing in growth companies in industries disrupted by digitization. Distributions will be made when the underlying investments are liquidated. (o) Other private investment represents the Company's closed end investment in a portfolio fund that invests in a wireless broadband communication provider in Italy. (p) The majority of these investment 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) Carried interest The Company applies an accounting policy election to recognize incentive income allocated to the Company under an equity ownership model in other investments in the accompanying condensed consolidated statements of financial condition (see Note 2n). Carried interest allocated to the Company from certain portfolio funds represents Cowen's general partner capital accounts from those funds. These balances are subject to change upon cash distributions, additional allocations or reallocations back to limited partners within the respective funds. All carried interest balances are earned from affiliates of the Company. A portion of the Company's carried interest is granted to employees through profit sharing awards designed to more closely align compensation with the overall realized performance of the Company. These arrangements enable certain employees to earn compensation based on performance revenue earned by the Company and are recorded within compensation payable in the accompanying condensed consolidated statements of financial condition and employee compensation and benefits expense in the accompanying condensed consolidated statements of operation based on the probable and estimable payments under the terms of the awards. The carried interest as of March 31, 2021 and December 31, 2020, included the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Cowen Healthcare Investments II LP $ 73,415 $ 62,112 Cowen Healthcare Investments III LP 31,034 11,520 Cowen Sustainable Investments I LP 13,581 — Cowen Sustainable Investments Offshore I LP 17,944 — CSI I Prodigy Co-Investment LP 6,617 — CSI PRTA Co- Investment LP 26,242 — TriArtisan TGIF Partners LLC 3,689 3,361 TriArtisan ES Partners LLC 4,514 3,152 TriArtisan PFC Partners LLC 2,329 1,455 Ramius Multi-Strategy Fund LP 638 734 Ramius Merger Fund LLC 162 368 RCG IO Renergys Sarl 187 190 $ 180,352 $ 82,892 (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 15% to 55%. The Company holds a majority of the outstanding ownership interest (i.e., more than 50%) in RCG Longview Partners II, LLC and 40% in Surf House Ocean Views Holdings, LLC (which is a joint venture in a real estate development project). The operating agreement that governs the management of day-to-day operations and affairs of these entities stipulates 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 entities requires 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 are the investments in (a) HealthCare Royalty Partners General Partners and (b) 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 several activist investment funds and related managed accounts. The Company completed assessments of the recoverability of the Company's equity method investments and determined that the carrying value of the investment in Surf House Ocean View Holdings, LLC exceeded the estimated fair value of the Company's interest, which was other than temporary. There were no impairment charges for the three months ended March 31, 2021. An other than temporary impairment charge of $7.3 million for the three months ended March 31, 2020 was recognized to reduce the carrying value of the investment to fair value, which was subsequently completely impaired at the end of 2020. Impairment charges are included in net gains (losses) on other investments on the accompanying condensed consolidated statements of operations. The Company elected to use the cumulative earnings approach for the distributions it receives from its equity method investments. Under the cumulative earnings approach, any distributions received up to the amount of cumulative earnings are treated as return on investment and classified in operating activities within the cash flows. Any excess distributions would be considered as return of investments and classified in investing activities. The following table summarizes equity method investments held by the Company: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Starboard Value LP $ 27,769 $ 31,528 HealthCare Royalty GP III, LLC 2,221 2,213 RCG Longview Management, LLC 268 268 HealthCare Royalty GP, LLC 442 920 HealthCare Royalty GP II, LLC 272 269 RCG Longview Debt Fund IV Management, LLC 331 331 RCG Longview Equity Management, LLC 105 105 HCR Stafford Fund GP, LLC 1,159 1,025 Liberty Harbor North 222 222 Other 1,709 1,800 $ 34,498 $ 38,681 The Company's income (loss) from equity method investments was income of $12.6 million and a loss of $0.06 million for the three months ended March 31, 2021 and 2020, respectively, and is included in net gains (losses) on other investments on the accompanying condensed consolidated statements of operations. Securities sold, not yet purchased, at fair value Securities sold, not yet purchased, at fair value represent obligations of t he 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. As of March 31, 2021 and December 31, 2020, securities sold, not yet purchased, at fair value consisted of the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Common stock $ 918,021 $ 699,894 Corporate bonds 453 11,358 Government bonds 522 1,500 Preferred stock 7,567 6,589 Warrants and rights 4,519 8,774 $ 931,082 $ 728,115 Securities purchased under agreements to resell/securities sold under agreements to repurchase and securities lending and borrowing transactions The following tables present the contractual gross and net securities borrowing and lending agreements and securities sold under agreements to repurchase and the related offsetting amount as of March 31, 2021 and December 31, 2020. Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition Gross amounts recognized, net of allowance Gross amounts offset on the Condensed Consolidated Statements of Financial Condition (a) Net amounts included on the Condensed Consolidated Statements of Financial Condition Additional Amounts Available Financial instruments Cash Collateral pledged (b) Net amounts (dollars in thousands) As of March 31, 2021 Securities borrowed $ 1,996,757 $ — $ 1,996,757 $ — $ 1,970,665 $ — $ 26,092 Securities loaned 3,083,945 — 3,083,945 — 3,100,800 — (16,855) Securities sold under agreements to repurchase 2,546 — 2,546 — 2,759 — (213) As of December 31, 2020 Securities borrowed $ 1,908,187 $ — $ 1,908,187 $ — $ 1,809,399 $ — $ 98,788 Securities loaned 2,476,414 — 2,476,414 — 2,383,342 — 93,072 Securities purchased under agreements to resell 191 — 191 — 204 — (13) Securities sold under agreements to repurchase 5,036 — 5,036 — 5,544 — (508) (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. The following tables present gross obligations for securities loaned and securities sold under agreements to repurchase by remaining contractual maturity and class of collateral pledged as of March 31, 2021 and December 31, 2020: Open and Overnight Up to 30 days 31 - 90 days Greater than 90 days Total (dollars in thousands) As of March 31, 2021 Securities loaned Common stock $ 2,827,291 $ — $ — $ — $ 2,827,291 Corporate bonds 256,654 — — — 256,654 Securities sold under agreements to repurchase Corporate bonds — — 2,546 — 2,546 As of December 31, 2020 Securities loaned Common stock 2,232,687 — — — 2,232,687 Corporate bonds 243,726 — — — 243,726 Securities sold under agreements to repurchase Corporate bonds $ — $ — $ 5,036 $ — $ 5,036 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, ar e $8.9 billion and $1.2 billion as of March 31, 2021 and $8.0 billion and $1.3 billion as of December 31, 2020, respectively. The carrying value of the Company's exposure to loss for these variable interest entities as of March 31, 2021 was $236.4 million , and as of December 31, 2020 was $210.7 million, all of which is included in other investments, at fair value in the accompanying condensed consolidated statements of financial condition. Additionally, the Company's maximum exposure to loss for the variable interest entities noted above as of March 31, 2021 and December 31, 2020, was $364.9 million and $326.0 million, respectively. The maximum exposure to loss often differs from the carrying value of exposure to loss of the variable interests. The maximum exposure to loss is dependent on the nature of the variable interests in the VIEs and is limited to the notional amounts of certain commitments and guarantees. b. Consolidated Funds Securities owned, at fair value As of March 31, 2021 and December 31, 2020, securities owned, at fair value, held by the Consolidated Funds consisted of the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Common stock $ 3,611 $ 4,816 Warrants and rights 5,329 5,806 $ 8,940 $ 10,622 Other investments, at fair value Investments in portfolio funds, at fair value As of March 31, 2021 and December 31, 2020, investments in portfolio funds, at fair value, included the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Investments of Enterprise LP $ 100,035 $ 104,475 Investments of Cowen Sustainable Investments I LP — 88,195 $ 100,035 $ 192,670 Consolidated portfolio fund investments of Enterprise LP On May 12, 2010, the Company announced its intention to close Enterprise Master. Enterprise LP operated under a "master-feeder" structure up until January 1, 2019, when Enterprise Master distributed its capital to each feeder and was liquidated. As of March 31, 2021 and December 31, 2020, the consolidated investments in portfolio funds include Enterprise LP's investment in RCG Special Opportunities Fund, Ltd which is a portfolio fund that invests in a limited number of private equity investments directly as well as through affiliated portfolio funds. Consolidated portfolio fund investments of Cowen Sustainable Investments I LP Cowen Sustainable Investments I LP ("CSI I LP") is a private investment fund making debt and equity investments in companies and real assets that are accelerating the global transition to a sustainable economy. The fund primarily focuses its investments around four themes: (i) renewable energy and battery storage; (ii) clean transportation; (iii) sustainable agriculture and food production; and (iv) resource and industrial efficiency. CSI I LP has made investments in ecoATM, LLC, a manufacturer and owner of automated kiosks that allow consumers to sell back unwanted smart phones, and Proterra, Inc, a designer and manufacturer of zero-emission electric transit vehicles and electric vehicle technology solutions for commercial applications. CSI I LP is a private equity-style vehicle that does not permit redemptions; proceeds realized from the fund’s investments are expected to be distributed after the end of the fund’s investment period. CSI I LP was deconsolidated during the first quarter of 2021 (See Note 2). Indirect Concentration of the Underlying Investments Held by Consolidated Funds From time to time, either directly held by the Company, indirectly through the Company's consolidated entities or indirectly through its investments in the Consolidated Funds, the Company may maintain exposure to a particular issue or issuer (both long and/or short) which may account for 5% or more of the Company's equity. Based on information that is available to the Company as of March 31, 2021 and December 31, 2020, the Company assessed whether or not its interests in an issuer for which the Company's pro-rata share exceeds 5% of the Company's equity. There was one indirect concentration that exceeded 5% of the Company's equity as of March 31, 2021 and December 31, 2020, respectively. Through its investments in a Consolidated Fund and combined with direct Company investments, the Company maintained exposure to a particular investment which accounted for 5% or more of the Company's equity. Investment's percentage of the Company's stockholders' equity Issuer Security Type Country Industry Percentage of Stockholders' Equity Market Value (dollars in thousands) As of March 31, 2021 Linkem S.p.A. Equity, loans and warrants Italy Wireless Broadband 7.62 % $ 84,324 As of December 31, 2020 Linkem S.p.A. Equity, loans and warrants Italy Wireless Broadband 9.07 % $ 87,944

Fair Value Measurements for Ope

Fair Value Measurements for Operating Entities and Consolidated Funds	3 Months Ended
	Mar. 31, 2021
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, 2021 and December 31, 2020: Assets at Fair Value as of March 31, 2021 Level 1 Level 2 Level 3 Netting (c) Total (dollars in thousands) Operating Entities Securities owned, at fair value Government bonds $ 19,671 $ — $ — $ — $ 19,671 Preferred stock 10,376 — 56,477 — 66,853 Common stock 2,911,824 74 22,706 — 2,934,604 Convertible bonds — — 3,137 — 3,137 Corporate bonds — 81,324 136 — 81,460 Trade claims — — 5,905 — 5,905 Term loan — — 12,424 — 12,424 Warrants and rights 23,037 — 7,924 — 30,961 Private investments — — 1,085 — 1,085 Receivable on derivative contracts, at fair value Currency forwards — 384 — — 384 Swaps — 142,266 — (89,238) 53,028 Options 41,883 — 241 — 42,124 Consolidated Funds Securities owned, at fair value Common stock 660 — 2,951 — 3,611 Warrants and rights — — 5,329 — 5,329 $ 3,007,451 $ 224,048 $ 118,315 $ (89,238) $ 3,260,576 Portfolio funds measured at net asset value (a) 151,933 Consolidated Funds' portfolio funds measured at net asset value (a) 100,035 Carried interest (a) 180,352 Equity method investments (a) 34,498 Total investments $ 3,727,394 Liabilities at Fair Value as of March 31, 2021 Level 1 Level 2 Level 3 Netting (c) Total (dollars in thousands) Operating Entities Securities sold, not yet purchased, at fair value Government bonds $ — $ — $ 522 $ — $ 522 Common stock 918,021 — — — 918,021 Corporate bonds — 38 415 — 453 Preferred stock 7,567 — — — 7,567 Warrants and rights 4,519 — — — 4,519 Payable for derivative contracts, at fair value Currency forwards — 16 — — 16 Swaps — 82,391 — (61,806) 20,585 Options 28,227 — 3,297 — 31,524 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 19,579 — 19,579 $ 958,334 $ 82,445 $ 23,813 $ (61,806) $ 1,002,786 (a) In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition. (b) In accordance with the terms of the purchase agreements for acquisitions that closed during the first quarter of 2019 and the fourth quarter of 2020, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired businesses, if certain targets are achieved through the periods ended December 31, 2020 and December 31, 2023. For both the Quarton Acquisition and the MHT Acquisition, the Company estimated the contingent consideration liabilities using a combination of Monte Carlo and Discounted Cash Flow methods which require 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 for the Quarton Acquisition can range from $10.1 million to $25.0 million. The undiscounted amounts for the MHT Acquisition have no minimum or maximum as it is calculated based on revenue. (c) Derivatives are reported on a net basis, by counterparty, when a legal right of offset exists under an enforceable netting agreement as well as net of cash collateral received or posted under enforceable credit support agreements. See Note 2f for further information on offsetting of derivative financial instruments. Assets at Fair Value as of December 31, 2020 Level 1 Level 2 Level 3 Netting (c) Total (dollars in thousands) Operating Entities Securities owned, at fair value Government bonds $ 19,721 $ — $ — $ — $ 19,721 Preferred stock 9,391 — 59,967 — 69,358 Common stock 1,746,407 108 23,786 — 1,770,301 Convertible bonds — — 6,040 — 6,040 Corporate bonds — 86,368 135 — 86,503 Trade claims — — 8,713 — 8,713 Term loan — — 12,623 — 12,623 Private investments — — 642 — 642 Warrants and rights 21,154 — 6,547 — 27,701 Receivable on derivative contracts, at fair value Currency forwards — 15 — — 15 Swaps — 64,634 — (62,269) 2,365 Options 48,851 — 251 — 49,102 Consolidated Funds Securities owned, at fair value Common stock 1,865 — 2,951 — 4,816 Warrants and rights — — 5,806 — 5,806 $ 1,847,389 $ 151,125 $ 127,461 $ (62,269) $ 2,063,706 Portfolio funds measured at net asset value (a) 133,454 Consolidated Funds' portfolio funds measured at net asset value (a) 192,670 Carried interest (a) 82,892 Equity method investments (a) 38,681 Total investments $ 2,511,403 Liabilities at Fair Value as of December 31, 2020 Level 1 Level 2 Level 3 Netting (c) Total (dollars in thousands) Operating Entities Securities sold, not yet purchased, at fair value US Government securities $ — $ — $ 1,500 $ — $ 1,500 Common stock 699,894 — — — 699,894 Corporate bonds — 10,654 704 — 11,358 Preferred stock 6,589 — — — 6,589 Warrants and rights 8,774 — — — 8,774 Payable for derivative contracts, at fair value Currency forwards — 3,067 — — 3,067 Swaps — 43,560 — (37,033) 6,527 Options 62,651 — 3,915 — 66,566 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 36,718 — 36,718 $ 777,908 $ 57,281 $ 42,837 $ (37,033) $ 840,993 (a) In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition. (b) In accordance with the terms of the purchase agreements for acquisitions that closed during the first quarter of 2019 and the fourth quarter of 2020, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired businesses, if certain targets are achieved through the periods ended December 31, 2020 and December 31, 2023. For both the Quarton Acquisition and the MHT Acquisition, the Company estimated the contingent consideration liabilities using a combination of Monte Carlo and Discounted Cash Flow methods which require 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 for the Quarton Acquisition can range from $10.1 million to $35.1 million. The undiscounted amounts for the MHT Acquisition have no minimum or maximum as it is calculated based on revenue. (c) Derivatives are reported on a net basis, by counterparty, when a legal right of offset exists under an enforceable netting agreement as well as net of cash collateral received or posted under enforceable credit support agreements. See Note 2f for further information on offsetting of derivative financial instruments. The following table includes a roll forward of the amounts for the three months ended March 31, 2021 and 2020 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, 2021 Balance at December 31, 2020 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at March 31, 2021 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 59,967 $ — $ — $ 1,859 $ (4,651) $ (698) $ 56,477 $ (698) Common stock 23,786 — (5,353) (b) 3,226 (1,387) 2,434 22,706 1,679 Convertible bonds 6,040 — — 1,050 (3,930) (23) 3,137 (23) Corporate bond 135 — — 70 (49) (20) 136 (49) Options, asset 251 — — — — (10) 241 (10) Options, liability 3,915 — — — — (618) 3,297 (618) Term loan 12,623 — — 322 — (521) 12,424 (521) Warrants and rights 6,547 — — 3,406 (1,206) (823) 7,924 (895) Trade claims 8,713 — 1,378 (4,216) 30 5,905 (1,021) Private investments 642 — — 443 — — 1,085 — Corporate bond, liability 704 — — — (289) — 415 — Government bonds, liability 1,500 — — — (1,278) 300 522 87 Contingent consideration liability 37,952 — — (11,312) — (7,061) 19,579 (7,061) Consolidated Funds Common stock 2,951 — — — — — 2,951 — Warrants and rights 5,806 — — — (670) 193 5,329 (477) Three Months Ended March 31, 2020 Balance at December 31, 2019 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at March 31, 2020 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 7,835 $ — $ — $ 365 $ — $ — $ 8,200 $ — Common stock 17,466 — — 1,798 (593) (1,161) 17,510 (1,257) Convertible bonds 2,500 — — 286 — — 2,786 — Corporate Bond, asset 2,421 — — 422 (24) (7) 2,812 12 Options, asset 336 — — — — (4) 332 (4) Options, liability 2,920 — — — — (1,118) 1,802 (1,118) Warrants and rights 594 — — — — 4 598 4 Trade claim 7,083 1,044 (a) — 1,166 — (110) 9,183 (110) Private investments 237 — — 233 — (5) 465 (5) Corporate bond, liability 1,000 — — — — (200) 800 (200) Government bonds, liability 1,950 — — — — (450) 1,500 (450) Contingent consideration liability 30,896 — — — (1,400) (838) 28,658 (838) Consolidated Funds Preferred stock 4,393 — — — — — 4,393 — Common stock — — — 100,000 — — 100,000 — Warrants and rights $ 5,567 $ — $ — $ — $ — $ 44 $ 5,611 $ 44 (1) Unrealized gains/losses are reported in Investment income - Securities principal transactions, net in the accompanying condensed consolidated statements of operations. (a) The security stopped trading on an open market. (b) The entity in which the Company is invested completed an initial public offering. 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 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. The following table includes quantitative information as of March 31, 2021 and December 31, 2020 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 March 31, 2021 Valuation Techniques Unobservable Inputs Range Weighted Average Level 3 Assets (dollars in thousands) Common and preferred stocks $ 70,935 Discounted cash flows Guideline companies Probability of Success Discount rate EBITDA Market Multiples Probability of Success 11% - 20% 6.25x - 6.75x 70% 12% 6.5x 70% Options 241 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 11% - 12% 6.25x - 6.75x 12% 6.5x Trade claims 3,713 Discounted cash flows Discount rate 20% 20% Warrants and rights 10,394 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 4% - 12% 6.25x - 6.75x 7.0% 6.5x Corporate, convertible bonds and term loan 12,424 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 11% - 12% 6.25x - 6.75x 12% 6.5x Other level 3 assets (a) 20,608 Total level 3 assets $ 118,315 Level 3 Liabilities Options 3,297 Option pricing models Volatility 35% 35% Contingent consideration liability 19,579 Discounted cash flows Monte Carlo simulation Discount rate Volatility 7% - 15% 18% - 20% 13% 18% Other level 3 liabilities (a) 937 Total level 3 liabilities $ 23,813 Quantitative Information about Level 3 Fair Value Measurements Fair Value at December 31, 2020 Valuation Techniques Unobservable Inputs Range Weighted Average Level 3 Assets (dollars in thousands) Common and preferred stocks $ 65,735 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 10% - 12% 6.25x - 6.75x 11% 6.5x Trade claims 3,500 Discounted cash flows Discount rate 15% 15% Warrants and rights 11,217 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 4% - 11% 6.25x - 6.75x 7% 6.5x Options 251 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 10% - 12% 6.25x - 6.75x 11% 6.5x Corporate, convertible bonds and term loan 12,623 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 10% - 12% 6.25x - 6.75x 11% 6.5x Other level 3 assets (a) 34,135 Total level 3 assets $ 127,461 Level 3 Liabilities Options 3,915 Option pricing models Volatility 35% 35% Contingent consideration liability 36,718 Discounted cash flows Monte Carlo simulation Discount rate Volatility 9% - 16% 22% - 24% 15% 22% Other level 3 liabilities (a) 2,204 Total level 3 liabilities $ 42,837 (a) The quantitative disclosures exclude financial instruments for which the determination of fair value is based on prices from recent transactions. The Company has established valuation policies, procedures and internal control infrastructure over the fair value measurement of financial instruments. In the event that observable inputs are not available, the control processes are designed to ensure that the valuation approach utilized is applicable, reasonable and consistently applied. Where a pricing model is used to determine fair value, these control processes include reviews of the methodology and inputs for both reasonableness and applicability. Consistent with best practices, recently executed comparable transactions and other observable market data are used for the purposes of validating both the model and the assumptions used to calculate fair value. Independent of trading and valuation functions, the Company’s Valuation Committee in conjunction with its Price Verification team, plays an important role in determining that financial instruments are appropriately valued and that fair value measurements are both reasonable and reliable. This is particularly important where prices or valuations that require inputs are less observable. 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. 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 regularly reviews a 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. Other financial assets and liabilities The following table presents the carrying values and fair values, at March 31, 2021 and December 31, 2020, of financial assets and liabilities and information on their classification within the fair value hierarchy which are not measured at fair value on a recurring basis. For additional information regarding the financial instruments within the scope of this disclosure, and the methods and significant assumptions used to estimate their fair value (see Note 2e). March 31, 2021 December 31, 2020 Fair Value Hierarchy Carrying Amount Fair Value Carrying Amount Fair Value (dollars in thousands) Financial Assets Operating companies Cash and cash equivalents $ 1,147,531 $ 1,147,531 $ 645,169 $ 645,169 Level 1 Cash collateral pledged 110,303 110,303 110,743 110,743 Level 2 Segregated cash 168,942 168,942 185,141 185,141 Level 1 Securities purchased under agreements to resell — — 191 204 Level 2 Securities borrowed 1,996,757 1,996,757 1,908,187 1,908,187 Level 2 Loans receivable 4,467 4,467 (d) 7,682 7,682 (d) Level 3 Consolidated Funds Cash and cash equivalents 935 935 417 417 Level 1 Financial Liabilities Securities sold under agreements to repurchase 2,546 2,759 5,036 5,544 Level 2 Securities loaned 3,083,945 3,083,945 2,476,414 2,476,414 Level 2 Convertible debt 81,682 (a) 181,597 (b) 80,808 (a) 135,444 (b) Level 2 Notes payable and other debt 542,519 (e) 568,212 (c) 383,067 (e) 405,840 (c) Level 2 (a) The carrying amount of the convertible debt includes an unamortized discount of $5.8 million and $6.7 million as of March 31, 2021 and December 31, 2020, respectively. (b) The convertible debt includes the conversion option and is based on the last broker quote available. (c) Notes payable and other debt are based on the last broker quote available. (d) The fair market value of level 3 loans is calculated using discounted cash flows where applicable.

Deposits with Clearing Organiza

Deposits with Clearing Organizations, Brokers and Banks	3 Months Ended
	Mar. 31, 2021
Deposits with Clearing Organizations, Brokers and Banks [Abstract]
Deposits with Clearing Organizations, Brokers and Banks	Deposits with Clearing Organizations, Brokers and BanksUnder the terms of agreements between the Company and some of its clearing organizations, brokers and banks, balances owed are collateralized by certain of the Company's cash and securities balances. As of March 31, 2021 and December 31, 2020, the Company had a total of $82.1 million and $105.0 million, respectively, in deposit accounts with clearing organizations, brokers and banks that could be used as collateral to offset losses incurred by the clearing organizations, brokers and banks, on behalf of the Company's activities, if such losses were to occur.

Receivables from and payables t

Receivables from and payables to brokers, dealers and clearing organizations	3 Months Ended
	Mar. 31, 2021
Brokers and Dealers [Abstract]
Receivables From and Payables to Brokers, Dealers and Clearing Organizations	Receivable From and Payable To Brokers, Dealers and Clearing Organizations Receivable from and payable to brokers, dealers and clearing organizations includes cash held at the clearing brokers, amounts receivable or payable for unsettled transactions, monies borrowed and proceeds from short sales equal to the fair value of securities sold, not yet purchased, at fair value, which are restricted until the Company purchases the securities sold short. Pursuant to the master netting agreements the Company entered into with its brokers, dealers and clearing organizations, these balances are presented net (assets less liabilities) across balances with the same counterparty. The Company's receivable from and payable to brokers, dealers and clearing organizations balances are held at multiple financial institutions. As of March 31, 2021 and December 31, 2020, amounts receivable from brokers, dealers and clearing organizations include: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Broker-dealers $ 1,753,510 $ 1,608,273 Securities failed to deliver 76,127 55,655 Clearing organizations 79,833 41,795 Securities borrowed/loaned interest receivable 11,283 24,021 $ 1,920,753 $ 1,729,744 As of March 31, 2021 and December 31, 2020, amounts payable to brokers, dealers and clearing organizations include: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Broker-dealers $ 326,231 $ 286,011 Securities failed to receive 100,528 68,036 Clearing organizations 48,466 33,732 Securities borrowed/loaned interest payable 13,246 27,364 $ 488,471 $ 415,143

Receivable from and Payable to

Receivable from and Payable to Customers	3 Months Ended
	Mar. 31, 2021
Receivables and Payable to Customers [Abstract]
Receivable from and Payables to Customers [Text Block]	Receivable From and Payable To CustomersAs of March 31, 2021 and December 31, 2020, receivable from customers of $199.7 million and $104.0 million, respectively, consist of amounts owed by customers relating to securities transactions not completed on settlement date and receivables arising from prepaid research. As of March 31, 2021 and December 31, 2020, payable to customers of $2.7 billion and $1.7 billion, respectively, include amounts due on cash and margin transactions to the Company's clients, some of which have their assets held by a Company omnibus account, which are included within receivables from brokers, dealers and clearing organizations in the accompanying condensed consolidated statements of financial condition. In the omnibus structure, positions that are owned by Cowen International Ltd are fully cross collateralized by client funds, meaning that the Company, for all intents and purposes, has no market risk. Additionally, Cowen International Ltd has no obligation to settle any trade that it deems inappropriate from a risk perspective, adding an important market and counterparty risk mitigating factor.

Commission Management Payable

Commission Management Payable	3 Months Ended
	Mar. 31, 2021
Commission Management Payable [Abstract]
Commission Management Payable	Commission Management PayableThe Company receives a gross commission from various brokers, which is then used to fund commission sharing and recapture arrangements, less the portion retained as income to the Company. Accrued commission sharing and commission recapture payable of $139.6 million and $117.0 million, as of March 31, 2021 and December 31, 2020, respectively, are classified as commission management payable in the accompanying condensed consolidated statements of financial condition.

