Cowen (COWN) 10-Q 2 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 01, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	Cowen Inc.
Entity Central Index Key	0001466538
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		29,586,343

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 235,838	$ 259,148
Cash collateral pledged	6,420	6,318
Segregated cash	136,964	176,647
Securities owned, at fair value	563,121	520,888
Receivable on derivative contracts, at fair value	21,663	25,125
Securities Borrowed, Gross	966,857	407,795
Other investments ($151,064 and $141,236 at fair value, respectively)	200,132	181,407
Deposits with clearing organizations, brokers and banks	109,310	89,423
Receivable from brokers, dealers and clearing organizations, net of allowance of $25 and $472, respectively	663,072	786,113
Receivable from customers, net of allowance of $520 and $516, respectively	36,719	37,858
Fees receivable, net of allowance of $1,636 and $1,569, respectively	130,099	111,946
Due from related parties	28,841	33,870
Fixed assets, net of accumulated depreciation and amortization of $28,662 and $31,630, respectively	27,537	26,443
Operating right of use assets	101,796	0
Goodwill	141,828	60,678
Intangible assets, net of accumulated amortization of $41,579 and $38,093, respectively	43,861	24,943
Deferred tax asset, net	90,208	93,057
Other assets	91,464	79,014
Consolidated Funds
Cash and cash equivalents, Consolidated Funds	2,178	38,118
Securities owned, at fair value	308,800	187,633
Receivable on derivative contracts, at fair value	3,184	4,416
Other Investments, Consolidated Funds	186,846	186,395
Receivable from brokers, Consolidated Funds	39,551	8,328
Other assets, Consolidated Funds	23,929	740
Total Assets	4,160,218	3,346,303
Liabilities
Securities sold, not yet purchased, at fair value	574,186	195,307
Payable for derivative contracts, at fair value	43,583	16,082
Securities Loaned, Gross	852,203	414,852
Payables to brokers, dealers and clearing organizations	174,532	228,731
Payable to customers	413,050	525,153
Commission management payable	103,634	95,270
Compensation payable	68,804	223,994
Operating Lease, Liability	108,368	0
Notes payable and other debt	264,273	262,965
Convertible debt	115,099	134,489
Fees payable	11,339	22,565
Due to related parties	760	571
Accounts payable, accrued expenses and other liabilities	153,194	110,423
Consolidated Funds
Payable for derivative contracts, at fair value	5,557	1,663
Payable to brokers	13,903	23,521
Contributions received in advance	1,000	0
Capital withdrawals payable	23,246	11,106
Accounts payable, accrued expenses and other liabilities	428	424
Total Liabilities	2,927,159	2,267,116
Commitments and Contingencies
Redeemable non-controlling interests	418,277	284,780
Stockholders' equity
Additional paid-in capital	1,084,534	1,062,877
(Accumulated deficit) retained earnings	(26,563)	(34,648)
Accumulated other comprehensive income (loss)	(5)	(5)
Less: Class A common stock held in treasury, at cost, 15,978,829 and 15,336,871 shares as of March 31, 2019 and December 31, 2018, respectively.	(243,519)	(234,142)
Total Stockholders' Equity	814,782	794,407
Total Liabilities and Stockholders' Equity	4,160,218	3,346,303
Convertible Preferred Stock
Stockholders' equity
Preferred stock	1	1
Common Stock Class A
Stockholders' equity
Common stock	334	324
Less: Class A common stock held in treasury, at cost, 15,978,829 and 15,336,871 shares as of March 31, 2019 and December 31, 2018, respectively.	(243,519)	(234,142)
Common Stock Class B
Stockholders' equity
Common stock	$ 0	$ 0

Consolidated Statements of Fi_2

Consolidated Statements of Financial Condition (Parenthetical) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Security Owned and Pledged as Collateral, Fair Value	$ 45,786,000	$ 57,583,000
Allowance for receivable from customers	520,000	516,000
Allowance for fees receivable	3,687,000	1,569,000
Allowance for receivable from brokers	25,000	472,000
Other investments fair value	145,566,000	141,236,000
Assets
Fixed assets, accumulated depreciation and amortization (in dollars)	28,662,000	31,630,000
Intangible assets, accumulated amortization (in dollars)	$ 41,579,000	$ 38,093,000
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, shares outstanding	120,750	120,750
Preferred Stock, Liquidation Preference, Value	$ 120,750,000	$ 120,750,000
Treasury Stock, Shares	15,978,829	15,336,871
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	45,559,516	43,774,371
Common stock, shares outstanding	29,580,687	28,437,860
Common stock, restricted shares	253,772	253,772
Treasury Stock, Shares	15,978,829	15,336,871
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, 2019	Mar. 31, 2018
Revenues
Investment banking	$ 80,106	$ 97,988
Brokerage	97,463	105,733
Management fees	7,141	7,417
Incentive income	15	16
Interest and dividends	29,092	25,954
Reimbursement from affiliates	288	377
Aircraft lease revenue	0	715
Reinsurance premiums	6,591	8,647
Other revenues	1,061	1,336
Consolidated Funds
Interest and dividends	2,325	3,196
Other revenues	15	5
Total revenues	224,097	251,384
Interest and dividends expense	29,084	24,540
Total net revenues	195,013	226,844
Expenses
Employee compensation and benefits	130,188	135,140
Brokerage and trade execution costs	25,646	30,198
Underwriting expenses	3,131	4,063
Professional, advisory and other fees	10,241	7,024
Service fees	5,664	5,195
Communications	8,081	7,566
Occupancy and equipment	9,922	9,861
Depreciation and amortization	4,956	3,225
Client services and business development	11,301	8,231
Reinsurance claims, commissions and amortization of deferred acquisition costs	6,162	8,731
Other expenses	4,015	4,081
Consolidated Funds
Interest and dividends	867	1,911
Professional, advisory and other fees	145	212
Floor brokerage and trade execution	53	64
Other expenses	417	244
Total expenses	220,789	225,746
Other income (loss)
Net gains (losses) on securities, derivatives and other investments	39,084	15,969
Consolidated Funds
Net realized and unrealized gains (losses) on investments and other transactions	2,644	15,736
Net realized and unrealized gains (losses) on derivatives	(762)	2,475
Net gains (losses) on foreign currency transactions	(24)	(346)
Total other income (loss)	40,942	33,834
Income (loss) before income taxes	15,166	34,932
Income tax expense (benefit)	3,177	6,923
Net income (loss)	11,989	28,009
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds	(2,206)	(11,156)
Net income (loss) attributable to Cowen Inc.	9,783	16,853
Preferred stock dividends	1,698	1,698
Net income (loss) attributable to Cowen Inc. common stockholders	$ 8,085	$ 15,155
Weighted average common shares outstanding:
Basic (in shares)	29,750	29,625
Diluted (in shares)	31,625	30,492
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 0.27	$ 0.51
Earnings Per Share, Diluted (in dollars per share)	$ 0.26	$ 0.50

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 11,989	$ 28,009
Other comprehensive income (loss), net of tax:
Foreign currency translation	0	1
Total other comprehensive income (loss), net of tax	0	1
Comprehensive income (loss)	$ 11,989	$ 28,010

Consolidated Statements of Chan

Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings/(Accumulated deficit)	Common Stock Class A	Preferred Stock	Convertible Preferred StockRetained Earnings/(Accumulated deficit)
Common stock, shares outstanding, start at Dec. 31, 2017						29,632,020
Balance, start at Dec. 31, 2017	$ 748,019	$ (186,846)	$ 1,004,664	$ (8)	$ (70,116)	$ 324	$ 1
Preferred stock, shares outstanding, start at Dec. 31, 2017							120,750
Redeemable Non-controlling Interest, start at Dec. 31, 2017	440,604
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect on Retained Earnings, Net of Tax	(559)
Net income (loss) attributable to Cowen Inc.	16,853				16,853
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds	11,156
Foreign currency translation	1			1
Capital contributions	8,259
Capital withdrawals	(35,134)
Deconsolidation of investment funds	(32,559)
Common stock issued during period, value, acquisitions	0
Restricted stock awards issued, shares						881,032
Purchase of treasury stock, at cost, shares						(995,834)
Purchase of treasury stock, at cost	(14,069)	(14,069)
Preferred stock dividends	(1,698)							$ (1,698)
Amortization of share based compensation	10,240		10,240
Common stock, shares outstanding, end at Mar. 31, 2018						29,517,218
Balance, end at Mar. 31, 2018	758,787	(200,915)	1,014,904	(7)	(55,520)	$ 324	$ 1
Preferred stock, shares outstanding, end at Mar. 31, 2018							120,750
Redeemable Non-controlling Interest, end at Mar. 31, 2018	392,326
Common stock, shares outstanding, start at Dec. 31, 2018						28,437,860
Balance, start at Dec. 31, 2018	$ 794,407	(234,142)	1,062,877	(5)	(34,648)	$ 324	$ 1
Preferred stock, shares outstanding, start at Dec. 31, 2018	120,750						120,750
Redeemable Non-controlling Interest, start at Dec. 31, 2018	$ 284,780
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to Cowen Inc.	9,783				9,783
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds	2,206
Foreign currency translation	0			0
Capital contributions	161,973
Capital withdrawals	(30,682)
Common stock issued during period, shares, acquisitions						1,033,350
Common stock issued during period, value, acquisitions	14,446		14,436			$ 10
Restricted stock awards issued, shares						751,436
Purchase of treasury stock, at cost, shares						(641,959)
Purchase of treasury stock, at cost	(9,377)	(9,377)
Preferred stock dividends	(1,698)							$ (1,698)
Embedded Cash Conversion Option	(596)		(596)
Amortization of share based compensation	7,817		7,817
Common stock, shares outstanding, end at Mar. 31, 2019						29,580,687
Balance, end at Mar. 31, 2019	$ 814,782	$ (243,519)	$ 1,084,534	$ (5)	$ (26,563)	$ 334	$ 1
Preferred stock, shares outstanding, end at Mar. 31, 2019	120,750						120,750
Redeemable Non-controlling Interest, end at Mar. 31, 2019	$ 418,277

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 11,989,000	$ 28,009,000
Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities:
Depreciation and amortization	4,956,000	3,225,000
Amortization of debt issuance costs	244,000	322,000
Amortization of debt discount	1,349,000	1,442,000
Non Cash Lease Expense	(806,000)	0
Share-based compensation	7,817,000	10,241,000
Change in deferred taxes	2,253,000	7,115,000
Deferred rent obligations	0	(888,000)
Purchases of securities owned, at fair value	(299,969,000)	(1,943,349,000)
Proceeds from sales of securities owned, at fair value	389,551,000	2,060,263,000
Proceeds from sales of securities sold, not yet purchased, at fair value	439,565,000	1,276,205,000
Payments to cover securities sold, not yet purchased, at fair value	(361,290,000)	(1,386,253,000)
Proceeds from the sale of other investments	3,529,000	0
Net (gains) losses on securities, derivatives and other investments	(32,320,000)	(7,924,000)
Consolidated Funds
Purchases of securities owned, at fair value	(674,220,000)	(148,548,000)
Proceeds from sales of securities owned, at fair value	565,460,000	175,010,000
Purchases of other investments	(296,000)	(81,000)
Proceeds from sales of other investments	1,174,000	4,774,000
Net realized and unrealized (gains) losses on investments and other transactions	(14,309,000)	(18,304,000)
(Increase) decrease in operating assets:
Cash at Deconsolidation entity	0	3,371,000
Securities owned, at fair value, held at broker-dealer	(105,939,000)	13,197,000
Receivable on derivative contracts, at fair value	3,462,000	34,265,000
Securities borrowed	(559,062,000)	(154,942,000)
Deposits with clearing organizations, brokers and banks	(19,887,000)	(7,403,000)
Receivable from brokers, dealers and clearing organizations	123,041,000	(54,163,000)
Receivable from customers, net of allowance	1,139,000	3,925,000
Fees receivable, net of allowance	(10,884,000)	(30,996,000)
Due from related parties	5,028,000	4,874,000
Other assets	(13,688,000)	8,062,000
Consolidated Funds
Cash and cash equivalents	35,995,000	18,322,000
Receivable on derivative contracts, at fair value	1,232,000	654,000
Receivable from brokers	(31,223,000)	1,731,000
Other assets	(22,456,000)	(58,000)
Increase (decrease) in operating liabilities:
Securities sold, not yet purchased, at fair value, held at broker dealer	283,919,000	40,622,000
Payable for derivative contracts, at fair value	27,501,000	6,125,000
Securities loaned	437,351,000	6,023,000
Payable to brokers, dealers and clearing organizations	(54,199,000)	(4,532,000)
Payable to customers	(112,103,000)	60,179,000
Commission management payable	8,364,000	9,354,000
Compensation payable	(160,498,000)	(69,441,000)
Fees payable	(11,226,000)	11,183,000
Due to related parties	(4,561,000)	(26,000)
Accounts payable, accrued expenses and other liabilities	9,272,000	13,193,000
Consolidated Funds
Contributions received in advance	1,000,000	670,000
Payable to brokers	(9,618,000)	865,000
Payable for derivative contracts, at fair value	3,894,000	(5,150,000)
Accounts payable, accrued expenses and other liabilities	(211,000)	73,000
Net Cash Provided by (Used in) Operating Activities	(129,680,000)	(35,506,000)
Cash flows from investing activities:
Purchases of other investments	(5,462,000)	(11,475,000)
Purchase of business	(48,581,000)	0
Proceeds from sales of other investments	6,337,000	10,271,000
Loans issued	0	(3,050,000)
Proceeds from loans held for investment	13,000	10,000
Purchase of fixed assets	(1,684,000)	(1,151,000)
Net Cash Provided by (Used in) Investing Activities	(49,377,000)	(5,395,000)
Cash flows from financing activities:
Repayments on convertible debt	(20,860,000)	0
Deferred debt issuance cost	0	(104,000)
Borrowings on notes and other debt	0	88,061,000
Repayments on notes and other debt	(513,000)	(1,475,000)
Purchase of treasury stock	(4,658,000)	(7,584,000)
Contingent liability payment	(1,235,000)	0
Capital contributions by redeemable non-controlling interests in operating entities	2,025,000	200,000
Capital withdrawals to redeemable non-controlling interests in operating entities	(696,000)	(513,000)
Consolidated Funds
Capital contributions by redeemable non-controlling interests in Consolidated Funds	159,948,000	8,059,000
Capital withdrawals to redeemable non-controlling interests in Consolidated Funds	(17,845,000)	(46,041,000)
Net Cash Provided by (Used in) Financing Activities	116,166,000	40,603,000
Change in cash and cash equivalents	(62,891,000)	(298,000)
Total cash beginning of period	442,113,000	264,208,000
Cash and cash equivalents	235,838,000	117,680,000
Cash collateral pledged	6,420,000	14,786,000
Segregated cash	136,964,000	131,444,000
Total cash at end of period	379,222,000	263,910,000
Supplemental information
Cash paid during the year for interest	8,822,000	12,265,000
Cash paid during the year for taxes	1,431,000	712,000
Purchase of treasury stock, at cost, through net settlement	4,671,000	4,910,000
Net assets (liabilities) acquired upon acquisition (net of cash)	90,727,000	0
Operating right of use assets	101,796,000
Operating Lease, Liability	108,368,000
Transfer of investment from consolidated funds, securities owned, fair value to securities owned, fair value	97,655,000	0
Net decrease in redeemable non-controlling interests in Consolidated Funds due to deconsolidation of consolidated fund		32,559,000
Separately recognized conversion option reclassification from a derivative liability to equity	(596,000)
Common stock issuance upon close of acquisition	14,446,000	0
Goodwill, Impairment Loss	$ 0	$ 0

Organization and Business

Organization and Business	3 Months Ended
	Mar. 31, 2019
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 which, together with its consolidated subsidiaries (collectively, “Cowen,” or the “Company”), operates through its two business segments: an investment management segment and an investment bank segment. The Company's investment management segment includes advisers to investment funds (including privately placed hedge funds, real estate funds and private equity structures), managed accounts, commodity pools, and registered funds . The Company's investment bank segment offers investment banking, research, sales and trading, prime brokerage, global clearing and commission management services to companies and primarily institutional investor clients. The investment bank segment's primary target sectors ("Target Sectors") are healthcare, technology, media and telecommunications, information and technology services, consumer, aerospace and defense, industrials, energy and transportation .