Non-Controlling Interests in Co

Non-Controlling Interests in Consolidated Subsidiaries and Funds	3 Months Ended
	Mar. 31, 2021
Noncontrolling Interest [Abstract]
Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds	Non-Controlling Interests in Consolidated Subsidiaries and Investment Funds Redeemable and nonredeemable non-controlling interests in consolidated subsidiaries and investment funds and the related net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds are comprised as follows: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Nonredeemable non-controlling interests in consolidated subsidiaries and investment funds Operating companies 92,629 83,818 Consolidated Funds 40,486 115,806 $ 133,115 $ 199,624 Three Months Ended March 31, 2021 2020 (dollars in thousands) Income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds Operating companies $ 7,661 $ 127 Consolidated Funds (3,099) (62,315) $ 4,562 $ (62,188)

Revenue from Contracts with Cus

Revenue from Contracts with Customers	3 Months Ended
	Mar. 31, 2021
Revenue Recognition and Deferred Revenue [Abstract]
Revenue from Contract with Customer	Revenue from Contracts with Customers For the three months ended March 31, 2021 and 2020, the following tables presents revenues from contracts with customers disaggregated by fee type and segment. Three Months Ended March 31, 2021 2020 (dollars in thousands) Revenue from contracts with customers Operating Company Investment banking Underwriting fees $ 154,304 $ 63,270 Strategic/financial advisory fees 73,555 21,996 Placement and sales agent fees 72,544 17,596 Expense reimbursements from clients 4,431 2,166 Total investment banking revenue 304,834 105,028 Brokerage Commissions 161,792 132,208 Trade conversion revenue 4,130 4,639 Equity research fees 4,593 4,005 Total brokerage revenue from customers 170,515 140,852 Management fees 25,499 11,346 Incentive income 2,258 — Total revenue from contracts with customers - Op Co $ 503,106 $ 257,226 Asset Company Management fees 243 258 Incentive income — — Total revenue from contracts with customers - Asset Co 243 258 Total revenue from contracts with customers $ 503,349 $ 257,484

Insurance and reinsurance

Insurance and reinsurance	3 Months Ended
	Mar. 31, 2021
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]
Reinsurance	Insurance and reinsurance The Company completed the acquisition of Cowen Insurance Co on February 26, 2021. (See Note 3 ) . Cowen Insurance Co is an insurance company that reinsures a significant proportion of its portfolio (“Outward Reinsurance”). The Company's wholly owned Luxembourg subsidiary, Hollenfels Re SA ("Hollenfels") provides reinsurance to third party insurance and reinsurance companies (“Inward Reinsurance”). Cowen Insurance Co’s and Hollenfels' share of claims incurred and paid during the periods below, as well as the change in claims outstanding and claims incurred but not reported ("IBNR") during these periods, net of reinsurance, were as follows: Three Months Ended March 31, 2021 2020 (dollars in thousands) Incurred and paid claims Insurance (net of Outward Reinsurance) $ 744 $ — Inward Reinsurance 3,904 4,235 Total $ 4,648 $ 4,235 Change in claims outstanding and claims IBNR Insurance (net of Outward Reinsurance) $ (136) $ — Inward Reinsurance (559) 17,293 Total $ (695) $ 17,293 Cowen Insurance Co and Hollenfels utilizes several methods to determine its claims IBNR. Cowen Insurance Co and Hollenfels generally employ an estimation methodology whereby historical average claims ratios over a period of up to 10 years are utilized, based on availability of data. In cases where current claims development contradicts historical results, Cowen Insurance Co and Hollenfels employ a method to average claims ratios derived through different actuarial calculation methods. If an event occurs that may give rise to significant future claims in excess of the amount calculated using the above-mentioned methodologies, the impact of such an event is calculated using existing claims data and actuarial estimation methods to adjust Cowen Insurance Co's and Hollenfels's IBNR provision. During the three months ended March 31, 2021, claims liability and claim adjustment expenses were calculated using the above-mentioned methods consistent with prior years. Whilst Cowen Insurance Co and Hollenfels typically settles its premiums and claim payments on a quarterly basis, the frequency of claims in the underlying policies is impractical for Cowen Insurance Co and Hollenfels to obtain. Certain contracts Cowen Insurance Co and Hollenfels has written are on a quota-share basis while the rest of the policies provide aggregate loss protection, rendering the collection of information for all underlying contracts impracticable. Cowen Insurance Co and Hollenfels did not discount any of its reserves and did not cede any portion of its exposures during the three months ended March 31, 2021 and 2020. From time to time, Cowen Insurance Co and Hollenfels may enter into insurance and reinsurance agreements that require it to post collateral of cash or U.S. government bonds to cover certain exposures as defined in the respective insurance and reinsurance agreements. As of March 31, 2021, Hollenfels pledged $120.5 million of collateral towards such reinsurance obligations, of which $106.8 million was cash and $13.7 million was U.S. government bond s. These are the same amounts that had been pledged at December 31, 2020. Hollenfels expects $101.2 million of the cash collateral pledged to be released on September 30, 2023. The remaining cash collateral of $5.6 million and all of the U.S. government bonds are expected to be released periodically between June 30, 2021 and March 31, 2024 in accordance with the terms of the underlying insurance and reinsurance agreements.

Share-Based Payments, Deferred

Share-Based Payments, Deferred Compensation and Employee Ownership Plans	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Share-Based Payments, Deferred Compensation and Employee Ownership Plans	Share-Based Payments, Deferred Compensation and Employee Ownership Plans The Company has issued share-based compensation under the 2010 and 2020 Equity and Incentive Plan (the "Equity Plans"). The Equity Plans permit the grant of options, restricted shares, restricted stock units, and other equity-based awards to the Company's employees and directors. Stock options granted generally vest over two five seven two five Under the Equity Plans, the Company awarded $34.1 million of deferred cash awards to its employees during the three months ended March 31, 2021. These awards vest over a four 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, net of estimated forfeitures. In relation to awards under the Equity Plan, the Company recognized compensation expense of $28.2 million and $8.3 million for the three months ended March 31, 2021 and 2020, respectively. The income tax effect recognized for the Equity Plans was a benefit of $10.8 million and $1.8 million for the three months ended March 31, 2021 and 2020, respectively. 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, 2021 and 2020: Three Months Ended March 31, 2021 Three Months Ended March 31, 2020 Nonvested Restricted Class A Common Shares and Class A Common Restricted Stock Units Weighted-Average Nonvested Restricted Class A Common Shares and Class A Common Restricted Stock Units Weighted-Average Beginning balance outstanding 5,450,191 $ 17.56 5,364,486 $ 16.67 Granted 1,593,941 34.85 2,140,932 17.39 Vested (291,062) 16.11 (640,084) 14.63 Canceled — — (87,348) 14.80 Forfeited (8,134) 20.22 (30,562) 15.86 Ending balance outstanding 6,744,936 $ 21.71 6,747,424 $ 17.12 Included in the restricted share and restricted stock unit activity are performance-linked restricted stock units of 1,603,630 which were awarded in March 2016, April 2019, July 2020 and February 2021. Certain of the awards granted have the ability to be cash settled when the attained award exceeds a certain percentage of granted amount. The cash portion of the award has been bifurcated from the equity component and recorded as a compensation payable in the accompanying condensed consolidated statement of financial condition. Of the awards granted, 379,319 have vested and 320,681 have been canceled, as they did not meet the performance criteria, through March 31, 2021. Included in vested shares are 233,333 shares that had an attainable value of 420,000, due to reaching certain performance goals, and were delivered in March 2021. Of this attainable value 350,000 shares were settled in the issuance of restricted stock units and were delivered in March 2021 with the remaining 70,000 shares being settled in cash at the volume weighted average price on settlement date. The remaining awards, included in the outstanding balance as of March 31, 2021, vest between December 2021 and December 2023 and will be earned only to the extent that the Company attains specified market conditions relating to its volume-weighted average share price and total shareholder return in relation to certain benchmark indices and performance goals relating to aggregate net income and average return on shareholder equity. The actual number of RSUs ultimately earned could vary from zero, if performance goals are not met, to as much as 200% 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 (excluding certain performance-linked units with market conditions which are valued using the Monte Carlo valuation model) 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, 2021, there was $118.1 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 2.13 years. Restricted Shares and Restricted Stock Units Granted to Non-Employee Board Members There were no restricted stock units awarded or delivered to non-employee board members during the three months ended March 31, 2021 and 2020. As of March 31, 2021 and December 31, 2020, there were 259,536 restricted stock units outstanding for non-employee board members. Other Share Based Payments In certain circumstances, the Company grants carried interest in consolidated managing member/general partner subsidiaries to third parties through the grant of equity awards in exchange for professional, advisory and other services. The equity awards are recorded within additional paid in capital in the accompanying condensed consolidated statements of financial condition and professional, advisory and other fees expense in the accompanying condensed consolidated statements of operations based on the fair value of the award granted and expensed over the terms of the award. In addition, the equity awards provide the third parties profit points aligned to the allocated carried interest distributions. Upon vesting of the awards, the third parties' allocation of carried interest is determined by applying an equity ownership model. Accordingly, the Company accrues carried interest allocations based on the fair value of the underlying investments assuming hypothetical liquidation at book value upon vesting as nonredeemable non-controlling interest.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
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, Inc. as well as stand-alone state and local tax returns. The Company has subsidiaries that are resident in foreign countries where tax filings are 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, Malta, Gibraltar, Germany, Switzerland, South Africa, Canada 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. To the extent that information is not available for the Company to fully determine the full year estimated impact of an item of income or tax adjustment, the Company calculates the tax impact of such item discretely. Accordingly, the Company uses the discrete methodology to calculate the income tax provision for its foreign subsidiaries and the tax impact of income attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds. Based on these methodologies, the Company’s effective income tax rate was 26.36% for the three months ended March 31, 2021. During the three months ended March 31, 2021, the items whose tax impact were recorded discretely related primarily to foreign taxes, as well as stock compensation. The Company's effective tax rate was 1.60% for the three months ended March 31, 2020. For the three months ended March 31, 2021, the effective tax rate differs from the statutory rate of 21% primarily due to income attributable to non-controlling interests in consolidated subsidiaries and investment funds, global intangible low-taxes income, stock compensation, as well as other nondeductible expen ses. For th e three months ended March 31, 2020, the effective tax rate differs from the statutory rate of 21% primarily due to losses attributable to non-controlling interests in consolidated subsidiaries and funds, foreign taxes, as well as other nondeductible expenses. As a result of the enactment of the American Rescue Plan Act signed on March 11, 2021, the Company is required to assess the tax impact of the Act in the quarter the law was enacted. Based on management analysis, there was no material impact on the Company's financial statements as of March 31, 2021. The Company maintained an uncertain tax position liability of $0.3 million as of March 31, 2021 and December 31, 2020 related to New York State tax matters. 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 futu re. As of March 31, 2021, the Company recorded a valuation allowance against deferred tax assets related to its foreign tax credits and foreign net operating losses. The Company is subject to examination by the United States Internal Revenue Service as well as state, local and foreign tax authorities in jurisdictions where the Company has significant business operations, such as New York, United Kingdom, Luxembourg, Malta, Germany and Switzerland. Currently, the Company is under audit by New York State for the 2013 to 2017 tax years. Management is not expecting a material tax liability from these audits.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Lease Obligations The Company has entered into leases for real estate and other facilities. These leases contain rent escalation clauses and options to extend the lease term. The Company does not include renewal options in the lease term for calculating the Company's lease liability as the renewal options allow the Company operational flexibility and the Company is not reasonably certain to exercise these renewal options at this time. The Company records the expenses related to occupancy and equipment on a straight-line basis over the lease term and these expenses are included in occupancy and equipment expense and client services and business development expense in the accompanying condensed consolidated statements of operations. For the three months ended March 31, 2021 and 2020, quantitative information regarding the Company's operating lease obligations reflected in the accompanying condensed consolidated statements of operations were as follows: Three Months Ended March 31, 2021 2020 (dollars in thousands) Lease cost Operating lease cost $ 5,770 $ 5,685 Short-term lease cost 33 146 Variable lease cost 906 788 Sublease income (160) (216) Total lease costs $ 6,549 $ 6,403 The following table summarizes the supplemental cash flow information and certain other information related to operating leases for the three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (dollars in thousands) Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 6,748 $ 8,578 Weighted average remaining lease term - operating leases (in years) 4.56 5.11 Weighted average discount rate - operating leases 4.10 % 4.14 % As of March 31, 2021, maturities of the outstanding operating lease liabilities for the Company were as follows: Equipment Leases (operating) Real Estate and Other Facility Rental (a) (b) (dollars in thousands) 2021 $ 207 $ 19,065 2022 150 22,612 2023 11 19,123 2024 — 15,883 2025 — 5,446 Thereafter — 7,862 Total operating leases 368 89,991 Less discount 21 8,927 Less short-term leases — 11 Total lease liability $ 347 $ 81,053 (a) The Company has entered into various agreements to sublease certain of its premises. (b) During the three months ended March 31, 2021, the Company recognized an increase of $5.3 million of operating right-of-use assets and leases liabilities related to for facility leases. See Note 18 for further information on the finance lease minimum payments. Other Commitments As of March 31, 2021, future minimum annual service payments for the Company were as follows: Service Payments (dollars in thousands) 2021 $ 17,854 2022 16,739 2023 8,934 2024 5,254 2025 3,366 Thereafter 10,594 Total service payment commitments $ 62,741 Unfunded Commitments The following table summarizes unfunded commitments as of March 31, 2021: Entity Unfunded Commitments Commitment Term (dollars in thousands) HealthCare Royalty Partners funds (a) $ 7,333 3.80 years Eclipse Ventures Fund I, L.P. $ 28 3.80 years Eclipse Fund II, L.P. $ 95 4.80 years Eclipse Continuity Fund I, L.P. $ 41 5.80 years Cowen Healthcare Investments III LP $ 4,126 5.80 years Cowen Sustainable Investments I LP $ 15,709 8.80 years (a) The Company is a limited partner of the HealthCare Royalty Partners funds (which are managed by Healthcare Royalty Management) and is a member of HealthCare Royalty Partners General Partners. The Company will make its pro-rata investment in the HealthCare Royalty Partners funds along with the other limited partners. Litigation In the ordinary course of business, the Company and its affiliates, 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 of the Company's affiliates and subsidiaries are 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 receives requests and orders seeking documents and other information in connection with various aspects of the Company's 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, 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 to which the Company and Related Parties are subject 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 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.

Convertible Debt and Notes Paya

Convertible Debt and Notes Payable	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Convertible Debt and Notes Payable	Convertible Debt and Notes Payable As of March 31, 2021 and December 31, 2020, the Company's outstanding debt was as follows: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Convertible debt $ 81,682 $ 80,808 Notes payable 173,656 307,653 Term loan 291,303 — Other notes payable 74,982 72,505 Finance lease obligations 2,578 2,909 $ 624,201 $ 463,875 Convertible Debt December 2022 Convertible Notes The Company, on December 14, 2017, issued $135.0 million aggregate principal amount of 3.00% convertible senior notes due December 2022 (the “December 2022 Convertible Notes”). The December 2022 Convertible Notes are due on December 15, 2022 unless earlier repurchased by the Company or converted by the holder in accordance with their terms prior to such date. The interest on the December 2022 Convertible Notes is payable semi-annually on December 15 and June 15 of each year. The December 2022 Convertible Notes are senior unsecured obligations of Cowen. The December 2022 Convertible Notes were issued with an initial conversion price of $17.375 per share of Cowen's Class A common stock. On June 26, 2018, the Company received shareholder approval for the Company to settle the December 2022 Convertible Notes entirely in Class A common stock. Upon receiving shareholder approval, the Company reclassified the separately recognized conversion option from a derivative liability to equity. Pursuant to the indenture governing the December 2022 Convertible Notes, conversions of the December 2022 Convertible Notes will be settled by the delivery and/or payment, as the case may be, of Cowen’s Class A Common Stock, cash, or a combination thereof, at the Company's election. The Company recognized the embedded cash conversion option at issuance date fair value, which also represents the initial unamortized discount on the December 2022 Convertible Notes of $23.4 million and is shown net in convertible debt in the accompanying condensed consolidated statements of financial condition. Amortization on the discount, included within interest and dividends expense in the accompanying condensed consolidated statements of operations is $0.8 million and $1.1 million for the three months ended March 31, 2021 and 2020, respectively, based on an effective interest rate of 7.13%. The Company capitalized the debt issuance costs in the amount of $2.2 million, which is a direct deduction from the carrying value of the debt and will be amortized over the life of the December 2022 Convertible Notes in interest and dividends expense in the accompanying condensed consolidated statements of operations. The Company recorded interest expense of $0.7 million and $1.0 million for the three months ended March 31, 2021 and 2020, respectively. During December 2020, the Company repurchased and extinguished $46.9 million of the outstanding principal amount of the December 2022 Convertible Notes for cash consideration of $70.5 million. In conjunction with the partial extinguishment of the December 2022 Convertible Notes, the Company accelerated the pro rata unamortized discount of $3.6 million and capitalized debt issuance costs of $0.4 million. The Company allocated $29.6 million of the cash consideration paid to the extinguishment of the equity component of the December 2022 Convertible Notes. The Company recognized $2.7 million of gain on debt extinguishment. As of March 31, 2021, the outstanding principal amount of the December 2022 Convertible Notes was $88.1 million. On March 24, 2021, the Company issued a redemption notice announcing that the Company will redeem all of the December 2022 Convertible Notes. The redemption date is June 24, 2021 ("Redemption Date"). The redemption price is 100.00% of the principal amount thereof plus accrued and unpaid interest on such principal amount, to, but not including the Redemption Date of the December 2022 Convertible Notes. As a result of the Company’s call for redemption of the December 2022 Convertible Notes, the December 2022 Convertible Notes are convertible, at the option of the holder at any time prior to June 22, 2021, the second business day prior to the December 2022 Convertible Notes' Redemption Date. The settlement method for the December 2022 Convertible Notes surrendered for conversion will be cash settlement up to the principal amount of the December 2022 Convertible Notes surrendered for conversion and share settlement through the delivery of shares of the Company’s Class A common stock for the remainder of the conversion obligation, if any, in excess of the principal amount. The conversion rate of the December 2022 Convertible Notes on March 24, 2021 was 58.3324 shares of the Company’s Class A common stock per $1,000 principal amount of December 2022 Convertible Notes c onverted.(see Note 19) Notes Payable May 2024 Notes On May 7, 2019, the Company completed its private placement of $53.0 million aggregate principal amount of 7.25% senior notes due May 2024 (the "May 2024 Notes") with certain institutional investors. On September 30, 2019, the Company issued an additional $25.0 million of the same series of notes. The additional May 2024 Notes were purchased at a premium of $0.5 million, which is shown net in notes payable in the accompanying condensed consolidated statement of financial condition. To date the May 2024 Notes have maintained their initial private rating, and the interest rate has remained unchanged. Interest on the May 2024 Notes is payable semi-annually in arrears on May 6 and November 6. The Company recorded interest expense of $1.4 million and $1.4 million for the three months ended March 31, 2021 and 2020, respectively. The Company capitalized debt issuance costs of approximately $1.5 million in May 2019 and $0.6 million in September 2019, which is a direct deduction from the carrying value of the debt and will be amortized over the life of the May 2024 Notes in interest and dividends expense in the accompanying condensed consolidated statements of operations. June 2033 Notes On June 11, 2018, the Company completed its public offering of $90.0 million of 7.75% senior notes due June 2033 (the "June 2033 Notes") and subsequently the underwriters exercised in full their option to purchase an additional $10.0 million principal amount of the June 2033 Notes. Interest on the June 2033 Notes is payable quarterly in arrears on March 15, June 15, September 15 and December 15. The Company recorded interest expense of $1.9 million and $1.9 million for the three months ended March 31, 2021 and 2020, respectively. The Company capitalized debt issuance costs of approximately $3.6 million which is a direct deduction from the carrying value of the debt and will be amortized over the life of the June 2033 Notes in interest and dividends expense in the accompanying condensed consolidated statements of operations. December 2027 Notes On December 8, 2017, the Company completed its public offering of $120.0 million of 7.35% senior notes due December 2027 (the "December 2027 Notes") and subsequently the underwriters exercised in full their option to purchase an additional $18.0 million principal amount of the December 2027 Notes. Interest on the December 2027 Notes is payable quarterly in arrears on March 15, June 15, September 15 and December 15. The Company recorded interest expense of $2.5 million for the three months ended March 31, 2021 and 2020, respectively. The Company capitalized debt issuance costs of approximately $5.0 million which is a direct deduction from the carrying value of the debt and will be amortized over the life of the December 2027 Notes in interest and dividends expense in the accompanying condensed consolidated statements of operations. The net proceeds of the offering, after deducting the underwriting discount and estimated offering expenses payable by the Company were used to redeem all of its 8.25% senior notes due October 2021 and for general corporate purposes. On March 24, 2021, the Company delivered payment of and discharged all $138.0 million outstanding aggregate principal of the December 2027 Notes plus accrued and unpaid interest through the effective redemption date of April 23, 2021. In conjunction with the extinguishment of the December 2027 Notes , the Company accelerated the pro-rata capitalized debt issuance costs. During the three months ended March 31, 2021, the Company recognized $4.4 million of loss on debt extinguishment. Term Loan March 2028 Term Loan On March 24, 2021, the Company borrowed $300 million of first lien term loan due March 24, 2028 (the “March 2028 Term Loan”). The interest on the March 2028 Term Loan is payable at the option of the Company on a monthly, quarterly or bi-annual rate equal to London Inter-bank Offered Rate ("LIBOR") (of no less than the floor of 0.75%) plus a margin of 3.25%. The Company is required to pay 1.00% per annum of the original principal amount of the March 2028 Term Loan. The obligations of the Company for the March 2028 Term Loan are guaranteed by certain of the Company’s wholly-owned domestic subsidiaries (excluding its broker-dealer subsidiaries) (the “Guarantors”) and secured by substantially all of the assets of the Company and the Guarantors, subject in each case to certain customary exceptions. The terms of the March 2028 Term Loan contain customary affirmative and negative covenants, including standard leverage and financial incurrence covenants. Proceeds from the term loan were or will be used to (i) satisfy and discharge and redeem the Company’s 2027 Senior Notes, (ii) redeem the Company’s December 2022 Convertible Notes that remain outstanding as of March 31, 2021 and pay the cash settlement amount in connection with the conversion of December 2022 Convertible Notes prior to that redemption date, and (iii) for the payment of fees, commissions, premiums, expenses and other transaction costs (including original issue discount or upfront fees) payable in connection with the transactions related thereto. As of March 31, 2021, the outstanding principal amount of the March 2028 Term Loan was $299.3 million. Interest expense for the March 2028 Term Loan for the three months ended March 31, 2021 was $0.2 million, based on an effective interest rate of 4.46%. The Company capitalized debt issuance costs of approximately $6.4 million and initial unamortized discount of $1.5 million which is a direct deduction from the carrying value of the debt and will be amortized over the life of the March 2028 Term loan in interest and dividends expense in the accompanying condensed consolidated statements of operations. June 2020 Term Loan On June 30, 2017, a subsidiary of the Company borrowed $28.2 million to fund general corporate purposes. In July 2019, the subsidiary of the Company borrowed separately, from the same lender, $4.0 million to fund general corporate purposes. Each loan was secured by the value of the Company's limited partnership interests in two affiliated investment funds. The Company had provided a guarantee for these loans. Both loans had an effective interest rate of LIBOR plus 3.75% with a lump sum payment of the entire combined principal amount due (as amended) on June 26, 2020 when they were both fully repaid. The Company recorded interest expense of $0.4 million for the three months ended March 31, 2020. Other Notes Payable During January 2021, the Company borrowed $3.0 million to fund insurance premium payments. This note had an effective interest rate of 2.01% and was due in December 2021, with monthly payment requirements of $0.3 million. As of March 31, 2021, the outstanding balance on this note was $2.4 million. Interest expense for the three months ended March 31, 2021 was insignificant. During November 2019, the Company borrowed $2.6 million to fund general corporate capital expenditures. This note had an effective interest rate of 6% and is due in November 2024, with monthly payment requirements of $0.1 million. As of March 31, 2021, the outstanding balance on this note was $1.9 million. Interest expense for the three months ended March 31, 2021 and 2020 was insignificant. On September 30, 2020, the Company borrowed $72.0 million from Purple Protected Asset S-81 ("PPA S-81"), a Luxembourg entity unrelated to Cowen. The loan is payable on September 30, 2023, had an initial interest rate of 1.4 times the Secured Overnight Financing Rate ("SOFR") plus 6.07% until December 31, 2020 and 1.4 times the SOFR plus 5.8% thereafter with quarterly interest payments. The loan obligation, as well as a loan issued by The Military Mutual Ltd (a United Kingdom company unrelated to Cowen) with principal of $28.4 million that was sold by Hollenfels to PPA S-81 at fair value for no gain or loss on September 30, 2020, are fully cash collateralized through a reinsurance policy provided by Hollenfels which is reflected in cash collateral pledged in the condensed consolidated statements of financial condition as of December 31, 2020 (see Notes 4 and 14). The Company capitalized debt issuance costs of approximately $1.7 million which is a direct deduction from the carrying value of the loan and will be amortized over the life of the loan in interest and dividends expense shown in the accompanying condensed consolidated statements of operations. The Company recorded interest expense of $1.1 million for the three months ended March 31, 2021 related to its loan payable to PPA S-81. Spike Line Pursuant to an amendment in May 2020, Cowen and Company replaced Cowen Execution Services LLC ("Cowen Execution") as the borrower and accepted, reaffirmed and assumed all of Cowen Execution’s rights, duties, obligations and liabilities under the spike line facility and the related loan documents. In August 2020, Cowen and Company renewed a one-year committed spike line facility to cover short term increases in National Securities Clearing Corporation margin deposit requirements. The spike line facility has a capacity of $70 million. This facility has (i) an effective interest rate equal to the Federal Funds rate plus 2.50% on any money drawn from the liquidity facility and (ii) a commitment or unused line fee that is 50 basis points on the undrawn amount. All amounts outstanding under this facility were fully repaid during the second quarter of 2020. Interest expense for the three months ended March 31, 2021 was $0.1 million. Revolving Credit Facility In December 2019, the Company entered into a two-year committed corporate credit facility with a capacity of $25.0 million. This credit facility has (i) an effective interest rate equal to LIBOR plus 3.25% on any money drawn from the credit facility and (ii) a commitment or unused line fee that is 50 basis points on the undrawn amount. All amounts outstanding under this credit facility were fully repaid during the second quarter of 2020. Interest expense for the three months ended March 31, 2020 was $0.2 million. Finance Lease Obligations The Company has entered into various finance leases for computer equipment. These finance lease obligations are included in notes payable and other debt in the accompanying condensed consolidated statements of financial condition. For the three months ended March 31, 2021 and 2020, quantitative information regarding the Company's finance lease obligations reflected in the accompanying condensed consolidated statements of operations, the supplemental cash flow information and certain other information related to finance leases were as follows: Three Months Ended March 31, 2021 2020 (dollars in thousands) Lease cost Finance lease cost: Amortization of finance lease right-of-use assets $ 309 $ 308 Interest on lease liabilities $ 34 $ 49 Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 34 $ 49 Financing cash flows from finance leases $ 332 $ 314 Weighted average remaining lease term - operating leases (in years) 2.01 2.97 Weighted average discount rate - operating leases 4.89 % 4.88 % Annual scheduled maturities of debt and minimum payments (of principal and interest) for all debt outstanding as of March 31, 2021, are as follows: Convertible Debt Notes Payable Term Loan Other Notes Payable Finance Lease (dollars in thousands) 2021 $ 2,644 $ 11,468 $ 11,205 $ 7,207 $ 1,117 2022 90,763 13,405 14,835 593 1,168 2023 — 13,405 14,715 72,593 411 2024 — 88,578 14,595 543 11 2025 — 7,750 14,475 — — Thereafter — 158,125 310,163 — — Subtotal 93,407 292,731 379,988 80,936 2,707 Less (a) (11,725) (119,075) (88,685) (5,954) (129) Total $ 81,682 $ 173,656 $ 291,303 $ 74,982 $ 2,578 (a) Amount necessary to reduce net minimum payments to present value calculated at the Company's implicit rate at inception. This amount also includes capitalized debt costs and the unamortized discount on the Company's convertible debt. Letters of Credit As of March 31, 2021, the Company has 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. The Company also has pledged cash collateral for reinsurance agreements (See Note 4). To the extent any letter of credit is drawn upon, interest will be assessed at the prime commercial lending rate. As of March 31, 2021 and December 31, 2020, there were no amounts due related to these letters of credit.

Stockholder's Equity

Stockholder's Equity	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Stockholder's Equity	Stockholder's Equity The Company is authorized to issue 125,000,000 shares of common stock, which shall consist of 62,500,000 shares of Class A common stock, par value $0.01 per share, and 62,500,000 shares of Class B common stock, par value $0.01 per share. The Company is also authorized to issue 10,000,000 shares of preferred stock, par value $0.01 per share. Subject to the rights of holders of any outstanding preferred stock, the number of authorized shares of common stock or preferred stock may be increased or decreased by the affirmative vote of the holders of a majority of the shares entitled to vote on such matters, but in no instance can the number of authorized shares be reduced below the number of shares then outstanding. Common stock The certificate of incorporation of the Company provides for two classes of common stock, and for the conversion of each class into the other, to provide a mechanism by which holders of Class A common stock of the Company who may be limited in the amount of voting common stock of the Company they can hold pursuant to federal, state or foreign bank laws, to convert their shares into non-voting Class B common stock to prevent being in violation of such laws. Each holder of Class A common stock is entitled to one vote per share in connection with the election of directors and on all other matters submitted to a stockholder vote, provided, however, that, except as otherwise required by law, holders of Class A common stock are not entitled to vote on any amendment to the Company's amended and restated certificate of incorporation that relates solely to the terms of one or more outstanding series of the Company's preferred stock, if holders of the preferred stock series are entitled to vote on the amendment under the Company's certificate of incorporation or Delaware law. No holder of Class A common stock may accumulate votes in voting for directors of the Company. No holder of Class B common stock is entitled to vote except as otherwise provided by law, provided however that the Company must obtain the consent of a majority of the holders of Class B common stock to effect any amendment, alteration or repeal of any provision of the Company's amended and restated certificate of incorporation or amended and restated by-laws that would adversely affect the voting powers, preferences or rights of holders of Class B common stock. Except as otherwise provided by law, Class B common stock shares will not be counted as shares held by stockholders for purposes of determining whether a vote or consent has been approved or given by the requisite percentage of shares. Each share of Class A common stock is convertible at the option of the holder and at no cost into one share of Class B common stock, and each share of Class B common stock is convertible at the option of the holder and at no cost into one share of Class A common stock. The conversion ratios will be adjusted proportionally to reflect any stock split, stock dividend, merger, reorganization, recapitalization or other change in the Class A common stock and Class B common stock. Upon conversion, converted shares resume the status of authorized and unissued shares. Subject to the preferences of the holders of any of the Company's preferred stock that may be outstanding from time to time, each share of Class A common stock and Class B common stock will have an equal and ratable right to receive dividends and other distributions in cash, property or shares of stock as may be declared by the Company's board of directors out of assets or funds legally available for the payment of dividends and other distributions. In the event of the liquidation, dissolution or winding up of the Company, subject to the preferences of the holders of any preferred stock of the Company that may be outstanding from time to time, holders of Class A common stock and Class B common stock will be entitled to share equally and ratably in the assets available for distribution to the Company's stockholders. There are no redemption or sinking fund provisions applicable to the Class A or the Class B common stock. Preferred Stock The Company's amended and restated certificate of incorporation permits the Company to issue up to 10,000,000 shares of preferred stock in one or more series with such designations, titles, voting powers, preferences and rights and such qualifications, limitations and restrictions as may be fixed by the board of directors of the Company without any further action by the Company's stockholders. The Company's board of directors may increase or decrease the number of shares of any series of preferred stock following the issuance of that series of preferred stock, but in no instance can the number of shares of a series of preferred stock be reduced below the number of shares of the series then outstanding. Preferred Stock and Purchase of Capped Call Option On May 19, 2015, the Company completed its offering of 120,750 shares of the Company's 5.625% Series A cumulative perpetual convertible preferred stock ("Series A Convertible Preferred Stock") that provided $117.2 million of proceeds, net of underwriting fees and issuance costs of $3.6 million. Each share of the Series A Convertible Preferred Stock is entitled to dividends at a rate of 5.625% per annum, which will be payable, when and if declared by the board of directors of the Company, quarterly, in arrears, on February 15, May 15, August 15 and November 15 of each year. The Company may, at its option, pay dividends in cash, common stock or a combination thereof. The Company declared and accrued a cash dividend in respect of the Series A Convertible Preferred Stock of $1.7 million and $1.7 million for the three months ended March 31, 2021 and 2020, respectively. Each share of Series A Convertible Preferred Stock is non-voting and has a liquidity preference over the Company's Class A common stock and ranks senior to all classes or series of the Company's Class A common stock, but junior to all of the Company's existing and future indebtedness with respect to dividend rights and rights upon the Company's involuntary liquidation, dissolution or winding down. Each share of Series A Convertible Preferred Stock is convertible, at the option of the holder, into a number of shares of the Company's Class A common stock equal to the liquidation preference of $1,000 divided by the conversion rate. The initial conversion rate (subsequent to the December 5, 2016 reverse stock split) is 38.0619 shares (which equates to $26.27 per share) of the Company's Class A common stock for each share of the Series A Convertible Preferred Stock. At any time on or after May 20, 2020, when the Company's capped call option expired, the Company may elect to convert all outstanding shares of the Series A Convertible Preferred Stock into shares of the Company's Class A common stock, cash or a combination thereof, at the Company's election, in each case, based on the then-applicable conversion rate (which at December 31, 2020 was 38.488), if the last reported sale price of the Company's Class A common stock equals or exceeds 150% of the then-current conversion price on at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days (including on the last trading day of such period) immediately prior to such election. At the time of conversion, the conversion rate may be adjusted based on certain events, including but not limited to the issuance of cash dividends or Class A common stock as dividends to the Company's Class A common shareholders or a share split or combination. The Company has the intent and ability to settle the preferred shares in cash and, as a result, the preferred shares do not have an impact on the Company's diluted earnings per share calculation (See Note 21). Embedded Cash Conversion Option on the December 2022 Convertible Notes Upon issuance of the December 2022 Convertible Notes (see Note 18), the Company recognized the embedded cash conversion option at fair value of $23.4 million which was valued as of June 26, 2018 at $29.0 million. On June 26, 2018, the Company received shareholder approval for the Company to settle the December 2022 Convertible Notes entirely in Class A common stock. Upon receiving shareholder approval, the Company reclassified the separately recognized conversion option from a derivative liability to equity. The Company allocated $29.6 million of the cash consideration paid on the December 2020 partial extinguishment of the Convertible Notes (see Note 18) to this equity component. Cash Dividends to Common Stockholders During the first quarter of 2020, the Company began the declaration of a quarterly cash dividend payable on its common stock. During March 2021, the Company's Board of Directors declared a cash dividend of $0.08 per share of Class A common stock. Dividends are payable on all outstanding shares of Class A common stock and on granted but unvested shares of Class A common stock under the Equity Plans on the date of record (See Note 15). During the three months ended March 31, 2021, the Company paid $2.3 million of cash dividends to its holders of Class A common stock. Treasury Stock Treasury stock of $373.8 million as of March 31, 2021, compared to $346.9 million as of December 31, 2020, resulted from $6.2 million acquired through repurchases of shares to cover employee minimum tax withholding obligations related to stock compensation vesting events under the Equity Plans or other similar transactions, $0.03 million received from an escrow account established to satisfy the Company's indemnification claims arising under the terms of the purchase agreement entered into in connection with the Company's acquisition of Convergex Group, LLC and $20.6 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, 2021: Treasury Stock Shares Cost Average Cost per Share Balance outstanding at December 31, 2020 22,619,863 $ 346,870 $ 15.33 Shares purchased for minimum tax withholding under the 2010 and 2020 Equity Plans or other similar transactions 148,752 6,246 41.99 Shares of stock received in respect of indemnification claims 1,155 29 25.33 Purchase of treasury stock 605,703 20,629 34.06 Balance outstanding at March 31, 2021 23,375,473 $ 373,774 $ 15.99

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2021
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 Other revenues in the accompanying condensed consolidated statement of operations. During the periods presented, the Company did not have material reclassifications out of other comprehensive income. Three Months Ended March 31, 2021 2020 (dollars in thousands) Beginning balance $ (7) $ (5) Foreign currency translation 4 — Ending balance $ (3) $ (5)

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic earnings per share is calculated by dividing net income attributable to the Company's common stockholders by the weighted average number of shares of Class A common stock outstanding for the period. As of March 31, 2021, there were 26,852,331 shares of Class A common stock outstanding. As of March 31, 2021, the Company has included 259,536 fully vested, unissued restricted stock units and restricted shares in its calculation of basic earnings per share. As of December 31, 2020, there were 26,845,628 shares of Class A common stock outstanding. As of December 31, 2020, the Company has included 334,230 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 items. The Company uses the treasury stock method to reflect the potential dilutive effect of the unvested restricted shares, restricted stock units and, during the first quarter of 2021, the remainder of the conversion obligation in excess of the principal amount of the December 2022 Convertible Notes which will be share settled. (see Note 18) 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 (including the conversion option of the December 2022 Convertible Notes) and warrants are assumed to have been exercised, for the entire period being presented. The number of performance-linked unvested restricted stock units that are included in the calculation are at the amount that could be earned using current payout rates. The assumed proceeds from the assumed vesting, delivery and exercising were calculated as the amount of compensation cost attributed to future services and not yet recognized. The Company previously concluded that it had the intent and ability to settle the December 2022 Convertible Notes in cash and, as a result, the convertible notes did not have an impact on the Company's diluted earnings per share calculation. On March 24, 2021, the Company issued a redemption notice announcing that the Company will redeem all of the December 2022 Convertible Notes (See Note 18). As a result of the Company’s call for redemption of the December 2022 Convertible Notes, they are convertible, at the option of the holder at any time prior to June 22, 2021, the second business day prior to the 2022 Convertible Notes' Redemption Date. The settlement method for the December 2022 Convertible Notes surrendered for conversion will be cash settlement up to the principal amount of the December 2022 Convertible Notes surrendered for conversion and share settlement through the delivery of shares of the Company’s Class A common stock for the remainder of the conversion obligation, if any, in excess of the principal amount. The conversion rate of the December 2022 Convertible Notes on March 24, 2021 was 58.3324 shares of the Company’s Class A common stock per $1,000 principal amount of December 2022 Convertible Notes converted. The Company has applied the if-converted method to the portion of the December 2022 notes above the principal amount that will be settled in shares upon a conversion. The Company can elect to settle the Series A Convertible Preferred Stock in shares, cash, or a combination of both. The Company's intent is to settle in cash and, based on current and projected liquidity needs, the Company has the ability to do so. The computation of earnings per share is as follows: Three Months Ended March 31, 2021 2020 (dollars and share data in thousands, except per share data) Net income (loss) $ 152,066 (72,111) Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds 4,562 (62,188) Net income (loss) attributable to Cowen Inc. 147,504 (9,923) Preferred stock dividends 1,698 1,698 Net income (loss) attributable to Cowen Inc. common stockholders $ 145,806 $ (11,621) Shares for basic and diluted calculations: Weighted average shares used in basic computation 27,359 28,598 Performance based restricted stock 445 — December 2022 Convertible Notes 2,659 — Restricted stock 3,102 — Weighted average shares used in diluted computation 33,565 28,598 Earnings (loss) per share: Basic $ 5.33 $ (0.41) Diluted $ 4.34 $ (0.41)

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company has two reportable business segments: Op Co and Asset Co. The Op Co segment consists of Cowen Investment Management ("CIM"), Investment Banking, Markets and Research. The Asset Co segment consists of the Company's private investments, private real estate investments and other legacy investment strategies. Segment Measures The measure of profit or loss 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. Expenses not directly associated with specific segments are allocated based on the most relevant measures applicable, including headcount, square footage and other factors. In general, Economic Income (Loss) is an after tax measure, which excludes the impact of deferred taxes and (i) includes management reclassifications which the Company believes provides additional insight into the performance of the Company’s core businesses and divisions (ii) eliminates the impact of consolidation for Consolidated Funds and (iii) excludes (1) goodwill and certain other impairments (2) certain other transaction-related adjustments and/or reorganization expenses and (3) certain costs associated with debt. The Company does not disclose total asset information for its business segments as the information is not reviewed by the Chief Operating Decision Maker ("CODM"). The Op Co and Asset Co segments do not conduct inter-segment transactions. The following table sets forth operating results for the Company's consolidated US GAAP net income (loss) and related reclassifications and adjustments necessary to reconcile to the Company's Economic Income (Loss) measure which represents the Company's Op Co and Asset Co segments' results: Three Months Ended March 31, 2021 2020 (dollars in thousands) Economic Income Op Co 143,858 3,650 Asset Co (1,476) (16,229) Adjustments made to arrive at Income (loss) before income taxes Non-controlling Interest 4,562 (62,188) Preferred stock dividends 1,698 1,698 Amortization of (discount)/premium on convertible debt (776) (1,110) Acquisition related amounts (238) — Contingent liability adjustments 6,798 895 Debt extinguishment gain (loss) (4,538) — Bargain purchase gain 3,855 — Net Income tax effect (1,677) 1,173 Net income (loss) 152,066 (72,111) Economic Income (Loss) information provided and reviewed by the CODM includes (i) non-interest revenue, (ii) interest revenue, (iii) interest expense, (iv) depreciation and amortization expense and (v) income taxes (subsequent to 2020 after all available net operating losses were utilized) presented on an Economic Income (Loss) basis by Segment. The following table sets forth the included segment information on a US GAAP basis with reconciliations to consolidated amounts. Three Months Ended March 31, 2021 2020 (dollars in thousands) Op Co Non-Interest Revenue 704,682 173,123 Interest Revenue 51,104 33,666 Interest Revenue, Consolidated funds — 577 Total Revenues 755,786 207,366 Interest Expense 53,803 33,639 Interest Expense, Consolidated funds — 1,061 Depreciation and Amortization 4,349 5,436 Income Taxes 55,085 — Asset Co Non-Interest Revenue (1,668) (10,695) Interest Revenue 203 50 Interest Revenue, Consolidated funds 2 2 Total Revenues (1,463) (10,643) Interest Expense 1,275 1,689 Interest Expense, Consolidated funds — — Depreciation and Amortization 5 6 Income Taxes (657) — Total Segment Non-Interest Revenue * 703,014 162,428 Interest Revenue 51,307 33,716 Interest Revenue, Consolidated funds 2 579 Total Revenues 754,323 196,723 Interest and Dividend Expense (includes dividend expense of $2.6 million, and $3.5 million for the three months ended March 31, 2021 and 2020, respectively) 57,641 38,792 Interest and Dividend Expense, Consolidated funds (includes dividend expense of $0.2 million for the three months ended March 31, 2020) — 1,252 Depreciation and Amortization 4,354 5,442 Income Taxes 54,428 — * Includes dividend revenue of $8.1 million and $8.3 million for the three months ended March 31, 2021 and 2020, respectively. In addition, includes dividend revenue, consolidated funds, of $2.6 million and $3.5 million for the three months ended March 31, 2021 and 2020, respectively.

Regulatory Requirements

Regulatory Requirements	3 Months Ended
	Mar. 31, 2021
Brokers and Dealers [Abstract]
Regulatory Requirements	Regulatory Requirements As registered broker-dealers, Cowen and Company, ATM Execution, Cowen Prime and Westminster are subject to the SEC's Uniform Net Capital Rule 15c3-1 ("SEC Rule 15c3-1"), which requires the maintenance of minimum net capital. Each registered broker-dealer has elected to compute net capital under the alternative method permitted by that rule. Under the alternative method, Cowen and Company's minimum net capital requirement, as defined in (a)(4) of SEC Rule 15c3-1, is equal to the greater of $1.0 million or 2% of aggregate debits arising from customer transactions. ATM Execution, Cowen Prime and Westminster are required to maintain minimum net capital, as defined in (a)(1)(ii) of SEC Rule 15c3-1, equal to the greater of $250,000 or 2% of aggregate debits arising from customer transactions. Advances to affiliates, repayment of borrowings, distributions, dividend payments, and other equity withdrawals are subject to certain notification and other provisions of SEC Rule 15c3-1 and other regulatory bodies. Cowen Prime is registered with the SEC as an investment advisor under Advisers Act. Cowen Prime is also subject to Commodity Futures Trading Commission ("CFTC") Regulation 1.17 ("Regulation 1.17"). Regulation 1.17 requires net capital equal to or in excess of $45,000 or the amount of net capital required by SEC Rule 15c3-1, whichever is greater. Cowen and Company is also subject to Options Clearing Corporation ("OCC") Rule 302. OCC Rule 302 requires maintenance of net capital equal to the greater of $2.0 million or 2% of aggregate debit items. At March 31, 2021, Cowen and Company ha d $325.9 million of net capital in excess of this minimum requirement. Cowen International Ltd and Cowen Ex ecution Ltd are subject to the capital requirements of the U.K. Financial Conduct Authority ("FCA"), as defined, and must exceed the minimum capital requirement set forth by the FCA. Cowen Asia, a previously established entity, was re-registered with regulatory approval on May 17, 2019. Cowen Asia is subject to the financial resources requirements of the Securities and Futures Commission ("SFC") of Hong Kong. Financial Resources must exceed the Total Financial Resources requirement of the SFC. As of March 31, 2021, these regulated broker-dealers had regulatory net capital or financial resources, regulatory net capital requirements or minimum FCA or SFC requirement and excess as follows: Subsidiary Net Capital Minimum Net Capital Requirement Excess Net Capital (dollars in thousands) Cowen and Company $ 332,197 $ 6,289 $ 325,908 ATM Execution $ 4,951 $ 250 $ 4,701 Cowen Prime $ 22,722 $ 250 $ 22,472 Westminster $ 31,116 $ 250 $ 30,866 Cowen International Ltd $ 39,812 $ 25,444 $ 14,368 Cowen Execution Ltd $ 13,205 $ 3,418 $ 9,787 Cowen Asia $ 2,272 $ 386 $ 1,886 The Company's U.S. broker-dealers must also comply with SEC Rule 15c3-3 or claim an exemption pursuant to subparagraphs (k)(2)(i) or (k)(2)(ii) of that rule. Firms can rely on more than one exemption. Cowen Prime and ATM Execution claim the (k)(2)(ii) exemption with regard to all of their customer accounts and transactions that are introduced on a fully-disclosed basis to their clearing agents for clearing, settlement and custody. Cowen Prime and Westminster claim the (k)(2)(i) exemption with regards to customer transactions and balances that are cleared, settled and custodied in bank accounts designated as Special Accounts for the Exclusive Benefit of Customers ("Special Bank Accounts"). Westminster also claims exemption for other business activities that are not covered under (k)(2)(i) contemplated by Footnote 74 of the SEC Release No. 34-70073 adopting amendments to 17 C.F.R. § 240.17a-5 for receiving transaction-based compensation in return for providing commission management services. In accordance with the requirements of SEC Rule 15c3-3, Cowen and Company may be required to deposit in a Special Reserve Account cash or acceptable qualified securities for the exclusive benefit of customers. As of March 31, 2021, Cowen and Company had segregated approximately $13.7 million of cash, while it had no required deposit. As a clearing broker-dealer, Cowen and Company is required to compute a reserve requirement for proprietary accounts of broker-dealers ("PAB"), as defined in SEC Rule 15c3-3. Cowen and Company conducts PAB reserve computations in order to determine the amount it is required to deposit in its PAB Reserve Bank Accounts pursuant to SEC Rule 15c3-3. This allows each correspondent firm that uses Cowen and Company as its clearing broker-dealer to classify its PAB account assets held at Cowen and Company as allowable assets in the correspondent's net capital calculation. At March 31, 2021, Cowen and Company had $30.3 million of cash on deposit in PAB Reserve Bank Accounts, which was more than its required deposit of $19.1 million. Cowen and Company, ATM Execution, and Cowen Prime also maintain certain assets in PAB accounts held at their respective clearing brokers. Each treats its assets held in those PAB accounts at the respective clearing brokers as allowable assets for net capital purposes. Cowen Insurance Co and Hollenfels are individually required to maintain a solvency capital ratio as calculated by relevant European Commission directives and local regulatory rules in Malta and Luxembourg, respectively. Each company's individual solvency capital ratio calculated as of December 31 of each year must exceed a minimum requirement. As of, December 31, 2020 (the last testing date), the solvency capital ratios of both Cowen Insurance Co and Hollenfels were in excess of the minimum requirement. Based on minimum capital and surplus requirements pursuant to the laws of the state of New York that apply to captive insurance companies, RCG Insurance Company, Cowen's captive insurance company incorporated and licensed in the state of New York, was required to maintain capital and surplus of approximately $0.3 million as of March 31, 2021. RCG Insurance Company’s capital and surplus as of March 31, 2021 totaled approximately $6.4 million.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2021
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 investment funds and certain managed accounts. Management fees and incentive income are primarily earned from affiliated entities. As of March 31, 2021 and December 31, 2020, $29.3 million and $28.4 million, respectively, included in fees receivable, are earned from related parties. The Company may, at its discretion, reimburse certain fees charged to the investment 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, 2021 and 2020, the amounts which the Company reimbursed the investment funds it manages were immaterial. Fees receivable and fees payable are recorded at carrying value, which approximates fair value. 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 accompanying condensed consolidated statements of financial condition. As of March 31, 2021 and December 31, 2020, loans to employees of $11.3 million and $9.5 million, respectively, were included in due from related parties on the accompanying condensed consolidated statements of financial condition. Of these amounts $6.7 million and $4.6 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 As of December 31, 2020, included in due from related parties is $3.6 million, which is related to the sales of portions of the Company's ownership interest in the activist business of Starboard Value to the Starboard principals. It is being financed through the profits of the relevant Starboard entities over a five The remaining balance included in due from related parties of $9.6 million and $7.9 million as of March 31, 2021 and December 31, 2020, respectively, relates to amounts due to the Company from affiliated investment funds and real estate entities due to expenses paid on their behalf. Included in due to related parties is approximately $0.2 million and $0.2 million as of March 31, 2021 and December 31, 2020, 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. Employees and certain other related parties invest on a discretionary basis within consolidated entities. These investments generally are subject to preferential management fee and performance fee arrangements. As of March 31, 2021 and December 31, 2020, such investments aggregated $34.8 million and $84.3 million, respectively, were included in non-controlling interests on the accompanying condensed consolidated statements of financial condition. Their share of the net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds aggregated $10.1 million and $0.1 million for the three months ended March 31, 2021 and 2020, respectively.

Guarantees and Off-Balance Shee

Guarantees and Off-Balance Sheet Arrangements	3 Months Ended
	Mar. 31, 2021
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 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 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. The Company may maintain cash and cash equivalents at financial institutions in excess of federally insured limits. The Company has not experienced any material losses in such accounts and does not believe it is exposed to significant credit risks in relation to such accounts. Off-Balance Sheet Arrangements The Company has no material off-balance sheet arrangements, which have not been disclosed, as of March 31, 2021 and December 31, 2020. Through indemnification provisions in clearing agreements with clients, 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. The Company's customer securities activities are transacted on a delivery versus payment, cash or margin basis. In delivery versus payment transactions, the Company is exposed to risk of loss in the event of the customers' or brokers' inability to meet the terms of their contracts. In margin transactions, the Company extends credit to clients collateralized by cash and securities in their account. In the event the customers or brokers fail to satisfy their obligations, the Company may be required to purchase or sell securities at prevailing market prices in order to fulfill the obligations. The Company's exposure to credit risk can be directly impacted by volatile securities markets, which may impair the ability of counterparties to satisfy their contractual obligations. The Company seeks to control its credit risk through a variety of reporting and control procedures, including establishing credit limits based upon a review of the customers' financial condition and credit ratings. The Company seeks to control the risk associated with its customer margin transactions by requiring customers to maintain margin collateral in compliance with various regulatory and internal guidelines. The Company also monitors required margin levels daily and, pursuant to its guidelines, requires customers to deposit additional collateral, or reduce positions, when necessary. 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. The Company enters into secured and unsecured borrowing agreements to obtain funding necessary to cover daily securities settlements with clearing corporations. At times, funding is required for unsettled customer delivery versus payment and riskless principal transactions, as well as to meet deposit requirements with clearing organizations. Secured arrangements are collateralized by the securities. The Company maintains uncommitted financing arrangements with large financial institutions, the details of which are summarized below as of March 31, 2021. Lender Contractual Amount Available Amount Maturity Date Description Pledge Lines (dollars in thousands) BMO Harris Bank $ 75,000 $ 75,000 None Secured Tri-Party Pledge Facility BMO Harris Bank 150,000 150,000 None Secured Depository Trust Company Pledge Line Total 225,000 225,000 Spike Line BMO Harris Bank 70,000 70,000 August 20, 2021 Unsecured committed spike line facility to cover short term increases in National Securities Clearing Corporation margin deposit requirements Revolving Credit Facility Morgan Stanley 25,000 25,000 March 24, 2026 Unsecured Corporate Revolver Total Credit Lines $ 320,000 $ 320,000

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 27, 2021 the Board of Directors declared a quarterly cash dividend payable on its common stock of $0.10 per common share, payable on June 15, 2021, to stockholders of record on June 1, 2021. During the same meeting, the Board of Directors also approved a $25.0 million increase in the Company's share repurchase program (see Note 19) bringing the total remaining shares available for repurchase to $50.0 million. The Company has evaluated events that have occurred after the balance sheet date but before the financial statements are issued and has determined that there were no other subsequent events requiring adjustment or disclosure in the condensed consolidated financial statements.