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
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 in consolidation. Certain fund entities 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 their specialized accounting. The Company serves as the managing member/general partner and/or investment manager to affiliated fund entities which it sponsors and manages. Funds in which the Company has a controlling financial interest are consolidated with the Company pursuant to US GAAP as described below. Consequently, the Company's condensed consolidated financial statements reflect the assets, liabilities, income and expenses of these funds on a gross basis. The ownership interests in these funds that are not owned by the Company are reflected as redeemable non-controlling interests in consolidated subsidiaries in the accompanying condensed consolidated financial statements. The management fees and incentive income earned by the Company from these funds are eliminated in consolidation. In this Form 10-Q, interest and dividends expense for the three months ended March 31, 2018 has been reclassified to be presented net of revenues on the condensed consolidated statement of operations. The Company believes that this presentation provides 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 change to the presentation of interest and dividend expense has no impact on net income. The year-end condensed balance sheet data was derived from the audited financial statements, but does not include all disclosures included in the audited financial statements. 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. In accordance with these standards, the Company consolidates four investment funds for which it acts as the general partner and investment manager. As of March 31, 2019 , the Company consolidated the following investment funds: Ramius Enterprise LP (“Enterprise LP”), Ramius Merger Fund LLC (the "Merger Fund"), Cowen Private Investments LP ("Cowen Private"), and Ramius Merger Arbitrage UCITS Fund ("UCITS Fund") (each a "Consolidated Fund" and collectively the "Consolidated Funds"). The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting operating entity ("VOE") or a variable interest entity ("VIE") under US GAAP. Voting Operating Entities — VOEs are entities in which (i) the total equity investment at risk is sufficient to enable the entity to finance its activities independently and (ii) the equity holders at risk have the obligation to absorb losses, the right to receive residual returns and the right to direct the activities of the entity that most significantly impact the entity's economic performance. Under US GAAP, the usual condition for a controlling financial interest in a VOE is ownership of a majority voting interest. Accordingly, the Company consolidates 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 reconsiders whether it is the primary beneficiary of a VIE by performing a periodic qualitative and/or quantitative analysis of the VIE that includes a review of, among other things, its capital structure, contractual agreements between the Company and the VIE, the economic interests that create or absorb variability, related party relationships and the design of the VIE. As of March 31, 2019 and December 31, 2018 , the total net assets of the consolidated VIEs were $571.2 million and $427.5 million , respectively. The increase is primarily related to other investors' subscriptions which increased 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. As of March 31, 2019 , the Company held a variable interest in Ramius Merger Master Fund Ltd ("Merger Master") (the “Unconsolidated Master Fund”) through the Consolidated Funds. As of December 31, 2018 , the Company held variable interests in Ramius Enterprise Master Fund Ltd (“Enterprise Master”) and Ramius Merger Master Fund Ltd ("Merger Master") (collectively the “Unconsolidated Master Funds”) through the Consolidated Funds. Investment companies, which account for their investments under the specialized industry accounting guidance for investment companies prescribed under US GAAP, are not subject to the consolidation provisions for their investments. Therefore, the Company has not consolidated the Unconsolidated Master Funds. In the ordinary course of business, the Company also sponsors various other entities that it has determined to be VIEs. These VIEs are primarily 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 Unconsolidated Master Fund(s) or real estate funds that are VIEs as it has concluded that it is not the primary beneficiary in each instance. Investment fund investors are entitled to all of their 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 GP and 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 securities, derivatives and 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) in accordance with US GAAP, at fair value with unrealized gains (losses) resulting from changes in fair value reflected within net gains (losses) on securities, derivatives and other investments in the 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 for investment companies. The Company has retained this specialized accounting for these investment funds pursuant to US GAAP. The Company reports its investments on the condensed consolidated statements of financial condition at their estimated fair value, with unrealized gains (losses) resulting from changes in fair value reflected within net realized and unrealized gains (losses) on investments and other transactions. Accordingly, the accompanying condensed consolidated financial statements reflect different accounting policies for investments depending on whether or not they are held through a consolidated investment company. In addition, the Company's broker-dealer subsidiaries , Cowen and Company, LLC ("Cowen and Company"), Cowen Execution Services LLC ("Cowen Execution") and Westminster Research Associates LLC ("Westminster"), Cowen Execution Services Limited ("Cowen Execution Ltd"), ATM Execution LLC ("ATM Execution"), Cowen International Limited ("Cowen International Ltd"), Cowen Prime Services LLC ("Cowen Prime") and Quarton Securities L.P. (subsequently renamed to Cowen Securities L.P.) ("Cowen Securities") apply the specialized industry accounting for brokers and dealers in securities also prescribed under US GAAP. The Company also retains specialized accounting 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, disclosure of contingent assets and liabilities at the date of the accompanying condensed consolidated financial statements, the accounting for goodwill and identifiable intangible assets and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates. d. Allowance for credit losses The allowance for credit losses is based on the Company’s assessment of the collectability of receivables related to securities transactions, prepaid research and other receivables. The Company considers factors such as historical experience, credit quality, age of balances and current economic conditions that may affect collectability in determining the allowance for credit losses. Specifically, for prepaid research, the Company reviews clients' historical, current and forecasted trading activity in determining the allowance for credit losses. 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. The Company and its operating subsidiaries act as the manager for the Consolidated Funds. Both the Company and the Consolidated Funds hold certain investments which are valued by the Company, acting as the investment manager. The fair value of these investments is generally estimated based on proprietary models developed by the Company, which include discounted cash flow analysis, public market comparables, and other techniques and may be based, at least in part, on independently sourced market information. The material estimates and assumptions used in these models include the timing and expected amount of cash flows, the appropriateness of discount rates used, and, in some cases, the ability to execute, timing of, and estimated proceeds from expected financings. Significant judgment and estimation goes into the selection of an appropriate valuation methodology as well as the assumptions used in these models, and the timing and actual values realized with respect to investments could be materially different from values derived based on the use of those estimates. The valuation methodologies applied impact the reported value of the Company's investments and the investments held by the Consolidated Funds in the condensed consolidated financial statements. Certain of the Company's investments are relatively illiquid or thinly traded and may not be immediately liquidated on demand if needed. Fair values assigned to these investments may differ significantly from the fair values that would have been used had a ready market for the investments existed and such differences could be material . The Company primarily uses the “market approach” to value its financial instruments measured at fair value. In determining an instrument's level within the hierarchy, the Company categorizes the Company's financial instruments into three categories: securities, derivative contracts and other investments. To the extent applicable, each of these categories can further be divided between those held long or sold short. 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. The Company does not adjust the quoted price for such instruments, even in situations where the Company holds a large position and a sale could reasonably impact the quoted price. Certain positions for which trading activity may not be readily visible, consisting primarily of convertible debt, corporate debt and loans 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, have inputs which can generally be corroborated by market data and are therefore classified within level 2. OTC derivatives, such as swaps and options where market data is not readily available or observable are classified as level 3. Other investments — Other investments consist primarily of investment funds, real estate investments and equity method investments, which are valued as follows : i. Portfolio funds— 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 follows US GAAP regarding fair value measurements and disclosures relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The guidance permits, as a practical expedient, an entity holding investments in certain entities that either are investment companies as defined by the American Institute of Certified Public Accountants ("AICPA") Audit and Accounting Guide, Investment Companies, or have attributes similar to an investment company, and calculate net asset value per share or its equivalent for which the fair value is not readily determinable, to measure the fair value of such investments on the basis of that NAV per share, or its equivalent, without adjustment. In accordance with US GAAP, investments which are valued using NAV per share as a practical expedient are not categorized within the fair value hierarchy. ii. Real estate investments— Real estate debt and equity investments are valued at fair value. The fair value of real estate investments is estimated based on the price that would be received to sell an asset in an orderly transaction between marketplace participants at the measurement date. Real estate investments without a public market are valued based on assumptions and valuation techniques used by the Company. Such valuation techniques may include discounted cash flow analysis, prevailing market capitalization rates or earnings multiples applied to earnings from the investment, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties, consideration of the amount that currently would be required to replace the asset, as adjusted for obsolescence, as well as independent external appraisals. In general, the Company considers several valuation techniques when measuring the fair value of a real estate investment. However, in certain circumstances, a single valuation technique may be appropriate. Real estate investments are reviewed on a quarterly basis by the Company for significant changes at the property level or a significant change in the overall market which would impact the value of the real estate investment resulting in unrealized appreciation or depreciation. Real estate and capital markets are cyclical in nature. Property and investment values are affected by, among other things, the availability of capital, occupancy rates, rental rates and interest and inflation rates. In addition, the Company invests in real estate and real estate related investments for which no liquid market exists. The market prices for such investments may be volatile and may not be readily ascertainable. Amounts ultimately realized by the Company from investments sold may differ from the fair values presented, and the differences could be material. The Company's real estate investments are typically categorized as level 3 investments within the fair value hierarchy as management uses significant unobservable inputs in determining their estimated fair value. See Notes 6 and 7 for further information regarding the Company's investments, including equity method investments and fair value measurements. f. Fees receivable Fees related to security transactions are reported net of an allowance for credit losses. An allowance for credit losses is assessed on any commission receivables aged over 180 days. Corporate finance and syndicate receivables, include receivables relating to the Company’s investment banking and advisory engagements net of allowance for credit losses. The Company records this allowance for credit losses on these receivables on a specific identification basis. The future collectability of the receivables is reviewed on a monthly basis based on the following factors: aging (usually if outstanding greater than 90 days), known financial stability of the paying company, as well as any other factors that might impact the collection of the outstanding fees. 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 2(k)). g. 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. The Company minimizes its credit risk by continuously monitoring its credit exposure and collateral values by demanding additional or returning excess collateral in accordance with the netting provisions available in the master securities lending contracts in place with the counterparties. Fees and interest received or paid are recorded in interest and 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 net gains (losses) on securities, derivatives and other investments 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, 2019 and December 31, 2018 , the Company did not have any securities lending transactions for which fair value basis of accounting was elected. h. Fixed assets Fixed assets are stated at cost less accumulated depreciation or amortization. Leasehold improvements are amortized on a straight-line basis over the lesser of their useful life or lease term. When the Company commits to a plan to abandon fixed assets or leasehold improvements before the end of its original useful life, the estimated depreciation or amortization period is revised to reflect the shortened useful life of the asset. Other fixed assets are depreciated on a straight-line basis over their estimated useful lives. Asset Depreciable Lives Depreciation and/or Amortization Method Telephone and computer equipment 3-5 years Straight-line Computer software 3-8 years Straight-line Furniture and fixtures 5 years Straight-line Leasehold improvements Term of Lease Straight-line Finance lease right-of-use asset 5 years Straight-line i. Debt Long-term debt is carried at the principal amount borrowed net of any unamortized discount/premium. The discount is accreted to interest expense using the effective interest method over the remaining life of the underlying debt obligations. Accrued but unpaid coupon interest is included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition. j. Right-of-use assets and lease liabilities Effective January 1, 2019, the Company adopted ASC Topic 842, Leases ("ASC 842"). The new guidance increases transparency and comparability by requiring the recognition of right-of-use assets and lease liabilities on the condensed consolidated statements of financial condition. The recognition of these lease assets and lease liabilities represents a change from previous US GAAP requirements, which did not require lease assets and lease liabilities to be recognized for most leases. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee, have not significantly changed from previous US GAAP requirements. Under the effective date transition method selected by the Company, leases existing at, or entered into after January 1, 2019 were required to be recognized and measured. Prior period amounts have not been adjusted and continue to be reflected in accordance with the Company’s historical Accounting Standards. In applying ASC 842, the Company made an accounting policy election not to recognize the right-of-use assets and lease liabilities relating to short term leases. Refer to the Company's Annual Report on Form 10-K for the year ended December 31, 2018 for discussions related to the Company's previous lease recognition policies. Implementation of ASC 842 included an analysis of contracts, including real estate leases and service contracts to identify embedded leases, to determine the initial recognition of right-of-use assets and lease liabilities, which required subjective assessment over the determination of the associated discount rates. ASC 842 also provided various practical expedients which were assessed to determine the ultimate impact of ASC 842 upon adoption. The standard includes a package of three practical expedients which permit the Company to not reassess (1) whether any expired or existing contracts are or contain a lease, (2) the lease classification for any expired or existing leases and (3) any initial direct costs for any existing leases as of the effective date. The Company has elected to apply the package of practical expedients, hindsight practical expedient, and land easement practical expedient. The adoption of ASC 842 resulted in the recording of operating lease right-of-use assets of $103.7 million and operating lease liabilities of $110.5 million at January 1, 2019. The Company determines if an arrangement is or contains a lease at inception. The Company’s operating lease arrangements are primarily for real estate and facility leases as well as office equipment. The Company has applied an accounting policy election to combine our lease and nonlease components for our real estate and facility leases. ROU assets represent the Company’s right to use the underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Right-of-use assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. Our variable lease payments consist of nonlease services related to the lease. Variable lease payments are excluded from the right-of-use asset and lease liabilities to the extent they are not based on consumer priced index or a market index and are recognized in the period in which the obligation for those payments is incurred. As most of our leases do not provide an implicit rate and the implicit rate is not readily determinable, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. Right-of-use assets also include any lease payments made and exclude lease incentives. Many of our operating lease agreements include options to extend the lease, which the Company does not include in the determination of the minimum lease term unless the options are reasonably certain to be exercised. Expense for lease payments related to operating leases is recognized on a straight-line basis over the lease term. Please refer to Note 18 for information on the Company’s finance leases (formerly capital leases). k. Revenue recognition The 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 t

Acquisition

Acquisition	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Acquisitions	Acquisition On January 2, 2019 (the "Acquisition Date"), the Company, together with its indirect wholly owned subsidiaries, Cowen International Ltd and Cowen QN Acquisition LLC, completed its previously announced acquisition (the "Acquisition") of Quarton International AG through the acquisition of all of the outstanding equity interest of Quarton International AG’s affiliated combining companies, Quarton Management AG, Quarton International Europe AG, Quarton Partners, LLC and Quarton Securities GP, LLC (which owns a U.S. Securities Exchange Commission ("SEC") registered broker-dealer that was subsequently renamed to Cowen Securities LP), comprising the U.S. and European operations of the acquired combining companies (collectively "Quarton"). Quarton is a group of leading global financial advisory companies serving the middle market. Quarton's operations were primarily conducted through eight entities based in the United States, Switzerland, and Germany. The acquisition was accounted for under the acquisition method of accounting in accordance with US GAAP. As such, results of operations for Quarton are included in the accompanying condensed consolidated statements of operations since the date of acquisition, and the assets acquired and liabilities assumed were recorded at their fair value as of the acquisition date. Subsequent to the acquisition, the operations of Quarton were integrated within the Company's existing businesses. The aggregate estimated purchase price of the Acquisition was $103.0 million . On the Acquisition Date the Company paid upfront consideration of $75.3 million subject to certain net working capital and other customary adjustments, with additional maximum contingent consideration of $40.0 million that will become payable dependent on the achievement of certain milestones by Quarton in each of the first four years (five years if certain conditions are met) following the Acquisition Date subject to a $10 million maximum in each year and a $40.0 million cumulative maximum. The Company estimated the contingent consideration at $27.7 million using the Monte Carlo valuation model which requires the Company to make estimates and assumptions regarding the future cash flows and profits. The contingent consideration liability is included within accounts payable, accrued expenses and other liabilities on the condensed consolidated statements of financial condition. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. A portion of the preliminary purchase price was deposited into escrow, in the amount of $0.6 million , as a reserve for any future claims against the sellers of Quarton. All consideration, including the upfront consideration and contingent consideration, consists of a combination of 80% cash and 20% shares of the Company’s Class A common stock. Shares issued on the Acquisition Date of 1,033,350 were valued based on the 30-trading day volume-weighted average price per share of $14.52 as of December 31, 2018. The fair value of the shares of Class A common stock issued was determined on the basis of the closing market price of the Company’s shares on the Acquisition Date. Any shares of Class A common stock issued in connection with any such contingent payments will be valued based on the 30-trading day volume-weighted average price per share as of the day immediately prior to the date on which such shares are to be issued. In addition, Quarton and the Company have established a retention bonus pool, for Quarton employees that remain employed at the end of each year there is a contingent payment which will be settled in a combination of 80% cash and 20% shares of the Company’s Class A common stock based on Quarton meeting certain economic performance hurdles. The bonus pool has an aggregate maximum of $10.0 million over a five -year period with $2.5 million maximum in each year. The Company is recognizing the retention bonus over each contingent payment period based upon the Company’s revenue projections for Quarton. The table below summarizes the preliminary purchase price allocation of net tangible and intangible assets acquired and liabilities assumed as of January 2, 2019: (dollars in thousands) Cash and cash equivalents $ 12,236 Fees receivable 7,269 Fixed assets 1,085 Operating lease right-of-use assets 3,200 Intangible assets 22,200 Other assets 667 Compensation payable (637 ) Operating lease liabilities (3,200 ) Due to related parties (4,750 ) Accounts payable, accrued expenses and other liabilities (16,257 ) Total identifiable net assets acquired and liabilities assumed 21,813 Goodwill 81,150 Total estimated purchase price $ 102,963 As of the acquisition date, the estimated fair value of the Company's intangible assets, as acquired through the Acquisition, was $22.2 million . The allocation of the intangible assets is shown within the following table: Estimated intangible assets acquired Estimated average remaining useful lives (dollars in thousands) (in years) Intangible asset class Trade name $ 900 3 Customer relationships 7,100 4 Backlog 12,600 2 Proprietary software 1,600 3 Total intangible assets $ 22,200 Amortization expense for the three months ended March 31, 2019 was $2.2 million and is included in depreciation and amortization in the accompanying condensed consolidated statements of operations. The estimated amortization expense related to these intangible assets in future periods is as follows: (dollars in thousands) 2019 $ 6,681 2020 8,908 2021 2,608 2022 1,775 2023 — Thereafter — $ 19,972 In addition to the purchase price consideration, for the three months ended March 31, 2019 , the Company has incurred acquisition related expenses of $1.1 million including financial advisory, legal and valuation services, which are included in professional, advisory and other fees in the accompanying condensed consolidated statements of operations. Included in the accompanying condensed consolidated statements of ope ration s for the three months ended March 31, 2019 are revenues of $5.3 million and net income of $1.6 million related to the results of operations of Quarton. Subsequent to the acquisition, Quarton's businesses were integrated within the investment bank businesses of the Company and therefore they are included within their respective line items in the accompanying condensed consolidated statements of operations. The following table provides supplemental pro forma financial information for the three months ended March 31, 2018 , as if the acquisition were completed as of January 1, 2018. This unaudited supplemental pro forma information has been prepared for comparative purposes only and is not intended to be indicative of what the Company's financial results would have been had the acquisition been completed on January 1, 2018, nor does it purport to be indicative of any future results. Three Months Ended March 31, 2018 (dollars in thousands, except per share data) Revenues $ 236,337 Net income (loss) attributable to Cowen Inc. common stockholders 16,418 Net income (loss) per common share: Basic $ 0.54 Diluted 0.52

Cash Collateral Pledged

Cash Collateral Pledged	3 Months Ended
	Mar. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash Collateral Pledged	Cash Collateral Pledged As of March 31, 2019 and December 31, 2018 , the Company pledged cash collateral in the amount of $5.2 million and $5.3 million , respectively, which relates to letters of credit issued to the landlords of the Company's premises in New York City, Boston, Stamford and San Francisco. The Company also has pledged collateral for reinsurance agreements which amounted to $1.2 million , as of March 31, 2019 , and $1.0 million , as of December 31, 2018 , which is anticipated to be due March 2021 (see Note 18 ).

Segregated Cash

Segregated Cash	3 Months Ended
	Mar. 31, 2019
Segregated Cash [Abstract]
Segregated Cash	Segregated Cash As of March 31, 2019 and December 31, 2018 , cash segregated in compliance with federal regulations and other restricted deposits of $137.0 million and $176.6 million , respectively, consisted of cash deposited in Special Reserve Accounts for the exclusive benefit of customers under SEC Rule 15c3-3 and cash held in accounts designated as Special Reserve Bank Accounts for Proprietary Accounts of Broker-Dealers ("PAB").