Significant Accounting Polici_2

Significant Accounting Policies - Quarterly (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of presentation	a. Basis of presentation These unaudited condensed consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America ("US GAAP") as promulgated by the Financial Accounting Standards Board ("FASB") through Accounting Standards Codification (the "Accounting Standards") as the source of authoritative accounting principles in the preparation of financial statements, and include the accounts of the Company, its operating and other subsidiaries, and entities in which the Company has a controlling financial interest or a general partner interest. All material intercompany transactions and balances have been eliminated on consolidation. Certain investment funds that are consolidated in these accompanying condensed consolidated financial statements, as further discussed below, are not subject to the consolidation provisions with respect to their own controlled investments pursuant to specialized industry accounting. The accompanying condensed financial statements should be read in conjunction with the Company’s financial statements and notes thereto included in the Company's Annual Report on Form 10-K for the year ended December 31, 2020 (the "2020 Form 10-K"). Certain footnote disclosures included in the 2020 Form 10-K have been condensed or omitted from the accompanying condensed financial statements as they are not required for interim reporting under US GAAP or are insignificant to the interim reporting period. During the first quarter of 2021, the Company changed the presentation of certain income streams on its condensed consolidated statements of operations by moving the income streams from Other income - net gains (losses) on securities, derivatives and other investments to Revenues. Additionally, the Company moved proprietary trading gains and losses generated by the Company’s broker dealer entities from Brokerage revenue to Investment income (loss) – securities principal transactions, net. The specified presentation changes included the following: From To Income Streams Other income - net gains (losses) on securities, derivatives and other investments Investment income (loss) – securities principal transactions, net proprietary trading gains and losses generated outside of the Company’s broker-dealer entities Other income - net gains (losses) on securities, derivatives and other investments Investment income (loss) – portfolio fund principal transactions, net gains and losses from portfolio funds Other income - net gains (losses) on securities, derivatives and other investments Investment income (loss) – carried interest allocations carried interest allocations Other income - net gains (losses) on securities, derivatives and other investments Other revenue net gains and losses on foreign currency transactions Brokerage revenue Investment income (loss) – securities principal transactions, net proprietary trading gains and losses generated by the Company’s broker-dealer entities Other income – Consolidated Funds – net realized and unrealized gains (losses) on investments and other transactions and other income – Consolidated Funds – net realized and unrealized gains (losses) on derivatives Consolidated Funds – principal transactions, net proprietary trading gains and losses generated from the Consolidated Funds Other income – Consolidated Funds – net gains (losses) on foreign currency transactions Consolidated Funds – other revenue net gains and losses on foreign currency transactions generated by the Consolidated Funds
Principles of consolidation	b. Principles of consolidation The Company consolidates all entities that it controls through a majority voting interest or otherwise, including those investment funds in which the Company either directly or indirectly has a controlling financial interest. In addition, the Company consolidates all variable interest entities for which it is the primary beneficiary. The Company consolidates two and three investment funds for which it acts as the managing member/general partner and investment manager as of March 31, 2021 and December 31, 2020, respectively. At March 31, 2021, the Company consolidated the following investment funds: Ramius Enterprise LP (“Enterprise LP”) and Cowen Private Investments LP ("Cowen Private"). At December 31, 2020, the Company consolidated the following investment funds: Enterprise LP, Cowen Private, and Cowen Sustainable Investments I LP ("CSI I LP"). These funds are referred to as each a "Consolidated Fund" and collectively the "Consolidated Funds". During the first quarter of 2021, the Company deconsolidated CSI I LP due the Company's portion being diluted through a capital equalization event. During the second quarter of 2020, the Company deconsolidated Ramius Merger Fund LLC (the "Merger Fund") and UCITS Fund ("UCITS Fund") due to a partial redemption of the Company’s direct portfolio fund investment in Merger Fund and a partial termination of the notional value of UCITS Fund units referenced in a total return swap with a third party. The Company continues to hold a direct retained portfolio fund investment in the Merger Fund and CSI I LP and continues to have economic exposure to the returns of UCITS Fund through a total return swap with a third party. Merger Fund, CSI I LP and UCITS Fund continue to be related parties of the Company after deconsolidation. CSI I Golden Holdco LP ("Golden HoldCo") and CSI I Prodigy Holdco LP ("Prodigy HoldCo") were consolidated through November 2020 when the Company raised additional capital within the sustainable investing strategy that diluted the Company's direct and indirect ownership. As a result, the Company's direct and indirect ownership in Golden Holdco and Prodigy Holdco is no longer expected to be significant to either entity and the entities were deconsolidated. 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, (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 and (iii) voting rights of equity holders are proportionate to their obligation to absorb losses or the right to receive returns. Under US GAAP consolidation requirements, the usual condition for a controlling financial interest in a VOE is ownership of a majority voting interest. Accordingly, the Company consolidates all VOEs in which it owns a majority of the entity's voting shares or units. 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. The Company determines whether it is the primary beneficiary of a VIE upon its initial involvement with the VIE and reassesses whether it is the primary beneficiary on an ongoing basis as long as it has any continuing involvement with the 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, 2021, the total assets and total liabilities of the consolidated VIEs were $243.3 million and $8.0 million, respectively. As of December 31, 2020, the total assets and total liabilities of the consolidated VIEs were $325.5 million and $10.1 million, respectively. The deconsolidation of one Consolidated Fund decreased the overall VIEs net assets. The VIEs act as investment managers and/or investment companies that may be managed by the Company or the Company may have equity interest in those investment companies. The VIEs are financed through their operations and/or loan agreements with the Company. In the ordinary course of business, the Company also sponsors various other entities that it has determined to be VIEs. These VIEs are primarily investment funds for which the Company serves as the general partner, managing member and/or investment manager with decision-making rights. The Company does not consolidate the real estate funds that are VIEs due to the Company's conclusion that it is not the primary beneficiary of these funds in each instance. Investment 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 has equity interests in the funds as both a general partner and a limited partner. In these instances the Company has concluded that the variable interests are not potentially significant to the VIE. Although the Company may advance amounts and pay certain expenses on behalf of the investment funds 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 6 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 accompanying 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 other investments in the accompanying condensed consolidated statements of operations. The Company evaluates its equity method investments for impairment 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 or apply the equity method of accounting, the Company accounts for such entities (primarily, all securities of such entity which are bought and held principally for the purpose of selling them in the near term as trading securities), at fair value with unrealized gains (losses) resulting from changes in fair value reflected within Investment income (loss) - Securities principal transactions, net or Investment income (loss) - portfolio fund investment income (loss) in the accompanying condensed consolidated statements of operations. Retention of Specialized Accounting —The Consolidated Funds and certain other consolidated companies are investment companies and apply specialized industry accounting. The Company reports its investments on the consolidated statements of financial condition at their estimated fair value, with unrealized gains (losses) resulting from changes in fair value reflected within Consolidated Funds - Principal transactions, net in the accompanying condensed consolidated statements of operations. 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. Certain portfolio fund investments qualify as equity method investments and are investment companies that apply specialized industry accounting. In applying equity method accounting guidance, the Company retains the specialized accounting of the investees and 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 Investment Income - portfolio fund principal transactions, net in the accompanying condensed consolidated statements of operations.
Use of estimates	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, and the disclosure of contingent assets and liabilities at the date of the accompanying condensed consolidated financial statements, as well as 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.
Allowance for credit losses	Allowance for credit losses The Company measures the allowance for credit losses in accordance with adopted ASC Topic 326, Financial Instruments – Credit Losses (“ASC 326”), which. ASC 326 impacts the prescribes the impairment model for certain financial assets measured at amortized cost by requiring a current expected credit loss ("CECL") methodology to estimate expected credit losses over the entire life of the financial asset, recorded at inception or purchase. Under the accounting update guidance, the Company has the ability to determine there are no expected credit losses in certain circumstances (e.g., based on collateral arrangements or based on the credit quality of the borrower or issuer). The Company applies the guidance in ASC 326 to securities borrowed and fees and other receivables carried at amortized cost (including, but not limited to, receivables related to securities transactions, corporate finance and syndicate receivables, management fees and incentive fees receivable). The allowance for credit losses is based on the Company's expectation of the collectability of financial instruments carried at amortized cost, including securities borrowed and fees and other receivables utilizing the CECL framework. The Company considers factors such as historical experience, credit quality, age of balances and current and future economic conditions that may affect the Company’s expectation of the collectability in determining the allowance for credit losses. The Company’s expectation is that the credit risk associated with fees and other receivables is not significant until they are 90 days past due based on the contractual arrangement and expectation of collection in accordance with industry standards. For securities borrowed, the Company applies a practical expedient to measure the allowance for credit losses based on the fair value of the collateral. If the fair value of the collateral held exceeds the amortized cost and the borrower is expected to continue to replenish the collateral as needed, the Company will not recognize an allowance. If the fair value of collateral is less than amortized cost and the borrower is expected to continue to replenish the collateral as needed, the Company applies the CECL model, utilizing a probability and loss given default methodology, only to the extent of the shortfall between the fair value of the collateral and amortized cost. The credit loss expense related to the allowance for credit losses as well as any recoveries of amounts previously charged is reflected in other expenses in the accompanying condensed consolidated statements of operations.
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. Inputs reflect unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. 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 based on their proportional rights of the underlying portfolio company, and 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 impact 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. The Company has the option to measure certain financial assets and financial liabilities at fair value with changes in fair value recognized in earnings each period. The election is made on an instrument by instrument basis at initial recognition of an asset or liability or upon an event that gives rise to a new basis of accounting for that instrument. The Company has elected the fair value option for certain of its investments held by its operating companies. This option has been elected because the Company believes that it is consistent with the manner in which the business is managed, as well as the way that financial instruments in other parts of the business are recorded. Securities —Securities with values based on quoted market prices in active markets for identical assets are classified within level 1 of the fair value hierarchy. These securities primarily include active listed equities, certain U.S. government and sovereign obligations, Exchange Traded Funds ("ETFs"), mutual funds and certain money market securities. Certain positions for which trading activity may not be readily visible, consisting primarily of convertible debt, corporate debt and loans and restricted equities, are stated at fair value and classified within level 2 of the fair value hierarchy. 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, are classified as level 2 when their inputs can be corroborated by market data. OTC derivatives, such as swaps and options, with significant inputs that cannot be corroborated by readily available or observable market data are classified as level 3. Other Investments —Other investments consist primarily of portfolio funds, real estate investments, carried interest and equity method investments, which are valued as follows: i. Portfolio Funds— Portfolio funds include interests in private investment partnerships, foreign investment companies and other collective investment vehicles which may be managed by the Company or its affiliates. The Company applies the practical expedient provided by the US GAAP fair value measurements and disclosures guidance relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The practical expedient permits an entity holding investments in certain entities that either are investment companies or have attributes similar to an investment company, and calculate NAV 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. Investments which are valued using NAV per share as a practical expedient are not categorized within the fair value hierarchy. ii. Carried Interest— For the private equity and debt fund products the Company offers, the Company is allocated incentive income by the investment funds based on the extent by which the investment funds performance exceeds predetermined thresholds. Carried interest allocations are generally structured from a legal standpoint as an allocation of capital in the Company’s capital account. The Company accounts for carried interest allocations by applying an equity ownership model. Accordingly, the Company accrues performance allocations quarterly based on the fair value of the underlying investments assuming hypothetical liquidation at book value. iii. 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 applies the equity method of accounting. The Company's investments in equity method investees are recorded in other investments in the accompanying 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 other investments in the accompanying condensed consolidated statements of operations.
Offsetting of derivative contracts	To reduce credit exposures on derivatives, the Company may enter into master netting agreements with counterparties that permit the Company the right, in the event of a default by a counterparty, to offset the counterparty’s rights and obligations under the agreement and to liquidate and offset any collateral against any net amount owed by the counterparty. Derivatives are reported on a net-by-counterparty basis (i.e., the net payable or receivable for derivative assets and liabilities for a given counterparty) in the condensed consolidated statements of financial condition when a legal right of offset exists under an enforceable netting agreement. Additionally, derivatives are reported net of cash collateral received and posted under enforceable credit support agreements in the condensed consolidated statements of financial position, provided a legal right of offset exists. See Notes 6 for further information about offsetting of derivative financial instruments.
Receivable from and payable to brokers	Receivable from and payable to brokers Receivable from brokers, dealers, and clearing organizations includes amounts receivable for securities failed to deliver by the Company to a purchaser by the settlement date, amounts receivable from broker-dealers and clearing organizations, commissions receivable from broker-dealers, and interest receivable from securities financing arrangements and are reported net of an allowance for credit losses. Payable to brokers, dealers and clearing organizations includes amounts payable for securities failed to receive by the Company from a seller by the settlement date, amounts payable to broker-dealers and clearing organizations for unsettled trades, interest payable for securities financing arrangements, and payables of deposits held in proprietary account of brokers and dealers. Pursuant to the master netting agreements the Company has entered into with its brokers, dealers and clearing organizations, receivables and payables arising from unsettled trade are presented net (assets less liabilities) across balances with the same counterparty. The Company's receivable from and payable to brokers, dealers and clearing organizations balances are held at multiple financial institutions.
Receivable from and payable to customers	Receivable from and payable to customers Receivable from customers includes amounts owed by customers on cash and margin transactions, recorded on a settlement-date basis and prepaid research, net of allowance for credit losses. For prepaid research, a prepaid research asset is established for research and related services disbursed in advance of anticipated client commission volumes. Payable to customers primarily consists of amounts owed to customers relating to securities transactions not completed on settlement date, recorded on a settlement-date basis on the statement of financial condition, and other miscellaneous customer payables. Securities owned by customers, including those that collateralize margin, are not reflected as assets of the Company on the statement of financial condition. The Company holds these securities with the intention of settlement against customer orders and are held as collateral for customer receivables.
Fees receivable	Fees receivable Fees related to security transactions are reported net of an allowance for credit losses. Management and incentive fees are earned as the managing member, general partner and/or investment manager to the Company's investment funds and are recognized in accordance with appropriate revenue recognition guidance (see Note 2n).
Securities financing arrangements	Securities financing arrangements 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 accompanying condensed consolidated statements of operations as interest and dividends income and interest and dividends expense. Securities borrowed transactions require the Company to deposit cash collateral with the lender. With respect to securities loaned, the Company receives cash or securities as collateral from the borrower. When the Company receives securities as collateral, and has concluded it (i) is the transferor and (ii) can pledge the securities to third parties, the Company recognizes the securities received as collateral at fair value in Securities owned, at fair value with the corresponding obligation to return the securities received as collateral at fair value in Securities sold, not yet purchased, at fair value. Securities received as collateral are not recognized when the Company either (i) is not the transferor or (ii) cannot pledge the securities to third parties. 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. See Note 2d for further information. Fees and interest received or paid are recorded in interest and dividends income and interest and dividends expense, respectively, on an accrual basis in the accompanying condensed consolidated statements of operations. In cases where the fair value basis of accounting is elected, any resulting change in fair value would be reported in Investment Income - Securities principal transactions, net in the accompanying condensed consolidated statements of operations. Accrued interest income and expense are recorded in receivable from brokers, dealers and clearing organizations and payable to brokers, dealers and clearing organizations, respectively, on an accrual basis in the accompanying condensed consolidated statements of financial condition. At March 31, 2021 and December 31, 2020, the Company did not have any securities lending transactions for which fair value basis of accounting was elected.
Securities sold under agreements to repurchase	Securities sold under agreements to repurchase Securities purchased under agreement to resell and securities sold under agreements to repurchase ("repurchase agreements") are accounted for as collateralized financing transactions and are recorded at their contracted resale or repurchase amount plus accrued interest. A repo is a transaction in which a firm buys or sells financial instruments from/to a counterparty, typically in exchange for cash, and simultaneously enters into an agreement to resell or repurchase the same or substantially the same financial instruments to/from such counterparty at a stated price plus accrued interest at a future date. When the Company receives securities as collateral, and has concluded it (i) is the transferor and (ii) can pledge the securities to third parties, the Company recognizes the securities received as collateral at fair value in Securities owned, at fair value with the corresponding obligation to return the securities received as collateral at fair value in Securities sold, not yet purchased, at fair value. Securities received as collateral are not recognized when the Company either (i) is not the transferor or (ii) cannot pledge the securities to third parties. The initial collateral advanced approximates or is greater than the market value of securities purchased or sold in the transaction. The Company typically enters into repurchase transactions with counterparties that prefer repurchase transactions to securities borrowed and securities loaned transactions. The Company has executed master repurchase agreements with such counterparties and utilizes such counterparties to finance its own positions, or replace a securities lending transaction with a repurchase for matched book purposes. The Company monitors the market value of repurchases on a daily basis, with additional collateral obtained or returned, as necessary. Repurchases may also result in credit exposures for the Company in an event that the counterparties are unable to fulfill their contractual obligations. The Company mitigates its credit risk by continuously monitoring its credit exposure and collateral values by demanding additional collateral or returning excess collateral in accordance with the netting provisions available in the master repurchase contracts in place with the counterparties. Interest paid is recorded in interest and dividends expense in accordance with US GAAP and market convention for the imputation of interest on repurchase agreement transactions on an accrual basis in the accompanying condensed consolidated statements of operations. In cases where the fair value basis of accounting is elected, any resulting change in fair value would be reported in Investment Income - Securities principal transactions, net in the accompanying condensed consolidated statements of operations. At March 31, 2021 and December 31, 2020, the Company did not have any repurchase agreements for which fair value basis of accounting was elected.
Goodwill and Intangible Assets	Goodwill and intangible assets Goodwill Goodwill represents the excess of the purchase price consideration of acquired companies over the estimated fair value assigned to the individual assets acquired and liabilities assumed. Goodwill is allocated to the Company's reporting units at the date the goodwill is initially recorded. Once goodwill has been allocated to the reporting units, it generally no longer retains its identification with a particular acquisition but instead becomes identifiable with the reporting unit. As a result, all of the fair value of each reporting unit is available to support the value of goodwill allocated to the unit. In accordance with US GAAP requirements for testing for impairment of goodwill, 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. In testing for goodwill impairment, the Company has the option to first assess qualitative factors to determine whether the existence of events or circumstances led to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events and circumstances, the Company concludes that fair value exceeds its carrying amount, then performing a quantitative impairment test is not necessary. If the Company concludes otherwise, the Company is required to perform a quantitative impairment test that requires a comparison of the fair value of the reporting unit to its carrying value, including goodwill. If the fair value of the reporting unit exceeds its carrying value, the related goodwill is not considered impaired and no further analysis is required. If the carrying value of the reporting unit exceeds its fair value, then the Company recognizes an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. Intangible assets
Non-controlling interests in consolidated subsidiaries	Non-controlling interests in consolidated subsidiariesNon-controlling interests represent the pro rata share of the income or loss of the non-wholly owned consolidated entities attributable to the other owners of such entities. When non-controlling interest holders have redemption features that can be exercised at the option of the holder currently or contingent upon the occurrence of future events, their ownership has been classified as temporary equity. Ownership which has been classified in permanent equity are non-controlling interests which are either not redeemable at the option of the holder or the holder does not have the unilateral right to redeem its ownership interests
Revenue recognition	Revenue recognitionThe Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers ("ASC Topic 606"), which requires that an entity recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company follows a five-step model to (a) identify the contract(s) with a customer, (b) identify the performance obligations in the contract, (c) determine the transaction price, (d) allocate the transaction price to the performance obligations in the contract, and (e) recognize revenue when (or as) the entity satisfies a performance obligation. In determining the transaction price, the Company includes variable consideration only to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur when the uncertainty associated with the variable consideration is resolved. Significant judgments are required in the application of the five-step model including; when determining whether performance obligations are satisfied at a point in time or over time; how to allocate transaction prices where multiple performance obligations are identified; when to recognize revenue based on the appropriate measure of the Company's progress under the contract; and whether constraints on variable consideration should be applied due to uncertain future events. The Company's principal sources of revenue are generated within two segments. The Op Co segment generates revenue through five principal sources: investment banking revenue, brokerage revenue, management fees, investment income (loss) and incentive income. Investment income is excluded from ASC Topic 606. The Asset Co segment generates revenue through investment income (loss), management fees and incentive income. Investment income is excluded from ASC Topic 606. Revenue from contracts with customers includes management fees, incentive income, investment banking revenue and brokerage services revenue excluding principal transactions. ASC Topic 606 does not apply to revenue associated with financial instruments, interest income and expense, leasing and insurance contracts. The following is a description of principal activities, from which the Company generates its revenue. For more detailed information about reportable segments, see Note 22. Investment banking The Company earns investment banking revenue primarily from fees associated with public and private capital raising transactions and providing strategic advisory services. Investment banking revenues are derived primarily from public and private small- and mid-capitalization companies within the Company's sectors. Investment banking revenue consists of underwriting fees, strategic/financial advisory fees, expenses reimbursed from clients and placement and sales agent fees. • Underwriting fees. The Company earns underwriting fees in securities offerings in which the Company acts as an underwriter, such as initial public offerings, follow-on equity offerings, debt offerings, and convertible securities offerings. Fee revenue relating to underwriting commitments is recorded at the point in time when all significant items relating to the underwriting process have been completed and the amount of the underwriting revenue has been determined. This generally is the point at which all of the following have occurred: (i) the issuer's registration statement has become effective with the SEC or the other offering documents are finalized; (ii) the Company has made a firm commitment for the purchase of securities from the issuer; (iii) the Company has been informed of the number of securities that it has been allotted; and (iv) the issuer obtains control and benefits of the offering; which generally occurs on trade date. Underwriting fees are recognized gross of transaction-related expenses, and such amounts are adjusted to reflect actual expenses in the period in which the Company receives the final settlement, typically within 90 days following the closing of the transaction. • Strategic/financial advisory fees. The Company's strategic advisory revenue includes success fees earned in connection with advising companies, principally in mergers, acquisitions and restructuring transactions. The Company also earns fees for related advisory work such as providing fairness opinions. A significant portion of the Company's advisory revenue (i.e., success-related advisory fees) is considered variable consideration and recognized when it is probable that the variable consideration will not be reversed in a future period. The variable consideration is constrained until satisfaction of the performance obligation. The Company records strategic advisory revenues at the point in time, gross of related expenses, when the services for the transactions are completed or the contract is canceled under the terms of each assignment or engagement. • Placement and sales agent fees. The Company earns placement agency fees and sales agent commissions in non-underwritten transactions, such as private placements of loans and debt and equity securities, including private investment in public equity transactions ("PIPEs"), and as sales agent in at-the-market offerings of equity securities. The Company records placement revenues (which may be in cash and/or securities) at the point in time when the services for the transactions are completed under the terms of each assignment or engagement. The Company records sales agent commissions on a trade-date basis. • Expense reimbursements from clients. Investment banking revenue includes expense reimbursements for transaction-related expenses, primarily consisting of legal, travel and other costs directly associated with the transaction. Expense reimbursements associated with investment banking engagements are recognized in revenue at the point in time when the Company is contractually entitled to reimbursement. The related expenses are presented gross within their respective expense category in the accompanying condensed consolidated statements of operations. Brokerage Brokerage revenue consists of commissions, principal transactions, equity research fees and trade conversion revenue. • Commissions. Commission revenue includes fees from executing and clearing client transactions and commission sharing arrangements. Trade execution and clearing services, when provided together, represent a single performance obligation as the services are not separately identifiable in the context of the contract. Commission revenues associated with combined trade execution and clearing services on a standalone basis, are recognized at a point in time on trade-date. Commission revenues are generally paid on settlement date and the Company records a receivable between trade-date and payment on settlement date. The Company permits institutional customers to allocate a portion of their commissions to pay for research products and other services provided by third parties. The amounts allocated for those purposes are commonly referred to as "soft dollar arrangements". The Company also offers institutional clients the ability to allocate a portion of their gross commissions incurred on trades executed with various brokers to pay for research products and other services provided by third parties by entering into commission sharing arrangements. The Company acts as an agent in the soft dollar and commission sharing arrangements as the customer controls the use of the soft dollars and directs payments to third-party service providers on its behalf. Accordingly, amounts allocated to soft dollar arrangements are netted against commission revenues and recorded on trade date. Commissions on soft dollar brokerage are recorded net of the related expenditures. The costs of commission sharing arrangements are recorded for each eligible trade and shown net of commission revenue. • Equity research fees. Equity research fees are paid to the Company for providing access to equity research. In the US, revenue is recognized once an arrangement exists, access to research has been provided and the customer has benefited from the research. As part of MiFID II, the international customers of the Company's broker-dealers have executed equity research contracts with its clients. The contracts either contain a fixed price for providing access to research or a price at the discretion of the customer with a contract minimum. Fixed equity research fees are recognized over the contract period as the customer is benefiting from the research throughout the contract term. When the equity research fees are based on the customer’s discretion with a contract minimum, the Company recognizes the contract minimum over the life of the contract as the customer benefits from the research provided and adjusts the revenue when the Company can estimate the amount of equity research fees over the contract minimum. Additionally, the Company earns variable consideration for attending client conferences and events. Revenue is recognized when the Company attends a client conference or event. • Trade conversion revenue. Trade conversion revenue includes fees earned from converting foreign securities into an American Depository Receipt ("ADR") and fees earned from converting an ADR into foreign securities on behalf of customers, and margins earned from facilitating customer foreign exchange transactions. Trade conversion revenue is recognized on a trade-date basis. Investment Income Investment income (loss) consists of securities principal transactions, net, portfolio fund principal transactions, net and carried interest allocations. Investment income is excluded from ASC Topic 606 • Securities principal transactions, net. Principal transactions, net includes realized gains and losses from transactions in financial instruments and unrealized gains and losses from ongoing changes in the fair value of the Company’s positions. Principal transactions, net generated by the Company's broker-dealers include net trading gains and losses from the Company's market-making activities in over-the-counter equity and fixed income securities, trading of convertible securities, and trading gains and losses on inventory and other Company positions, which include securities previously received as part of investment banking transactions. In certain cases, the Company provides liquidity to clients by buying or selling blocks of shares of listed stocks without previously identifying the other side of the trade at execution, which subjects the Company to market risk. These positions are typically held for a short duration. With respects to the Company's proprietary trading strategies, purchases and sales of securities, net of commissions, derivative contracts, and the related revenues and expenses are recorded on a trade-date basis with net trading gains and losses included as a component of Investment income - Securities principal transactions, net, in the accompanying condensed consolidated statements of operations. • Portfolio Fund principal transactions, net. Portfolio funds include interests in private investment partnerships, foreign investment companies and other collective investment vehicles which may be managed by the Company or its affiliates. The Company applies the practical expedient provided by the US GAAP fair value measurements and disclosures guidance relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The practical expedient permits an entity holding investments in certain entities that either are investment companies or have attributes similar to an investment company, and calculate NAV 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. Investments which are valued using NAV per share as a practical expedient are not categorized within the fair value hierarchy. Realized and unrealized gains (losses) resulting from changes in NAV per share are reflected within Investment income – portfolio fund principal transactions, net in the accompanying condensed consolidated statements of operations. • Carried interest allocations. The Company is allocated carried interest based on net profits (as defined in the respective investment management or partnership agreement) related to certain of the Company's private equity investment funds. For the private equity and debt fund products the Company offers, the carried interest earned is typically up to 30% of the distributions made to investors after return of their contributed capital and generally a preferred return. The Company recognizes carried interest allocated to the Company under an equity ownership model as investment income - carried interest allocations in the accompanying condensed consolidated statements of operations accordance with ASC Topic 323. Under the equity method of accounting the Company recognizes its allocations of incentive income or carried interest within Investment Income - Carried interest allocations in the accompanying condensed consolidated statements of operations along with the allocations proportionate to the Company's ownership interests in the investment funds. Generally, carried interest is earned after the investor has received a full return of its invested capital, plus a preferred return. However, for certain private equity structures, the Company is entitled to receive incentive fees earlier, provided that the investors have received their preferred return on a current basis or on an investor by investor basis. These private equity structures are generally subject to a potential clawback of these incentive fees upon the liquidation of the private equity structure if the investor has not received a full return of its invested capital plus the preferred return thereon. Management fees The Company earns management fees from investment funds and certain managed accounts for which it serves as the investment manager; such fees earned are typically based on committed and invested capital. The Company has determined that the primary drivers of management fees are committed and invested capital relating to private equity funds. The management fees are earned as the investment management services are provided and are not subject to reversals. The performance obligation related to the transfer of these services is satisfied over time because the customer is receiving and consuming the benefits as they are provided by the Company. Management fees are generally paid on a quarterly basis and are prorated for capital inflows (or commitments) and redemptions (or distributions) and are recognized as revenue at that time as they relate specifically to the services provided in that period, which are distinct from the services provided in other periods. While some investors may have separately negotiated fees, in general the management fees are as follows: • Private equity funds. Management fees for the Company's private equity or debt funds are generally charged at an annual rate of 1% to 2% of committed capital during the investment period (as defined in the relevant partnership agreement). After the investment period, management fees for these private equity funds are generally charged at an annual rate of 1% to 2% of the net asset value or the aggregate cost basis of the unrealized investments held by the private equity funds. For certain other private equity funds (and managed accounts), the management fees range from 0.2% to 1% and there is no adjustment based on the investment period. Management fees for the Company's private equity funds are generally paid on a quarterly basis. • Hedge funds. Management fees for the Company's hedge funds are generally charged at an annual rate of up to 2% of utilized invested capital, committed capital or notional trading level. Management fees are generally calculated monthly at the end of each month. • Cowen trading strategies. Advisory fees for the Company's collateral management advisory business are typically paid quarterly based on utilized invested capital or committed capital, generally subject to a minimum fee. Incentive income The Company earns incentive income based on net profits (as defined in the respective investment management or partnership agreement) related to certain of the Company's investment funds and managed accounts. The incentive income is charged to the investment funds in accordance with their corresponding investment management or partnership agreement. For the hedge funds the Company offers, incentive income earned is typically up to 20% (in certain cases on performance in excess of a benchmark) of the net profits earned for the full year that are attributable to each fee-paying investor. The Company recognizes incentive income charged to the Company's hedge funds based on the net profits of the hedge funds. The Company recognizes such incentive income when the fees are no longer subject to reversal or are crystallized. For certain hedge funds, the incentive fee crystallizes annually when the high-water mark for such hedge funds is reset, which delays recognition of the incentive fee until year end. In periods following a period of a net loss attributable to an investor, the Company generally does not earn incentive income on any future profits attributable to such investor until the accumulated net loss from prior periods is recovered, an arrangement commonly referred to as a "high-water mark." Generally, incentive income is earned after the investor has received a full return of its invested capital, plus a preferred return. Consolidated Funds – principal transaction, net Purchases and sales of securities, net of commissions, derivative contracts, and the related revenues and expenses are recorded on a trade-date basis with net trading gains and losses included as a component of Consolidated Funds - Principal transactions, net in the accompanying condensed consolidated statements of operations. Certain of the Companies Consolidated Funds invest in other investment funds for which the Company applies the practical expedient provided by the US GAAP fair value measurements and disclosures guidance relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The practical expedient permits an entity holding investments in certain entities that either are investment companies or have attributes similar to an investment company, and calculate NAV 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. Investments which are valued using NAV per share as a practical expedient are not categorized within the fair value hierarchy. Realized and unrealized gains (losses) resulting from changes in NAV per share are reflected within Consolidated Funds – Principal transaction, net. Interest and dividends Interest and dividends are earned by the Company from various sources. The Company receives interest and dividends primarily from securities finance activities and securities held by the Company for purposes of investing capital, investments held by its Consolidated Funds and its brokerage balances. Interest is recognized in accordance with US GAAP and market convention for the imputation of interest of the host financial instrument. Interest income is recognized on the debt of those issuers that is deemed collectible. Interest income and expense includes premiums and discounts amortized and accreted on debt investments based on criteria determined by the Company using the effective yield method, which assumes the reinvestment of all interest payments. Dividends are recognized on the ex-dividend date. Reimbursement from affiliates The Company allocates, at its discretion, certain expenses incurred on behalf of its investment management businesses. These expenses relate to the administration of such subsidiaries and assets that the Company manages for its investment funds. In addition, pursuant to the investment funds' offering documents, the Company charges certain allowable expenses to the investment funds, including charges and personnel costs for legal, compliance, accounting, tax compliance, risk and technology expenses that directly relate to administering the assets of the investment funds. Such expenses that have been reimbursed at their actual costs are included in the accompanying condensed consolidated statements of operations as employee compensation and benefits, professional, advisory and other fees, communications, occupancy and equipment, client services and business development and other expenses. Insurance and reinsurance Premiums for insurance and reinsurance contracts are earned over the coverage period. In most cases, premiums are recognized as revenues ratably over the term of the contract with unearned premiums computed on a monthly basis. For each of its contracts, the Company determines if the contract provides indemnification against loss or liability relating to insurance risk, in accordance with US GAAP. If the Company determines that a contract does not expose it to a reasonable possibility of a significant loss from insurance risk, the Company records the contract under the deposit method of accounting with any net amount receivable reflected as an asset in other assets, and any net amount payable reflected as a liability within accounts payable, accrued expenses and other liabilities on the condensed consolidated statements of financial condition. The liabilities for losses and loss adjustment expenses are recorded at the estimated ultimate payment amounts, including reported losses. Estimated ultimate payment amounts are based upon (1) reports of losses from policyholders, (2) individual case estimates and (3) estimates of incurred but unreported losses. Provisions for losses and loss adjustment expenses are charged to earnings after deducting amounts recovered and estimates of recoverable amounts and are included in other expenses on the condensed consolidated statements of operations. Costs of acquiring new policies, which vary with and are directly related to the production of new policies, have been deferred to the extent that such costs are deemed recoverable from future premiums or gross profits. Such costs include commissions and allowances as well as certain costs of policy issuance and underwriting and are included within other assets in the condensed consolidated statements of financial condition. All of the items above are reported net of any Outward Reinsurance (see Note 14), which is determined as the portion of the Company’s premiums, liabilities for losses and loss adjustment expenses, provisions for losses and loss adjustment expenses, and costs of acquiring new policies that are ceded to providers of such Outward Reinsurance pursuant to their terms and conditions. These ceded amounts are calculated based on the same principles outlined above. Interest and dividends expense Interest and dividends expense relates primarily to securities finance activities, trading activity with respect to the Company's investments and interest expense on debt.
Income taxes	Income taxes The Company accounts for income taxes in accordance with US GAAP which requires the recognition of tax benefits or expenses based on the estimated future tax effects of temporary differences between the financial statement and tax basis of its assets and liabilities. The effect on deferred taxes of a change in tax rates is recognized as income or loss in the period that includes the enactment date. Valuation allowances are established to reduce deferred tax assets to an amount that is more likely than not to be realized. The Company evaluates its deferred tax assets for recoverability considering negative and positive evidence, including its historical financial performance, projections of future taxable income, future reversals of existing taxable temporary differences, and tax planning strategies. The Company records a valuation allowance against its deferred tax assets to bring them to a level that it is more likely than not to be utilized. US GAAP clarifies the accounting for uncertainty in income taxes recognized in an enterprise's financial statements, requiring the Company to determine whether a tax position is more likely than not to be sustained upon examination, including resolution of any related appeals or litigation processes, based on the technical merits of the position. For tax positions meeting the more likely than not threshold, the tax amount recognized in the financial statements is reduced by the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement with the relevant taxing authority. The Company recognizes accrued interest and penalties related to its uncertain tax positions as a component of income tax expense. In accordance with federal and state tax laws, the Company and its subsidiaries file consolidated federal, state, and local income tax returns as well as stand-alone state and local tax returns. The Company also has subsidiaries that are residents in foreign countries where tax filings have to be submitted on a stand-alone or combined basis. These subsidiaries are subject to taxes in their respective countries and the Company is responsible for and therefore reports all taxes incurred by these subsidiaries in the condensed consolidated statements of operations. The foreign jurisdictions where the Company owns subsidiaries and has tax filing obligations are the United Kingdom, Luxembourg, Malta, Gibraltar, Germany, Switzerland, South Africa, Canada and Hong Kong.
Recent pronouncements	Recent pronouncements In August 2020, the FASB issued guidance simplifying an issuer’s accounting for convertible instruments by eliminating two of the three models in ASC 470-20 that require separate accounting for embedded conversion features; separate accounting is still required in certain cases. The guidance also simplifies the settlement assessment that entities are required to perform to determine whether a contract qualifies for equity classification. The guidance requires entities to use the if-converted method for all convertible instruments in the diluted earnings per share calculation and include the effect of potential share settlement (if the effect is more dilutive) for instruments that may be settled in cash or shares, except for certain liability-classified share-based payment awards. The guidance requires new disclosures about events that occur during the reporting period and cause conversion contingencies to be met and about the fair value of a public business entity’s convertible debt at the instrument level. For public business entities, the guidance is effective for reporting periods beginning after December 15, 2021 and interim periods within those fiscal years with early adoption permitted. The Company is currently evaluating the impact of the new guidance.
Earnings Per Share	Diluted earnings per common share are calculated by adjusting the weighted average outstanding shares to assume conversion of all potentially dilutive items. The Company uses the treasury stock method to reflect the potential dilutive effect of the unvested restricted shares, restricted stock units and, during the first quarter of 2021, the remainder of the conversion obligation in excess of the principal amount of the December 2022 Convertible Notes which will be share settled. (see Note 18) 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 (including the conversion option of the December 2022 Convertible Notes) and warrants are assumed to have been exercised, for the entire period being presented. The number of performance-linked unvested restricted stock units that are included in the calculation are at the amount that could be earned using current payout rates. The assumed proceeds from the assumed vesting, delivery and exercising were calculated as the amount of compensation cost attributed to future services and not yet recognized. The Company previously concluded that it had the intent and ability to settle the December 2022 Convertible Notes in cash and, as a result, the convertible notes did not have an impact on the Company's diluted earnings per share calculation. On March 24, 2021, the Company issued a redemption notice announcing that the Company will redeem all of the December 2022 Convertible Notes (See Note 18). As a result of the Company’s call for redemption of the December 2022 Convertible Notes, they are convertible, at the option of the holder at any time prior to June 22, 2021, the second business day prior to the 2022 Convertible Notes' Redemption Date. The settlement method for the December 2022 Convertible Notes surrendered for conversion will be cash settlement up to the principal amount of the December 2022 Convertible Notes surrendered for conversion and share settlement through the delivery of shares of the Company’s Class A common stock for the remainder of the conversion obligation, if any, in excess of the principal amount. The conversion rate of the December 2022 Convertible Notes on March 24, 2021 was 58.3324 shares of the Company’s Class A common stock per $1,000 principal amount of December 2022 Convertible Notes converted. The Company has applied the if-converted method to the portion of the December 2022 notes above the principal amount that will be settled in shares upon a conversion.

Acquisition (Tables)

Acquisition (Tables) - Cowen Insurance	3 Months Ended
	Mar. 31, 2021
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The table below summarizes the preliminary purchase price allocation of net tangible and intangible assets acquired and liabilities assumed as of February 26, 2021: (dollars in thousands) Cash $ 14,844 Securities owned, at fair value 1,571 Fixed assets 30 Intangible assets 4,794 Other assets 12,828 Compensation payable (17) Other liabilities (16,099) Total net identifiable assets acquired and liabilities assumed 17,951 Bargain purchase gain (5,216) Total estimated purchase price $ 12,735
Finite-lived Intangible Assets Amortization Expense [Table Text Block]	he estimated amortization expense related to these intangible assets in future periods is as follows: (dollars in thousands) 2021 $ 343 2022 458 2023 458 2024 458 2025 458 Thereafter 2,365 $ 4,540

Cash Collateral Pledge (Tables)

Cash Collateral Pledge (Tables)	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Schedule of Cash Collateral Pledged	As of March 31, 2021 , the Company has the following irrevocable letters of credit, rela ted 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) New York $ 215 April 2022 New York $ 1,424 October 2022 New York $ 1,252 November 2021 Boston $ 194 March 2028 San Francisco $ 458 October 2025 $ 3,543

Investments of Operating Enti_2

Investments of Operating Entities and Consolidated Funds - (Tables)	3 Months Ended
	Mar. 31, 2021
Investment Holdings [Line Items]
Marketable Securities	As of March 31, 2021 and December 31, 2020, securities owned, at fair value consisted of the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Common stock $ 2,934,604 $ 1,770,301 Preferred stock 66,853 69,358 Warrants and rights 30,961 27,701 Government bonds 19,671 19,721 Corporate bonds 81,460 86,503 Convertible bonds 3,137 6,040 Term loan (*) 12,424 12,623 Trade claims (*) 5,905 8,713 Private investments 1,085 642 $ 3,156,100 $ 2,001,602
Schedule of Derivative Instruments	The Company's long and short exposure to derivatives is as follows: Receivable on derivative contracts As of March 31, 2021 As of December 31, 2020 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Currency forwards $ 132,960 $ 384 $ 4,902 $ 15 Swaps $ 1,746,919 142,266 $ 944,544 64,634 Options other (a) 163,622 42,124 371,188 49,102 Netting - swaps (b) (89,238) (62,269) $ 95,536 $ 51,482 Payable for derivative contracts As of March 31, 2021 As of December 31, 2020 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Currency forwards $ 1,990 $ 16 $ 123,346 $ 3,067 Swaps $ 1,603,710 82,391 $ 896,863 43,560 Options other (a) 130,627 31,524 198,320 66,566 Netting - swap (b) (61,806) (37,033) $ 52,125 $ 76,160 (a) Includes the volume of contracts for index, equity, commodity future and cash conversion options. (b) Derivatives are reported on a net basis, by counterparty, when a legal right of offset exists under an enforceable netting agreement as well as net of cash collateral received or posted under enforceable credit support agreements. See Note 2f for further information on offsetting of derivative financial instruments. The following tables present the gross and net derivative positions and the related offsetting amount, as of March 31, 2021 and December 31, 2020. This table does not include the impact of over-collateralization. Gross amounts offset on the Condensed Consolidated Statements of Financial Condition (a) Net amounts included on the Condensed Consolidated Statements of Financial Condition Gross amounts not offset in the Condensed Consolidated Statements of Financial Condition Gross amounts recognized Financial instruments (a) Cash Collateral pledged (a) Net amounts (dollars in thousands) As of March 31, 2021 Receivable on derivative contracts, at fair value $ 184,774 $ 89,238 $ 95,536 $ 2,694 $ 48,448 $ 44,394 Payable for derivative contracts, at fair value 113,931 61,806 52,125 2,694 1,124 48,307 As of December 31, 2020 Receivable on derivative contracts, at fair value $ 113,751 $ 62,269 $ 51,482 $ 691 $ 169 $ 50,622 Payable for derivative contracts, at fair value 113,193 37,033 76,160 691 3,174 72,295 (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.
Schedule of Other Investments	As of March 31, 2021 and December 31, 2020, other investments included the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Portfolio funds, at fair value (1) $ 151,933 $ 133,454 Carried interest (2) 180,352 82,892 Equity method investments (3) 34,498 38,681 $ 366,783 $ 255,027
Schedule of Other Investments, Portfolio Funds	The portfolio funds, at fair value as of March 31, 2021 and December 31, 2020, included the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Starboard Value and Opportunity Fund LP (c)(*) $ 46,008 $ 42,519 Formation8 Partners Fund I, L.P. (f) 33,408 31,894 Cowen Healthcare Investments II LP (i) (*) 26,733 26,186 Lagunita Biosciences, LLC (d) 3,785 3,850 Eclipse Ventures Fund I, L.P. (b) 4,804 4,457 HealthCare Royalty Partners II LP (a)(*) 1,605 1,588 HealthCare Royalty Partners LP (a)(*) 1,035 1,072 Starboard Leaders Fund LP (e)(*) 2,328 2,020 Eclipse SPV I, LP (j)(*) 1,809 1,708 Ramius Merger Fund LLC (m)(*) 2,252 2,197 TriArtisan ES Partners LLC (k)(*) 1,848 1,657 Cowen Healthcare Investments III LP (i)(*) 7,717 5,714 TriArtisan PFC Partners LLC (l)(*) 760 691 Starboard Value and Opportunity Fund Ltd (c) (*) 2,556 2,364 Eclipse Ventures Fund II, L.P. (b) 1,910 1,733 Eclipse Continuity Fund I, L.P. (b) 1,252 1,101 Cowen Sustainable Investments I LP (i)(*) 9,299 — Difesa Partners, LP (h) 985 848 BDC Fund I Coinvest 1, L.P. (n) 1,250 1,250 Other private investment (o)(*) 311 326 Other affiliated funds (p)(*) 278 279 $ 151,933 $ 133,454 * 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 17. (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) Each of Eclipse Ventures Fund I, L.P., Eclipse Ventures Fund II, L.P. and Eclipse Continuity Fund I, L.P. are venture capital funds which invests in early stage and growth stage hardware companies. Distributions will be made when the underlying investments are liquidated. (c) Starboard Value and Opportunity Fund LP and Starboard Value and Opportunity Fund Ltd permits quarterly withdrawals upon 90 days' notice. (d) Lagunita Biosciences, LLC, is a healthcare investment company that creates and grows early stage companies to commercialize impactful translational science that addresses significant clinical needs, is a private equity structure and therefore distributions will be made when the underlying investments are liquidated. (e) Starboard Leaders Fund LP does not permit withdrawals, but instead allows terminations with respect to capital commitments upon 30 days' prior written notice at any time following the first anniversary of an investor's initial capital contribution. (f) Formation8 Partners Fund I, L.P. is a private equity fund which invests in early stage and growth transformational information and energy technology companies. Distributions will be made when the underlying investments are liquidated. (g) RCG Longview Debt Fund V, L.P. is a real estate private equity structures. The timing of distributions depends on the nature of the underlying investments and therefore will be made either quarterly or when the underlying investments are liquidated. (h) Difesa Partners, LP permits semi-annual withdrawals occurring on or after the anniversary of initial contribution upon 90 days written notice. (i) Cowen Healthcare Investments II LP, Cowen Healthcare Investments III LP and Cowen Sustainable Investments I LP are private equity funds. Distributions are made from the fund when cash flows or securities are received from the underlying investments. Investors do not have redemption rights. (j) Eclipse SPV I, L.P. is a co-investment vehicle organized to invest in a private company focused on software-driven automation projects. Distributions will be made when the underlying investments are liquidated. (k) TriArtisan ES Partners LLC is a co-investment vehicle organized to invest in a privately held nuclear services company. Distributions will be made when the underlying investment is liquidated. (l) TriArtisan PFC Partners LLC is a co-investment vehicle organized to invest in a privately held casual dining restaurant chain. Distributions will be made when the underlying investment in liquidated. (m) Ramius Merger Fund LLC permits monthly withdrawals on 45 days prior notice. (n) BDC Fund I Coinvest 1, L.P. is a private equity fund focused on investing in growth companies in industries disrupted by digitization. Distributions will be made when the underlying investments are liquidated. (o) Other private investment represents the Company's closed end investment in a portfolio fund that invests in a wireless broadband communication provider in Italy.
Carried Interest	The carried interest as of March 31, 2021 and December 31, 2020, included the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Cowen Healthcare Investments II LP $ 73,415 $ 62,112 Cowen Healthcare Investments III LP 31,034 11,520 Cowen Sustainable Investments I LP 13,581 — Cowen Sustainable Investments Offshore I LP 17,944 — CSI I Prodigy Co-Investment LP 6,617 — CSI PRTA Co- Investment LP 26,242 — TriArtisan TGIF Partners LLC 3,689 3,361 TriArtisan ES Partners LLC 4,514 3,152 TriArtisan PFC Partners LLC 2,329 1,455 Ramius Multi-Strategy Fund LP 638 734 Ramius Merger Fund LLC 162 368 RCG IO Renergys Sarl 187 190 $ 180,352 $ 82,892
Schedule Equity Method Investments	The following table summarizes equity method investments held by the Company: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Starboard Value LP $ 27,769 $ 31,528 HealthCare Royalty GP III, LLC 2,221 2,213 RCG Longview Management, LLC 268 268 HealthCare Royalty GP, LLC 442 920 HealthCare Royalty GP II, LLC 272 269 RCG Longview Debt Fund IV Management, LLC 331 331 RCG Longview Equity Management, LLC 105 105 HCR Stafford Fund GP, LLC 1,159 1,025 Liberty Harbor North 222 222 Other 1,709 1,800 $ 34,498 $ 38,681
Schedule of Securities Sold, Not yet Purchased	As of March 31, 2021 and December 31, 2020, securities sold, not yet purchased, at fair value consisted of the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Common stock $ 918,021 $ 699,894 Corporate bonds 453 11,358 Government bonds 522 1,500 Preferred stock 7,567 6,589 Warrants and rights 4,519 8,774 $ 931,082 $ 728,115
Schedule of Assets and Associated Liabilities Accounted for as Secured Borrowings	The following tables present the contractual gross and net securities borrowing and lending agreements and securities sold under agreements to repurchase and the related offsetting amount as of March 31, 2021 and December 31, 2020. Gross amounts not offset on the Condensed Consolidated Statements of Financial Condition Gross amounts recognized, net of allowance Gross amounts offset on the Condensed Consolidated Statements of Financial Condition (a) Net amounts included on the Condensed Consolidated Statements of Financial Condition Additional Amounts Available Financial instruments Cash Collateral pledged (b) Net amounts (dollars in thousands) As of March 31, 2021 Securities borrowed $ 1,996,757 $ — $ 1,996,757 $ — $ 1,970,665 $ — $ 26,092 Securities loaned 3,083,945 — 3,083,945 — 3,100,800 — (16,855) Securities sold under agreements to repurchase 2,546 — 2,546 — 2,759 — (213) As of December 31, 2020 Securities borrowed $ 1,908,187 $ — $ 1,908,187 $ — $ 1,809,399 $ — $ 98,788 Securities loaned 2,476,414 — 2,476,414 — 2,383,342 — 93,072 Securities purchased under agreements to resell 191 — 191 — 204 — (13) Securities sold under agreements to repurchase 5,036 — 5,036 — 5,544 — (508) (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.
Investments Classified by Contractual Maturity Date	The following tables present gross obligations for securities loaned and securities sold under agreements to repurchase by remaining contractual maturity and class of collateral pledged as of March 31, 2021 and December 31, 2020: Open and Overnight Up to 30 days 31 - 90 days Greater than 90 days Total (dollars in thousands) As of March 31, 2021 Securities loaned Common stock $ 2,827,291 $ — $ — $ — $ 2,827,291 Corporate bonds 256,654 — — — 256,654 Securities sold under agreements to repurchase Corporate bonds — — 2,546 — 2,546 As of December 31, 2020 Securities loaned Common stock 2,232,687 — — — 2,232,687 Corporate bonds 243,726 — — — 243,726 Securities sold under agreements to repurchase Corporate bonds $ — $ — $ 5,036 $ — $ 5,036
Fair Value, Concentration of Risk	Investment's percentage of the Company's stockholders' equity Issuer Security Type Country Industry Percentage of Stockholders' Equity Market Value (dollars in thousands) As of March 31, 2021 Linkem S.p.A. Equity, loans and warrants Italy Wireless Broadband 7.62 % $ 84,324 As of December 31, 2020 Linkem S.p.A. Equity, loans and warrants Italy Wireless Broadband 9.07 % $ 87,944
Consolidated Funds
Investment Holdings [Line Items]
Marketable Securities	As of March 31, 2021 and December 31, 2020, securities owned, at fair value, held by the Consolidated Funds consisted of the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Common stock $ 3,611 $ 4,816 Warrants and rights 5,329 5,806 $ 8,940 $ 10,622
Schedule of Other Investments, Portfolio Funds	Investments in portfolio funds, at fair value As of March 31, 2021 and December 31, 2020, investments in portfolio funds, at fair value, included the following: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Investments of Enterprise LP $ 100,035 $ 104,475 Investments of Cowen Sustainable Investments I LP — 88,195 $ 100,035 $ 192,670

Fair Value Measurements for O_2

Fair Value Measurements for Operating Entities and Consolidated Funds (Tables)	3 Months Ended
	Mar. 31, 2021
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, 2021 and December 31, 2020: Assets at Fair Value as of March 31, 2021 Level 1 Level 2 Level 3 Netting (c) Total (dollars in thousands) Operating Entities Securities owned, at fair value Government bonds $ 19,671 $ — $ — $ — $ 19,671 Preferred stock 10,376 — 56,477 — 66,853 Common stock 2,911,824 74 22,706 — 2,934,604 Convertible bonds — — 3,137 — 3,137 Corporate bonds — 81,324 136 — 81,460 Trade claims — — 5,905 — 5,905 Term loan — — 12,424 — 12,424 Warrants and rights 23,037 — 7,924 — 30,961 Private investments — — 1,085 — 1,085 Receivable on derivative contracts, at fair value Currency forwards — 384 — — 384 Swaps — 142,266 — (89,238) 53,028 Options 41,883 — 241 — 42,124 Consolidated Funds Securities owned, at fair value Common stock 660 — 2,951 — 3,611 Warrants and rights — — 5,329 — 5,329 $ 3,007,451 $ 224,048 $ 118,315 $ (89,238) $ 3,260,576 Portfolio funds measured at net asset value (a) 151,933 Consolidated Funds' portfolio funds measured at net asset value (a) 100,035 Carried interest (a) 180,352 Equity method investments (a) 34,498 Total investments $ 3,727,394 Liabilities at Fair Value as of March 31, 2021 Level 1 Level 2 Level 3 Netting (c) Total (dollars in thousands) Operating Entities Securities sold, not yet purchased, at fair value Government bonds $ — $ — $ 522 $ — $ 522 Common stock 918,021 — — — 918,021 Corporate bonds — 38 415 — 453 Preferred stock 7,567 — — — 7,567 Warrants and rights 4,519 — — — 4,519 Payable for derivative contracts, at fair value Currency forwards — 16 — — 16 Swaps — 82,391 — (61,806) 20,585 Options 28,227 — 3,297 — 31,524 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 19,579 — 19,579 $ 958,334 $ 82,445 $ 23,813 $ (61,806) $ 1,002,786 (a) In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition. (b) In accordance with the terms of the purchase agreements for acquisitions that closed during the first quarter of 2019 and the fourth quarter of 2020, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired businesses, if certain targets are achieved through the periods ended December 31, 2020 and December 31, 2023. For both the Quarton Acquisition and the MHT Acquisition, the Company estimated the contingent consideration liabilities using a combination of Monte Carlo and Discounted Cash Flow methods which require 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 for the Quarton Acquisition can range from $10.1 million to $25.0 million. The undiscounted amounts for the MHT Acquisition have no minimum or maximum as it is calculated based on revenue. (c) Derivatives are reported on a net basis, by counterparty, when a legal right of offset exists under an enforceable netting agreement as well as net of cash collateral received or posted under enforceable credit support agreements. See Note 2f for further information on offsetting of derivative financial instruments. Assets at Fair Value as of December 31, 2020 Level 1 Level 2 Level 3 Netting (c) Total (dollars in thousands) Operating Entities Securities owned, at fair value Government bonds $ 19,721 $ — $ — $ — $ 19,721 Preferred stock 9,391 — 59,967 — 69,358 Common stock 1,746,407 108 23,786 — 1,770,301 Convertible bonds — — 6,040 — 6,040 Corporate bonds — 86,368 135 — 86,503 Trade claims — — 8,713 — 8,713 Term loan — — 12,623 — 12,623 Private investments — — 642 — 642 Warrants and rights 21,154 — 6,547 — 27,701 Receivable on derivative contracts, at fair value Currency forwards — 15 — — 15 Swaps — 64,634 — (62,269) 2,365 Options 48,851 — 251 — 49,102 Consolidated Funds Securities owned, at fair value Common stock 1,865 — 2,951 — 4,816 Warrants and rights — — 5,806 — 5,806 $ 1,847,389 $ 151,125 $ 127,461 $ (62,269) $ 2,063,706 Portfolio funds measured at net asset value (a) 133,454 Consolidated Funds' portfolio funds measured at net asset value (a) 192,670 Carried interest (a) 82,892 Equity method investments (a) 38,681 Total investments $ 2,511,403 Liabilities at Fair Value as of December 31, 2020 Level 1 Level 2 Level 3 Netting (c) Total (dollars in thousands) Operating Entities Securities sold, not yet purchased, at fair value US Government securities $ — $ — $ 1,500 $ — $ 1,500 Common stock 699,894 — — — 699,894 Corporate bonds — 10,654 704 — 11,358 Preferred stock 6,589 — — — 6,589 Warrants and rights 8,774 — — — 8,774 Payable for derivative contracts, at fair value Currency forwards — 3,067 — — 3,067 Swaps — 43,560 — (37,033) 6,527 Options 62,651 — 3,915 — 66,566 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 36,718 — 36,718 $ 777,908 $ 57,281 $ 42,837 $ (37,033) $ 840,993 (a) In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	The following table includes a roll forward of the amounts for the three months ended March 31, 2021 and 2020 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, 2021 Balance at December 31, 2020 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at March 31, 2021 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 59,967 $ — $ — $ 1,859 $ (4,651) $ (698) $ 56,477 $ (698) Common stock 23,786 — (5,353) (b) 3,226 (1,387) 2,434 22,706 1,679 Convertible bonds 6,040 — — 1,050 (3,930) (23) 3,137 (23) Corporate bond 135 — — 70 (49) (20) 136 (49) Options, asset 251 — — — — (10) 241 (10) Options, liability 3,915 — — — — (618) 3,297 (618) Term loan 12,623 — — 322 — (521) 12,424 (521) Warrants and rights 6,547 — — 3,406 (1,206) (823) 7,924 (895) Trade claims 8,713 — 1,378 (4,216) 30 5,905 (1,021) Private investments 642 — — 443 — — 1,085 — Corporate bond, liability 704 — — — (289) — 415 — Government bonds, liability 1,500 — — — (1,278) 300 522 87 Contingent consideration liability 37,952 — — (11,312) — (7,061) 19,579 (7,061) Consolidated Funds Common stock 2,951 — — — — — 2,951 — Warrants and rights 5,806 — — — (670) 193 5,329 (477) Three Months Ended March 31, 2020 Balance at December 31, 2019 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at March 31, 2020 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 7,835 $ — $ — $ 365 $ — $ — $ 8,200 $ — Common stock 17,466 — — 1,798 (593) (1,161) 17,510 (1,257) Convertible bonds 2,500 — — 286 — — 2,786 — Corporate Bond, asset 2,421 — — 422 (24) (7) 2,812 12 Options, asset 336 — — — — (4) 332 (4) Options, liability 2,920 — — — — (1,118) 1,802 (1,118) Warrants and rights 594 — — — — 4 598 4 Trade claim 7,083 1,044 (a) — 1,166 — (110) 9,183 (110) Private investments 237 — — 233 — (5) 465 (5) Corporate bond, liability 1,000 — — — — (200) 800 (200) Government bonds, liability 1,950 — — — — (450) 1,500 (450) Contingent consideration liability 30,896 — — — (1,400) (838) 28,658 (838) Consolidated Funds Preferred stock 4,393 — — — — — 4,393 — Common stock — — — 100,000 — — 100,000 — Warrants and rights $ 5,567 $ — $ — $ — $ — $ 44 $ 5,611 $ 44 (1) Unrealized gains/losses are reported in Investment income - Securities principal transactions, net in the accompanying condensed consolidated statements of operations. (a) The security stopped trading on an open market. (b) The entity in which the Company is invested completed an initial public offering.
Fair Value Inputs, Assets, Quantitative Information	The following table includes quantitative information as of March 31, 2021 and December 31, 2020 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 March 31, 2021 Valuation Techniques Unobservable Inputs Range Weighted Average Level 3 Assets (dollars in thousands) Common and preferred stocks $ 70,935 Discounted cash flows Guideline companies Probability of Success Discount rate EBITDA Market Multiples Probability of Success 11% - 20% 6.25x - 6.75x 70% 12% 6.5x 70% Options 241 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 11% - 12% 6.25x - 6.75x 12% 6.5x Trade claims 3,713 Discounted cash flows Discount rate 20% 20% Warrants and rights 10,394 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 4% - 12% 6.25x - 6.75x 7.0% 6.5x Corporate, convertible bonds and term loan 12,424 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 11% - 12% 6.25x - 6.75x 12% 6.5x Other level 3 assets (a) 20,608 Total level 3 assets $ 118,315 Level 3 Liabilities Options 3,297 Option pricing models Volatility 35% 35% Contingent consideration liability 19,579 Discounted cash flows Monte Carlo simulation Discount rate Volatility 7% - 15% 18% - 20% 13% 18% Other level 3 liabilities (a) 937 Total level 3 liabilities $ 23,813 Quantitative Information about Level 3 Fair Value Measurements Fair Value at December 31, 2020 Valuation Techniques Unobservable Inputs Range Weighted Average Level 3 Assets (dollars in thousands) Common and preferred stocks $ 65,735 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 10% - 12% 6.25x - 6.75x 11% 6.5x Trade claims 3,500 Discounted cash flows Discount rate 15% 15% Warrants and rights 11,217 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 4% - 11% 6.25x - 6.75x 7% 6.5x Options 251 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 10% - 12% 6.25x - 6.75x 11% 6.5x Corporate, convertible bonds and term loan 12,623 Discounted cash flows Guideline companies Discount rate EBITDA Market Multiples 10% - 12% 6.25x - 6.75x 11% 6.5x Other level 3 assets (a) 34,135 Total level 3 assets $ 127,461 Level 3 Liabilities Options 3,915 Option pricing models Volatility 35% 35% Contingent consideration liability 36,718 Discounted cash flows Monte Carlo simulation Discount rate Volatility 9% - 16% 22% - 24% 15% 22% Other level 3 liabilities (a) 2,204 Total level 3 liabilities $ 42,837
Fair Value Measurements, Nonrecurring	For additional information regarding the financial instruments within the scope of this disclosure, and the methods and significant assumptions used to estimate their fair value (see Note 2e). March 31, 2021 December 31, 2020 Fair Value Hierarchy Carrying Amount Fair Value Carrying Amount Fair Value (dollars in thousands) Financial Assets Operating companies Cash and cash equivalents $ 1,147,531 $ 1,147,531 $ 645,169 $ 645,169 Level 1 Cash collateral pledged 110,303 110,303 110,743 110,743 Level 2 Segregated cash 168,942 168,942 185,141 185,141 Level 1 Securities purchased under agreements to resell — — 191 204 Level 2 Securities borrowed 1,996,757 1,996,757 1,908,187 1,908,187 Level 2 Loans receivable 4,467 4,467 (d) 7,682 7,682 (d) Level 3 Consolidated Funds Cash and cash equivalents 935 935 417 417 Level 1 Financial Liabilities Securities sold under agreements to repurchase 2,546 2,759 5,036 5,544 Level 2 Securities loaned 3,083,945 3,083,945 2,476,414 2,476,414 Level 2 Convertible debt 81,682 (a) 181,597 (b) 80,808 (a) 135,444 (b) Level 2 Notes payable and other debt 542,519 (e) 568,212 (c) 383,067 (e) 405,840 (c) Level 2 (a) The carrying amount of the convertible debt includes an unamortized discount of $5.8 million and $6.7 million as of March 31, 2021 and December 31, 2020, respectively. (b) The convertible debt includes the conversion option and is based on the last broker quote available. (c) Notes payable and other debt are based on the last broker quote available. (d) The fair market value of level 3 loans is calculated using discounted cash flows where applicable.