Investments of Operating Entiti

Investments of Operating Entities and Consolidated Funds	3 Months Ended
	Mar. 31, 2019
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, 2019 and December 31, 2018 , securities owned, at fair value consisted of the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Common stock (b) $ 428,952 $ 472,299 Preferred stock (b) 11,707 5,617 Warrants and rights (b) 6,787 7,990 Government bonds (a) 93,176 13,398 Corporate bonds (d) 12,012 13,041 Convertible bonds (c) 5,000 3,000 Trade claims 5,487 5,543 $ 563,121 $ 520,888 (a) As of March 31, 2019 , maturities range from April 2019 to February 2041 with an interest rate of 0% to 6.50% . As of December 31, 2018 , maturities ranged from April 2019 to August 2019 with an interest rate of 0% . (b) The Company has elected the fair value option for investments in securities of preferred and common stock with a fair value of $2.9 million and $3.1 million , respectively, at March 31, 2019 and $2.9 million and $7.1 million , respectively, at December 31, 2018 . At December 31, 2018, the Company elected the fair value option for investments in warrants and rights with a fair value of $1.1 million . (c) As of March 31, 2019 , maturities range from June 2020 to March 2022 with an interest rate of 8% . As of December 31, 2018 , the maturity was June 2020 with an interest rate of 8% . (d) As of March 31, 2019 , maturities ranged from April 2019 to March 2026 and interest rates ranged from 0% to 15.5% . As of December 31, 2018 , maturities ranged from April 2019 to April 2049 and interest rates ranged from 2% to 15.50% . Receivable on and Payable for derivative contracts, at fair value The Company's direct involvement with derivative financial instruments includes total return swaps, futures, currency forwards, equity swaps, credit default swaps and options. The Company's derivatives trading activities exposes the Company to certain risks, such as price and interest rate fluctuations, volatility risk, credit risk, counterparty risk, foreign currency movements and changes in the liquidity of markets. The Company's long and short exposure to derivatives is as follows: Receivable on derivative contracts As of March 31, 2019 As of December 31, 2018 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Futures $ — $ — $ 42,288 $ 334 Currency forwards $ 99,791 543 $ 395 1 Swaps $ 141,108 1,915 $ 13,702 917 Options other (a) 325,571 18,971 654,506 23,130 Pay to hold $ — 234 $ — 743 $ 21,663 $ 25,125 (a) Includes index, equity, commodity future and cash conversion options. Payable for derivative contracts As of March 31, 2019 As of December 31, 2018 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Futures $ 12,464 $ 307 $ — $ — Currency forwards $ 6,273 81 $ 96,406 709 Swaps $ 41,031 3,183 $ 52,905 2,162 Options other (a) 140,452 40,012 90,730 13,211 $ 43,583 $ 16,082 (a) Includes index, equity, commodity future and cash conversion options. The following tables present the gross and net derivative positions and the related offsetting amount, as of March 31, 2019 and December 31, 2018 . This table does not include the impact of over-collateralization. Gross amounts not offset in the Condensed Consolidated Statement of Financial Condition Gross amounts recognized Gross amounts offset on the Condensed Consolidated Statements of Financial Condition (a) Net amounts included on the Condensed Consolidated Statements of Financial Condition Financial instruments Cash Collateral pledged (b) Net amounts (dollars in thousands) As of March 31, 2019 Receivable on derivative contracts, at fair value $ 21,663 $ — $ 21,663 $ — $ 2,691 $ 18,972 Payable for derivative contracts, at fair value 43,583 — 43,583 — 3,264 40,319 As of December 31, 2018 Receivable on derivative contracts, at fair value $ 25,125 $ — $ 25,125 $ — $ 1,662 $ 23,463 Payable for derivative contracts, at fair value 16,082 — 16,082 — 2,871 13,211 (a) Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred. (b) Includes the amount of collateral held or posted. The realized and unrealized gains/(losses) related to derivatives trading activities were $(2.2) million and $7.9 million for the three months ended March 31, 2019 and 2018 , respectively, and are included in other income in the accompanying condensed consolidated statements of operations. Pursuant to the various derivatives transactions discussed above, except for the cash convertible note hedge (see Note 18 ), exchange traded derivatives, and certain options, the Company is required to post/receive collateral. As of March 31, 2019 and December 31, 2018 , collateral consisting of $6.7 million and $11.2 million of cash is included in receivable from brokers, dealers and clearing organizations and payable to brokers, dealers and clearing organizations, respectively, on the accompanying condensed consolidated statements of financial condition. As of March 31, 2019 and December 31, 2018 , all derivative contracts were with multiple major financial institutions. Other investments As of March 31, 2019 and December 31, 2018 , other investments included the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Portfolio Funds, at fair value (1) $ 145,566 $ 141,236 Equity method investments (2) 54,566 40,171 $ 200,132 $ 181,407 (1) Portfolio Funds, at fair value The Portfolio Funds, at fair value as of March 31, 2019 and December 31, 2018 , included the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Starboard Value and Opportunity Fund LP (c)(*) $ 36,270 $ 32,579 Formation8 Partners Fund I, L.P. (f) 33,613 34,099 RCG Longview Debt Fund V, L.P. (g)(*) 2,667 4,394 RCG Longview II LP (g) (*) 4,431 4,400 Cowen Healthcare Investments II LP (j) (*) 23,941 21,717 Eclipse Ventures Fund I, L.P. (b) 4,469 4,412 HealthCare Royalty Partners LP (a)(*) 1,825 1,833 Lagunita Biosciences, LLC (d) 4,080 3,833 RCG IO Renergys Sarl (j) (*) 6,329 6,369 Starboard Leaders Fund LP (e)(*) 1,424 1,230 Eclipse SPV I, LP (k)(*) 1,447 1,447 RCG Longview Equity Fund, LP (g) (*) 797 802 RCG Longview Debt Fund VI, LP (g) (*) 1,614 1,586 RCG Park Liberty GP Member LLC (g) (*) 1,129 1,023 HealthCare Royalty Partners II LP (a)(*) 1,106 1,037 RCGL PE MPA, LLC (g)(*) 618 618 RCG LPP2 PNW5 Co-Invest, L.P. (h)(*) 12 296 Other private investment (l)(*) 15,723 15,898 Other affiliated funds (m)(*) 4,071 3,663 $ 145,566 $ 141,236 * 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) Eclipse Ventures Fund I, L.P. is a private equity fund which invests in early stage and growth hardware companies. Distributions will be made when the underlying investments are liquidated. (c) Starboard Value and Opportunity Fund LP 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 investors' 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., RCG Longview II LP, RCG Park Liberty GP Member LLC, RCG Longview Equity Fund, LP, RCGL PE MPA, LLC and RCG Longview Debt Fund VI, LP are real estate private equity structures. The timing of distributions depend on the nature of the underlying investments and therefore will be made either quarterly or when the underlying investments are liquidated. (h) RCG LPP2 PNW5 Co-Invest, L.P. is a single purpose entity formed to participate in a joint venture which acquired five multi-unit residential rental properties located in the Pacific Northwest. RCG LPP2 PNW5 Co-Invest, L.P. is a private equity structure and therefore distributions will be made when the underlying investments are liquidated. (i) Effective January 31, 2018, the Company is no longer affiliated with Quadratic Capital Management LLC. (j) Cowen Healthcare Investments II LP and RCG IO Renergys Sarl are private equity funds. Distributions are made from these funds when cash flows or securities are received from the underlying investments. Investors do not have redemption rights. (k) 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. (l) Other private investment represents the Company's closed end investment in a Portfolio Fund that invests in a wireless broadband communication provider in Italy. (m) 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) 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 1% to 56% . 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. As part of its equity method investment in operating companies, the Company incurs certain expenses on behalf of its equity method investees. These expenses reflect direct and indirect costs associated with the respective business and are included in their respective line items in the accompanying condensed consolidated statements of operations. For the three months ended March 31, 2019 and 2018 , the Company incurred $2.7 million and $1.9 million , of these costs, respectively. The Company recorded no impairment charges in relation to its equity method investments for the three months ended March 31, 2019 and 2018 . 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, 2019 As of December 31, 2018 (dollars in thousands) Surf House Ocean Views Holdings, LLC $ 8,493 $ 7,589 Starboard Value LP 26,240 12,699 RCG Longview Debt Fund V Partners, LLC 10,362 11,000 RCG Longview Management, LLC 1,167 1,167 RCG Longview Debt Fund VI Partners LLC 1,425 1,254 HealthCare Royalty GP, LLC 149 149 HealthCare Royalty GP II, LLC 187 176 RCG Longview Debt Fund IV Management, LLC 331 331 HealthCare Royalty GP III, LLC 1,645 1,573 Triartisan ES Partners LLC 1,026 1,500 Triartisan PFC Partners LLC 1,000 — RCG Kennedy House, LLC 131 131 RCG Longview Equity Management, LLC 110 114 RCG LPP II GP, LLC 94 272 RCG Park Liberty GP Member Manager, LLC 1,248 1,248 Other 958 968 $ 54,566 $ 40,171 For the period ended March 31, 2019, several equity method investments have met the significance criteria as defined under Regulation S-X Rule 4-08(g) of the SEC guidance ("Reg S-X 4-08(g)"). For the three months ended March 31, 2018 and for the period ended December 31, 2018, no equity method investments have met the significance criteria as defined under Reg S-X 4-08(g). As such, the Company is presenting the following summarized financial information: As of March 31, 2019 (dollars in thousands) Assets Cash $ 3,261 Performance & management fee receivable 73,336 Investments 715,831 Liabilities 20,900 Equity $ 771,528 Three Months Ended March 31, 2019 (dollars in thousands) Revenues $ 68,579 Expenses (18,210 ) Net realized and unrealized gains (losses) 89,560 Net Income $ 139,929 As of March 31, 2019 and December 31, 2018 , the Company's share of losses in its equity method investment in RCG Longview Partners II, LLC has exceeded the carrying amount recorded in this investee. These amounts are included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition. RCG Longview Partners II, LLC, as general partner to a real estate fund, has reversed previously recorded incentive income allocations and has recorded a current clawback obligation to the limited partners in such fund. This obligation is due to a change in unrealized value of the real estate fund on which there have previously been distributed carried interest realizations; however, the settlement of a potential obligation is not due until the end of the life of the respective real estate fund. As the Company is obligated to return previous distributions it received from RCG Longview Partners II, LLC, it has continued to record its share of gains/losses in the investee including reflecting its share of the clawback obligation in the amount of $6.5 million and $6.5 million as of March 31, 2019 and December 31, 2018 , respectively. The Company's income (loss) from equity method investments was $16.3 million and $3.9 million for the three months ended March 31, 2019 and 2018 , respectively, and is included in net gains (losses) on securities, derivatives and 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 the Company to deliver a specified security at a contracted price and, thereby, create a liability to purchase that security at prevailing prices. The Company's liability for securities to be delivered is measured at their fair value as of the date of the condensed consolidated financial statements. However, these transactions result in off-balance sheet risk, as the Company's ultimate cost to satisfy the delivery of securities sold, not yet purchased, at fair value may exceed the amount reflected in the accompanying condensed consolidated statements of financial condition. Substantially all equity securities and options are pledged to the clearing broker under terms which permit the clearing broker to sell or re-pledge the securities to others subject to certain limitations. As of March 31, 2019 and December 31, 2018 , securities sold, not yet purchased, at fair value consisted of the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Common stock $ 463,319 $ 194,305 Corporate bonds (a) 3,207 750 Government bonds (b) 84,459 — Preferred stock 3,959 199 Warrants and rights 19,242 53 $ 574,186 $ 195,307 (a) As of March 31, 2019 , the maturities ranged from October 2019 to April 2037 with interest rates ranged from 5.38% to 14.00% . As of December 31, 2018 , the maturities ranged from October 2022 to January 2034 with interest rates ranged from 2.25% to 9.38% . (b) As of March 31, 2019 , the maturities ranged from October 2019 to February 2041 with interest rates ranged from 5.38% to 8.25% . Securities lending and borrowing transactions The following tables present the contractual gross and net securities borrowing and lending agreements and the related offsetting amount as of March 31, 2019 and December 31, 2018 . Gross amounts not offset on the Condensed Consolidated Statement of Financial Condition Gross amounts recognized 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, 2019 Securities borrowed $ 966,857 $ — $ 966,857 $ — $ 957,787 $ — $ 9,070 Securities loaned 852,203 — 852,203 — 858,175 — (5,972 ) As of December 31, 2018 Securities borrowed $ 407,795 $ — $ 407,795 $ — $ 383,593 $ — $ 24,202 Securities loaned 414,852 — 414,852 — 391,310 — 23,542 (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 transactions by remaining contractual maturity and class of collateral pledged as of March 31, 2019 and December 31, 2018 : Open and Overnight Up to 30 days 31 - 90 days Greater than 90 days Total (dollars in thousands) As of March 31, 2019 Securities loaned Common stock $ 710,449 $ — $ — $ — $ 710,449 Corporate bonds 70,565 — — — 70,565 Government bonds 71,189 — — — 71,189 Securities sold, not yet purchased, at fair value - obligation to return securities received as collateral Common stock 79,778 — — — 79,778 As of December 31, 2018 Securities loaned Common stock $ 414,852 $ — $ — $ — $ 414,852 Variable Interest Entities The total assets and liabilities of the variable interest entities for which the Company has concluded that it holds a variable interest, but for which it is not the primary beneficiary, are $5.4 billion and $282.0 million as of March 31, 2019 and $5.1 billion and $157.6 million as of December 31, 2018 , respectively. The carrying value of the Company's exposure to loss for these variable interest entities as of March 31, 2019 was $231.6 million , and as of December 31, 2018 was $301.4 million , all of which is included in other investments, at fair value in the accompanying condensed consolidated statements of financial condition. The exposure to loss primarily relates to the Consolidated Funds' investment in their Unconsolidated Master Funds and the Company's investment in unconsolidated investment companies. Additionally, the Company’s maximum exposure to loss for the variable interest entities noted above as of March 31, 2019 and December 31, 2018 , was $263.3 million and $332.4 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, 2019 and 2018 , securities owned, at fair value, held by the Consolidated Funds consisted of the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Preferred stock $ 24,322 $ 24,314 Common stock 178,701 95,565 Government bonds (a) 47,034 38,377 Corporate bonds (b) 54,035 24,098 Warrants and rights 4,708 5,279 $ 308,800 $ 187,633 (a) As of March 31, 2019 , maturities ranged from April 2019 to May 2019 and interest rates were 0% . As of December 31, 2018 , maturities ranged from January 2019 to April 2019 and interest rates ranged from 0% . (b) As of March 31, 2019 , maturities ranged from December 2019 to March 2026 and interest rates ranged from 4.90% to 19.00% . As of December 31, 2018 , maturities ranged from August 2020 to March 2026 and interest rates ranged from 5.88% to 7.63% . Receivable on derivative contracts As of March 31, 2019 and December 31, 2018 , receivable on derivative contracts, at fair value, held by the Consolidated Funds are comprised of: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Currency forwards $ 25 $ 186 Equity swaps 1,196 2,477 Options 1,963 1,753 $ 3,184 $ 4,416 Payable for derivative contracts As of March 31, 2019 and December 31, 2018 , payable for derivative contracts, at fair value, held by the Consolidated Funds are comprised of: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Currency forwards $ 1,327 $ 96 Equity swaps 3,921 713 Options 309 854 $ 5,557 $ 1,663 Other investments, at fair value Investments in Portfolio Funds, at fair value As of March 31, 2019 and December 31, 2018 , investments in Portfolio Funds, at fair value, included the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Investments of Enterprise LP $ 95,414 $ 97,656 Investments of Merger Fund 91,432 88,739 $ 186,846 $ 186,395 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, 2019, 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 investment directly as well as through affiliated portfolio funds. As of December 31, 2018, the consolidated investments in Portfolio Funds included Enterprise LP's investment of $97.7 million in Enterprise Master. Prior to liquidation, strategies utilized by Enterprise Master included merger arbitrage and activist investing, investments in distressed securities, convertible hedging, capital structure arbitrage, equity market neutral, investments in private placements of convertible securities, proprietary mortgages, structured credit investments, investments in mortgage backed securities and other structured finance products, investments in real estate and real property interests, structured private placements and other relative value strategies. Enterprise Master had broad investment powers and maximum flexibility in seeking to achieve its investment objective. Enterprise Master was permitted to invest in equity securities, debt instruments, options, futures, swaps, credit default swaps and other derivatives. There are no unfunded commitments at Enterprise LP. Consolidated portfolio fund investments of Merger Fund The Merger Fund operates under a “master-feeder” structure, whereby Ramius Merger Master Ltd.'s ("Merger Master") shareholders are Merger Fund and Ramius Merger Fund Ltd. The consolidated investments in Portfolio Funds include Merger Fund's investment of $91.4 million and $88.7 million in Merger Master as of March 31, 2019 and December 31, 2018 , respectively. The Merger Master’s investment objective is to achieve consistent absolute returns while emphasizing the preservation of investor capital. The Merger Master seeks to achieve these objectives by taking a fundamental, research-driven approach to investing, primarily in the securities of issuers engaged in, or subject to, announced (or unannounced but otherwise anticipated) extraordinary corporate transactions, which may include, but are not limited to, mergers, acquisitions, leveraged buyouts, tender offers, hostile takeover bids, sale processes, exchange offers, and recapitalizations. Merger Master invests in the securities of one or more issuers engaged in or subject to such extraordinary corporate transactions. Merger Master typically seeks to derive a profit by realizing the price differential, or “spread,” between the market price of securities purchased or sold short and the market price or value of securities realized in connection with the completion or termination of the extraordinary corporate transaction, or in connection with the adjustment of market prices in anticipation thereof, while seeking to minimize the market risk associated with the aforementioned investment activities. Merger Master will, depending on market conditions, generally focus the majority of its investment program on announced transactions. If the investment manager of Merger Master considers it necessary, it may either alone or as part of a group, also initiate shareholder actions seeking to maximize value. Such shareholder actions may include, but are not limited to, re-orienting management’s focus or initiating the sale of the company (or one or more of its divisions) to a third party. There are no unfunded commitments at Merger Fund. Indirect Concentration of the Underlying Investments Held by Consolidated Funds From time to time, either directly 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, 2019 and December 31, 2018 , 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, 2019 and one at December 31, 2018 . 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 equity Issuer Security Type Country Industry Percentage of Equity Market Value (dollars in thousands) As of March 31, 2019 Linkem Equity Italy Wireless Broadband 8.08 % $ 65,842 As of December 31, 2018 Linkem Equity Italy Wireless Broadband 8.36 % $ 66,439 Underlying Investments of Unconsolidated Funds Held by Consolidated Funds Enterprise Master and Merger Master At December 31, 2018, Enterprise LP's investment in Enterprise Master represented Enterprise LP's proportionate share of Enterprise Master's net assets; as a result, the investment balances of Enterprise Master reflected below may exceed the net investment which Enterprise LP has recorded. Merger Fund's investment in Merger Master represents Merger Fund's proportionate share of Merger Master's net assets; as a result, the investment balances of Merger Master reflected below may exceed the net investment which Merger Fund has recorded. The following tables present summarized investment information for the underlying investments and derivatives held by Enterprise Master and Merger Master as of March 31, 2019 and December 31, 2018 : Securities owned by Enterprise Master, at fair value As of December 31, 2018 (dollars in thousands) Common stock $ 469 $ 469 Portfolio Funds, owned by Enterprise Master, at fair value As of December 31, 2018 Strategy (dollars in thousands) RCG Special Opportunities Fund, Ltd* Multi-Strategy $ 111,548 Other Private Investments Various 846 $ 112,394 * Affiliates of the Company. Merger Master As of March 31, 2019 , Merger Master held common stock and corporate bonds of $249.7 million and $74.2 million , respectively, and common stock, sold not yet purchased, of $104.2 million . As of December 31, 2018 , Merger Master held common stock, securities owned, and corporate bonds of $162.8 million and $116.5 million and common stock, sold not yet purchased, of $9.6 million , respectively. Receivable on derivative contracts, at fair value, owned by Merger Master As of March 31, 2019 As of December 31, 2018 Description (dollars in thousands) Options $ 1,973 $ 3,450 Equity swaps 219 5,320 $ 2,192 $ 8,770 Payable for derivative contracts, at fair value, owned by Merger Master As of March 31, 2019 As of December 31, 2018 Description (dollars in thousands) Options $ 287 $ 1,430 Currency forwards 22,523 270 Equity swaps 1,547 28 $ 24,357 $ 1,728

Fair Value Measurements for Ope

Fair Value Measurements for Operating Entities and Consolidated Funds	3 Months Ended
	Mar. 31, 2019
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, 2019 and December 31, 2018 : Assets at Fair Value as of March 31, 2019 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities owned, at fair value Government bonds $ 13,398 $ 79,778 $ — $ 93,176 Preferred stock 4,550 — 7,157 11,707 Common stock 421,177 2,824 4,951 428,952 Convertible bonds — — 5,000 5,000 Corporate bonds — 11,751 261 12,012 Trade claims — — 5,487 5,487 Warrants and rights 6,333 — 454 6,787 Receivable on derivative contracts, at fair value Currency forwards — 543 — 543 Swaps — 1,915 — 1,915 Options 18,971 — — 18,971 Pay to hold — 234 — 234 Consolidated Funds Securities owned, at fair value Government bonds 47,034 — — 47,034 Preferred stock — — 24,322 24,322 Common stock 177,684 — 1,017 178,701 Corporate bonds — 54,035 — 54,035 Warrants and rights — — 4,708 4,708 Receivable on derivative contracts, at fair value Currency forwards — 25 — 25 Equity swaps — 1,196 — 1,196 Options 1,963 — — 1,963 $ 691,110 $ 152,301 $ 53,357 $ 896,768 Percentage of total assets measured at fair value on a recurring basis 77.1 % 17.0 % 5.9 % Portfolio Funds measured at net asset value (a) 145,566 Consolidated Funds' Portfolio Funds measured at net asset value (a) 186,846 Equity method investments 54,566 Total investments $ 1,283,746 Liabilities at Fair Value as of March 31, 2019 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities sold, not yet purchased, at fair value Government bonds $ — $ 84,459 $ — $ 84,459 Common stock 463,319 — — 463,319 Corporate bonds — 3,207 — 3,207 Preferred stock 3,959 — — 3,959 Warrants and rights 19,242 — — 19,242 Payable for derivative contracts, at fair value Futures 307 — — 307 Currency forwards — 81 — 81 Swaps — 3,183 — 3,183 Options 38,279 — 1,733 40,012 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 29,536 29,536 Consolidated Funds Payable for derivative contracts, at fair value Currency forwards — 1,327 — 1,327 Options 309 — — 309 Equity swaps — 3,921 — 3,921 $ 525,415 $ 96,178 $ 31,269 $ 652,862 Percentage of total liabilities measured at fair value 80.5 % 14.7 % 4.8 % (a) In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table 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 second quarter of 2016 and the first quarter of 2019, 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 2019 and December 2023, respectively. For the acquisition that closed during 2016, the Company estimated the contingent consideration liability using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. For the acquisition that closed during 2019, the Company estimated the contingent consideration liability using the present value of the monte carlo simulated revenue. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts as of March 31, 2019 can range from $1.6 million to $40.0 million . Assets at Fair Value as of December 31, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities owned, at fair value Government bonds $ 13,398 $ — $ — $ 13,398 Preferred stock 449 — 5,168 5,617 Common stock 459,601 2,848 9,850 472,299 Convertible bonds — — 3,000 3,000 Corporate bonds — 13,041 — 13,041 Trade claims — — 5,543 5,543 Warrants and rights 6,324 — 1,666 7,990 Receivable on derivative contracts, at fair value Futures 334 — — 334 Currency forwards — 1 — 1 Swaps — 917 — 917 Options 23,130 — — 23,130 Pay to hold — 743 — 743 Consolidated Funds Securities owned, at fair value Government bonds 38,377 — — 38,377 Preferred stock — — 24,314 24,314 Common stock 95,471 — 94 95,565 Corporate bonds — 24,098 — 24,098 Warrants and rights — — 5,279 5,279 Receivable on derivative contracts, at fair value Currency forwards — 186 — 186 Equity swaps — 2,477 — 2,477 Options 1,753 — — 1,753 $ 638,837 $ 44,311 $ 54,914 $ 738,062 Percentage of total assets measured at fair value on a recurring basis 86.6 % 6.0 % 7.4 % Portfolio Funds measured at net asset value (a) 141,236 Consolidated Funds' Portfolio Funds measured at net asset value (a) 186,395 Equity method investments 40,171 Total investments $ 1,105,864 Liabilities at Fair Value as of December 31, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities sold, not yet purchased, at fair value Common stock $ 194,305 $ — $ — $ 194,305 Corporate bonds — 750 — 750 Preferred stock 199 — — 199 Warrants and rights 53 — — 53 Payable for derivative contracts, at fair value Currency forwards — 709 — 709 Swaps — 2,162 — 2,162 Options 11,115 — 2,096 13,211 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 3,070 3,070 Consolidated Funds Payable for derivative contracts, at fair value Currency forwards — 96 — 96 Options 854 — — 854 Equity swaps — 713 — 713 $ 206,526 $ 4,430 $ 5,166 $ 216,122 Percentage of total liabilities measured at fair value 95.6 % 2.0 % 2.4 % (a) In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table 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 the acquisition that closed during the second quarter of 2016, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired business, if certain targets are achieved through the periods ended December 2020. The Company estimated the contingent consideration liability using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts as of December 31, 2018 can range from $2.8 million to $3.4 million . The following table includes a roll forward of the amounts for the three months ended March 31, 2019 and 2018 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, 2019 Balance at December 31, 2018 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at March 31, 2019 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 5,168 $ — $ — $ 2,000 $ — $ (11 ) $ 7,157 $ (11 ) Common stock 9,850 — — 1,262 (5,952 ) (209 ) 4,951 (7 ) Convertible bonds 3,000 — — 5,000 (3,000 ) — 5,000 — Corporate bond — — — 261 — — 261 — Options, liability 2,096 — — — (4 ) (359 ) 1,733 (359 ) Warrants and rights 1,666 — — — (116 ) (1,096 ) 454 (109 ) Trade claims 5,543 — — — (56 ) — 5,487 — Contingent consideration liability 3,070 — — 27,700 (1,234 ) — 29,536 — Consolidated Funds Preferred stock 24,314 — — — — 8 24,322 8 Common stock 94 — — 407 — 516 1,017 516 Warrants and rights 5,279 — — (1,088 ) — 517 4,708 (570 ) Three Months Ended March 31, 2018 Balance at December 31, 2017 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at March 31, 2018 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 8,115 $ — $ — $ 1,415 $ (478 ) $ (235 ) $ 8,817 $ 486 Common stock 7,570 — — 310 (133 ) (347 ) 7,400 412 Convertible bonds 282 — — — (307 ) 25 — — Options, asset 1,455 — — — (1,455 ) — — — Options, liability 22,401 — — — — (1,006 ) 21,395 (1,006 ) Warrants and rights 2,517 — — — — (815 ) 1,702 510 Trade claim 5,950 — — — — 5 5,955 5 Lehman claim 301 — — — — 11 312 12 Contingent consideration liability 3,440 — — — — — 3,440 — Consolidated Funds Preferred stock 50,445 — (38,552 ) (a) — — — 11,893 — Common stock 50 — — — — — 50 — Warrants and rights 3,568 — (20 ) (a) — — 1,706 5,254 1,706 (1) Unrealized gains/losses are reported in other income (loss) in the accompanying condensed consolidated statements of operations. (a) The Company deconsolidated an investment fund. All realized and unrealized gains (losses) in the table above are reflected in other income (loss) in the accompanying condensed consolidated statements of operations. Certain assets and liabilities are measured at fair value on a nonrecurring basis and therefore are not included in the tables above. The Company recognizes all transfers and the related unrealized gain (loss) at the beginning of the reporting period. Transfers between level 1 and 2 generally relate to whether the principal market for the security becomes active or inactive. Transfers between level 2 and 3 generally relate to whether significant relevant observable inputs are available for the fair value measurements or due to change in liquidity restrictions for the investments. During the three months ended March 31, 2019 and 2018 , there were no transfers between level 1 and level 2 assets and liabilities. The following table includes quantitative information as of March 31, 2019 and December 31, 2018 for financial instruments classified within level 3. The table below quantifies information about the significant unobservable inputs used in the fair value measurement of the Company's level 3 financial instruments. Quantitative Information about Level 3 Fair Value Measurements Fair Value at March 31, 2019 Valuation Techniques Unobservable Inputs Range Level 3 Assets (dollars in thousands) Common and preferred stocks $ 320 Discounted cash flows Discount rate 8% Trade claims 25 Discounted cash flows Discount rate 20% Warrants and rights 5,162 Model based Discounted cash flows Volatility Discount rate 30% 7% to 8% Other level 3 assets (a) 47,850 Total level 3 assets $ 53,357 Level 3 Liabilities Options 1,733 Option pricing models Volatility 35% to 40% Contingent consideration liability 29,536 Discounted cash flows Monte Carlo simulation Discount rate Volatility 14%-22% 14%-15% Total level 3 liabilities $ 31,269 Quantitative Information about Level 3 Fair Value Measurements Fair Value at Valuation Techniques Unobservable Inputs Range Level 3 Assets (dollars in thousands) Common and preferred stocks $ 4,323 Guideline companies/Discounted cash flows Discount rate 8%-14% Trade claims 25 Discounted cash flows Discount rate 20% Warrants and rights 1,666 Model based Discounted cash flows Discount rate 7% to 9% Other level 3 assets (a) 48,900 Total level 3 assets $ 54,914 Level 3 Liabilities Options 2,096 Option pricing models Volatility 35% to 40% Contingent consideration liability 3,070 Discounted cash flows Projected cash flow and discount rate 23% Total level 3 liabilities $ 5,166 (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 and procedures and an internal control infrastructure over its fair value measurement of financial instruments which includes ongoing oversight by the valuation committee as well as periodic audits performed by the Company's internal audit group. The valuation committee is comprised of senior management, including non-investment professionals, who are responsible for overseeing and monitoring the pricing of the Company's investments, including the review of the results of the independent price verification process, approval of new trading asset classes and use of applicable pricing models and approaches. The US GAAP fair value leveling hierarchy is designated and monitored on an ongoing basis. In determining the designation, the Company takes into consideration a number of factors including the observability of inputs, liquidity of the investment and the significance of a particular input to the fair value measurement. Designations, models, pricing vendors, third party valuation providers and inputs used to derive fair market value are subject to review by the valuation committee and the internal audit group. The Company reviews its valuation policy guidelines on an ongoing basis and may adjust them in light of, improved valuation metrics and models, the availability of reliable inputs and information, and prevailing market conditions. The Company reviews a daily profit and loss report, as well as other periodic reports, and analyzes material changes from period-to-period in the valuation of its investments as part of its control procedures. The Company also performs back testing on a regular basis by comparing prices observed in executed transactions to previous valuations. The fair market value for level 3 securities may be highly sensitive to the use of industry standard models, unobservable inputs and subjective assumptions. The degree of fair market value sensitivity is also contingent upon the subjective weight given to specific inputs and valuation metrics. The Company holds various equity and debt instruments where different weight may be applied to industry standard models representing standard valuation metrics such as: discounted cash flows, market multiples, comparative transactions, capital rates, recovery rates and timing, and bid levels. Generally, changes in the weights ascribed to the various valuation metrics and the significant unobservable inputs in isolation may result in significantly lower or higher fair value measurements. Volatility levels for warrants and options are not readily observable and subject to interpretation. Changes in capital rates, discount rates and replacement costs could significantly increase or decrease the valuation of the real estate investments. The interrelationship between unobservable inputs may vary significantly amongst level 3 securities as they are generally highly idiosyncratic. Significant increases (decreases) in any of those inputs in isolation can result in a significantly lower (higher) fair value measurement. Other financial assets and liabilities The following table presents the carrying values and fair values, at March 31, 2019 and December 31, 2018 , 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 2 . March 31, 2019 December 31, 2018 Fair Value Hierarchy Carrying Amount Fair Value Carrying Amount Fair Value (dollars in thousands) Financial Assets Operating companies Cash and cash equivalents $ 235,838 $ 235,838 $ 259,148 $ 259,148 Level 1 Cash collateral pledged 6,420 6,420 6,318 6,318 Level 2 Segregated cash 136,964 136,964 176,647 176,647 Level 1 Securities borrowed 966,857 $ 957,787 407,795 383,593 Level 2 Loans receivable 34,898 34,898 (d) 36,021 36,021 (d) Level 3 Consolidated Funds Cash and cash equivalents 2,178 2,178 38,118 38,118 Level 1 Financial Liabilities Securities loaned 852,203 858,175 414,852 391,310 Level 2 Convertible debt 115,099 (a) 142,628 (b) 134,489 (a) 157,433 (b) Level 2 Notes payable and other debt 264,273 207,543 (c) 262,965 258,546 (c) Level 2 (a) The carrying amount of the convertible debt includes an unamortized discount of $23.4 million and $24.9 million as of March 31, 2019 and December 31, 2018 , 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.

Deposits with Clearing Organiza

Deposits with Clearing Organizations, Brokers and Banks	3 Months Ended
	Mar. 31, 2019
Deposits with Clearing Organizations, Brokers and Banks [Abstract]
Deposits with Clearing Organizations, Brokers and Banks	Deposits with Clearing Organizations, Brokers and Banks Under 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, 2019 and December 31, 2018 , the Company had a total of $109.3 million and $89.4 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, 2019
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, 2019 and December 31, 2018 , amounts receivable from brokers, dealers and clearing organizations include: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Broker-dealers $ 608,841 $ 692,581 Securities failed to deliver 44,037 72,918 Clearing organizations 2,702 15,319 Securities borrowed interest receivable 7,492 5,295 $ 663,072 $ 786,113 As of March 31, 2019 and December 31, 2018 , amounts payable to brokers, dealers and clearing organizations include: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Broker-dealers $ 134,424 $ 159,443 Securities failed to receive 23,619 28,826 Clearing organizations 9,876 36,338 Securities loaned interest payable 6,613 4,124 $ 174,532 $ 228,731

Receivable from and Payable to

Receivable from and Payable to Customers	3 Months Ended
	Mar. 31, 2019
Receivables and Payable to Customers [Abstract]
Payable to Customers [Text Block]	Receivable From and Payable To Customers As of March 31, 2019 and December 31, 2018 , receivable from customers of $36.7 million and $37.9 million , respectively, consist of amounts owed by customers relating to securities transactions not completed on settlement date and receivables arising from the prepayment of Commission Sharing Agreements (“CSA”), net of an allowance for credit losses. A prepaid CSA is established for research-related disbursements in advance of anticipated customer commission volumes. As of March 31, 2019 and December 31, 2018 , payable to customers of $413.1 million and $525.2 million , 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.

Goodwill and Intangibles

Goodwill and Intangibles	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangibles [Abstract]
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	Goodwill and Intangible Assets In accordance with US GAAP, the Company tests goodwill for impairment on an annual basis or at an interim period if events or changed circumstances would more likely than not reduce the fair value of a reporting unit below its carrying amount. Under US GAAP, the Company first assesses the qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amounts as a basis for determining if it is necessary to perform the two-step approach. Periodically estimating the fair value of a reporting unit requires significant judgment and often involves the use of significant estimates and assumptions. These estimates and assumptions could have a significant effect on whether or not an impairment charge is recorded and the magnitude of such a charge. In connection with the Quarton transaction (see Note 3 ), in January 2019, the Company recognized goodwill of $81.2 million and intangible assets (including customer relationships, trade name, backlog and proprietary software) with an estimated fair value of $22.2 million which are included within intangible assets, net in the condensed consolidated statements of financial condition with the expected useful lives ranging from 2 to 4 years with a weighted average useful life of 2.8 years . Amortization expense related to intangibles from the Quarton acquisition for the three months ended March 31, 2019 is $2.2 million . Goodwill, the excess of the purchase price over the fair value of net assets, primarily relates to expected synergies from combining operations and has been assigned to the investment bank segment of the Company. Tax deductible goodwill will differ from goodwill recognized by the Company in an amount equal to the difference between actual contingent consideration and estimated contingent consideration (see Note 3 ).

Commission Management Payable

Commission Management Payable	3 Months Ended
	Mar. 31, 2019
Commission Management Payable [Abstract]
Commission Management Payable	Commission Management Payable The Company receives a gross commission from various clearing 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 $103.6 million and $95.3 million , as of March 31, 2019 and December 31, 2018 , respectively, are classified as commission management payable in the accompanying condensed consolidated statements of financial condition.

Redeemable Non-Controlling Inte

Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds	Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Investment Funds Redeemable non-controlling interests in consolidated subsidiaries and investment funds and the related net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds are comprised as follows: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Redeemable non-controlling interests in consolidated subsidiaries and investment funds Operating companies $ 13,568 $ 10,434 Consolidated Funds 404,709 274,346 $ 418,277 $ 284,780 Three Months Ended March 31, 2019 2018 (dollars in thousands) Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds Operating companies $ 1,806 $ 1,620 Consolidated Funds 400 9,536 $ 2,206 $ 11,156

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2019
Reinsurance [Abstract]
Reinsurance	Reinsurance The Company’s wholly-owned Luxembourg subsidiary, Hollenfels Re SA (“Hollenfels”) provides reinsurance to third party insurance and reinsurance companies. During the three months ended March 31, 2019 and 2018 , Hollenfels’s share of incurred and paid claims, as reported to it by the underlying insurance and reinsurance companies, amounted to $2.9 million and $3.6 million respectively. During the same periods, Hollenfels’ share of claims incurred but not reported plus expected development on reported claims totaled $10.1 million and $8.3 million , respectively. Hollenfels generally employs an estimation methodology whereby historical average claims ratios over a period of up to 10 years are utilized, based on availability of data. Other methods may also be used that average claims ratios derived through different actuarial calculation methods in cases where current claims development contradicts historical results. In cases where an event may have occurred that could give rise to claims in excess of the amount calculated using the above-mentioned methodologies, then actuarial methods are used to calculate the impact of such an event. During the year, Hollenfels calculated its claim liability or claim adjustment expenses using the above-mentioned methods consistent with prior years. While Hollenfels typically settles its premiums and claim payments on a quarterly basis, the frequency of claims in the underlying policies is impractical for Hollenfels to obtain. This is because certain contracts Hollenfels has written are on a quota-share basis while the other policies provide aggregate loss protection, rendering the collection of information for all underlying contracts impracticable. Hollenfels did not discount any of its reserves and did not cede any portion of its exposures during the three months ended March 31, 2019 and March 31, 2018 , respectively.