Receivables from and payables_2

Receivables from and payables to brokers, dealers and clearing organizations receivables from brokers, dealers, and clearing organization (Tables)	3 Months Ended
	Mar. 31, 2021
Receivables from Brokers-Dealers and Clearing Organizations [Abstract]
Schedule of Due to (from) Broker-Dealers and Clearing Organizations	As of March 31, 2021 and December 31, 2020, amounts receivable from brokers, dealers and clearing organizations include: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Broker-dealers $ 1,753,510 $ 1,608,273 Securities failed to deliver 76,127 55,655 Clearing organizations 79,833 41,795 Securities borrowed/loaned interest receivable 11,283 24,021 $ 1,920,753 $ 1,729,744 As of March 31, 2021 and December 31, 2020, amounts payable to brokers, dealers and clearing organizations include: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Broker-dealers $ 326,231 $ 286,011 Securities failed to receive 100,528 68,036 Clearing organizations 48,466 33,732 Securities borrowed/loaned interest payable 13,246 27,364 $ 488,471 $ 415,143

Non-Controlling Interests in _2

Non-Controlling Interests in Consolidated Subsidiaries and Funds (Tables)	3 Months Ended
	Mar. 31, 2021
Noncontrolling Interest [Abstract]
Noncontrolling interests in consolidated subsidiaries and investment funds	Redeemable and nonredeemable non-controlling interests in consolidated subsidiaries and investment funds and the related net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds are comprised as follows: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Nonredeemable non-controlling interests in consolidated subsidiaries and investment funds Operating companies 92,629 83,818 Consolidated Funds 40,486 115,806 $ 133,115 $ 199,624
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and funds	Three Months Ended March 31, 2021 2020 (dollars in thousands) Income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds Operating companies $ 7,661 $ 127 Consolidated Funds (3,099) (62,315) $ 4,562 $ (62,188)

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	3 Months Ended
	Mar. 31, 2021
Revenue Recognition and Deferred Revenue [Abstract]
Revenue from External Customers by Products and Services	For the three months ended March 31, 2021 and 2020, the following tables presents revenues from contracts with customers disaggregated by fee type and segment. Three Months Ended March 31, 2021 2020 (dollars in thousands) Revenue from contracts with customers Operating Company Investment banking Underwriting fees $ 154,304 $ 63,270 Strategic/financial advisory fees 73,555 21,996 Placement and sales agent fees 72,544 17,596 Expense reimbursements from clients 4,431 2,166 Total investment banking revenue 304,834 105,028 Brokerage Commissions 161,792 132,208 Trade conversion revenue 4,130 4,639 Equity research fees 4,593 4,005 Total brokerage revenue from customers 170,515 140,852 Management fees 25,499 11,346 Incentive income 2,258 — Total revenue from contracts with customers - Op Co $ 503,106 $ 257,226 Asset Company Management fees 243 258 Incentive income — — Total revenue from contracts with customers - Asset Co 243 258 Total revenue from contracts with customers $ 503,349 $ 257,484

Insurance and reinsurance (Tabl

Insurance and reinsurance (Tables)	3 Months Ended
	Mar. 31, 2021
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Abstract]
Effects of Reinsurance	Three Months Ended March 31, 2021 2020 (dollars in thousands) Incurred and paid claims Insurance (net of Outward Reinsurance) $ 744 $ — Inward Reinsurance 3,904 4,235 Total $ 4,648 $ 4,235 Change in claims outstanding and claims IBNR Insurance (net of Outward Reinsurance) $ (136) $ — Inward Reinsurance (559) 17,293 Total $ (695) $ 17,293

Share-Based Payments, Deferre_2

Share-Based Payments, Deferred Compensation and Employee Ownership Plans (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
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, 2021 and 2020: Three Months Ended March 31, 2021 Three Months Ended March 31, 2020 Nonvested Restricted Class A Common Shares and Class A Common Restricted Stock Units Weighted-Average Nonvested Restricted Class A Common Shares and Class A Common Restricted Stock Units Weighted-Average Beginning balance outstanding 5,450,191 $ 17.56 5,364,486 $ 16.67 Granted 1,593,941 34.85 2,140,932 17.39 Vested (291,062) 16.11 (640,084) 14.63 Canceled — — (87,348) 14.80 Forfeited (8,134) 20.22 (30,562) 15.86 Ending balance outstanding 6,744,936 $ 21.71 6,747,424 $ 17.12

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Operating Lease, Lease Income [Table Text Block]	For the three months ended March 31, 2021 and 2020, quantitative information regarding the Company's operating lease obligations reflected in the accompanying condensed consolidated statements of operations were as follows: Three Months Ended March 31, 2021 2020 (dollars in thousands) Lease cost Operating lease cost $ 5,770 $ 5,685 Short-term lease cost 33 146 Variable lease cost 906 788 Sublease income (160) (216) Total lease costs $ 6,549 $ 6,403 The following table summarizes the supplemental cash flow information and certain other information related to operating leases for the three months ended March 31, 2021 and 2020: Three Months Ended March 31, 2021 2020 (dollars in thousands) Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 6,748 $ 8,578 Weighted average remaining lease term - operating leases (in years) 4.56 5.11 Weighted average discount rate - operating leases 4.10 % 4.14 %
Future Minimum Annual Lease and Service Payments	As of March 31, 2021, maturities of the outstanding operating lease liabilities for the Company were as follows: Equipment Leases (operating) Real Estate and Other Facility Rental (a) (b) (dollars in thousands) 2021 $ 207 $ 19,065 2022 150 22,612 2023 11 19,123 2024 — 15,883 2025 — 5,446 Thereafter — 7,862 Total operating leases 368 89,991 Less discount 21 8,927 Less short-term leases — 11 Total lease liability $ 347 $ 81,053 (a) The Company has entered into various agreements to sublease certain of its premises. (b) During the three months ended March 31, 2021, the Company recognized an increase of $5.3 million of operating right-of-use assets and leases liabilities related to for facility leases. As of March 31, 2021, future minimum annual service payments for the Company were as follows: Service Payments (dollars in thousands) 2021 $ 17,854 2022 16,739 2023 8,934 2024 5,254 2025 3,366 Thereafter 10,594 Total service payment commitments $ 62,741
Other Commitments	The following table summarizes unfunded commitments as of March 31, 2021: Entity Unfunded Commitments Commitment Term (dollars in thousands) HealthCare Royalty Partners funds (a) $ 7,333 3.80 years Eclipse Ventures Fund I, L.P. $ 28 3.80 years Eclipse Fund II, L.P. $ 95 4.80 years Eclipse Continuity Fund I, L.P. $ 41 5.80 years Cowen Healthcare Investments III LP $ 4,126 5.80 years Cowen Sustainable Investments I LP $ 15,709 8.80 years

Convertible Debt and Notes Pa_2

Convertible Debt and Notes Payable (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of Debt and Capital Lease Obligations	As of March 31, 2021 and December 31, 2020, the Company's outstanding debt was as follows: As of March 31, 2021 As of December 31, 2020 (dollars in thousands) Convertible debt $ 81,682 $ 80,808 Notes payable 173,656 307,653 Term loan 291,303 — Other notes payable 74,982 72,505 Finance lease obligations 2,578 2,909 $ 624,201 $ 463,875
Direct Financing Lease, Lease Income [Table Text Block]	For the three months ended March 31, 2021 and 2020, quantitative information regarding the Company's finance lease obligations reflected in the accompanying condensed consolidated statements of operations, the supplemental cash flow information and certain other information related to finance leases were as follows: Three Months Ended March 31, 2021 2020 (dollars in thousands) Lease cost Finance lease cost: Amortization of finance lease right-of-use assets $ 309 $ 308 Interest on lease liabilities $ 34 $ 49 Other information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases $ 34 $ 49 Financing cash flows from finance leases $ 332 $ 314 Weighted average remaining lease term - operating leases (in years) 2.01 2.97 Weighted average discount rate - operating leases 4.89 % 4.88 %
Schedule of Maturities of Debt and Future Minimum Lease Payments for Capital Leases	Annual scheduled maturities of debt and minimum payments (of principal and interest) for all debt outstanding as of March 31, 2021, are as follows: Convertible Debt Notes Payable Term Loan Other Notes Payable Finance Lease (dollars in thousands) 2021 $ 2,644 $ 11,468 $ 11,205 $ 7,207 $ 1,117 2022 90,763 13,405 14,835 593 1,168 2023 — 13,405 14,715 72,593 411 2024 — 88,578 14,595 543 11 2025 — 7,750 14,475 — — Thereafter — 158,125 310,163 — — Subtotal 93,407 292,731 379,988 80,936 2,707 Less (a) (11,725) (119,075) (88,685) (5,954) (129) Total $ 81,682 $ 173,656 $ 291,303 $ 74,982 $ 2,578

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	3 Months Ended
	Mar. 31, 2021
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, 2021: Treasury Stock Shares Cost Average Cost per Share Balance outstanding at December 31, 2020 22,619,863 $ 346,870 $ 15.33 Shares purchased for minimum tax withholding under the 2010 and 2020 Equity Plans or other similar transactions 148,752 6,246 41.99 Shares of stock received in respect of indemnification claims 1,155 29 25.33 Purchase of treasury stock 605,703 20,629 34.06 Balance outstanding at March 31, 2021 23,375,473 $ 373,774 $ 15.99

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income / (Loss) [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Three Months Ended March 31, 2021 2020 (dollars in thousands) Beginning balance $ (7) $ (5) Foreign currency translation 4 — Ending balance $ (3) $ (5)

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Earnings Per Share, Basic and Diluted	The computation of earnings per share is as follows: Three Months Ended March 31, 2021 2020 (dollars and share data in thousands, except per share data) Net income (loss) $ 152,066 (72,111) Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds 4,562 (62,188) Net income (loss) attributable to Cowen Inc. 147,504 (9,923) Preferred stock dividends 1,698 1,698 Net income (loss) attributable to Cowen Inc. common stockholders $ 145,806 $ (11,621) Shares for basic and diluted calculations: Weighted average shares used in basic computation 27,359 28,598 Performance based restricted stock 445 — December 2022 Convertible Notes 2,659 — Restricted stock 3,102 — Weighted average shares used in diluted computation 33,565 28,598 Earnings (loss) per share: Basic $ 5.33 $ (0.41) Diluted $ 4.34 $ (0.41)

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Segment Reporting Information, by Segment	The following table sets forth operating results for the Company's consolidated US GAAP net income (loss) and related reclassifications and adjustments necessary to reconcile to the Company's Economic Income (Loss) measure which represents the Company's Op Co and Asset Co segments' results: Three Months Ended March 31, 2021 2020 (dollars in thousands) Economic Income Op Co 143,858 3,650 Asset Co (1,476) (16,229) Adjustments made to arrive at Income (loss) before income taxes Non-controlling Interest 4,562 (62,188) Preferred stock dividends 1,698 1,698 Amortization of (discount)/premium on convertible debt (776) (1,110) Acquisition related amounts (238) — Contingent liability adjustments 6,798 895 Debt extinguishment gain (loss) (4,538) — Bargain purchase gain 3,855 — Net Income tax effect (1,677) 1,173 Net income (loss) 152,066 (72,111) Economic Income (Loss) information provided and reviewed by the CODM includes (i) non-interest revenue, (ii) interest revenue, (iii) interest expense, (iv) depreciation and amortization expense and (v) income taxes (subsequent to 2020 after all available net operating losses were utilized) presented on an Economic Income (Loss) basis by Segment. The following table sets forth the included segment information on a US GAAP basis with reconciliations to consolidated amounts. Three Months Ended March 31, 2021 2020 (dollars in thousands) Op Co Non-Interest Revenue 704,682 173,123 Interest Revenue 51,104 33,666 Interest Revenue, Consolidated funds — 577 Total Revenues 755,786 207,366 Interest Expense 53,803 33,639 Interest Expense, Consolidated funds — 1,061 Depreciation and Amortization 4,349 5,436 Income Taxes 55,085 — Asset Co Non-Interest Revenue (1,668) (10,695) Interest Revenue 203 50 Interest Revenue, Consolidated funds 2 2 Total Revenues (1,463) (10,643) Interest Expense 1,275 1,689 Interest Expense, Consolidated funds — — Depreciation and Amortization 5 6 Income Taxes (657) — Total Segment Non-Interest Revenue * 703,014 162,428 Interest Revenue 51,307 33,716 Interest Revenue, Consolidated funds 2 579 Total Revenues 754,323 196,723 Interest and Dividend Expense (includes dividend expense of $2.6 million, and $3.5 million for the three months ended March 31, 2021 and 2020, respectively) 57,641 38,792 Interest and Dividend Expense, Consolidated funds (includes dividend expense of $0.2 million for the three months ended March 31, 2020) — 1,252 Depreciation and Amortization 4,354 5,442 Income Taxes 54,428 — * Includes dividend revenue of $8.1 million and $8.3 million for the three months ended March 31, 2021 and 2020, respectively. In addition, includes dividend revenue, consolidated funds, of $2.6 million and $3.5 million for the three months ended March 31, 2021 and 2020, respectively.

Regulatory Requirements Regulat

Regulatory Requirements Regulatory (Tables)	3 Months Ended
	Mar. 31, 2021
Regulatory [Abstract]
Computation of Net Capital under Securities and Exchange Commission Regulation	As of March 31, 2021, these regulated broker-dealers had regulatory net capital or financial resources, regulatory net capital requirements or minimum FCA or SFC requirement and excess as follows: Subsidiary Net Capital Minimum Net Capital Requirement Excess Net Capital (dollars in thousands) Cowen and Company $ 332,197 $ 6,289 $ 325,908 ATM Execution $ 4,951 $ 250 $ 4,701 Cowen Prime $ 22,722 $ 250 $ 22,472 Westminster $ 31,116 $ 250 $ 30,866 Cowen International Ltd $ 39,812 $ 25,444 $ 14,368 Cowen Execution Ltd $ 13,205 $ 3,418 $ 9,787 Cowen Asia $ 2,272 $ 386 $ 1,886

Guarantees and Off-Balance Sh_2

Guarantees and Off-Balance Sheet Arrangements Details (Tables)	3 Months Ended
	Mar. 31, 2021
Guarantees and Off Balance Sheet Arrangements [Abstract]
Schedule of Subordinated Borrowing	The Company maintains uncommitted financing arrangements with large financial institutions, the details of which are summarized below as of March 31, 2021. Lender Contractual Amount Available Amount Maturity Date Description Pledge Lines (dollars in thousands) BMO Harris Bank $ 75,000 $ 75,000 None Secured Tri-Party Pledge Facility BMO Harris Bank 150,000 150,000 None Secured Depository Trust Company Pledge Line Total 225,000 225,000 Spike Line BMO Harris Bank 70,000 70,000 August 20, 2021 Unsecured committed spike line facility to cover short term increases in National Securities Clearing Corporation margin deposit requirements Revolving Credit Facility Morgan Stanley 25,000 25,000 March 24, 2026 Unsecured Corporate Revolver Total Credit Lines $ 320,000 $ 320,000

Organization and Business (Deta

Organization and Business (Details)	3 Months Ended
	Mar. 31, 2021segmentdivision
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business segments | segment	2
Number of divisions | division	4

Significant Accounting Polici_3

Significant Accounting Policies All Other - Quarterly (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)cowenfund	Dec. 31, 2020USD ($)cowenfund
Assets	$ 9,946,796	$ 7,828,199
Liabilities	8,706,816	6,659,078
Variable Interest Entity, Primary Beneficiary [Member]
Assets	243,300	325,500
Liabilities	$ 8,000	$ 10,100
Other investment companies
Number of Funds | cowenfund	2	3
Operating Company | Hedge Funds
Asset Management Fees, Percent Fee	2.00%
Operating Company | During investment period | Minimum
Asset Management Fees, Percent Fee	1.00%
Operating Company | During investment period | Maximum
Asset Management Fees, Percent Fee	2.00%
Operating Company | After investment period | Healthcare Royalty Partners | Minimum
Asset Management Fees, Percent Fee	1.00%
Operating Company | After investment period | Healthcare Royalty Partners | Maximum
Asset Management Fees, Percent Fee	2.00%
Operating Company | After investment period | Other Healthcare Royalty Partners | Minimum
Asset Management Fees, Percent Fee	0.20%
Operating Company | After investment period | Other Healthcare Royalty Partners | Maximum
Asset Management Fees, Percent Fee	1.00%

Acquisition (Narrative) (Detail

Acquisition (Narrative) (Details) - USD ($) $ in Thousands	Feb. 26, 2021	Mar. 31, 2021	Mar. 31, 2020
Business Acquisition [Line Items]
Purchase of business		$ (2,109)	$ 0
Cowen Insurance
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		12,700
Payments to Acquire Businesses, Gross		12,500
Other payments to acquire businesses		200
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed		200
Cowen Insurance | Scenario, Plan
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 12,735
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 17,951
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	4,794
Business Combination, Bargain Purchase, Gain Recognized, Amount	5,216
Business Combination Bargain Purchase Gain Related Tax Expense	$ 1,300

Acquisition (Preliminary Purcha

Acquisition (Preliminary Purchase Price Allocation) (Details) - Cowen Insurance - USD ($) $ in Thousands	Feb. 26, 2021	Mar. 31, 2021
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 12,700
Scenario, Plan
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	$ 14,844
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities	1,571
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	30
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	4,794
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	12,828
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Compensation Payable	(17)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	(16,099)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	17,951
Business Combination, Bargain Purchase, Gain Recognized, Amount	$ (5,216)
Business Combination, Consideration Transferred		$ 12,735

Acquisition (Intangible Assets)

Acquisition (Intangible Assets) (Details) - Cowen Insurance - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Feb. 26, 2021
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	10 years
License
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 200
Customer-Related Intangible Assets
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 4,600

Acquisition (Amortization Expen

Acquisition (Amortization Expense) (Details) - Scenario, Plan - Cowen Insurance $ in Thousands	Mar. 31, 2021USD ($)
Business Acquisition [Line Items]
2021	$ 343
2022	458
2023	458
2024	458
2025	458
Finite-Lived Intangible Asset, Expected Amortization, after Year Five	2,365
Finite-Lived Intangible Assets, Net	$ 4,540

Cash Collateral Pledged (Detail

Cash Collateral Pledged (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Cash collateral pledged	$ 110,303,000	$ 110,743,000	$ 7,538,000
Letter of credit, borrowing capacity	320,000,000
Letters of Credit Outstanding, Amount	0	0
Letter of Credit | Letter of Credit, NY Office 1, Expires April 2022
Letter of credit, borrowing capacity	215,000
Letter of Credit | Letter of Credit, NY Office 3, Expires October 2022
Letter of credit, borrowing capacity	1,424,000
Letter of Credit | Letter of Credit, NY Office 5, Expires November 2021
Letter of credit, borrowing capacity	1,252,000
Letter of Credit | Letter of Credit, Boston Office, Expires March 2028
Letter of credit, borrowing capacity	194,000
Letter of Credit | Letter of Credit, San Francisco Office, Expires October 2025
Letter of credit, borrowing capacity	458,000
Facility Leases
Cash collateral pledged	3,543,000	4,000,000
Collateral Reinsurance Agreement
Cash collateral pledged	$ 106,800,000	$ 106,800,000

Segregated Cash (Details)

Segregated Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Segregated Cash [Abstract]
Segregated cash	$ 168,942	$ 185,141	$ 131,266

Investments of Operating Enti_3

Investments of Operating Entities and Consolidated Funds - Operating Entities - Securities Owned at Fair Value (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Securities owned, at fair value		$ 3,156,100	$ 2,001,602
Estimate of Fair Value Measurement [Member]
Investment Holdings [Line Items]
Securities owned, at fair value		5,900	8,800
Common Stock
Investment Holdings [Line Items]
Trading Securities, Equity		2,934,604	1,770,301
Preferred Stock
Investment Holdings [Line Items]
Trading Securities, Equity		66,853	69,358
Warrants and Rights
Investment Holdings [Line Items]
Trading Securities, Equity		30,961	27,701
Government Securities
Investment Holdings [Line Items]
Debt Securities, Trading		19,671	19,721
Corporate Bonds
Investment Holdings [Line Items]
Debt Securities, Trading		81,460	86,503
Convertible Bonds
Investment Holdings [Line Items]
Debt Securities, Trading		3,137	6,040
Term Loans
Investment Holdings [Line Items]
Debt Securities, Trading	[1]	12,424	12,623
Trade Claims
Investment Holdings [Line Items]
Debt Securities, Trading	[1]	5,905	8,713
Private Equity Investments
Investment Holdings [Line Items]
Debt Securities, Trading		$ 1,085	$ 642
[1]	The Company has elected the fair value option for securities owned, at fair value with a fair value of $5.9 million and $8.8 million, respectively, at March 31, 2021 and December 31, 2020.

Investments Of Operating Enti_4

Investments Of Operating Entities And Consolidated Funds - Operating Entities - Receivable On And Payable For Derivative Contracts, At Fair Value (Details)		Mar. 31, 2021USD ($)contract	Dec. 31, 2020USD ($)contract
Derivative [Line Items]
Receivable on derivative contracts, at fair value		$ 95,536,000	$ 51,482,000
Payable for derivative contracts, at fair value		52,125,000	76,160,000
Receivable on derivatives contracts, at fair value [Member]
Derivative [Line Items]
Receivable on derivative contracts, at fair value		95,536,000	51,482,000
Derivative Asset, Fair Value, Amount Offset Against Collateral	[1],[2]	(89,238,000)	(62,269,000)
Payable for derivatives contracts, at fair value [Member]
Derivative [Line Items]
Payable for derivative contracts, at fair value		52,125,000	76,160,000
Derivative Liability, Fair Value, Amount Offset Against Collateral	[2]	(61,806,000)	(37,033,000)
Currency Forwards
Derivative [Line Items]
Derivative Asset, Notional Amount		132,960,000	4,902,000
Receivable on derivative contracts, at fair value		384,000	15,000
Derivative Liability, Notional Amount		1,990,000	123,346,000
Payable for derivative contracts, at fair value		16,000	3,067,000
Swaps
Derivative [Line Items]
Derivative Asset, Notional Amount		1,746,919,000	944,544,000
Receivable on derivative contracts, at fair value		142,266,000	64,634,000
Derivative Liability, Notional Amount		1,603,710,000	896,863,000
Payable for derivative contracts, at fair value		$ 82,391,000	$ 43,560,000
Options
Derivative [Line Items]
Derivative Asset, Number of Instruments Held | contract	[3]	163,622	371,188
Receivable on derivative contracts, at fair value	[3]	$ 42,124,000	$ 49,102,000
Option
Derivative [Line Items]
Derivative Liability, Number of Instruments Held | contract	[3]	130,627	198,320
Payable for derivative contracts, at fair value	[3]	$ 31,524,000	$ 66,566,000
[1]	Derivatives are reported on a net basis, by counterparty, when a legal right of offset exists under an enforceable netting agreement as well as net of cash collateral received or posted under enforceable credit support agreements. See Note 2f for further information on offsetting of derivative financial instruments.
[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 volume of contracts for index, equity, commodity future and cash conversion options.

Investments Of Operating Enti_5

Investments Of Operating Entities And Consolidated Funds - Operating Entities - Gross And Net Derivative Positions And The Related Offsetting Amount (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Receivable on derivative contracts, at fair value		$ 95,536	$ 51,482
Payable for derivative contracts, at fair value		52,125	76,160
Receivable on derivatives contracts, at fair value [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset		184,774	113,751
Derivative Asset, Fair Value, Amount Offset Against Collateral	[1],[2]	89,238	62,269
Receivable on derivative contracts, at fair value		95,536	51,482
Financial Instruments, Owned and Pledged as Collateral, at Fair Value	[2]	2,694	691
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	[2]	48,448	169
Derivative asset, net of offset		44,394	50,622
Payable for derivatives contracts, at fair value [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability		113,931	113,193
Derivative Liability, Fair Value, Amount Offset Against Collateral	[2]	61,806	37,033
Payable for derivative contracts, at fair value		52,125	76,160
Financial Instruments, Owned and Pledged as Collateral, at Fair Value	[2]	2,694	691
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	[2]	1,124	3,174
Derivative Liability, net of offset		$ 48,307	$ 72,295
[1]	Derivatives are reported on a net basis, by counterparty, when a legal right of offset exists under an enforceable netting agreement as well as net of cash collateral received or posted under enforceable credit support agreements. See Note 2f for further information on offsetting of derivative financial instruments.
[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

Investments Of Operating Enti_6

Investments Of Operating Entities And Consolidated Funds - Operating Entities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Other Income [Member]
Derivative [Line Items]
Realized and unrealized gains/(losses) related to derivatives trading activities	$ 35.5	$ 28.8

Investments Of Operating Enti_7

Investments Of Operating Entities And Consolidated Funds - Operating Entities - Other Investments (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Other investments		$ 366,783	$ 255,027
Portfolio Funds
Investment Holdings [Line Items]
Other investments	[1]	151,933	133,454
Carried interest
Investment Holdings [Line Items]
Other investments	[1]	180,352	82,892
Equity Method Investments
Investment Holdings [Line Items]
Other investments	[1]	$ 34,498	$ 38,681
[1]	In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.

Investments Of Operating Enti_8

Investments Of Operating Entities And Consolidated Funds - Operating Entities - Portfolio Funds (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Other investments		$ 366,783	$ 255,027
Portfolio Funds
Investment Holdings [Line Items]
Other investments	[1]	151,933	133,454
Starboard Value and Opportunity Fund LP | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[2],[3]	$ 46,008	42,519
Required notice period, withdrawal		90 days
Formation 8 Partners Fund I LP | Portfolio Funds
Investment Holdings [Line Items]
Other investments	[4]	$ 33,408	31,894
Cowen Healthcare Investments II LP | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[5]	26,733	26,186
Lagunita Biosciences, LLC | Portfolio Funds
Investment Holdings [Line Items]
Other investments	[6]	3,785	3,850
Eclipse Ventures Fund I, L.P. | Portfolio Funds
Investment Holdings [Line Items]
Other investments	[7]	4,804	4,457
Healthcare Royalty Partners II | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[8]	1,605	1,588
Healthcare Royalty Partners | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[8]	1,035	1,072
Starboard Leaders Fund LP | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[9]	$ 2,328	2,020
Unfunded Commitment cancellation		30 days
Elipse SPV I,LP | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[10]	$ 1,809	1,708
Ramius Merger Fund LLC | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[11]	2,252	2,197
Triartisan ES Partners, LLC | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[12]	1,848	1,657
Cowen Healthcare Investments III LP | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[5]	7,717	5,714
Triartisan PFC Partners, LLC | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[13]	760	691
Starboard Value and Opportunity Fund Ltd | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[2],[3]	2,556	2,364
Eclipse Venture Fund II, L.P. | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[7]	1,910	1,733
Eclipse Continuity Fund I, L.P. | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[7]	1,252	1,101
Cowen Sustainable Investments I LP | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[5]	9,299	0
Difesa Partners LP | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[14]	985	848
BDC Fund I Coinvest 1, L.P. | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[15]	1,250	1,250
Other Private Investment | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[16]	311	326
Other Funds | Portfolio Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[17]	$ 278	$ 279
[1]	In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.
[2]	Starboard Value and Opportunity Fund LP and Starboard Value and Opportunity Fund Ltd permits quarterly withdrawals upon 90 days' notice.
[3]	These portfolio funds are affiliates of the Company.
[4]	Formation8 Partners Fund I, L.P. is a private equity fund which invests in early stage and growth transformational information and energy technology companies. Distributions will be made when the underlying investments are liquidated.
[5]	Cowen Healthcare Investments II LP, Cowen Healthcare Investments III LP and Cowen Sustainable Investments I LP are private equity funds.  Distributions are made from the fund when cash flows or securities are received from the underlying investments. Investors do not have redemption rights
[6]	Lagunita Biosciences, LLC, is a healthcare investment company that creates and grows early stage companies to commercialize impactful translational science that addresses significant clinical needs, is a private equity structure and therefore distributions will be made when the underlying investments are liquidated.
[7]	Each of Eclipse Ventures Fund I, L.P., Eclipse Ventures Fund II, L.P. and Eclipse Continuity Fund I, L.P. are venture capital funds which invests in early stage and growth stage hardware companies. Distributions will be made when the underlying investments are liquidated.
[8]	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.
[9]	Starboard Leaders Fund LP does not permit withdrawals, but instead allows terminations with respect to capital commitments upon 30 days' prior written notice at any time following the first anniversary of an investor's initial capital contribution.
[10]	Eclipse SPV I, L.P. is a co-investment vehicle organized to invest in a private company focused on software-driven automation projects.  Distributions will be made when the underlying investments are liquidated.
[11]	Ramius Merger Fund LLC permits monthly withdrawals on 45 days prior notice.
[12]	TriArtisan ES Partners LLC is a co-investment vehicle organized to invest in a privately held nuclear services company. Distributions will be made when the underlying investment is liquidated.
[13]	TriArtisan PFC Partners LLC is a co-investment vehicle organized to invest in a privately held casual dining restaurant chain. Distributions will be made when the underlying investment in liquidated.
[14]	Difesa Partners, LP permits semi-annual withdrawals occurring on or after the anniversary of initial contribution upon 90 days written notice.
[15]	BDC Fund I Coinvest 1, L.P. is a private equity fund focused on investing in growth companies in industries disrupted by digitization. Distributions will be made when the underlying investments are liquidated.
[16]	Other private investment represents the Company's closed end investment in a portfolio fund that invests in a wireless broadband communication provider in Italy.
[17]	The majority of these investment funds are affiliates of the Company or are managed by the Company and the investors can redeem from these funds as investments are liquidated.

Investments of Operating Enti_9

Investments of Operating Entities and Consolidated Funds - Operating Entities - Carried Interest (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Other investments		$ 366,783	$ 255,027
Carried interest
Investment Holdings [Line Items]
Other investments	[1]	180,352	82,892
Cowen Healthcare Investments II LP | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		73,415	62,112
Cowen Healthcare Investments III LP | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		31,034	11,520
Cowen Sustainable Investments I LP | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		13,581	0
Cowen Sustainable Investments Offshore I LP | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		17,944	0
CSI I Prodigy Co-Investment LP | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		6,617	0
CSI PRTA Co-Investment LP | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		26,242	0
Triartisan TGIF Partners LLC | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		3,689	3,361
Triartisan ES Partners, LLC | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		4,514	3,152
Triartisan PFC Partners, LLC | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		2,329	1,455
Ramius Multi-Strategy Fund LP | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		638	734
Ramius Merger Fund LLC | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		162	368
RCG IO Renergys Sarl | Carried interest | Affiliated Entity
Investment Holdings [Line Items]
Other investments		$ 187	$ 190
[1]	In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.