Share-Based Compensation and Em

Share-Based Compensation and Employee Ownership Plans	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation and Employee Ownership Plans	Share-Based and Deferred Compensation and Employee Ownership Plans The Company issues share-based compensation under the 2006 Equity and Incentive Plan, the 2007 Equity and Incentive Plan (both established prior to the November 2009 transaction between Ramius Capital Group LLC and Cowen) and the 2010 Equity and Incentive Plan (collectively, the “Equity Plans”). The Equity Plans permit the grant of options, restricted shares, restricted stock units, stock appreciation rights ("SARs") and other equity-based awards to the Company's employees and directors. Stock options granted generally vest over two -to- five -year periods and expire seven years from the date of grant. Restricted shares and restricted share units issued may be immediately vested or may generally vest over a two -to- five -year period. SARs vest and expire after five years from grant date. Awards are subject to the risk of forfeiture. As of March 31, 2019 , there were 0.5 million shares available for future issuance under the Equity Plans. Under the 2010 Equity and Incentive Plan, the Company awarded $41.8 million of deferred cash awards to its employees during the three months ended March 31, 2019 . These awards vest over a four year period and accrue interest at 0.70% per year. As of March 31, 2019 , the Company had unrecognized compensation expense related to the 2010 Equity and Incentive Plan deferred cash awards of $82.2 million . The Company also maintains a Nonqualified Deferred Compensation Plan from a 2017 acquisition, which is a deferred cash award plan that is expensed over a 27 month service period. As of March 31, 2019 , the Company had unrecognized compensation expense related to these deferred cash awards of $0.1 million . The Company measures compensation cost for share based awards according to the equity method. In accordance with the expense recognition provisions of those standards, the Company amortizes unearned compensation associated with share based awards on a straight-line basis over the vesting period of the option or award, net of estimated forfeitures. In relation to awards under the Equity Plans, the Company recognized compensation expense of $7.8 million and $10.2 million for the three months ended March 31, 2019 and 2018 , respectively. The income tax effect recognized for the Equity Plans was a benefit of $2.1 million and $2.4 million for the three months ended March 31, 2019 and 2018 , 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, 2019 and 2018 : Three Months Ended March 31, 2019 Three Months Ended March 31, 2018 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 5,962,295 $ 15.73 5,579,293 $ 16.33 Granted 1,781,949 16.97 2,108,184 14.23 Vested (768,468 ) 16.69 (858,433 ) 16.2 Canceled (233,333 ) 14.12 — — Forfeited (144,346 ) 13.84 (21,412 ) 13.11 Ending balance outstanding 6,598,097 $ 16.05 6,807,632 $ 15.71 Included in the restricted share and restricted stock unit activity are performance linked restricted stock units of 481,438 which were awarded to employees of the Company in December 2013 and January 2014. An additional 700,000 performance linked restricted stock units were awarded in March 2016. Of the awards granted, 130,438 have been forfeited and 233,333 have been canceled, as they did not meet the performance criteria, through March 31, 2019 . The remaining awards, included in the outstanding balance as of March 31, 2019 , will vest between May 2019 and December 2020 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 150% 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 performance linked units 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, 2019 , there was $76.7 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 2.55 years. Restricted Shares and Restricted Stock Units Granted to Non-employee Board Members There were no restricted stock units awarded during the three months ended March 31, 2019 . As of March 31, 2019 there were 253,772 restricted stock units outstanding. There were no restricted stock units awarded during the three months ended March 31, 2018. As of December 31, 2018 there were 253,772 restricted stock units outstanding.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
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 have to be submitted on a stand‑alone basis. These subsidiaries are subject to tax in their respective countries and the Company is responsible for and, thus, reports all taxes incurred by these subsidiaries. The countries where the Company owns subsidiaries that file tax returns are United Kingdom, Luxembourg, Gibraltar, Germany, Switzerland, 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 funds. Based on these methodologies, the Company’s effective income tax rate was 20.95% and 19.82% for the three months ended March 31, 2019 and 2018 , respectively. For the three months ended March 31, 2019 and 2018 , the unusual or infrequent items whose tax impact were recorded discretely related primarily to foreign taxes and stock compensation. For the three months ended March 31, 2019 and 2018 , the effective tax rate differs from the statutory rate of 21% primarily due to income attributable to redeemable non-controlling interests in consolidated subsidiaries and funds, stock compensation, foreign taxes, as well as other nondeductible expenses. The Company recorded an uncertain tax position liability of $0.3 million as of March 31, 2019 and December 31, 2018 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 future. As of March 31, 2019 , 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, 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. The Company continues to permanently reinvest the capital and accumulated earnings of its subsidiaries in the United Kingdom, Germany, Switzerland, Canada and Hong Kong.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
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 as such the company has not incorporated the effect of the renewal options into the determination of the lease term. The Company records the expenses related to occupancy and equipment on a straight-line basis over the lease term and 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, 2019 , quantitative information regarding the Company's operating lease obligations reflected in the accompanying condensed consolidated statement of operations were as follows: Three Months Ended March 31, 2019 (dollars in thousands) Lease Cost Operating lease cost $ 6,010 Short-term lease cost 128 Variable lease cost 299 Sublease income (267 ) Total lease costs $ 6,170 The following table summarizes the supplemental cash flow information and certain other information related to operating leases for the three months ended March 31, 2019 : Three Months Ended March 31, 2019 (dollars in thousands) Other Information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 7,793 Weighted average remaining lease term - operating leases (in Years) 5.73 Weighted average discount rate - operating leases 4.15 % As of March 31, 2019 , 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) 2019 $ 770 $ 16,967 2020 384 23,828 2021 144 23,270 2022 55 20,023 2023 29 16,950 Thereafter 5 23,552 Total Operating Leases 1,387 124,590 Less discount 365 14,950 Less short term leases — 128 Less not yet commenced leases — 2,165 Total Lease Liability $ 1,022 $ 107,347 (a) The Company has entered into various agreements to sublease certain of its premises. (b) The Company has entered into a new operating real estate lease that is expected to commence during the second quarter of 2019. The Company is currently planning improvements to the leased asset of which the lessor has granted a tenant allowance of $0.4 million . Payments on the lease asset do not begin until five months after the Company completes its leasehold improvements and begins occupying the space. The total rent payment commitments are $2.2 million , which are included in the table. See Note 18 for further information on the finance lease minimum payments. Prior to the adoption of the new lease accounting guidance, the minimum rental commitments under non-cancelable operating leases at December 31, 2018, were as follows: Equipment Leases (a) Service Payments Real Estate and other Facility Rental (b) (dollars in thousands) 2019 $ 2,434 $ 21,758 $ 24,584 2020 1,492 7,514 22,608 2021 1,382 1,877 22,321 2022 1,123 1,372 19,166 2023 374 735 16,204 Thereafter — 735 21,478 $ 6,805 $ 33,991 $ 126,361 (a) Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 18 for further information on the capital lease minimum payments which are included in the table. (b) The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $1.4 million , $1.1 million , and $2.2 million for the years ended December 31, 2018 , 2017 , and 2016 respectively. Other Commitments As of March 31, 2019 , future minimum annual service payments for the Company were as follows: Service Payments (dollars in thousands) 2019 $ 16,420 2020 9,082 2021 4,675 2022 5,031 2023 3,573 Thereafter 6,331 Total Operating Leases $ 45,112 Clawback Obligations For financial reporting purposes, the general partners of a real estate fund have recorded a liability for potential clawback obligations to the limited partners, due to changes in the unrealized value of the real estate fund's remaining investments and where the real estate fund's general partner has previously received carried interest distributions. The clawback liability, however, is not realized until the end of the real estate fund's life. The real estate fund is currently in a winding-up phase whereby the remaining assets of the real estate fund are being liquidated as promptly as possible so as to maximize value. However a final date for liquidation has not been set. The clawback obligations for the real estate fund were $6.5 million and $6.5 million at March 31, 2019 and December 31, 2018 , which is included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition. The Company serves as the general partner/managing member and/or investment manager to various affiliated and sponsored investment funds. As such, the Company is contingently liable for obligations for those entities. These amounts are not included above as the Company believes that the assets in these investment funds are sufficient to discharge any liabilities. Unfunded Commitments The following table summarizes unfunded commitments as of March 31, 2019 : Entity Unfunded Commitments Commitment term (dollars in millions) Real estate (a) $ 24.3 (a) HealthCare Royalty Partners funds (b) 5.9 2 years Eclipse Ventures Fund I, L.P. (formerly Formation8 Partners Hardware Fund I, L.P.) 0.1 5 years Lagunita Biosciences, LLC 1.0 3 years Eclipse Fund II, L.P. 0.3 6 years Eclipse Continuity Fund I, L.P. 0.3 7 years Cowen Healthcare Investments II LP 6.9 2 years (a) The Company had unfunded commitments pertaining to capital commitments in five real estate investments held by the Company, all of which pertain to related party investments. Such commitments can be called at any time between two to four years, subject to advance notice. (b) 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 our 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, we receive requests, and orders seeking documents and other information in connection with various aspects of our 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 . The Company appropriately reserves for certain matters where, in the opinion of management, the likelihood of liability is probable and the extent of such liability is reasonably estimable. Such amounts are included within accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition. Estimates, by their nature, are based on judgment and currently available information and involve a variety of factors, including, but not limited to, the type and nature of the litigation, claim or proceeding, the progress of the matter, the advice of legal counsel, the Company's defenses and its experience in similar cases or proceedings as well as its assessment of matters, including settlements, involving other defendants in similar or related cases or proceedings. The Company may increase or decrease its legal reserves in the future, on a matter-by-matter basis, to account for developments in such matters. The Company accrues legal fees as incurred. The following information reflects developments with respect to the Company’s legal proceedings that occurred during the quarter ended March 31, 2019 . On December 27, 2013, Landol Fletcher filed a putative class action lawsuit against Convergex Holdings, LLC, Convergex Group, LLC, Cowen Execution, Convergex Global Markets Limited and G-Trade Services LLC (collectively, “Convergex”) in the United States District Court for the Southern District of New York (Landol Fletcher and all others similarly situated v. Convergex Group LLC, Cowen Execution, Convergex Global Markets Ltd., Convergex Holdings LLC, G-Trade Services LLC, & Does 1-10, No. 1:13-CV-09150-LLS). The suit alleges breaches of fiduciary duty and prohibited transactions under ERISA and seeks to maintain a class action on behalf of all ERISA plan participants, beneficiaries and named fiduciaries whose plans were impacted by net trading by Convergex Global Markets Limited from October 2006 to December 2011. On April 11, 2014, Landol Fletcher and Frederick P. Potter Jr., filed an amended complaint raising materially similar allegations. This matter was assumed by the Company as a result of the Company’s previously announced acquisition of Convergex Group, which was completed on June 1, 2017. On February 17, 2016, the District Court granted Convergex’s motion to dismiss the amended complaint. Plaintiffs filed an appeal to the Second Circuit, and the AARP and Department of Labor filed amicus briefs on plaintiffs' behalf. The appeal was argued on December 12, 2016. On February 10, 2017, the Second Circuit Court of Appeals (1) reversed the District Court, finding that plaintiff has constitutional standing in a “representative” capacity to sue for damages to the ERISA defined benefit plan in which he is a participant, and (2) remanded to the District Court to reconsider, in light of the Circuit Court’s decision, the issue whether plaintiff has standing to pursue claims on behalf of ERISA plans in which plaintiff is not a participant. Convergex filed a petition for rehearing, and the Court of Appeals denied the petition. On June 30, 2017, the Company filed a notice of motion and memorandum of law in support of a motion to stay the proceedings in the District Court pending resolution of its petition for writ of certiorari, which the Company intended to file with the U.S. Supreme Court. On August 16, 2017, the District Court granted the Company’s motion to stay the proceedings in the District Court pending resolution of the Company’s petition for writ of certiorari. On September 1, 2017, the Company filed a petition with the United States Supreme Court for a writ of certiorari requesting review of the decision of the Court of Appeals. On January 8, 2018, the U.S. Supreme Court denied the Company’s petition for a writ of certiorari. The previously granted stay of the proceedings in the District Court has been lifted, and the case is proceeding in the District Court. Status conferences were held on April 6, 2018, October 12, 2018, and December 4, 2018. On March 15, 2019, the Company filed a motion to dismiss the plaintiff’s amended complaint. We are indemnified against losses arising from this matter pursuant to, and subject to, the provisions of the purchase agreement relating to the acquisition of Convergex Group. Because the case is in its preliminary stages, the Company cannot predict the outcome at this time, but it does not currently expect this case to have a material effect on its financial position or its results of operations.

Convertible Debt and Notes Paya

Convertible Debt and Notes Payable	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Convertible Debt and Notes Payable	Convertible Debt and Notes Payable As of March 31, 2019 and December 31, 2018 , the Company's outstanding debt was as follows: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Convertible debt $ 115,099 $ 134,489 Notes payable 229,863 229,740 Term loan 28,200 28,200 Other notes payable 1,579 — Finance lease obligations 4,631 5,025 $ 379,372 $ 397,454 Convertible Debt 2022 Convertible Notes The Company, on December 14, 2017, issued $135.0 million a ggregate principal amount of 3.00% convertible senior notes due 2022 (the “2022 Convertible Notes”). The 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 2022 Convertible Notes is payable semi-annually on December 15 and June 15 of each year. The 2022 Convertible Notes are senior unsecured obligations of Cowen. The 2022 Convertible Notes may be converted into cash or shares of Class A common stock at the Company's election based on the current conversion price. The 2022 Convertible Notes were issued with an initial conversion price of $17.375 per share of Cowen’s Class A common stock. The Company used the net proceeds, together with cash on hand, from the offering for general corporate purposes, including the repurchase or repayment of $115.1 million of the Company’s outstanding 3.0% cash convertible senior notes due 2019 (the "2019 Convertible Notes") and the repurchase of approximately $19.5 million of the Company’s shares of its Class A common stock, which were consummated substantially concurrently with the closing of the offering. As of March 31, 2019 , the outstanding principal amount of the 2022 Convertible Notes was $135.0 million . On June 26, 2018, the Company received shareholder approval for the Company to settle the 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 recorded interest expense of $1.0 million and $1.0 million for the three months ended March 31, 2019 and 2018 , respectively. The Company recognized the embedded cash conversion option at issuance date fair value, which also represents the initial unamortized discount on the 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 $1.1 million and $1.0 million for the three months ended March 31, 2019 and 2018 , respectively, based on an effective interest rate of 7.57% . 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 2022 Convertible Notes. 2019 Convertible Notes On March 10, 2014, the Company issued $149.5 million of 3.0% cash convertible senior notes (the "2019 Convertible Notes"). The 2019 Convertible Notes matured on March 15, 2019 and were fully repaid by the Company. The Company recorded interest expense of $0.1 million and $0.5 million for the three months ended March 31, 2019 and 2018 . Amortization on the discount, included within interest and dividends expense in the accompanying condensed consolidated statements of operations was $0.3 million and $0.5 million for the three months ended March 31, 2019 and 2018 , respectively, based on an effective interest rate of 8.89% . Notes Payable 2033 Notes On June 11, 2018, the Company completed its public offering of $90.0 million of 7.75% senior notes due 2033 (the “2033 Notes”) and subsequently the underwriters exercised in full their option to purchase an additional $10.0 million principal amount of the 2033 Notes. Interest on the 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 for the three months ended March 31, 2019 . 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 2033 Notes. 2027 Notes On December 8, 2017, the Company completed its public offering of $120.0 million of 7.35% senior notes due 2027 (the “2027 Notes”) and subsequently the underwriters exercised in full their option to purchase an additional $18.0 million principal amount of the 2027 Notes. Interest on the 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 and $2.5 million for the three months ended March 31, 2019 and 2018 , respectively. The Company capitalized debt issuance costs of approximately $5.0 million w hich is a direct deduction from the carrying value of the debt and will be amortized over the life of the 2027 Notes. 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 2021 (the "2021 Notes") and for general corporate purposes. Term Loan On June 30, 2017, the Company borrowed $28.2 million to fund general corporate purposes. This term loan has an effective interest rate of LIBOR plus 3.75% with a lump sum payment of the entire principal amount due on June 28, 2019. The loan is secured by the value of the Company's limited partnership interests in two affiliated investment funds. The Company has provided a guarantee for this loan. The Company recorded interest expense of $0.4 million and $0.4 million for the three months ended March 31, 2019 and 2018 , respectively. Other Notes Payable During January 2019, the Company borrowed $2.2 million to fund insurance premium payments. This note had an effective interest rate of 2.51% and was due on December 31, 2019, with monthly payment requirements of $0.2 million . As of March 31, 2019 , the outstanding balance on this note was $1.6 million . Interest expense for the three months ended March 31, 2019 was insignificant. Finance Lease Obligations The Company has entered into various finance leases for computer equipment. The Company's finance lease right-of-use asset amounted to $6.0 million and is recorded in fixed assets in the accompanying condensed consolidated statements of financial condition. T hese finance lease obligations are included in notes payable and other debt in the accompanying condensed consolidated statements of financial condition, and have a weighted average lease term of 3.9 years and weighted average interest rate of 4.93% as of March 31, 2019 . As of March 31, 2019 and December 31, 2018, the remaining balance on these finance leases was $4.6 million and $5.0 million , respectively. For the three months ended March 31, 2019 , quantitative information regarding the Company's finance lease obligations reflected in the accompanying condensed consolidated statement of operations, the supplemental cash flow information and certain other information related to finance leases were as follows: Three Months Ended March 31, 2019 2018 (dollars in thousands) Lease Cost Finance Lease Cost: Amortization of finance lease right-of-use assets $ 368 $ 352 Interest on lease liabilities 63 43 Other Information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases 63 43 Financing cash flows from finance leases $ 394 $ 506 Annual scheduled maturities of debt and minimum payments (of principal and interest) for all debt outstanding as of March 31, 2019 , are as follows: Convertible Debt Notes Payable Term loan Other Notes Payable Finance Lease (dollars in thousands) 2019 $ 4,050 $ 13,420 $ 28,508 $ 2,171 $ 896 2020 4,050 17,893 — — 1,360 2021 4,050 17,893 — — 1,360 2022 139,050 17,893 — — 1,127 2023 — 17,893 — — 374 Thereafter — 352,197 — — — Subtotal 151,200 437,189 28,508 2,171 5,117 Less (a) (36,101 ) (207,326 ) (308 ) (592 ) (486 ) Total $ 115,099 $ 229,863 $ 28,200 $ 1,579 $ 4,631 (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 convertible debt. Letters of Credit As of March 31, 2019 , the Company has the following seven 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 collateral for reinsurance agreements which amounted to $1.2 million , as of March 31, 2019 , and $1.0 million , as of December 31, 2018 , which is anticipated to be due March 2021 . Location Amount Maturity (dollars in thousands) Boston $ 389 March 2020 New York $ 358 April 2020 New York $ 71 October 2019 New York $ 397 October 2019 New York $ 1,687 October 2019 New York $ 1,611 November 2019 San Francisco $ 708 October 2025 To the extent any letter of credit is drawn upon, interest will be assessed at the prime commercial lending rate . As of March 31, 2019 and December 31, 2018 , there were no amounts due related to these letters of credit .

Stockholder's Equity

Stockholder's Equity	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Stockholder's Equity	Stockholder's Equity 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 of $1.7 million and $1.7 million for the three months ended March 31, 2019 and 2018 , 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 divided 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 our 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, 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, 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. In connection with the issuance and sale of the Series A Convertible Preferred Stock, the Company entered into a capped call option transaction (the “Capped Call Option Transaction”) with Nomura Global Financial Products Inc. (the “option counterparty”) for $15.9 million . The Capped Call Option Transaction is expected generally to reduce the potential dilution to the Company’s Class A common stock (if the Company elects to convert to common shares) and/or offset any cash payments that the Company is required to make upon conversion of any Series A Convertible Preferred Stock. The Capped Call Option Transaction has an initial effective strike price of $26.27 per share, which matches the initial conversion price of the Series A Convertible Preferred Stock, and a cap price of $33.54 per share. However, to the extent that the market price of Class A common stock, as measured under the terms of the Capped Call Option Transaction, exceeds the cap price thereof, there would nevertheless be dilution and/or such cash payments would not be offset. As the Capped Call Option Transaction is a free standing derivative that is indexed to the Company's own stock price and the Company controls if it is settled in cash or stock it qualifies for equity classification as a reduction to additional paid in capital. Treasury Stock Treasury stock of $243.5 million as of March 31, 2019 , compared to $234.1 million as of December 31, 2018 , resulted from $4.7 million acquired through repurchases of shares to cover employee minimum tax withholding obligations related to stock compensation vesting events under the Company's Equity Plans or other similar transactions, $0.1 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 $4.7 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, 2019 : Treasury stock shares Cost Average cost per share Balance outstanding at December 31, 2018 15,336,871 $ 234,142 $ 15.27 Shares purchased for minimum tax withholding under the Equity Plans or other similar transactions 323,227 4,671 14.45 Shares of stock received in respect of indemnification claims 3,331 48 14.41 Purchase of treasury stock 315,400 4,658 14.77 Balance outstanding at March 31, 2019 15,978,829 $ 243,519 $ 15.24

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2019
Accumulated Other Comprehensive Income / (Loss) [Abstract]
Accumulated other comprehensive income (loss)	Accumulated Other Comprehensive Income (Loss) Accumulated other comprehensive income includes the after tax change in unrealized gains and losses on foreign currency translation adjustments. During the periods presented, the Company did not have material reclassifications out of other comprehensive income. Three Months Ended March 31, 2019 2018 (dollars in thousands) Beginning Balance $ (5 ) $ (8 ) Foreign currency translation — 1 Ending Balance $ (5 ) $ (7 )

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The Company calculates its basic and diluted earnings per share in accordance with US GAAP. Basic earnings per share is calculated by dividing net income attributable to the Company's common stockholders by the weighted average number of common shares outstanding for the period. As of March 31, 2019 , there were 29,580,687 shares of Class A common stock outstanding. As of March 31, 2019 , the Company has included 253,772 fully vested, unissued restricted stock units in its calculation of basic earnings per share. As of December 31, 2018, there were 28,437,860 shares of Class A common stock outstanding. As of December 31, 2018, the Company has included 253,772 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 warrants (see Note 6 (a)), unvested restricted shares, restricted stock units, and SAR's. In calculating the number of dilutive shares outstanding, the shares of common stock underlying unvested restricted shares and restricted stock units are assumed to have been delivered, and options and warrants are assumed to have been exercised, 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 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, 2019 2018 (dollars in thousands, except share and per share data) Net income (loss) $ 11,989 $ 28,009 Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds 2,206 11,156 Net income (loss) attributable to Cowen Inc. 9,783 16,853 Preferred stock dividends 1,698 1,698 Net income (loss) attributable to Cowen Inc. common stockholders $ 8,085 $ 15,155 Shares for basic and diluted calculations: Weighted average shares used in basic computation 29,750 29,625 Restricted stock 1,875 867 Weighted average shares used in diluted computation 31,625 30,492 Earnings (loss) per share: Basic $ 0.27 $ 0.51 Diluted $ 0.26 $ 0.50

Segment Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company conducts its operations through two segments: the investment management segment and the investment bank segment. These activities are conducted primarily in the United States and substantially all of its revenues are generated domestically. The performance measure for these segments is Economic Income (Loss), which management uses to evaluate the financial performance of and make operating decisions for the segments including determining appropriate compensation levels. 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) (which is attributable to Cowen Inc.) is a pre-tax measure that (i) eliminates the impact of consolidation for Consolidated Funds and excludes (ii) goodwill and intangible impairment (iii) certain other transaction-related adjustments and/or reorganization expenses (iv) certain costs associated with debt and (v) preferred stock dividends. Economic Operating Income (Loss) represents Economic Income (Loss) before depreciation and amortization expenses. In addition, Economic Income (Loss) revenues include investment income that represents the income the Company has earned in investing its own capital, including realized and unrealized gains and losses, interest and dividends, net of associated investment related expenses. For US GAAP purposes, these items are included in each of their respective line items. Economic Income (Loss) revenues also include management fees, incentive income and investment income earned through the Company's investment as a general partner in certain real estate entities and the Company's investment in the activist business and certain investment funds. For US GAAP purposes, all of these items, are recorded in other income (loss). Economic Income (Loss) recognizes (a) incentive fees during periods when the fees are not yet crystallized for US GAAP reporting and (b) retainer fees, relating to investment banking activities, earned during the period that would otherwise be deferred until closing for US GAAP reporting. In addition, Economic Income (Loss) expenses are reduced by reimbursement from affiliates, which for US GAAP purposes is presented gross as part of revenue. As further stated below, one major difference between Economic Income (Loss) and US GAAP net income (loss) is that Economic Income (Loss) presents the segments' results of operations without the impact resulting from the full consolidation of any of the Consolidated Funds. The consolidation of these investment funds' results include the pro rata share of the income or loss attributable to other owners of such entities which is reflected in net income (loss) attributable to redeemable non-controlling interest in consolidated subsidiaries in the accompanying condensed consolidated statements of operations. This pro rata share has no effect on the overall financial performance for the investment management segment, as ultimately, this income or loss is not income or loss for the investment management segment itself. Included in Economic Income (Loss) is the actual pro rata share of the income or loss attributable to the Company as an investor in such entities, which is relevant in management making operating decisions and evaluating financial performance. The following tables set forth operating results for the Company's investment management and investment bank segments and related adjustments necessary to reconcile the Company's Economic Income (Loss) measure to arrive at the Company's consolidated US GAAP net income (loss): Three Months Ended March 31, 2019 Adjustments Investment Investment Bank Total Economic Income (Loss) Funds Consolidation Other Adjustments US GAAP Net Income (Loss) (dollars in thousands) Revenues Investment banking $ — $ 82,991 $ 82,991 $ — $ (2,885 ) (a) $ 80,106 Brokerage — 105,157 105,157 — (7,694 ) (b) 97,463 Management fees 9,633 798 10,431 (501 ) (2,789 ) (c) 7,141 Incentive income (loss) 16,747 — 16,747 (544 ) (16,188 ) (c)(a) 15 Investment income (loss) 7,029 9,955 16,984 — (16,984 ) (d)(e) — Interest and dividends — — — — 29,092 (d) 29,092 Reimbursement from affiliates — — — (34 ) 322 (f) 288 Aircraft lease revenue — — — — — (e) — Reinsurance premiums — — — — 6,591 (g) 6,591 Other revenue 439 720 1,159 — (98 ) (g) 1,061 Consolidated Funds revenues — — — 2,340 — 2,340 Total revenues 33,848 199,621 233,469 1,261 (10,633 ) 224,097 Interest expense (Economic Income/(Loss)) / Interest and dividend expense (US GAAP) 2,806 3,758 6,564 — 22,520 (d) 29,084 Total net revenues 31,042 195,863 226,905 1,261 (33,153 ) 195,013 Expenses Non interest expense 22,023 185,162 207,185 — 12,122 (d)(h)(i) 219,307 Consolidated Funds expenses — — — 1,482 — 1,482 Total expenses 22,023 185,162 207,185 1,482 12,122 220,789 Total other income (loss) — — — 621 40,321 (d)(k)(j) 40,942 Income taxes expense / (benefit) — — — — 3,177 (h) 3,177 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds 2,748 — 2,748 400 (942 ) 2,206 Income (Loss) attributable to Cowen Inc. $ 6,271 $ 10,701 $ 16,972 $ — $ (7,189 ) $ 9,783 Less: Preferred stock dividends 1,698 1,698 Income (Loss) attributable to Cowen Inc. common stockholders 15,274 $ 8,085 Add back: Depreciation and amortization expense 4,956 Economic Operating Income (Loss) attributable to Cowen Inc. common stockholders $ 20,230 Three Months Ended March 31, 2018 Adjustments Investment Investment Bank Total Economic Income (Loss) Funds Consolidation Other Adjustments US GAAP Net Income (Loss) (dollars in thousands) Revenues Investment banking $ — $ 93,924 $ 93,924 $ — $ 4,064 (a) $ 97,988 Brokerage — 114,071 114,071 — (8,338 ) (b) 105,733 Management fees 12,355 771 13,126 (1,203 ) (4,506 ) (c) 7,417 Incentive income (loss) 5,197 — 5,197 (9 ) (5,172 ) (a) (c) 16 Investment income (loss) 11,896 2,405 14,301 — (14,301 ) (d)(e) — Interest and dividends — — — — 25,954 (d) 25,954 Reimbursement from affiliates — — — (68 ) 445 (f) 377 Aircraft lease revenue — — — — 715 (e) 715 Reinsurance premiums — — — — 8,647 (g) 8,647 Other revenue 361 527 888 — 448 (g) 1,336 Consolidated Funds revenues — — — 3,201 — 3,201 Total revenues 29,809 211,698 241,507 1,921 7,956 251,384 Interest expense (Economic Income/(Loss)) / Interest and dividend expense (US GAAP) 3,854 2,104 5,958 — 18,582 (d) 24,540 Total net revenues 25,955 209,594 235,549 1,921 (10,626 ) 226,844 Expenses Non interest expense 22,881 186,452 209,333 — 13,982 (d)(h)(i) 223,315 Consolidated Funds expenses — — — 2,431 — 2,431 Total expenses 22,881 186,452 209,333 2,431 13,982 225,746 Total other income (loss) — — — 10,047 23,787 (d)(j)(k) 33,834 Income taxes expense / (benefit) — — — — 6,923 (h) 6,923 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds 2,158 — 2,158 9,537 (539 ) 11,156 Income (Loss) attributable to Cowen Inc. $ 916 $ 23,142 $ 24,058 $ — $ (7,205 ) $ 16,853 Less: Preferred stock dividends 1,698 1,698 Income (Loss) attributable to Cowen Inc. common stockholders 22,360 $ 15,155 Add back: Depreciation and amortization expense 2,986 Economic Operating Income (Loss) attributable to Cowen Inc. common stockholders $ 25,346 The following is a summary of the adjustments made to US GAAP net income (loss) for the segment to arrive at Economic Income (Loss): Funds Consolidation: The impacts of consolidation and the related elimination entries of the Consolidated Funds are not included in Economic Income (Loss). Adjustments to reconcile to US GAAP net income (loss) included elimination of incentive income and management fees earned from the Consolidated Funds and addition of investment fund expenses excluding management fees paid, investment fund revenues and investment income (loss). Other Adjustments: (a) Economic Income (Loss) presents underwriting expenses net of investment banking revenues, expenses reimbursed from clients within their respective expense category and records income from uncrystallized incentive fees. Economic Income (Loss) also records retainer fees, relating to investment banking activities, collectible during the period that would otherwise be deferred until closing for US GAAP reporting. (b) Economic Income (Loss) brokerage revenues included net securities borrowed and securities loaned activities. (c) Economic Income (Loss) recognizes revenues (i) net of distribution fees paid to agents and (ii) our proportionate share of management and incentive fees of certain real estate operating entities, the healthcare royalty business and the activist business. (d) Economic Income (Loss) recognizes Company income from proprietary trading (including interest and dividends). (e) Aircraft lease revenue is shown net of expenses in investment income for Economic Income (Loss). (f) Reimbursement from affiliates is shown as a reduction of Economic Income expenses, but is included as a part of revenues under US GAAP. (g) Economic Income (Loss) recognizes underwriting income from the Company's insurance related activities, net of expenses, within other revenue. (h) Economic Income (Loss) excludes income taxes and acquisition related adjustments as management does not consider these items when evaluating the performance of the segment. (i) Economic Income (Loss) recognizes the Company's proportionate share of expenses, for certain real estate operating entities and the activist business, for which the investments are recorded under the equity method of accounting for investments. (j) Economic Income (Loss) excludes gain/(loss) on debt extinguishment. (k) Economic Income (Loss) excludes the bargain purchase gain which resulted from the Convergex Group acquisition. For the three months ended March 31, 2019 and 2018 , there was no one investment fund or other customer which represented more than 10% of the Company's total revenues.

Regulatory Requirements

Regulatory Requirements	3 Months Ended
	Mar. 31, 2019
Brokers and Dealers [Abstract]
Regulatory Requirements	Regulatory Requirements As registered broker-dealers, Cowen and Company, Cowen Execution, 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 the Rule. Under the alternative method, Cowen and Company's minimum net capital requirement, as defined in (a)(4) of the Rule, is $1.0 million . Cowen Execution, ATM Execution, Cowen Prime and Westminster are required to maintain minimum net capital, as defined in (a)(1)(ii) of the Rule, equal to the greater of $250,000 or 2% of aggregate debits arising from customer transactions. Cowen Securities, a registered broker-dealer, is required to maintain minimum net capital, as defined in (a)(2)(vi) of the Rule, equal to or greater than $5,000 and had less than $0.1 million excess net capital at March 31, 2019. Advances to affiliates, repayment of borrowings, distributions, dividend payments and other equity withdrawals are subject to certain notification and other requirements of the Rule and other regulatory bodies. On February 7, 2019, FINRA approved the transfer of all of Cowen Securities’ business and personnel to Cowen and Company. Cowen Securities subsequently filed a Form BDW, pursuant to Section 15(b) of the Securities Exchange Act of 1934, with FINRA to withdraw its status as a broker-dealer given that it will no longer conduct a securities business, and the application was pending at March 31, 2019. Cowen Prime is also subject to Commodity Futures Trading Commission 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 Execution is also subject to Options Clearing Corporation ("OCC") Rule 302. OCC Rule 302 requires maintenance of net capital equal to the greater of $2,000,000 or 2% of aggregate debit items. At March 31, 2019 , Cowen Execution had $114.8 million of net capital in excess of this minimum requirement. Cowen International Ltd and Cowen Execution Ltd are subject to the capital requirements of the FCA, as defined, must exceed the minimum capital requirement set forth by the FCA. Effective June 1, 2018, the FCA approved Ramius UK’s application to cancel all of its FCA authorization permissions. Accordingly, Ramius UK is no longer an FCA regulated and authorized firm. Ramius UK sought the cancellation. Effective December 20, 2018, Cowen Execution Ltd was formally approved to trade in a principal capacity conditional upon the completion, and communication to the Wholesale Supervision, of the implementation of its order management system. As of March 31, 2019 , these regulated broker-dealers had regulatory net capital or financial resources, regulatory net capital requirements or minimum FCA requirement and excess as follows : Subsidiary Net Capital Minimum Net Capital Requirement Excess Net Capital (dollars in millions) Cowen and Company $101.5 $1.0 $100.5 Cowen Execution $116.8 $2.0 $114.8 ATM Execution $3.2 $0.3 $2.9 Cowen Prime $8.4 $0.3 $8.1 Westminster $19.4 $0.3 $19.1 Cowen International Ltd $14.9 $9.9 $5.0 Cowen Execution Ltd $5.0 $3.2 $1.8 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 and Company, Cowen Prime and ATM Execution claim the (k)(2)(ii) exemption with regards to some or 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 and Company, Cowen Prime and Westminster claim the (k)(2)(i) exemption with regards to customer transactions and balances that are cleared, settled and custodied in Special Bank Accounts. In accordance with the requirements of SEC Rule 15c3-3, Cowen Execution 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, 2019 , Cowen Execution had segregated approximately $15.1 million of cash, while its required deposit was $3.0 million . As a clearing broker-dealer, Cowen Execution is required to compute a reserve requirement for proprietary accounts of broker-dealers (“PAB accounts”), as defined in SEC Rule 15c3-3. Cowen Execution 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 Execution as its clearing broker-dealer to classify its PAB account assets held at Cowen Execution as allowable assets in the correspondent's net capital calculation. At March 31, 2019 , Cowen Execution had $25.6 million of cash on deposit in PAB Reserve Bank Accounts, which was more than its required deposit of $16.3 million . Cowen and Company, ATM Execution, Cowen Prime and Cowen Execution 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’s Luxembourg reinsurance companies, Vianden RCG Re SCA and Hollenfels, individually and their Luxembourg parent holding company, Ramius Enterprise Luxembourg Holdco S.à r.l., on a combined basis with the reinsurance companies, are required to maintain a solvency capital ratio as calculated by relevant European Commission directives and local regulatory rules in Luxembourg. Each reinsurance company’s individual solvency capital ratio as well as the combined solvency capital ratio of the holding and reinsurance companies as of March 31, 2019 were in excess of this 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, 2019 . RCG Insurance Company’s capital and surplus as of March 31, 2019 totaled approximately $32.1 million .

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2019
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, 2019 and December 31, 2018 , $20.0 million and $19.4 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, 2019 and 2018, 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, 2019 and December 31, 2018 , loans to employees of $14.5 million and $17.0 million , respectively, were included in due from related parties on the accompanying condensed consolidated statements of financial condition. Of these amounts $7.9 million and $8.8 million , respectively, are related to forgivable loans. These forgivable loans provide for a cash payment up-front to employees, with the amount due back to the Company forgiven over a vesting period. An employee that voluntarily ceases employment, or is terminated with cause, is generally required to pay back to the Company any unvested forgivable loans granted to them. The forgivable loans are recorded as an asset to the Company on the date of grant and payment, and then amortized to compensation expense on a straight-line basis over the vesting period. The vesting period on forgivable loans is generally one to three years. The Company recorded compensation expense of $0.9 million and $0.6 million for the three months ended March 31, 2019 , and 2018 , respectively. This expense is included in employee compensation and benefits in the accompanying condensed consolidated statement of operations. For the three months ended March 31, 2019 and 2018, the interest income was immaterial for these related party loans and advances, respectively, and are included in interest and dividends in the accompanying condensed consolidated statement of operations. As of March 31, 2019 and December 31, 2018 , included in due from related parties is $6.7 million and $7.7 million , respectively, 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 5 year period and earns interest at 5% per annum. The interest income for the three months ended March 31, 2019 and 2018 , was $0.1 million and $0.1 million , respectively. The remaining balance included in due from related parties of $7.5 million and $8.9 million as of March 31, 2019 and December 31, 2018 , 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 $0.6 million and $0.6 million March 31, 2019 and December 31, 2018 , 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, 2019 and December 31, 2018 , such investments aggregated $ 27.3 million and $ 25.1 million , respectively, were included in redeemable non-controlling interests on the accompanying condensed consolidated statements of financial condition. Their share of the net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds aggregated $ 1.5 million and $ 2.9 million , for the three months ended March 31, 2019 and 2018 , respectively. The Company may, at times, have unfunded commitment amounts pertaining to related parties. See Note 17 "Commitments and Contingencies" for amounts committed as of March 31, 2019 and December 31, 2018 .