Investments of Operating Ent_10

Investments of Operating Entities and Consolidated Funds - Operating Entities - Equity Method Investment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Net gains (losses) on other investments	$ 12,645	$ (62)
Equity Method Investment, Other than Temporary Impairment	0	0
Equity method investments	$ 34,498		$ 38,681
Surf House Ocean Views Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	40.00%
Other than Temporary Impairment Losses, Investments		$ 7,300
Minimum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	15.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	55.00%
Starboard Value LP
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 27,769		31,528
Healthcare Royalty GP III, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	2,221		2,213
RCG Longview Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	268		268
Healthcare Royalty GP, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	442		920
Healthcare Royalty GP II, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	272		269
RCG Longview Debt Fund IV Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	331		331
RCG Longview Equity Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	105		105
HCR Stafford Fund GP, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,159		1,025
Liberty Harbor North
Schedule of Equity Method Investments [Line Items]
Equity method investments	222		222
Equity Method Investee, Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 1,709		$ 1,800

Investments of Operating Ent_11

Investments of Operating Entities and Consolidated Funds - Operating Entities - Equity Method Investment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule of Equity Method Investments [Line Items]
Net gains (losses) on other investments	$ 12,645	$ (62)

Investments of Operating Ent_12

Investments of Operating Entities and Consolidated Funds - Operating Entities - Securities Sold, Not Yet Purchased (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	$ 931,082,000	$ 728,115,000
Common Stock
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	918,021,000	699,894,000
Corporate Bonds
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	453,000	11,358,000
US Government Debt Securities
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	522,000	1,500,000
Preferred Stock
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	7,567,000	6,589,000
Warrants and Rights
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	$ 4,519,000	$ 8,774,000

Investments of Operating Ent_13

Investments of Operating Entities and Consolidated Funds - Operating Entities - Securities Sold/Purchased Under Agreements To Repurchase/Resell And Securities Lending And Borrowing Transactions (Details) - USD ($)		Mar. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Securities borrowed		$ 1,996,757,000	$ 1,908,187,000
Securities Borrowed, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election	[1]	0	0
Securities Borrowed		1,996,757,000	1,908,187,000
Securities borrowed, additional amounts, asset		0	0
Securities Borrowed, Not Offset, Policy Election Deduction		1,970,665,000	1,809,399,000
Securities Borrowed, Collateral, Obligation to Return Cash	[2]	0	0
Securities Borrowed, Amount Offset Against Collateral		26,092,000	98,788,000
Securities Loaned		3,083,945,000	2,476,414,000
Securities Loaned, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election	[1]	0	0
Securities Loaned, Gross amounts recognized		3,083,945,000	2,476,414,000
Securities Loaned, Additional Amounts Available		0	0
Securities Loaned, Not Offset, Policy Election Deduction		3,100,800,000	2,383,342,000
Securities Loaned, Collateral, Right to Reclaim Cash	[2]	0	0
Securities Loaned, Amount Offset Against Collateral		(16,855,000)	(93,072,000)
Securities Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement		0	0
Securities Sold under Agreements to Repurchase		2,546,000	5,036,000
Securities sold under agreements to repurchase, additional amounts		0	0
Securities sold under agreements to repurchase, Fair value		2,759,000	5,544,000
Securities borrowed, cash collateral pledged			0
Securities Loaned, Net amounts		(213,000)	(508,000)
Securities Purchased under Agreements to Resell		0	191,000
Securities Sold under Agreements to Repurchase, Gross			0
Securities purchased under agreements to resell, additional amounts			0
Securities Purchased under Agreements to Resell, Fair Value of Collateral			204,000
Securities Purchased under Agreements to Resell, Collateral, Obligation to Return Securities			(13,000)
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash		$ 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.

Investments of Operating Ent_14

Investments of Operating Entities and Consolidated Funds - Operating Entities - Gross Obligations For Securities Loaned And Securities Sold Under Agreements To Repurchase (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	$ 3,083,945,000	$ 2,476,414,000
Securities sold, not yet purchased, at fair value	931,082,000	728,115,000
Common stock
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	2,827,291,000	2,232,687,000
Common stock | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	2,827,291,000	2,232,687,000
Common stock | Up to 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Common stock | 31 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Common stock | Greater than 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	256,654,000	243,726,000
Securities sold, not yet purchased, at fair value	2,546,000	5,036,000
Corporate Bonds | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	256,654,000	243,726,000
Securities sold, not yet purchased, at fair value	0	0
Corporate Bonds | Up to 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Securities sold, not yet purchased, at fair value	0	0
Corporate Bonds | 31 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Securities sold, not yet purchased, at fair value	2,546,000	5,036,000
Corporate Bonds | Greater than 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Securities sold, not yet purchased, at fair value	$ 0	$ 0

Investments of Operating Ent_15

Investments of Operating Entities and Consolidated Funds - Operating Entities - Variable Interest Entities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets	$ 9,946,796	$ 7,828,199
Liabilities	8,706,816	6,659,078
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	8,900,000	8,000,000
Liabilities	1,200,000	1,300,000
Variable Interest Entity, Nonconsolidated, Comparison of Carrying Amount of Assets and Liabilities to Maximum Loss Exposure	236,400	210,700
Maximum exposure regarding nonconsolidated variable interest entities	$ 364,900	$ 326,000

Investments of Operating Ent_16

Investments of Operating Entities and Consolidated Funds - Consolidated Funds - Securities Owned at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Securities owned, at fair value	$ 8,940	$ 10,622
Common Stock
Investment Holdings [Line Items]
Securities owned, at fair value	3,611	4,816
Warrants and Rights
Investment Holdings [Line Items]
Securities owned, at fair value	$ 5,329	$ 5,806

Investments Of Operating Ent_17

Investments Of Operating Entities And Consolidated Funds - Consolidated Funds - Other Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	$ 100,035	$ 192,670
Enterprise LP [Member]
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	100,035	104,475
Cowen Sustainable Investments I LP
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	$ 0	$ 88,195

Investments Of Operating Ent_18

Investments Of Operating Entities And Consolidated Funds - Consolidated Funds - Indirect Concentration of the Underlying Investments Held by Consolidated Funds (Details) - Equity Securities - Linkem - ITALY - Wireless Broadband - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Percentage of Stockholders' Equity	7.62%	9.07%
Market Value	$ 84,324	$ 87,944

Fair Value Measurements for O_3

Fair Value Measurements for Operating Entities and Consolidated Funds - Assets and Liabilities at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands		Mar. 31, 2021		Dec. 31, 2020		Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		$ 95,536		$ 51,482
Other investments		366,783		255,027
Other Investments, Consolidated Funds		100,035		192,670
Investments		3,727,394		2,511,403
Securities sold, not yet purchased, at fair value		931,082		728,115
Securities sold, not yet purchased, at fair value		931,082		728,115
Payable for derivative contracts, at fair value		52,125		76,160
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low		10,100		10,100
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High		25,000		35,100
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance Liability Value		23,813		42,837
Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance Liability Value		415		704			$ 1,000
Contingent liability payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance Liability Value		19,579		37,952		$ 28,658	$ 30,896
Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		142,266		64,634
Payable for derivative contracts, at fair value		82,391		43,560
Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value	[1]	42,124		49,102
Portfolio Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	[2]	151,933		133,454
Other Investments, Consolidated Funds	[2]	100,035		192,670
Carried interest
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	[2]	180,352		82,892
Equity Method Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	[2]	34,498		38,681
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		3,260,576		2,063,706
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		1,002,786		840,993
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		3,007,451		1,847,389
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		958,334		777,908
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		224,048		151,125
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		82,445		57,281
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring		118,315		127,461
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		23,813		42,837
Fair Value, Measurements, Recurring | Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		522		1,500
Fair Value, Measurements, Recurring | Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		522		1,500
Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		918,021		699,894
Fair Value, Measurements, Recurring | Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		918,021		699,894
Fair Value, Measurements, Recurring | Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		453		11,358
Fair Value, Measurements, Recurring | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		38		10,654
Fair Value, Measurements, Recurring | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		415		704
Fair Value, Measurements, Recurring | Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		7,567		6,589
Fair Value, Measurements, Recurring | Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		7,567		6,589
Fair Value, Measurements, Recurring | Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		4,519		8,774
Fair Value, Measurements, Recurring | Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		4,519		8,774
Fair Value, Measurements, Recurring | Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0		0
Fair Value, Measurements, Recurring | Contingent liability payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent Consideration Payable		19,579	[3]	36,718	[4]
Fair Value, Measurements, Recurring | Contingent liability payable | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent Consideration Payable		0	[3]	0	[4]
Fair Value, Measurements, Recurring | Contingent liability payable | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent Consideration Payable		0	[3]	0	[4]
Fair Value, Measurements, Recurring | Contingent liability payable | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent Consideration Payable	[4]			36,718
Fair Value, Measurements, Recurring | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value				15
Fair Value, Measurements, Recurring | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value				0
Fair Value, Measurements, Recurring | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value				15
Fair Value, Measurements, Recurring | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value				0
Fair Value, Measurements, Recurring | Currency forward | Derivative Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		16		3,067
Fair Value, Measurements, Recurring | Currency forward | Derivative Liabilities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		0		0
Fair Value, Measurements, Recurring | Currency forward | Derivative Liabilities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		16		3,067
Fair Value, Measurements, Recurring | Currency forward | Derivative Liabilities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		0		0
Fair Value, Measurements, Recurring | Swaps | Derivative Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		20,585		6,527
Fair Value, Measurements, Recurring | Swaps | Derivative Liabilities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		0		0
Fair Value, Measurements, Recurring | Swaps | Derivative Liabilities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		82,391		43,560
Fair Value, Measurements, Recurring | Swaps | Derivative Liabilities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	[5]	(61,806)		(37,033)
Fair Value, Measurements, Recurring | Options | Derivative Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		31,524		66,566
Fair Value, Measurements, Recurring | Options | Derivative Liabilities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		28,227		62,651
Fair Value, Measurements, Recurring | Options | Derivative Liabilities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		0		0
Fair Value, Measurements, Recurring | Options | Derivative Liabilities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payable for derivative contracts, at fair value		3,297		3,915
Fair Value, Measurements, Recurring | Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		19,671		19,721
Fair Value, Measurements, Recurring | Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		19,671		19,721
Fair Value, Measurements, Recurring | Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		66,853		69,358
Fair Value, Measurements, Recurring | Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		10,376		9,391
Fair Value, Measurements, Recurring | Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		56,477		59,967
Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		2,934,604		1,770,301
Fair Value, Measurements, Recurring | Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		2,911,824		1,746,407
Fair Value, Measurements, Recurring | Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		74		108
Fair Value, Measurements, Recurring | Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		22,706		23,786
Fair Value, Measurements, Recurring | Convertible Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		3,137		6,040
Fair Value, Measurements, Recurring | Convertible Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Convertible Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Convertible Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		3,137		6,040
Fair Value, Measurements, Recurring | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		81,460		86,503
Fair Value, Measurements, Recurring | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		81,324		86,368
Fair Value, Measurements, Recurring | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		136		135
Fair Value, Measurements, Recurring | Trade Claims
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		5,905		8,713
Fair Value, Measurements, Recurring | Trade Claims | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Trade Claims | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Trade Claims | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		5,905		8,713
Fair Value, Measurements, Recurring | Term Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		12,424		12,623
Fair Value, Measurements, Recurring | Term Loans | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Term Loans | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0		0
Fair Value, Measurements, Recurring | Term Loans | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		12,424		12,623
Fair Value, Measurements, Recurring | Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		30,961		27,701
Fair Value, Measurements, Recurring | Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		23,037		21,154
Fair Value, Measurements, Recurring | Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		7,924		6,547
Fair Value, Measurements, Recurring | Private Equity Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading				642
Trading Securities, Equity		1,085
Fair Value, Measurements, Recurring | Private Equity Investments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading				0
Trading Securities, Equity		0
Fair Value, Measurements, Recurring | Private Equity Investments | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading				0
Trading Securities, Equity		0
Fair Value, Measurements, Recurring | Private Equity Investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading				642
Trading Securities, Equity		1,085
Fair Value, Measurements, Recurring | Derivative Assets | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		384
Fair Value, Measurements, Recurring | Derivative Assets | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		0
Fair Value, Measurements, Recurring | Derivative Assets | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		384
Fair Value, Measurements, Recurring | Derivative Assets | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		0
Fair Value, Measurements, Recurring | Derivative Assets | Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		53,028		2,365
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		0		0
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		142,266		64,634
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		0		0
Derivative Asset, Fair Value, Amount Offset Against Collateral	[5]	(89,238)		(62,269)
Fair Value, Measurements, Recurring | Derivative Assets | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		42,124		49,102
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		41,883		48,851
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		0		0
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Receivable on derivative contracts, at fair value		241		251
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		3,611		4,816
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		660		1,865
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		2,951		2,951
Fair Value, Measurements, Recurring | Consolidated Funds | Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		5,329		5,806
Fair Value, Measurements, Recurring | Consolidated Funds | Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		$ 5,329		$ 5,806
[1]	Includes the volume of contracts for index, equity, commodity future and cash conversion options.
[2]	In accordance with US GAAP, portfolio funds are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient are not classified in the fair value hierarchy. Carried interest and equity method investments presented in the table above are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.
[3]	In accordance with the terms of the purchase agreements for acquisitions that closed during the first quarter of 2019 and the fourth quarter of 2020, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired businesses, if certain targets are achieved through the periods ended December 31, 2020 and December 31, 2023. For both the Quarton Acquisition and the MHT Acquisition, the Company estimated the contingent consideration liabilities using a combination of Monte Carlo and Discounted Cash Flow methods which require 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 for the Quarton Acquisition can range from $10.1 million to $25.0 million. The undiscounted amounts for the MHT Acquisition have no minimum or maximum as it is calculated based on revenue.
[4]	In accordance with the terms of the purchase agreements for acquisitions that closed during the first quarter of 2019 and the fourth quarter of 2020, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired businesses, if certain targets are achieved through the periods ended December 31, 2020 and December 31, 2023. For both the Quarton Acquisition and the MHT Acquisition, the Company estimated the contingent consideration liabilities using a combination of Monte Carlo and Discounted Cash Flow methods which require 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 for the Quarton Acquisition can range from $10.1 million to $35.1 million. The undiscounted amounts for the MHT Acquisition have no minimum or maximum as it is calculated based on revenue.
[5]	Derivatives are reported on a net basis, by counterparty, when a legal right of offset exists under an enforceable netting agreement as well as net of cash collateral received or posted under enforceable credit support agreements. See Note 2f for further information on offsetting of derivative financial instruments.

Fair Value Measurements for O_4

Fair Value Measurements for Operating Entities and Consolidated Funds - Unobservable Input Roll Forward (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021		Mar. 31, 2020		Dec. 31, 2020	Dec. 31, 2019
Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 56,477		$ 8,200		$ 59,967	$ 7,835
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		1,859		365
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		4,651		0
Realized and unrealized gains (losses), asset		(698)		0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(698)		0
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		22,706		17,510		23,786	17,466
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		5,353	[2]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		3,226		1,798
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		1,387		593
Realized and unrealized gains (losses), asset		2,434		(1,161)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	1,679		(1,257)
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		3,137		2,786		6,040	2,500
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		1,050		286
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		3,930		0
Realized and unrealized gains (losses), asset		(23)		0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(23)		0
Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		136		2,812		135	2,421
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		70		422
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		49		24
Realized and unrealized gains (losses), asset		(20)		(7)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(49)		12
Options
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		241		332		251	336
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0
Realized and unrealized gains (losses), asset		(10)		(4)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(10)		(4)
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		7,924		598		6,547	594
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		3,406		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		1,206		0
Realized and unrealized gains (losses), asset		(823)		4
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(895)		4
Trade Claims
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,905		9,183		8,713	7,083
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		1,044	[3]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		1,378		1,166
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		4,216		0
Realized and unrealized gains (losses), asset		30		(110)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(1,021)		(110)
Term Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		12,424				12,623
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		322
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0
Realized and unrealized gains (losses), asset		(521)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(521)
Private Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		1,085		465		642	237
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		443		233
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0
Realized and unrealized gains (losses), asset		0		(5)
Change in Unrealized Gain (Loss), instruments still held, asset		0		(5)
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				4,393			4,393
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				0
Realized and unrealized gains (losses), asset				0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]			0
Consolidated Funds | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		2,951		100,000		2,951	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		100,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0
Realized and unrealized gains (losses), asset		0		0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	0		0
Consolidated Funds | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,329		5,611		5,806	5,567
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		670		0
Realized and unrealized gains (losses), asset		193		44
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(477)		44
Option
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		3,297		1,802		3,915	2,920
Liability, Transfers In		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		0
Liability, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		618		1,118
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	[1]	(618)		(1,118)
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		19,579		28,658		37,952	30,896
Liability, Transfers In		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		0
Liability, Purchases		(11,312)		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		0		1,400
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		7,061		838
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	[1]	(7,061)		(838)
Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				800
Balance Liability Value		415				704	1,000
Liability, Transfers In		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		0
Liability, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		(289)		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		0		(200)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	[1]	0		(200)
US Government Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				1,500
Balance Liability Value		522				$ 1,500	$ 1,950
Liability, Transfers In		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		0
Liability, Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales		(1,278)		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		300		(450)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	[1]	$ 87		$ (450)
[1]	Unrealized gains/losses are reported in Investment income - Securities principal transactions, net in the accompanying condensed consolidated statements of operations
[2]	The entity in which the Company is invested completed an initial public offering
[3]	The security stopped trading on an open market.

Fair Value Measurements for O_5

Fair Value Measurements for Operating Entities and Consolidated Funds - Fair Value Inputs, Unobservable Inputs, Quantitative Information (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2021		Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Other investments		$ 366,783		$ 255,027
Contingent liability payable
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value		19,579		37,952	$ 28,658	$ 30,896
Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		241		251	332	336
Trade Claims
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		5,905		8,713	9,183	7,083
Warrants and Rights
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		7,924		6,547	598	594
Corporate Bonds
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		136		135	$ 2,812	$ 2,421
Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		118,315		127,461
Balance Liability Value		23,813		42,837
Level 3 | Derivative Liabilities | Valuation Technique, Option Pricing Model
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value		3,297
Level 3 | Contingent liability payable | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value	[1]	19,579
Level 3 | Contingent liability payable | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value		$ 19,579		$ 36,718
Weighted average percent Fair Value technique		13.00%		15.00%
Level 3 | Contingent liability payable | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		7.00%		9.00%
Level 3 | Contingent liability payable | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		15.00%		16.00%
Level 3 | Contingent liability payable | Monte Carlo [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		18.00%		22.00%
Level 3 | Contingent liability payable | Monte Carlo [Member] | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		18.00%		22.00%
Level 3 | Contingent liability payable | Monte Carlo [Member] | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		20.00%		24.00%
Level 3 | Other Liabilities [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value		$ 937	[2]	$ 2,204
Level 3 | Common and Preferred Stock | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 70,935		$ 65,735
Level 3 | Common and Preferred Stock | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		12.00%		11.00%
Level 3 | Common and Preferred Stock | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		11.00%		10.00%
Level 3 | Common and Preferred Stock | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		20.00%		12.00%
Level 3 | Common and Preferred Stock | Valuation, Market Approach
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		650.00%		650.00%
Level 3 | Common and Preferred Stock | Valuation, Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		625.00%		625.00%
Level 3 | Common and Preferred Stock | Valuation, Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		675.00%		675.00%
Level 3 | Common and Preferred Stock | Valuation technique, probability of success
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		70.00%
Weighted average percent Fair Value technique		70.00%
Level 3 | Options | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 241		$ 251
Level 3 | Options | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		12.00%		11.00%
Level 3 | Options | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		11.00%		10.00%
Level 3 | Options | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		12.00%		12.00%
Level 3 | Trade Claims | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 3,713		$ 3,500
Level 3 | Warrants and Rights | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value				$ 11,217
Level 3 | Warrants and Rights | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 10,394
Level 3 | Warrants and Rights | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		7.00%		7.00%
Level 3 | Warrants and Rights | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		4.00%		4.00%
Level 3 | Warrants and Rights | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		12.00%		11.00%
Level 3 | Warrants and Rights | Valuation, Market Approach
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		6.50%		6.50%
Level 3 | Warrants and Rights | Valuation, Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		6.25%		6.25%
Level 3 | Warrants and Rights | Valuation, Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		6.75%		6.75%
Level 3 | Corporate Bonds | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 12,424		$ 12,623
Level 3 | Bonds | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		12.00%		11.00%
Level 3 | Bonds | Valuation Technique, Discounted Cash Flow | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		11.00%		10.00%
Level 3 | Bonds | Valuation Technique, Discounted Cash Flow | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		12.00%		12.00%
Level 3 | Bonds | Valuation, Market Approach
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		650.00%
Level 3 | Bonds | Valuation, Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		625.00%
Level 3 | Bonds | Valuation, Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		675.00%
Level 3 | Bonds | Probability of recovery valuation technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique				650.00%
Level 3 | Bonds | Probability of recovery valuation technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				625.00%
Level 3 | Bonds | Probability of recovery valuation technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				675.00%
Level 3 | Other Investments
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	[2]	$ 20,608		$ 34,135
Level 3 | Options | Valuation, Market Approach
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Weighted average percent Fair Value technique		650.00%		650.00%
Level 3 | Options | Valuation, Market Approach | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		625.00%		625.00%
Level 3 | Options | Valuation, Market Approach | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		675.00%		675.00%
Fair Value, Measurements, Recurring | Level 3 | Option | Derivative Liabilities | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure				$ 3,915
Discount rate | Level 3 | Trade Claims | Valuation Technique, Discounted Cash Flow
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		20.00%		15.00%
Weighted average percent Fair Value technique		20.00%		15.00%
Volatility | Level 3 | Option | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		35.00%
Weighted average percent Fair Value technique		35.00%		35.00%
Volatility | Level 3 | Option | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs				35.00%
[1]	In accordance with the terms of the purchase agreements for acquisitions that closed during the first quarter of 2019 and the fourth quarter of 2020, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired businesses, if certain targets are achieved through the periods ended December 31, 2020 and December 31, 2023. For both the Quarton Acquisition and the MHT Acquisition, the Company estimated the contingent consideration liabilities using a combination of Monte Carlo and Discounted Cash Flow methods which require 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 for the Quarton Acquisition can range from $10.1 million to $25.0 million. The undiscounted amounts for the MHT Acquisition have no minimum or maximum as it is calculated based on revenue.
[2]	The quantitative disclosures exclude financial instruments for which the determination of fair value is based on prices from recent transactions.

Fair Value Measurements for O_6

Fair Value Measurements for Operating Entities and Consolidated Funds - Carrying Value Disclosures (Details) - USD ($)		Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Cash and cash equivalents		$ 1,147,531,000	$ 645,169,000	$ 270,079,000
Cash collateral pledged		110,303,000	110,743,000	7,538,000
Segregated cash		168,942,000	185,141,000	$ 131,266,000
Securities Purchased under Agreements to Resell		0	191,000
Securities borrowed		1,996,757,000	1,908,187,000
Loans Receivable, Net		4,467,000	7,682,000
Cash and cash equivalents, Consolidated Funds		935,000	417,000
Securities Sold under Agreements to Repurchase		2,546,000	5,036,000
Securities sold under agreements to repurchase, Fair value		2,759,000	5,544,000
Securities Loaned		3,083,945,000	2,476,414,000
Convertible debt	[1]	81,682,000	80,808,000
Long-term Debt	[2]	542,519,000	383,067,000
Convertible Debt
Convertible debt		81,682,000
Unamortized discount		5,800,000	6,700,000
Notes Payable, Other Payables
Unamortized discount		1,500,000
Debt Instrument, Unamortized Premium		300,000	400,000
Level 1
Cash and cash equivalents, Fair Value		1,147,531,000	645,169,000
Segregated cash fair value disclosures		168,942,000	185,141,000
Cash and cash equivalents, Consolidated Funds, Fair Value		935,000	417,000
Level 2
Cash collateral pledged, Fair Value		110,303,000	110,743,000
Federal Funds Sold and Securities Borrowed or Purchased under Agreements to Resell, Fair Value Disclosure		0	204,000
Securities Borrowed, Fair Value Disclosure		1,996,757,000	1,908,187,000
Securities sold under agreements to repurchase, Fair value		2,759,000	5,544,000
Securities loaned, fair value disclosure		3,083,945,000	2,476,414,000
Convertible debt, Fair Value	[3]	181,597,000	135,444,000
Notes payable and other debt, Fair Value	[4]	568,212,000	405,840,000
Level 3
Loans Receivable, Fair Value Disclosure	[5]	$ 4,467,000	$ 7,682,000
[1]	The carrying amount of the convertible debt includes an unamortized discount of $5.8 million and $6.7 million as of March 31, 2021 and December 31, 2020, respectively.
[2]	The carrying amount of the notes payable and other debt includes an unamortized discount and unamortized premium of $1.5 million and $0.3 million as of March 31, 2021, respectively and unamortized premium of $0.4 million as of December 31, 2020
[3]	The convertible debt includes the conversion option and is based on the last broker quote available.
[4]	Notes payable and other debt are based on the last broker quote available.
[5]	The fair market value of level 3 loans is calculated using discounted cash flows where applicable.

Deposits with Clearing Organi_2

Deposits with Clearing Organizations, Brokers and Banks (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Deposits with Clearing Organizations, Brokers and Banks [Abstract]
Deposits with clearing organizations, brokers and banks	$ 82,078	$ 104,952

Receivables from and payables_3

Receivables from and payables to brokers, dealers and clearing organizations (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Brokers and Dealers [Abstract]
Receivable from Broker-dealers	$ 1,753,510	$ 1,608,273
Securities Failed-to-Deliver	76,127	55,655
Clearing organizations	79,833	41,795
Securities borrowed/loaned interest receivable	11,283	24,021
Receivable from brokers, dealers and clearing organizations	1,920,753	1,729,744
Payable to Broker-Dealers	326,231	286,011
Securities Failed-to-Receive	100,528	68,036
Clearing organizations	48,466	33,732
Securities loaned interest payable	13,246	27,364
Payables to brokers, dealers and clearing organizations	$ 488,471	$ 415,143

Receivable from and Payable t_2

Receivable from and Payable to Customers (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Receivables and Payable to Customers [Abstract]
Receivable from customers	$ 199,668	$ 103,963
Payable to customers	$ 2,657,600	$ 1,680,326

Commission Management Payable (

Commission Management Payable (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Commission Management Payable [Abstract]
Commission management payable	$ 139,621	$ 116,987

Non-Controlling Interests in _3

Non-Controlling Interests in Consolidated Subsidiaries and Funds (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Noncontrolling Interest [Line Items]
Nonredeemable Noncontrolling Interest	$ 133,115		$ 199,624
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	4,562	$ (62,188)
Operating Entities
Noncontrolling Interest [Line Items]
Nonredeemable Noncontrolling Interest	92,629		83,818
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	7,661	127
Consolidated Funds
Noncontrolling Interest [Line Items]
Nonredeemable Noncontrolling Interest	40,486		$ 115,806
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	$ (3,099)	$ (62,315)

Revenue from Contracts with C_3

Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 503,349	$ 257,484
Management Fees	25,742	11,604
Incentive income	2,258	0
Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	503,106	257,226
Management Fees	25,499	11,346
Incentive income	2,258	0
Asset Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	243	258
Management Fees	243	258
Incentive income	0	0
Underwriting fees | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	154,304	63,270
Strategic/financial advisory fees | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	73,555	21,996
Placement and sales agent fees | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	72,544	17,596
Expense reimbursements from clients | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,431	2,166
Investment banking revenue | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	304,834	105,028
Commissions | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	161,792	132,208
Trade conversion | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,130	4,639
Equity and credit research fees | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,593	4,005
Brokerage | Operating Company
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 170,515	$ 140,852

Insurance and reinsurance (Deta

Insurance and reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Incurred and paid claims	$ 4,648,000	$ 4,235,000
Change in claims outstanding and claims IBNR	695,000	17,293,000
Cash collateral pledged	110,303	7,538	$ 110,743
Total collateral posted for reinsurance business	120,500
Outward insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Incurred and paid claims	744,000	0
Change in claims outstanding and claims IBNR	136,000	0
Inward Reinsurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Incurred and paid claims	3,904,000	4,235,000
Change in claims outstanding and claims IBNR	559,000	$ 17,293,000
Collateral Reinsurance Agreement
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Cash collateral pledged	106,800		$ 106,800
Collateral Reinsurance Agreement, Released September 30, 2023
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Cash collateral pledged	101,200
Collateral Reinsurance Agreement, Released March 31, 2024
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Cash collateral pledged	$ 5,600
Hollenfels
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Historical Average Claims Ratios, Period, Maximum	10 years
Cash and Cash Equivalents
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Total collateral posted for reinsurance business	$ 106,800
US Treasury Bond Securities [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Total collateral posted for reinsurance business	$ 13,700

Share-Based Payments, Deferre_3

Share-Based Payments, Deferred Compensation and Employee Ownership Plans - Share-Based Payments and Deferred Compensation Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	800,000
Equity Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-compensation expense recognized in connection with compensation plan	$ 28.2	$ 8.3
Tax benefit of stock-compensation expense recognized in connection with compensation plan	$ 10.8	$ 1.8
Equity Plans | Restricted Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation award, vesting period	2 years
Equity Plans | Restricted Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation award, vesting period	5 years
Equity Plans | Employee Stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation award, vesting period	2 years
Equity Plans | Employee Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation award, vesting period	5 years
Expiration period	7 years
Deferred Cash Award | Equity Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation award, vesting period	4 years
Deferred Cash Award | Cowen Group, Inc. 2010 and 2020 Equity and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred cash awards granted	$ 34.1
Deferred cash award, interest rate	0.70%
Deferred cash awards, unrecognized compensation expense	$ 90.5

Share-Based Payments, Deferre_4

Share-Based Payments, Deferred Compensation and Employee Ownership Plans - Restricted Stock Units Rollforward (Details) - Equity Plans - Restricted Shares and Restricted Stock Units (RSUs) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Nonvested Restricted Shares and Restricted Stock Units
Balance outstanding, beginning of period, shares	5,450,191	5,364,486
Granted, shares	1,593,941	2,140,932
Vested, shares	(291,062)	(640,084)
Canceled, shares	0	(87,348)
Forfeited, shares	(8,134)	(30,562)
Balance outstanding, end of period, shares	6,744,936	6,747,424
Weighted-Average Grant Date Fair Value
Balance outstanding, beginning of period, in dollars per share	$ 17.56	$ 16.67
Granted, in dollars per share	34.85	17.39
Vested, in dollars per share	16.11	14.63
Canceled, in dollars per share	0	14.80
Forfeited, in dollars per share	20.22	15.86
Balance outstanding, end of period, in dollars per share	$ 21.71	$ 17.12

Share-Based Payments, Deferre_5

Share-Based Payments, Deferred Compensation and Employee Ownership Plans - Performance Awards Narrative (Details) - USD ($)	1 Months Ended				3 Months Ended
	Feb. 28, 2021	Jul. 30, 2020	Apr. 30, 2019	Mar. 31, 2016	Mar. 31, 2021	Mar. 31, 2020
Performance based restricted stock | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of RSU's earned					0.00%
Performance based restricted stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of RSU's earned					200.00%
Equity Plans | Performance based restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares	1,603,630	1,603,630	1,603,630	1,603,630
Vested, shares					379,319
Forfeited, shares					320,681
Equity Plans | Performance based restricted stock | Share Distribution
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested, shares					350,000
Equity Plans | Performance based restricted stock | Cash and Cash Equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested, shares					70,000
Equity Plans | Performance based restricted stock | Share-based Payment Arrangement, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested, shares					233,333
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested					$ 420,000
Equity Plans | Restricted Shares and Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares					1,593,941	2,140,932
Vested, shares					291,062	640,084
Forfeited, shares					8,134	30,562
Unrecognized compensation expense					$ 118,100,000
Period for recognition					2 years 1 month 17 days

Share-Based Payments, Deferre_6

Share-Based Payments, Deferred Compensation and Employee Ownership Plans - Restricted Shares and Other Share Based Payments Narrative (Details) - Equity Plans - Restricted Stock Units (RSUs) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			334,230
Non-employee Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Other	0	0
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number	259,536		259,536

Income Taxes (Details) - Quarte

Income Taxes (Details) - Quarterly - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Effective income tax rate, percent	26.36%	1.60%
Statutory rate, percent	21.00%	21.00%
Unrecognized Tax Benefits	$ 0.3		$ 0.3

Commitments and Contingencies O

Commitments and Contingencies Operating Lease Obligations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021		Mar. 31, 2020
Contractual Commitments, Commitment [Line Items]
Lease cost	$ 5,770		$ 5,685
Variable lease cost	906		788
Sublease income	(160)		(216)
Total lease costs	6,549		6,403
Facility Leases
Contractual Commitments, Commitment [Line Items]
Short-term lease cost	$ 33	[1],[2]	$ 146
[1]	During the three months ended March 31, 2021, the Company recognized an increase of $5.3 million of operating right-of-use assets and leases liabilities related to for facility leases.
[2]	The Company has entered into various agreements to sublease certain of its premises.