Guarantees and Off-Balance Shee

Guarantees and Off-Balance Sheet Arrangements	3 Months Ended
	Mar. 31, 2019
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, 2019 and December 31, 2018 . 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, 2019 . Lender Contractual Amount Available Amount Maturity Date Description Pledge Lines (dollars in thousands) Texas Capital Bank $ 75,000 $ 75,000 None Secured Depository Trust Company Pledge Line 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 300,000 300,000 Revolving Credit Facility BMO Harris Bank Canadian Imperial Bank of Commerce Texas Capital Bank 70,000 70,000 August 23, 2019 (Syndicated) Unsecured liquidity facility to cover increases in National Securities Clearing Corporation margin deposit requirements Total Credit Lines $ 370,000 $ 370,000

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On April 23, 2019, the Company's Board of Directors approved a $19.7 million increase in the Company's share repurchase program (see Note 19 ) bringing the total remaining shares available for repurchase to $25.0 million . On April 25, 2019, the Company entered into a private placement of $45.0 million aggregate principal of 7.25% senior unsecured notes due May 6, 2024 with semi-annual interest payments in arrears on May 6 and November 6 of each year . 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, 2019
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 in consolidation. Certain fund entities 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 their specialized accounting. The Company serves as the managing member/general partner and/or investment manager to affiliated fund entities which it sponsors and manages. Funds in which the Company has a controlling financial interest are consolidated with the Company pursuant to US GAAP as described below. Consequently, the Company's condensed consolidated financial statements reflect the assets, liabilities, income and expenses of these funds on a gross basis. The ownership interests in these funds that are not owned by the Company are reflected as redeemable non-controlling interests in consolidated subsidiaries in the accompanying condensed consolidated financial statements. The management fees and incentive income earned by the Company from these funds are eliminated in consolidation. In this Form 10-Q, interest and dividends expense for the three months ended March 31, 2018 has been reclassified to be presented net of revenues on the condensed consolidated statement of operations. The Company believes that this presentation provides 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 change to the presentation of interest and dividend expense has no impact on net income. The year-end condensed balance sheet data was derived from the audited financial statements, but does not include all disclosures included in the audited financial statements. 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. In accordance with these standards, the Company consolidates four investment funds for which it acts as the general partner and investment manager. As of March 31, 2019 , the Company consolidated the following investment funds: Ramius Enterprise LP (“Enterprise LP”), Ramius Merger Fund LLC (the "Merger Fund"), Cowen Private Investments LP ("Cowen Private"), and Ramius Merger Arbitrage UCITS Fund ("UCITS Fund") (each a "Consolidated Fund" and collectively the "Consolidated Funds"). The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting operating entity ("VOE") or a variable interest entity ("VIE") under US GAAP. Voting Operating Entities — VOEs are entities in which (i) the total equity investment at risk is sufficient to enable the entity to finance its activities independently and (ii) the equity holders at risk have the obligation to absorb losses, the right to receive residual returns and the right to direct the activities of the entity that most significantly impact the entity's economic performance. Under US GAAP, the usual condition for a controlling financial interest in a VOE is ownership of a majority voting interest. Accordingly, the Company consolidates 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 reconsiders whether it is the primary beneficiary of a VIE by performing a periodic qualitative and/or quantitative analysis of the VIE that includes a review of, among other things, its capital structure, contractual agreements between the Company and the VIE, the economic interests that create or absorb variability, related party relationships and the design of the VIE. As of March 31, 2019 and December 31, 2018 , the total net assets of the consolidated VIEs were $571.2 million and $427.5 million , respectively. The increase is primarily related to other investors' subscriptions which increased 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. As of March 31, 2019 , the Company held a variable interest in Ramius Merger Master Fund Ltd ("Merger Master") (the “Unconsolidated Master Fund”) through the Consolidated Funds. As of December 31, 2018 , the Company held variable interests in Ramius Enterprise Master Fund Ltd (“Enterprise Master”) and Ramius Merger Master Fund Ltd ("Merger Master") (collectively the “Unconsolidated Master Funds”) through the Consolidated Funds. Investment companies, which account for their investments under the specialized industry accounting guidance for investment companies prescribed under US GAAP, are not subject to the consolidation provisions for their investments. Therefore, the Company has not consolidated the Unconsolidated Master Funds. In the ordinary course of business, the Company also sponsors various other entities that it has determined to be VIEs. These VIEs are primarily 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 Unconsolidated Master Fund(s) or real estate funds that are VIEs as it has concluded that it is not the primary beneficiary in each instance. Investment fund investors are entitled to all of their 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 GP and 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 securities, derivatives and 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) in accordance with US GAAP, at fair value with unrealized gains (losses) resulting from changes in fair value reflected within net gains (losses) on securities, derivatives and other investments in the 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 for investment companies. The Company has retained this specialized accounting for these investment funds pursuant to US GAAP. The Company reports its investments on the condensed consolidated statements of financial condition at their estimated fair value, with unrealized gains (losses) resulting from changes in fair value reflected within net realized and unrealized gains (losses) on investments and other transactions. Accordingly, the accompanying condensed consolidated financial statements reflect different accounting policies for investments depending on whether or not they are held through a consolidated investment company. In addition, the Company's broker-dealer subsidiaries , Cowen and Company, LLC ("Cowen and Company"), Cowen Execution Services LLC ("Cowen Execution") and Westminster Research Associates LLC ("Westminster"), Cowen Execution Services Limited ("Cowen Execution Ltd"), ATM Execution LLC ("ATM Execution"), Cowen International Limited ("Cowen International Ltd"), Cowen Prime Services LLC ("Cowen Prime") and Quarton Securities L.P. (subsequently renamed to Cowen Securities L.P.) ("Cowen Securities") apply the specialized industry accounting for brokers and dealers in securities also prescribed under US GAAP. The Company also retains specialized accounting 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, disclosure of contingent assets and liabilities at the date of the accompanying condensed consolidated financial statements, the accounting for goodwill and identifiable intangible assets and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates. d. Allowance for credit losses The allowance for credit losses is based on the Company’s assessment of the collectability of receivables related to securities transactions, prepaid research and other receivables. The Company considers factors such as historical experience, credit quality, age of balances and current economic conditions that may affect collectability in determining the allowance for credit losses. Specifically, for prepaid research, the Company reviews clients' historical, current and forecasted trading activity in determining the allowance for credit losses. 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. The Company and its operating subsidiaries act as the manager for the Consolidated Funds. Both the Company and the Consolidated Funds hold certain investments which are valued by the Company, acting as the investment manager. The fair value of these investments is generally estimated based on proprietary models developed by the Company, which include discounted cash flow analysis, public market comparables, and other techniques and may be based, at least in part, on independently sourced market information. The material estimates and assumptions used in these models include the timing and expected amount of cash flows, the appropriateness of discount rates used, and, in some cases, the ability to execute, timing of, and estimated proceeds from expected financings. Significant judgment and estimation goes into the selection of an appropriate valuation methodology as well as the assumptions used in these models, and the timing and actual values realized with respect to investments could be materially different from values derived based on the use of those estimates. The valuation methodologies applied impact the reported value of the Company's investments and the investments held by the Consolidated Funds in the condensed consolidated financial statements. Certain of the Company's investments are relatively illiquid or thinly traded and may not be immediately liquidated on demand if needed. Fair values assigned to these investments may differ significantly from the fair values that would have been used had a ready market for the investments existed and such differences could be material . The Company primarily uses the “market approach” to value its financial instruments measured at fair value. In determining an instrument's level within the hierarchy, the Company categorizes the Company's financial instruments into three categories: securities, derivative contracts and other investments. To the extent applicable, each of these categories can further be divided between those held long or sold short. 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. The Company does not adjust the quoted price for such instruments, even in situations where the Company holds a large position and a sale could reasonably impact the quoted price. Certain positions for which trading activity may not be readily visible, consisting primarily of convertible debt, corporate debt and loans 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, have inputs which can generally be corroborated by market data and are therefore classified within level 2. OTC derivatives, such as swaps and options where market data is not readily available or observable are classified as level 3. Other investments — Other investments consist primarily of investment funds, real estate investments and equity method investments, which are valued as follows : i. Portfolio funds— 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 follows US GAAP regarding fair value measurements and disclosures relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The guidance permits, as a practical expedient, an entity holding investments in certain entities that either are investment companies as defined by the American Institute of Certified Public Accountants ("AICPA") Audit and Accounting Guide, Investment Companies, or have attributes similar to an investment company, and calculate net asset value per share or its equivalent for which the fair value is not readily determinable, to measure the fair value of such investments on the basis of that NAV per share, or its equivalent, without adjustment. In accordance with US GAAP, investments which are valued using NAV per share as a practical expedient are not categorized within the fair value hierarchy. ii. Real estate investments— Real estate debt and equity investments are valued at fair value. The fair value of real estate investments is estimated based on the price that would be received to sell an asset in an orderly transaction between marketplace participants at the measurement date. Real estate investments without a public market are valued based on assumptions and valuation techniques used by the Company. Such valuation techniques may include discounted cash flow analysis, prevailing market capitalization rates or earnings multiples applied to earnings from the investment, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties, consideration of the amount that currently would be required to replace the asset, as adjusted for obsolescence, as well as independent external appraisals. In general, the Company considers several valuation techniques when measuring the fair value of a real estate investment. However, in certain circumstances, a single valuation technique may be appropriate. Real estate investments are reviewed on a quarterly basis by the Company for significant changes at the property level or a significant change in the overall market which would impact the value of the real estate investment resulting in unrealized appreciation or depreciation. Real estate and capital markets are cyclical in nature. Property and investment values are affected by, among other things, the availability of capital, occupancy rates, rental rates and interest and inflation rates. In addition, the Company invests in real estate and real estate related investments for which no liquid market exists. The market prices for such investments may be volatile and may not be readily ascertainable. Amounts ultimately realized by the Company from investments sold may differ from the fair values presented, and the differences could be material. The Company's real estate investments are typically categorized as level 3 investments within the fair value hierarchy as management uses significant unobservable inputs in determining their estimated fair value. See Notes 6 and 7 for further information regarding the Company's investments, including equity method investments and fair value measurements. f. Fees receivable Fees related to security transactions are reported net of an allowance for credit losses. An allowance for credit losses is assessed on any commission receivables aged over 180 days. Corporate finance and syndicate receivables, include receivables relating to the Company’s investment banking and advisory engagements net of allowance for credit losses. The Company records this allowance for credit losses on these receivables on a specific identification basis. The future collectability of the receivables is reviewed on a monthly basis based on the following factors: aging (usually if outstanding greater than 90 days), known financial stability of the paying company, as well as any other factors that might impact the collection of the outstanding fees. 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 2(k)). g. 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. The Company minimizes its credit risk by continuously monitoring its credit exposure and collateral values by demanding additional or returning excess collateral in accordance with the netting provisions available in the master securities lending contracts in place with the counterparties. Fees and interest received or paid are recorded in interest and 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 net gains (losses) on securities, derivatives and other investments 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, 2019 and December 31, 2018 , the Company did not have any securities lending transactions for which fair value basis of accounting was elected. h. Fixed assets Fixed assets are stated at cost less accumulated depreciation or amortization. Leasehold improvements are amortized on a straight-line basis over the lesser of their useful life or lease term. When the Company commits to a plan to abandon fixed assets or leasehold improvements before the end of its original useful life, the estimated depreciation or amortization period is revised to reflect the shortened useful life of the asset. Other fixed assets are depreciated on a straight-line basis over their estimated useful lives. Asset Depreciable Lives Depreciation and/or Amortization Method Telephone and computer equipment 3-5 years Straight-line Computer software 3-8 years Straight-line Furniture and fixtures 5 years Straight-line Leasehold improvements Term of Lease Straight-line Finance lease right-of-use asset 5 years Straight-line i. Debt Long-term debt is carried at the principal amount borrowed net of any unamortized discount/premium. The discount is accreted to interest expense using the effective interest method over the remaining life of the underlying debt obligations. Accrued but unpaid coupon interest is included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition. j. Right-of-use assets and lease liabilities Effective January 1, 2019, the Company adopted ASC Topic 842, Leases ("ASC 842"). The new guidance increases transparency and comparability by requiring the recognition of right-of-use assets and lease liabilities on the condensed consolidated statements of financial condition. The recognition of these lease assets and lease liabilities represents a change from previous US GAAP requirements, which did not require lease assets and lease liabilities to be recognized for most leases. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee, have not significantly changed from previous US GAAP requirements. Under the effective date transition method selected by the Company, leases existing at, or entered into after January 1, 2019 were required to be recognized and measured. Prior period amounts have not been adjusted and continue to be reflected in accordance with the Company’s historical Accounting Standards. In applying ASC 842, the Company made an accounting policy election not to recognize the right-of-use assets and lease liabilities relating to short term leases. Refer to the Company's Annual Report on Form 10-K for the year ended December 31, 2018 for discussions related to the Company's previous lease recognition policies. Implementation of ASC 842 included an analysis of contracts, including real estate leases and service contracts to identify embedded leases, to determine the initial recognition of right-of-use assets and lease liabilities, which required subjective assessment over the determination of the associated discount rates. ASC 842 also provided various practical expedients which were assessed to determine the ultimate impact of ASC 842 upon adoption. The standard includes a package of three practical expedients which permit the Company to not reassess (1) whether any expired or existing contracts are or contain a lease, (2) the lease classification for any expired or existing leases and (3) any initial direct costs for any existing leases as of the effective date. The Company has elected to apply the package of practical expedients, hindsight practical expedient, and land easement practical expedient. The adoption of ASC 842 resulted in the recording of operating lease right-of-use assets of $103.7 million and operating lease liabilities of $110.5 million at January 1, 2019. The Company determines if an arrangement is or contains a lease at inception. The Company’s operating lease arrangements are primarily for real estate and facility leases as well as office equipment. The Company has applied an accounting policy election to combine our lease and nonlease components for our real estate and facility leases. ROU assets represent the Company’s right to use the underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Right-of-use assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. Our variable lease payments consist of nonlease services related to the lease. Variable lease payments are excluded from the right-of-use asset and lease liabilities to the extent they are not based on consumer priced index or a market index and are recognized in the period in which the obligation for those payments is incurred. As most of our leases do not provide an implicit rate and the implicit rate is not readily determinable, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. Right-of-use assets also include any lease payments made and exclude lease incentives. Many of our operating lease agreements include options to extend the lease, which the Company does not include in the determination of the minimum lease term unless the options are reasonably certain to be exercised. Expense for lease payments related to operating leases is recognized on a straight-line basis over the lease term. Please refer to Note 18 for information on the Company’s finance leases (formerly capital leases). k. Revenue recognition The 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 t
Basis of presentation	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 in consolidation. Certain fund entities 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 their specialized accounting. The Company serves as the managing member/general partner and/or investment manager to affiliated fund entities which it sponsors and manages. Funds in which the Company has a controlling financial interest are consolidated with the Company pursuant to US GAAP as described below. Consequently, the Company's condensed consolidated financial statements reflect the assets, liabilities, income and expenses of these funds on a gross basis. The ownership interests in these funds that are not owned by the Company are reflected as redeemable non-controlling interests in consolidated subsidiaries in the accompanying condensed consolidated financial statements. The management fees and incentive income earned by the Company from these funds are eliminated in consolidation. In this Form 10-Q, interest and dividends expense for the three months ended March 31, 2018 has been reclassified to be presented net of revenues on the condensed consolidated statement of operations. The Company believes that this presentation provides 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 change to the presentation of interest and dividend expense has no impact on net income. The year-end condensed balance sheet data was derived from the audited financial statements, but does not include all disclosures included in the audited financial statements.
Principles of consolidation	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. In accordance with these standards, the Company consolidates four investment funds for which it acts as the general partner and investment manager. As of March 31, 2019 , the Company consolidated the following investment funds: Ramius Enterprise LP (“Enterprise LP”), Ramius Merger Fund LLC (the "Merger Fund"), Cowen Private Investments LP ("Cowen Private"), and Ramius Merger Arbitrage UCITS Fund ("UCITS Fund") (each a "Consolidated Fund" and collectively the "Consolidated Funds"). The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting operating entity ("VOE") or a variable interest entity ("VIE") under US GAAP. Voting Operating Entities — VOEs are entities in which (i) the total equity investment at risk is sufficient to enable the entity to finance its activities independently and (ii) the equity holders at risk have the obligation to absorb losses, the right to receive residual returns and the right to direct the activities of the entity that most significantly impact the entity's economic performance. Under US GAAP, the usual condition for a controlling financial interest in a VOE is ownership of a majority voting interest. Accordingly, the Company consolidates 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 reconsiders whether it is the primary beneficiary of a VIE by performing a periodic qualitative and/or quantitative analysis of the VIE that includes a review of, among other things, its capital structure, contractual agreements between the Company and the VIE, the economic interests that create or absorb variability, related party relationships and the design of the VIE. As of March 31, 2019 and December 31, 2018 , the total net assets of the consolidated VIEs were $571.2 million and $427.5 million , respectively. The increase is primarily related to other investors' subscriptions which increased 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. As of March 31, 2019 , the Company held a variable interest in Ramius Merger Master Fund Ltd ("Merger Master") (the “Unconsolidated Master Fund”) through the Consolidated Funds. As of December 31, 2018 , the Company held variable interests in Ramius Enterprise Master Fund Ltd (“Enterprise Master”) and Ramius Merger Master Fund Ltd ("Merger Master") (collectively the “Unconsolidated Master Funds”) through the Consolidated Funds. Investment companies, which account for their investments under the specialized industry accounting guidance for investment companies prescribed under US GAAP, are not subject to the consolidation provisions for their investments. Therefore, the Company has not consolidated the Unconsolidated Master Funds. In the ordinary course of business, the Company also sponsors various other entities that it has determined to be VIEs. These VIEs are primarily 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 Unconsolidated Master Fund(s) or real estate funds that are VIEs as it has concluded that it is not the primary beneficiary in each instance. Investment fund investors are entitled to all of their 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 GP and 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 securities, derivatives and 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) in accordance with US GAAP, at fair value with unrealized gains (losses) resulting from changes in fair value reflected within net gains (losses) on securities, derivatives and other investments in the 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 for investment companies. The Company has retained this specialized accounting for these investment funds pursuant to US GAAP. The Company reports its investments on the condensed consolidated statements of financial condition at their estimated fair value, with unrealized gains (losses) resulting from changes in fair value reflected within net realized and unrealized gains (losses) on investments and other transactions. Accordingly, the accompanying condensed consolidated financial statements reflect different accounting policies for investments depending on whether or not they are held through a consolidated investment company. In addition, the Company's broker-dealer subsidiaries , Cowen and Company, LLC ("Cowen and Company"), Cowen Execution Services LLC ("Cowen Execution") and Westminster Research Associates LLC ("Westminster"), Cowen Execution Services Limited ("Cowen Execution Ltd"), ATM Execution LLC ("ATM Execution"), Cowen International Limited ("Cowen International Ltd"), Cowen Prime Services LLC ("Cowen Prime") and Quarton Securities L.P. (subsequently renamed to Cowen Securities L.P.) ("Cowen Securities") apply the specialized industry accounting for brokers and dealers in securities also prescribed under US GAAP. The Company also retains specialized accounting upon consolidation.
Use of estimates	Use of estimates The preparation of the accompanying condensed consolidated financial statements in conformity with US GAAP requires the management of the Company to make estimates and assumptions that affect the fair value of securities and other investments, the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the accompanying condensed consolidated financial statements, the accounting for goodwill and identifiable intangible assets and the reported amounts of revenues and expenses during the reporting period. Actual results could materially differ from those estimates.