Commitments and Contingencies S

Commitments and Contingencies Supplemental Cash Flow Information And Certain Other Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Operating Lease, Payments	$ 6,748	$ 8,578
Weighted average remaining lease term - operating leases (in years)	4 years 6 months 21 days	5 years 1 month 9 days
Weighted average discount rate - operating leases	4.10%	4.14%

Commitments and Contingencies_2

Commitments and Contingencies Outstanding Operating Lease Liabilities (Details) - USD ($)		3 Months Ended
		Mar. 31, 2021	Dec. 31, 2020
Future minimum annual lease and service payments
Total lease liability		$ 81,400,000	$ 82,735,000
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability		5,300,000
Equipment Leases
Future minimum annual lease and service payments
2021		207,000
2022		150,000
2023		11,000
2024		0
2025		0
Thereafter		0
Future minimum annual lease and service payments		368,000
Less discount		21,000
Less short-term leases		0
Total lease liability		347,000
Facility Leases
Future minimum annual lease and service payments
2021	[1],[2]	19,065,000
2022	[1],[2]	22,612,000
2023	[1],[2]	19,123,000
2024	[1],[2]	15,883,000
2025	[1],[2]	5,446,000
Thereafter	[1],[2]	7,862,000
Future minimum annual lease and service payments	[1],[2]	89,991,000
Less discount	[1],[2]	8,927,000
Less short-term leases		11,000
Total lease liability	[1],[2]	$ 81,053,000
[1]	During the three months ended March 31, 2021, the Company recognized an increase of $5.3 million of operating right-of-use assets and leases liabilities related to for facility leases.
[2]	The Company has entered into various agreements to sublease certain of its premises.

Commitments and Contingencies_3

Commitments and Contingencies Service Payments (Details) - Service Payments $ in Thousands	Mar. 31, 2021USD ($)
Other Commitments [Line Items]
2021	$ 17,854
2022	16,739
2023	8,934
2024	5,254
2025	3,366
Thereafter	10,594
Total service payment commitments	$ 62,741

Commitments and Contingencies_4

Commitments and Contingencies Schedules of Unfunded Commitments (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Healthcare Royalty Partners | Unfunded Commitments
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 7,333	[1]
Healthcare Royalty Partners | Commitment to Invest
Other Commitments [Line Items]
Commitments term	3 years 9 months 18 days
Eclipse Ventures Fund I, L.P. | Unfunded Commitments
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 28
Eclipse Ventures Fund I, L.P. | Commitment to Invest
Other Commitments [Line Items]
Commitments term	3 years 9 months 18 days
Eclipse Fund II, L.P. | Unfunded Commitments
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 95
Eclipse Fund II, L.P. | Commitment to Invest
Other Commitments [Line Items]
Commitments term	4 years 9 months 18 days
Eclipse Continuity Fund I, L.P. | Unfunded Commitments
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 41
Eclipse Continuity Fund I, L.P. | Commitment to Invest
Other Commitments [Line Items]
Commitments term	5 years 9 months 18 days
Cowen Healthcare Investments III LP | Unfunded Commitments
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 4,126
Cowen Healthcare Investments III LP | Commitment to Invest
Other Commitments [Line Items]
Commitments term	5 years 9 months 18 days
Cowen Sustainable Investments I LP | Unfunded Commitments
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 15,709
Cowen Sustainable Investments I LP | Commitment to Invest
Other Commitments [Line Items]
Commitments term	8 years 9 months 18 days
[1]	The Company is a limited partner of the HealthCare Royalty Partners funds (which are managed by Healthcare Royalty Management) and is a member of HealthCare Royalty Partners General Partners. The Company will make its pro-rata investment in the HealthCare Royalty Partners funds along with the other limited partners.

Convertible Debt and Notes Pa_3

Convertible Debt and Notes Payable - Outstanding Debt (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Convertible debt	[1]	$ 81,682	$ 80,808
Note payable		173,656	307,653
Term Loan		291,303	0
Other Notes Payable		74,982	72,505
Finance Lease, Liability		2,578	2,909
Outstanding debt		624,201	$ 463,875
Letter of credit, borrowing capacity		$ 320,000
[1]	The carrying amount of the convertible debt includes an unamortized discount of $5.8 million and $6.7 million as of March 31, 2021 and December 31, 2020, respectively.

Convertible Debt and Notes Pa_4

Convertible Debt and Notes Payable - Convertible Debt (Details) - USD ($)		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 14, 2017
Debt and Capital Lease Obligations [Line Items]
Convertible debt	[1]	$ 81,682,000		$ 80,808,000
Amortization of debt discount (premium)		776,000	$ 1,109,000
Gain/(loss) on debt extinguishment		(4,538,000)	0
Convertible Debt
Debt and Capital Lease Obligations [Line Items]
Convertible debt		81,682,000
Unamortized discount		5,800,000		$ 6,700,000
2022 convertible note | Convertible Debt
Debt and Capital Lease Obligations [Line Items]
Debt Instrument, Face Amount					$ 135,000,000
Debt Instrument, Convertible, Conversion Price					$ 17.375
Convertible debt		88,100,000
Interest on Convertible Debt, Net of Tax		700,000	1,000,000
Unamortized discount					$ 23,400,000
Amortization of debt discount (premium)		800,000	$ 1,100,000
Debt Instrument, Interest Rate, Effective Percentage					7.13%
Debt Issuance Costs, Gross					$ 2,200,000
Extinguishment of Debt, Amount		70,500,000
Gain/(loss) on debt extinguishment		2,700,000
Debt Instrument, Repurchased Face Amount		46,900,000
Embedded Derivative, No Longer Bifurcated, Amount Reclassified to Stockholders' Equity		29,600,000
Write off of Deferred Debt Issuance Cost		400,000
Write off of pro rate unamortized discount while extinguishing debt		$ 3,600,000
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		58.3324%
[1]	The carrying amount of the convertible debt includes an unamortized discount of $5.8 million and $6.7 million as of March 31, 2021 and December 31, 2020, respectively.

Convertible Debt and Notes Pa_5

Convertible Debt and Notes Payable - Notes Payable (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 24, 2021	Sep. 30, 2019	May 07, 2019	Jun. 11, 2018	Dec. 14, 2017	Dec. 08, 2017
Debt and Capital Lease Obligations [Line Items]
Gain/(loss) on debt extinguishment	$ (4,538,000)	$ 0
2024 Notes | Senior Notes
Debt and Capital Lease Obligations [Line Items]
Debt Instrument, Face Amount					$ 53,000,000
Interest rate					7.25%
Debt Instrument, Additional amount issued				$ 25,000,000
Debt Instrument, Unamortized Premium				500,000
Interest Expense, Debt, Excluding Amortization	1,400,000	1,400,000
Debt Issuance Costs, Gross				600,000	$ 1,500,000
2033 Notes | Senior Notes
Debt and Capital Lease Obligations [Line Items]
Debt Instrument, Face Amount				$ 10,000,000		$ 90,000,000
Interest Expense, Debt, Excluding Amortization	1,900,000	1,900,000
Debt Issuance Costs, Gross						$ 3,600,000
2027 Notes | Senior Notes
Debt and Capital Lease Obligations [Line Items]
Debt Instrument, Face Amount			$ 138,000,000				$ 18,000,000	$ 120,000,000
Interest Expense, Debt, Excluding Amortization	2,500,000	$ 2,500,000
Debt Issuance Costs, Gross								$ 5,000,000
Gain/(loss) on debt extinguishment	$ 4,400,000

Convertible Debt and Notes Pa_6

Convertible Debt and Notes Payable - Term Loans, Other Notes Payable and Revolver (Details) - USD ($)

3 Months Ended

Mar. 31, 2021

Mar. 31, 2020

Mar. 24, 2021

Jan. 31, 2021

Dec. 31, 2020

Sep. 30, 2020

Nov. 01, 2019

Sep. 30, 2019

Jul. 01, 2019

May 07, 2019

Dec. 14, 2017

Jun. 30, 2017

Debt and Capital Lease Obligations [Line Items]

Letter of credit, borrowing capacity

$ 320,000,000

Other Notes Payable

74,982,000

$ 72,505,000

Term Loan

291,303,000

0

The Military Mutual Ltd [Member]

Debt and Capital Lease Obligations [Line Items]

Other Receivables

$ 28,400,000

BMO Harris Bank | Revolving Credit Facility

Debt and Capital Lease Obligations [Line Items]

Letter of credit, borrowing capacity

$ 25,000,000

Notes Payable to Banks

Debt and Capital Lease Obligations [Line Items]

Debt Instrument, Face Amount

$ 4,000,000

$ 28,200,000

Short-term Debt, Percentage Bearing Variable Interest Rate

3.75%

Interest Expense, Debt, Excluding Amortization

$ 400,000

Convertible Debt

Debt and Capital Lease Obligations [Line Items]

Unamortized discount

$ 5,800,000

$ 6,700,000

Insurance Note

Debt and Capital Lease Obligations [Line Items]

Interest rate

2.01%

Debt Instrument, Periodic Payment, Principal

300,000

Other Notes Payable

2,400,000

$ 3,000,000

Revolving Credit Facility | BMO Harris Bank

Debt and Capital Lease Obligations [Line Items]

Interest Expense, Debt, Excluding Amortization

$ 200,000

Corporate Debt

Debt and Capital Lease Obligations [Line Items]

Interest rate

6.00%

Debt Instrument, Periodic Payment, Principal

$ 100,000

Other Long-term Debt

1,900,000

$ 2,600,000

Purple Protect Asset S-91

Debt and Capital Lease Obligations [Line Items]

Interest Expense, Debt, Excluding Amortization

1,100,000

Interest rate

5.80%

6.07%

Other Notes Payable

72,000,000

Debt Issuance Costs, Gross

$ 1,700,000

2028 Term Loan | Term Loan

Debt and Capital Lease Obligations [Line Items]

Debt Instrument, Face Amount

$ 300,000,000

Interest Expense, Debt, Excluding Amortization

200,000

Interest rate

3.25%

Debt Issuance Costs, Gross

$ 6,400,000

Term Loan

299,300,000

Unamortized discount

$ 1,500,000

Debt Instrument, Interest Rate, Effective Percentage

4.46%

2022 convertible note | Convertible Debt

Debt and Capital Lease Obligations [Line Items]

Debt Instrument, Face Amount

$ 135,000,000

Debt Issuance Costs, Gross

2,200,000

Unamortized discount

$ 23,400,000

Debt Instrument, Interest Rate, Effective Percentage

7.13%

2024 Notes | Senior Notes

Debt and Capital Lease Obligations [Line Items]

Debt Instrument, Face Amount

$ 53,000,000

Interest Expense, Debt, Excluding Amortization

1,400,000

$ 1,400,000

Interest rate

7.25%

Debt Issuance Costs, Gross

$ 600,000

$ 1,500,000

Spike Line

Debt and Capital Lease Obligations [Line Items]

Interest Expense, Debt, Excluding Amortization

100,000

Maximum | Spike Line

Debt and Capital Lease Obligations [Line Items]

Line of Credit, Current

$ 70,000,000

Convertible Debt and Notes Pa_7

Convertible Debt and Notes Payable - Finance Lease Obligations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Debt Disclosure [Abstract]
Finance Lease, Right-of-Use Asset, Amortization	$ 309	$ 308
Finance Lease, Interest Expense	34	49
Finance Lease, Interest Payment on Liability	34	49
Finance Lease, Principal Payments	$ 332	$ 314
Finance Lease, Weighted Average Remaining Lease Term	2 years 3 days	2 years 11 months 19 days
Finance Lease, Weighted Average Discount Rate, Percent	4.89%	4.88%

Convertible Debt and Notes Pa_8

Convertible Debt and Notes Payable - Scheduled Maturities (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Repayments on long-term and short-term borrowings
Convertible debt	[1]	$ 81,682	$ 80,808
Note payable		173,656	307,653
Other Notes Payable		74,982	72,505
Future minimum lease payments for finance lease obligations
2021		1,117
2022		1,168
2023		411
2024		11
2025		0
Thereafter		0
Subtotal		2,707
Finance Lease, Interest Payment on Liability	[2]	(129)
Finance lease obligations		2,578
Term Loan		291,303	$ 0
Convertible Debt
Repayments on long-term and short-term borrowings
2021		2,644
2022		90,763
2023		0
2024		0
2025		0
Thereafter		0
Subtotal		93,407
Long-term Debt and Short-term Borrowings, Amount Representing Interest	[2]	11,725
Convertible debt		81,682
Senior Notes
Repayments on long-term and short-term borrowings
2021		11,468
2022		13,405
2023		13,405
2024		88,578
2025		7,750
Thereafter		158,125
Subtotal		292,731
Long-term Debt and Short-term Borrowings, Amount Representing Interest	[2]	119,075
Note payable		173,656
Term Loan
Repayments on long-term and short-term borrowings
2021		11,205
2022		14,835
2023		14,715
2024		14,595
2025		14,475
Thereafter		310,163
Subtotal		379,988
Long-term Debt and Short-term Borrowings, Amount Representing Interest		88,685
Notes Payable, Other Payables
Repayments on long-term and short-term borrowings
2021		7,207
2022		593
2023		72,593
2024		543
2025		0
Thereafter		0
Subtotal		80,936
Long-term Debt and Short-term Borrowings, Amount Representing Interest	[2]	5,954
Other Notes Payable		$ 74,982
[1]	The carrying amount of the convertible debt includes an unamortized discount of $5.8 million and $6.7 million as of March 31, 2021 and December 31, 2020, respectively.
[2]	Amount necessary to reduce net minimum payments to present value calculated at the Company's implicit rate at inception. This amount also includes capitalized debt costs and the unamortized discount on the Company's convertible debt.

Stockholders Equity - (Details)

Stockholders Equity - (Details) $ / shares in Units, $ in Thousands	May 19, 2015USD ($)$ / sharesshares	Mar. 31, 2021USD ($)class$ / sharesshares	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)$ / sharesshares	Jun. 26, 2018USD ($)	Dec. 14, 2017USD ($)
Equity, Class of Stock [Line Items]
Common stock, shares authorized | shares		125,000,000
Preferred stock, shares authorized | shares		10,000,000		10,000,000
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.01		$ 0.01
Number of classes | class		2
Preferred stock dividends declared		$ 1,698	$ 1,698
Convertible Preferred Stock, Shares Issued upon Conversion | shares	38.0619
Convertible Preferred Stock, Threshold Percentage of Stock Price Trigger		150.00%
Dividends, Cash		$ 2,777	1,429
Treasury Stock, Cost [Roll Forward]
Treasury stock, cost, beginning of period		346,900
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions		6,245	2,825
Purchase of treasury stock, cost		20,600
Treasury stock, cost, end of period		373,800
Dividend Paid
Equity, Class of Stock [Line Items]
Dividends, Cash		$ 2,300
Treasury Stock
Treasury Stock, Shares [Roll Forward]
Treasury stock, shares, beginning of period | shares		22,619,863
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions | shares		148,752
Treasury stock shares received, other | shares		1,155
Purchase of treasury stock, shares | shares		605,703
Treasury stock, shares, end of period | shares		23,375,473
Treasury Stock, Cost [Roll Forward]
Treasury stock, cost, beginning of period		$ 346,870
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions		6,246
Treasury stock received, value, other		29
Purchase of treasury stock, cost		20,629
Treasury stock, cost, end of period		$ 373,774
Treasury Stock, Average Cost Per Share [Roll Forward]
Treasury stock, average cost per share, beginning of period, in dollars per share | $ / shares		$ 15.33
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions, Average Cost Per Share | $ / shares		41.99
Treasury stock received, per share, other | $ / shares		25.33
Purchase of treasury stock, average cost per share, in dollars per share | $ / shares		34.06
Treasury stock, average cost per share, end of period, in dollars per share | $ / shares		$ 15.99
Additional Paid-in Capital | Convertible Debt
Equity, Class of Stock [Line Items]
Embedded Derivative, No Longer Bifurcated, Amount Reclassified to Stockholders' Equity		$ 29,600
Convertible Preferred Stock
Equity, Class of Stock [Line Items]
Stock Issued During Period, Shares, Other | shares	120,750
Preferred Stock, Dividend Rate, Percentage	5.625%
Proceeds from Issuance of Preferred Stock, net of issuance costs	$ 117,200
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs	$ 3,600
Preferred Stock, Liquidation Preference Per Share | $ / shares	$ 1,000
Convertible Preferred Stock, Shares Issued upon Conversion | shares				38.488
Convertible Preferred Stock | Retained Earnings/(Accumulated deficit)
Equity, Class of Stock [Line Items]
Preferred stock dividends declared		$ 1,698	1,698
Common Stock Class A
Equity, Class of Stock [Line Items]
Common stock, shares authorized | shares		62,500,000		62,500,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.01		$ 0.01
Treasury Stock, Shares [Roll Forward]
Treasury stock, shares, beginning of period | shares		22,619,863
Treasury stock, shares, end of period | shares		23,375,473
Treasury Stock, Cost [Roll Forward]
Treasury stock, cost, beginning of period		$ 346,870
Treasury stock, cost, end of period		373,774
Common Stock Class A | Retained Earnings/(Accumulated deficit)
Equity, Class of Stock [Line Items]
Dividends, Cash		$ 2,777	$ 1,429
Common Stock Class B
Equity, Class of Stock [Line Items]
Common stock, shares authorized | shares		62,500,000		62,500,000
Common stock, par value (in dollars per share) | $ / shares		$ 0.01		$ 0.01
Maximum
Equity, Class of Stock [Line Items]
Convertible Preferred Stock, Threshold Consecutive Trading Days		30 days
Minimum
Equity, Class of Stock [Line Items]
Convertible Preferred Stock, Threshold Consecutive Trading Days		20 days
Minimum | Call Option
Equity, Class of Stock [Line Items]
Option Indexed to Issuer's Equity, Strike Price | $ / shares		$ 26.27
Convertible Debt
Equity, Class of Stock [Line Items]
Unamortized discount		$ 5,800		$ 6,700
Convertible Debt | 2022 convertible note
Equity, Class of Stock [Line Items]
Unamortized discount						$ 23,400
Option Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value					$ 29,000
Embedded Derivative, No Longer Bifurcated, Amount Reclassified to Stockholders' Equity		$ 29,600

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income / (Loss) [Abstract]
Beginning balance	$ (7)	$ (5)
Foreign currency translation	4	0
Ending balance	$ (3)	$ (5)

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Computation of earnings per share:
Net income (loss)	$ 152,066	$ (72,111)
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	4,562	(62,188)
Net income (loss) attributable to Cowen Inc.	147,504	(9,923)
Preferred stock dividends	1,698	1,698
Net income (loss) attributable to Cowen Inc. common stockholders	$ 145,806	$ (11,621)
Shares for basic and diluted calculations:
Weighted average shares used in basic computation, shares	27,359,000	28,598,000
Weighted average shares used in diluted computation, shares	33,565,000	28,598,000
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 5.33	$ (0.41)
Earnings Per Share, Diluted (in dollars per share)	$ 4.34	$ (0.41)
2022 convertible note | Convertible Debt
Shares for basic and diluted calculations:
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	2,659,000	0
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger	58.3324%
Restricted Stock
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares	3,102,000	0
Restricted Stock Units (RSUs) | Equity Plans
Shares for basic and diluted calculations:
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			334,230
Performance based restricted stock
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares	445,000	0
Common Stock Class A
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares outstanding, shares	26,852,331	27,628,117	26,845,628	28,610,357
Common stock, restricted shares, shares	259,536
Common Stock Class A | Restricted Stock
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares outstanding, shares	292,968		334,230

Segment Reporting (Details)

Segment Reporting (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2021USD ($)segment	Mar. 31, 2020USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment		2
Reconciliation to U.S. GAAP Company's Economic Income (Loss)
Preferred stock dividends		$ 1,698	$ 1,698
Amortization of (discount)/premium on convertible debt		776	1,109
Bargain Purchase Gain, net of tax		3,855	0
Income tax expense (benefit)		54,428	(1,173)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		206,494	(73,284)
Segment Information
Total revenues		754,323	196,723
Depreciation and Amortization		4,354	5,442
Income tax expense (benefit)		54,428	(1,173)
Interest and Dividend Expense		57,641	38,792
Dividend expense		2,600	3,500
Dividend revenue		8,100	8,300
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		152,066	(72,111)
Consolidated Funds
Segment Information
Interest and Dividend Expense		0	1,252
Dividend expense			200
Dividend revenue		2,600	3,500
Operating Segments
Segment Information
Non-Interest Revenue	[1]	703,014	162,428
Interest Revenue		51,307	33,716
Total revenues		754,323	196,723
Operating Segments | Consolidated Funds
Segment Information
Interest Revenue		2	579
Adjustments
Reconciliation to U.S. GAAP Company's Economic Income (Loss)
Noncontrolling Interest (Adjusted)		4,562	(62,188)
Preferred stock dividends		1,698	1,698
Amortization of (discount)/premium on convertible debt		(776)	(1,110)
Acquisition related amounts		(238)	0
Contingent Consideration Payable		6,798	895
Debt extinguishment gain (loss)		(4,538)	0
Bargain Purchase Gain, net of tax		3,855	0
Income tax expense (benefit)		(1,677)	1,173
Segment Information
Income tax expense (benefit)		(1,677)	1,173
OpCo | Operating Segments
Reconciliation to U.S. GAAP Company's Economic Income (Loss)
Economic Income		143,858	3,650
Income tax expense (benefit)		55,085
Segment Information
Non-Interest Revenue		704,682	173,123
Interest Revenue		51,104	33,666
Total revenues		755,786	207,366
Interest Expense		53,803	33,639
Depreciation and Amortization		4,349	5,436
Income tax expense (benefit)		55,085
OpCo | Operating Segments | Consolidated Funds
Segment Information
Interest Revenue		0	577
Interest Expense		0	1,061
Asset Co | Operating Segments
Reconciliation to U.S. GAAP Company's Economic Income (Loss)
Economic Income		(1,476)	(16,229)
Income tax expense (benefit)		(657)
Segment Information
Non-Interest Revenue		(1,668)	(10,695)
Interest Revenue		203	50
Total revenues		(1,463)	(10,643)
Interest Expense		1,275	1,689
Depreciation and Amortization		5	6
Income tax expense (benefit)		(657)
Asset Co | Operating Segments | Consolidated Funds
Segment Information
Interest Revenue		2	2
Interest Expense		$ 0	$ 0
[1]	Includes dividend revenue of $8.1 million and $8.3 million for the three months ended March 31, 2021 and 2020, respectively. In addition, includes dividend revenue, consolidated funds, of $2.6 million and $3.5 million for the three months ended March 31, 2021 and 2020, respectively.

Regulatory Requirements (Detail

Regulatory Requirements (Details)	3 Months Ended
	Mar. 31, 2021USD ($)
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	$ 250,000
Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	6,289,000
Minimum net capital required	1,000,000
Net capital	332,197,000
Excess capital	325,908,000
ATM Execution LLC
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	250,000
Net capital	4,951,000
Excess capital	4,701,000
Cowen Prime
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	250,000
Net capital	22,722,000
Excess capital	22,472,000
Westminster Research
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	250,000
Net capital	31,116,000
Excess capital	30,866,000
Cowen and Company (Asia) Limited [Member]
Regulatory Requirements for Broker-Dealers [Line Items]
Financial resources	2,272,000
Financial resources requirement	386,000
Excess financial resources	1,886,000
RCG Insurance Company
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	300,000
Net capital	6,400,000
Options Clearing Corporation | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	$ 2,000,000
Minimum net capital required, percent	2.00%
U.K. Financial Services Authority | Cowen International Limited
Regulatory Requirements for Broker-Dealers [Line Items]
Financial resources	$ 39,812,000
Financial resources requirement	25,444,000
Excess financial resources	14,368,000
U.K. Financial Services Authority | Cowen Execution Services Ltd
Regulatory Requirements for Broker-Dealers [Line Items]
Financial resources	13,205,000
Financial resources requirement	3,418,000
Excess financial resources	9,787,000
Minimum | Cowen Prime
Regulatory Requirements for Broker-Dealers [Line Items]
Required net capital under commodity exchange act	45,000
Special Reserve Accounts | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	13,700,000
Special Reserve Accounts | Minimum | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	0
PAB Reserve Bank Accounts | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	30,300,000
PAB Reserve Bank Accounts | Minimum | Cowen and Company
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	$ 19,100,000

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Fees receivable	$ 208,898		$ 160,349
Interest Income, Related Party	100	$ 100
Due from related parties	20,921		21,068
Redeemable non-controlling interests, Related Party	0		0
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	0	(60,990)
Employees
Related Party Transaction [Line Items]
Redeemable non-controlling interests, Related Party	34,800		84,300
Net income (loss) attributable to non-controlling interests in consolidated subsidiaries and investment funds	10,100	100
Employee Loans
Related Party Transaction [Line Items]
Due from employees	11,300		9,500
Forgivable Loan Balances	6,700		4,600
Amortization on Forgivable Loans	$ 1,200	$ 1,100
Employee Loans | Minimum
Related Party Transaction [Line Items]
Forgivable Loans, Vesting Period	1 year
Employee Loans | Maximum
Related Party Transaction [Line Items]
Forgivable Loans, Vesting Period	3 years
Affiliated Entity
Related Party Transaction [Line Items]
Fees receivable	$ 29,300		28,400
Investor
Related Party Transaction [Line Items]
Due to Affiliate	200		200
Other Funds
Related Party Transaction [Line Items]
Due from related parties	$ 9,600		7,900
Starboard Value LP
Related Party Transaction [Line Items]
Effective interest rate		5.00%
Interest Income, Related Party		$ 100
Due from related parties			$ 3,600
Finance Period	5 years

Guarantees and Off-Balance Sh_3

Guarantees and Off-Balance Sheet Arrangements (Details) $ in Thousands	Mar. 31, 2021USD ($)
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	$ 320,000
Line of credit facility, remaining borrowing capacity	320,000
Pledge Lines
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	225,000
Line of credit facility, remaining borrowing capacity	225,000
BMO Harris Bank | Pledge Lines
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	150,000
Line of credit facility, remaining borrowing capacity	150,000
BMO Harris Bank | Tri-Party Pledge Line
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	75,000
Line of credit facility, remaining borrowing capacity	75,000
BMO Harris Bank | Spike Line
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	70,000
Line of credit facility, remaining borrowing capacity	70,000
Morgan Stanley | Revolving Credit Facility
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	25,000
Line of credit facility, remaining borrowing capacity	$ 25,000

Subsequent Events - Narrative (

Subsequent Events - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Apr. 27, 2021	Mar. 31, 2021
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared		$ 0.08
Subsequent Event
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.10
Stock Repurchase Program Additional Authorized Amount	$ 25
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 50