Allowance for doubtful accounts	Allowance for credit losses The allowance for credit losses is based on the Company’s assessment of the collectability of receivables related to securities transactions, prepaid research and other receivables. The Company considers factors such as historical experience, credit quality, age of balances and current economic conditions that may affect collectability in determining the allowance for credit losses. Specifically, for prepaid research, the Company reviews clients' historical, current and forecasted trading activity in determining the allowance for credit losses. 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. The Company and its operating subsidiaries act as the manager for the Consolidated Funds. Both the Company and the Consolidated Funds hold certain investments which are valued by the Company, acting as the investment manager. The fair value of these investments is generally estimated based on proprietary models developed by the Company, which include discounted cash flow analysis, public market comparables, and other techniques and may be based, at least in part, on independently sourced market information. The material estimates and assumptions used in these models include the timing and expected amount of cash flows, the appropriateness of discount rates used, and, in some cases, the ability to execute, timing of, and estimated proceeds from expected financings. Significant judgment and estimation goes into the selection of an appropriate valuation methodology as well as the assumptions used in these models, and the timing and actual values realized with respect to investments could be materially different from values derived based on the use of those estimates. The valuation methodologies applied impact the reported value of the Company's investments and the investments held by the Consolidated Funds in the condensed consolidated financial statements. Certain of the Company's investments are relatively illiquid or thinly traded and may not be immediately liquidated on demand if needed. Fair values assigned to these investments may differ significantly from the fair values that would have been used had a ready market for the investments existed and such differences could be material . The Company primarily uses the “market approach” to value its financial instruments measured at fair value. In determining an instrument's level within the hierarchy, the Company categorizes the Company's financial instruments into three categories: securities, derivative contracts and other investments. To the extent applicable, each of these categories can further be divided between those held long or sold short. 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. The Company does not adjust the quoted price for such instruments, even in situations where the Company holds a large position and a sale could reasonably impact the quoted price. Certain positions for which trading activity may not be readily visible, consisting primarily of convertible debt, corporate debt and loans 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, have inputs which can generally be corroborated by market data and are therefore classified within level 2. OTC derivatives, such as swaps and options where market data is not readily available or observable are classified as level 3. Other investments — Other investments consist primarily of investment funds, real estate investments and equity method investments, which are valued as follows : i. Portfolio funds— 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 follows US GAAP regarding fair value measurements and disclosures relating to investments in certain entities that calculate net asset value (“NAV”) per share (or its equivalent). The guidance permits, as a practical expedient, an entity holding investments in certain entities that either are investment companies as defined by the American Institute of Certified Public Accountants ("AICPA") Audit and Accounting Guide, Investment Companies, or have attributes similar to an investment company, and calculate net asset value per share or its equivalent for which the fair value is not readily determinable, to measure the fair value of such investments on the basis of that NAV per share, or its equivalent, without adjustment. In accordance with US GAAP, investments which are valued using NAV per share as a practical expedient are not categorized within the fair value hierarchy. ii. Real estate investments— Real estate debt and equity investments are valued at fair value. The fair value of real estate investments is estimated based on the price that would be received to sell an asset in an orderly transaction between marketplace participants at the measurement date. Real estate investments without a public market are valued based on assumptions and valuation techniques used by the Company. Such valuation techniques may include discounted cash flow analysis, prevailing market capitalization rates or earnings multiples applied to earnings from the investment, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties, consideration of the amount that currently would be required to replace the asset, as adjusted for obsolescence, as well as independent external appraisals. In general, the Company considers several valuation techniques when measuring the fair value of a real estate investment. However, in certain circumstances, a single valuation technique may be appropriate. Real estate investments are reviewed on a quarterly basis by the Company for significant changes at the property level or a significant change in the overall market which would impact the value of the real estate investment resulting in unrealized appreciation or depreciation. Real estate and capital markets are cyclical in nature. Property and investment values are affected by, among other things, the availability of capital, occupancy rates, rental rates and interest and inflation rates. In addition, the Company invests in real estate and real estate related investments for which no liquid market exists. The market prices for such investments may be volatile and may not be readily ascertainable. Amounts ultimately realized by the Company from investments sold may differ from the fair values presented, and the differences could be material. The Company's real estate investments are typically categorized as level 3 investments within the fair value hierarchy as management uses significant unobservable inputs in determining their estimated fair value. See Notes 6 and 7 for further information regarding the Company's investments, including equity method investments and fair value measurements.
Fees receivable	Fees receivable Fees related to security transactions are reported net of an allowance for credit losses. An allowance for credit losses is assessed on any commission receivables aged over 180 days. Corporate finance and syndicate receivables, include receivables relating to the Company’s investment banking and advisory engagements net of allowance for credit losses. The Company records this allowance for credit losses on these receivables on a specific identification basis. The future collectability of the receivables is reviewed on a monthly basis based on the following factors: aging (usually if outstanding greater than 90 days), known financial stability of the paying company, as well as any other factors that might impact the collection of the outstanding fees. 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 2(k)).
Securities borrowed and securities loaned	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. The Company minimizes its credit risk by continuously monitoring its credit exposure and collateral values by demanding additional or returning excess collateral in accordance with the netting provisions available in the master securities lending contracts in place with the counterparties. Fees and interest received or paid are recorded in interest and 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 net gains (losses) on securities, derivatives and other investments 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, 2019 and December 31, 2018 , the Company did not have any securities lending transactions for which fair value basis of accounting was elected.
Fixed Assets	Fixed assets Fixed assets are stated at cost less accumulated depreciation or amortization. Leasehold improvements are amortized on a straight-line basis over the lesser of their useful life or lease term. When the Company commits to a plan to abandon fixed assets or leasehold improvements before the end of its original useful life, the estimated depreciation or amortization period is revised to reflect the shortened useful life of the asset. Other fixed assets are depreciated on a straight-line basis over their estimated useful lives. Asset Depreciable Lives Depreciation and/or Amortization Method Telephone and computer equipment 3-5 years Straight-line Computer software 3-8 years Straight-line Furniture and fixtures 5 years Straight-line Leasehold improvements Term of Lease Straight-line Finance lease right-of-use asset 5 years Straight-line
Property, Plant and Equipment Useful Life	Asset Depreciable Lives Depreciation and/or Amortization Method Telephone and computer equipment 3-5 years Straight-line Computer software 3-8 years Straight-line Furniture and fixtures 5 years Straight-line Leasehold improvements Term of Lease Straight-line Finance lease right-of-use asset 5 years Straight-line
Debt	Debt Long-term debt is carried at the principal amount borrowed net of any unamortized discount/premium. The discount is accreted to interest expense using the effective interest method over the remaining life of the underlying debt obligations. Accrued but unpaid coupon interest is included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition.
Revenue recognition	Revenue recognition The 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 principle sources of revenue are derived from two segments: an investment management segment and an investment bank segment, as more fully described below. Revenue from contracts with customers includes management fees, incentive, investment banking revenue, brokerage services revenue excluding principal transactions from investment management and investment banking services. 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, separated by reportable segments, from which the Company generates its revenue. For more detailed information about reportable segments, see Note 22 . Investment Management Our investment management segment generates revenue through three principle sources: management fees, incentive income and investment income from the Company's own capital. Investment income is excluded from ASC Topic 606. 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. Several investment managers and/or general partners of the investment funds are owned jointly by the Company and third parties. Accordingly, the management fees generated by these funds are split between the Company and these third parties based on the proportionate ownership of the management company. Pursuant to US GAAP, these fees received by the management companies are accounted for under the equity method of accounting and are reflected under net gains (losses) on securities, derivatives and other investments in the accompanying condensed consolidated statements of operations. 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: • 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. • Real Estate. Management fees from the Company's real estate business are generally charged at an annual rate from 0.25% to 1.50% of total capital commitments during the investment period and of invested capital or net asset value of the applicable real estate fund after the investment period has ended. Management fees are typically paid to the general partners on a quarterly basis, at the beginning of the quarter in arrears. • 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 agreements). After the investment period, management fees for these private equity funds are generally charged at an annual rate of 0.5% 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. • 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 agreements) with respect to certain of the Company's investment funds and managed accounts. The incentive income is either allocated to the Company or is charged to the investment funds in accordance with their respective investment management or partnership agreements. 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. For the private equity and debt fund products the Company offers, the carried interest earned is typically up to 20% of the distributions made to investors after return of their contributed capital and generally a preferred return. In relation to ASC Topic 606, the Company applies an accounting policy election to recognize incentive income allocated to the Company under an equity ownership model as net gains (losses) on securities, derivatives and other investments in the accompanying condensed consolidated statements of operations. The Company previously recognized these amounts as incentive income. Under the equity method of accounting the Company recognizes its allocations of incentive income or carried interest within net gains (losses) along with the allocations proportionate to the Company’s ownership interests in the investment funds. 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 crystalized. For a majority of the 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 or carried interest is earned after the investor has received a full return of their 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. Incentive income or carried interest in the HealthCare Royalty Partners investment funds is generally earned only after investors receive a full return of their capital plus a preferred return. The Company recognizes incentive income at the end of the performance period. Several investment managers and/or general partners of the Company's investment funds are jointly owned by the Company and third parties. Accordingly, the incentive fees generated by these investment funds are split between the Company and these third parties. Pursuant to US GAAP, incentive income received by the general partners that are accounted for under the equity method of accounting are reflected under net gains (losses) on securities, derivatives and other investments in the accompanying condensed consolidated statements of operations. Investment Bank 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 Target 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 security 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 if the offering; which generally occurs on trade date. Underwriting fees are recognized gross of transaction-related expenses, 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 revenues include 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 agency placement 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 and credit 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. Commissions 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 clearing 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. • Principal transactions. Principal transactions revenue includes 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 very short duration. • Equity and credit research fees. Equity and credit research fees are paid to the Company for providing equity and credit research. Revenue is recognized once an arrangement exists, access to research has been provided and the customer has benefited from the research. • 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 earned by the investment management and investment bank segments are earned from investing the Company's capital in various strategies and from investments in private capital raising transactions of its investment banking clients. 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 on an accrual basis and 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 business. 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. Revenue from contracts with customers For the three months ended March 31, 2019 and 2018 , the following table presents revenues from contracts with customers disaggregated by fee type. Three Months Ended March 31, 2019 2018 Revenue from contracts with customers (dollars in thousands) Investment Banking Underwriting fees $ 48,036 $ 71,767 Strategic/financial advisory fees 20,544 14,360 Placement and sales agent fees 9,498 11,861 Expense reimbursements from clients 2,028 — Total Investment Banking Revenue 80,106 97,988 Brokerage Commissions 87,359 94,692 Trade conversion revenue 4,106 3,522 Equity and credit research fees 3,590 3,839 Total Brokerage Revenue from Customers 95,055 102,053 Management Fees 7,141 7,417 Incentive Income 15 16 Total revenue from contracts with customers $ 182,317 $ 207,474 Reinsurance-related contracts Premiums for reinsurance-related 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. 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.
Recently issued accounting pronouncements	Recent pronouncements Recently adopted In 2018, the FASB issued guidance related to the Tax Cuts and Jobs Act of 2017 (“TCJ Act”) for the optional reclassification of the residual tax effects, arising from the change in corporate tax rate, in accumulated other comprehensive loss to retained earnings. The reclassification is the difference between the amount previously recorded in other comprehensive income at the historical U.S. federal tax rate that remains in accumulated other comprehensive loss at the time the TCJ Act was effective and the amount that would have been recorded using the newly enacted rate. This guidance became effective during the first quarter of 2019; however, we did not elect to make the optional reclassification. In 2018, the FASB issued final guidance aligning the measurement and classification guidance for share-based payments to nonemployees with the guidance for share-based payments to employees, with certain exceptions. Under the guidance, the measurement of equity-classified nonemployee awards will be fixed at the grant date, which may lower their cost and reduce volatility in the income statement. The guidance became effective during the first quarter of 2019 and impacted the Company’s recognition and measurement of the retention bonus pool established in connection with the Company’s acquisition of Quarton International AG, which include share based payment to employees and nonemployees. Please refer to Note 3 for more information. In 2017, the FASB issued guidance to amend the amortization period for certain purchased callable debt securities held at a premium. Under prior guidance, entities generally amortized the premium as an adjustment of yield over the contractual life of the instrument. The new guidance shortened the amortization period for the premium to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. This guidance became effective during the first quarter of 2019; however, the guidance did not have an impact on our financials as we do not have investments in callable debt securities measured on an amortized cost basis. In 2016, the FASB issued guidance that amends and supersedes its previous guidance regarding leases. The new guidance requires the lessee to recognize the right to use lease assets and lease liabilities that arise from leases greater than one year, and present them in its statement of financial condition. The guidance became effective during the first quarter of 2019. Please refer to Note 2j for more information. Recently issued In October 2018, the FASB issued guidance that made targeted changes to the related party consolidation guidance. The new guidance changes how entities evaluate decision-making fees under the variable interest entity guidance. To determine whether decision-making fees represent a variable interest, an entity will consider indirect interests held through related parties under common control on a proportionate basis under the new guidance, rather than in their entirety, as has been the case under current guidance. The guidance is effective in annual periods beginning after December 15, 2019 and interim periods within those fiscal years with early adoption permitted. The Company is currently evaluating the impact of the new guidance and does not expect this guidance to have a material impact on its consolidated statements of financial condition or its consolidated statements of operations. In August 2018, the FASB issued guidance for accounting for upfront costs and fees paid by a customer in a cloud computing arrangement. The guidance requires capitalization of implementation costs incurred in connection with a hosting arrangement or the development or obtainment of internal use software. The guidance is effective for public business entities for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years for any implementation costs incurred after adoption. The Company is currently evaluating the impact of this guidance on the Company’s consolidated financial statements and does not expect this guidance to have a material impact on its consolidated statements of financial condition or its consolidated statements of operations. In August 2018, as part of its disclosure framework project, the FASB amended the disclosure requirements for fair value measurement. The amendments update and eliminate various disclosure requirements that improve the overall usefulness of the disclosure requirement for financial statement users and reduce costs by eliminating disclosures that may not be useful. The guidance is effective for public business entities for fiscal years beginning after December 15, 2019 and interim periods within those fiscal years. Since the guidance only relates to disclosure requirements, the Company does not expect this guidance to have a material impact on its consolidated statements of financial condition or its consolidated statements of operations. In January 2017, the FASB issued guidance that simplifies the subsequent measurement of goodwill. The new guidance eliminated Step 2 from the goodwill impairment test which was required in computing the implied fair value of goodwill. Instead, under the new amendments, an entity should perform its annual or interim goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. If applicable, an entity should consider income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss. The amendments in this guidance are effective for public business entities for annual and interim goodwill impairment tests performed in fiscal years beginning after December 15, 2019 with early adoption permitted after January 1, 2017. The Company is currently evaluating the impact of this guidance on the Company’s consolidated financial statements. The Company expects this guidance to simplify its goodwill impairment analysis. In June 2016, the FASB issued guidance that impacts 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. CECL will replace the loss model currently applicable to loans, held to maturity securities and other receivables carried at amortized cost. The guidance also eliminates the concept of other-than-temporary impairment for available-for-sale securities. Impairments on available-for-sale securities will be required to be recognized in earnings through an allowance, when the fair value is less than amortized cost and a credit loss exists or the securities are expected to be sold before recovery of amortized cost. Under the accounting update, there may be an ability to determine there are no expected credit losses in certain circumstances, e.g., based on collateral arrangements for lending and financing transactions or based on the credit quality of the borrower or issuer. For public business entities, the guidance is effective for reporting periods beginning after December 15, 2019 and interim periods within those fiscal years. The Company is currently evaluating the impact of this guidance on the Company’s consolidated financial statements and does not expect this guidance to have a material impact.
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 warrants (see Note 6 (a)), unvested restricted shares, restricted stock units, and SAR's. In calculating the number of dilutive shares outstanding, the shares of common stock underlying unvested restricted shares and restricted stock units are assumed to have been delivered, and options and warrants are assumed to have been exercised, 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.
Segment Reporting	Segment Reporting The Company conducts its operations through two segments: the investment management segment and the investment bank segment. These activities are conducted primarily in the United States and substantially all of its revenues are generated domestically. The performance measure for these segments is Economic Income (Loss), which management uses to evaluate the financial performance of and make operating decisions for the segments including determining appropriate compensation levels. 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) (which is attributable to Cowen Inc.) is a pre-tax measure that (i) eliminates the impact of consolidation for Consolidated Funds and excludes (ii) goodwill and intangible impairment (iii) certain other transaction-related adjustments and/or reorganization expenses (iv) certain costs associated with debt and (v) preferred stock dividends. Economic Operating Income (Loss) represents Economic Income (Loss) before depreciation and amortization expenses. In addition, Economic Income (Loss) revenues include investment income that represents the income the Company has earned in investing its own capital, including realized and unrealized gains and losses, interest and dividends, net of associated investment related expenses. For US GAAP purposes, these items are included in each of their respective line items. Economic Income (Loss) revenues also include management fees, incentive income and investment income earned through the Company's investment as a general partner in certain real estate entities and the Company's investment in the activist business and certain investment funds. For US GAAP purposes, all of these items, are recorded in other income (loss). Economic Income (Loss) recognizes (a) incentive fees during periods when the fees are not yet crystallized for US GAAP reporting and (b) retainer fees, relating to investment banking activities, earned during the period that would otherwise be deferred until closing for US GAAP reporting. In addition, Economic Income (Loss) expenses are reduced by reimbursement from affiliates, which for US GAAP purposes is presented gross as part of revenue. As further stated below, one major difference between Economic Income (Loss) and US GAAP net income (loss) is that Economic Income (Loss) presents the segments' results of operations without the impact resulting from the full consolidation of any of the Consolidated Funds. The consolidation of these investment funds' results include the pro rata share of the income or loss attributable to other owners of such entities which is reflected in net income (loss) attributable to redeemable non-controlling interest in consolidated subsidiaries in the accompanying condensed consolidated statements of operations. This pro rata share has no effect on the overall financial performance for the investment management segment, as ultimately, this income or loss is not income or loss for the investment management segment itself. Included in Economic Income (Loss) is the actual pro rata share of the income or loss attributable to the Company as an investor in such entities, which is relevant in management making operating decisions and evaluating financial performance.
Leases of Lessee Disclosure [Text Block]	Right-of-use assets and lease liabilities Effective January 1, 2019, the Company adopted ASC Topic 842, Leases ("ASC 842"). The new guidance increases transparency and comparability by requiring the recognition of right-of-use assets and lease liabilities on the condensed consolidated statements of financial condition. The recognition of these lease assets and lease liabilities represents a change from previous US GAAP requirements, which did not require lease assets and lease liabilities to be recognized for most leases. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee, have not significantly changed from previous US GAAP requirements. Under the effective date transition method selected by the Company, leases existing at, or entered into after January 1, 2019 were required to be recognized and measured. Prior period amounts have not been adjusted and continue to be reflected in accordance with the Company’s historical Accounting Standards. In applying ASC 842, the Company made an accounting policy election not to recognize the right-of-use assets and lease liabilities relating to short term leases. Refer to the Company's Annual Report on Form 10-K for the year ended December 31, 2018 for discussions related to the Company's previous lease recognition policies. Implementation of ASC 842 included an analysis of contracts, including real estate leases and service contracts to identify embedded leases, to determine the initial recognition of right-of-use assets and lease liabilities, which required subjective assessment over the determination of the associated discount rates. ASC 842 also provided various practical expedients which were assessed to determine the ultimate impact of ASC 842 upon adoption. The standard includes a package of three practical expedients which permit the Company to not reassess (1) whether any expired or existing contracts are or contain a lease, (2) the lease classification for any expired or existing leases and (3) any initial direct costs for any existing leases as of the effective date. The Company has elected to apply the package of practical expedients, hindsight practical expedient, and land easement practical expedient. The adoption of ASC 842 resulted in the recording of operating lease right-of-use assets of $103.7 million and operating lease liabilities of $110.5 million at January 1, 2019. The Company determines if an arrangement is or contains a lease at inception. The Company’s operating lease arrangements are primarily for real estate and facility leases as well as office equipment. The Company has applied an accounting policy election to combine our lease and nonlease components for our real estate and facility leases. ROU assets represent the Company’s right to use the underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Right-of-use assets and lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. Our variable lease payments consist of nonlease services related to the lease. Variable lease payments are excluded from the right-of-use asset and lease liabilities to the extent they are not based on consumer priced index or a market index and are recognized in the period in which the obligation for those payments is incurred. As most of our leases do not provide an implicit rate and the implicit rate is not readily determinable, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. Right-of-use assets also include any lease payments made and exclude lease incentives. Many of our operating lease agreements include options to extend the lease, which the Company does not include in the determination of the minimum lease term unless the options are reasonably certain to be exercised. Expense for lease payments related to operating leases is recognized on a straight-line basis over the lease term. Please refer to Note 18 for information on the Company’s finance leases (formerly capital leases).

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Property, Plant and Equipment Useful Life	Asset Depreciable Lives Depreciation and/or Amortization Method Telephone and computer equipment 3-5 years Straight-line Computer software 3-8 years Straight-line Furniture and fixtures 5 years Straight-line Leasehold improvements Term of Lease Straight-line Finance lease right-of-use asset 5 years Straight-line
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	Revenue from contracts with customers For the three months ended March 31, 2019 and 2018 , the following table presents revenues from contracts with customers disaggregated by fee type. Three Months Ended March 31, 2019 2018 Revenue from contracts with customers (dollars in thousands) Investment Banking Underwriting fees $ 48,036 $ 71,767 Strategic/financial advisory fees 20,544 14,360 Placement and sales agent fees 9,498 11,861 Expense reimbursements from clients 2,028 — Total Investment Banking Revenue 80,106 97,988 Brokerage Commissions 87,359 94,692 Trade conversion revenue 4,106 3,522 Equity and credit research fees 3,590 3,839 Total Brokerage Revenue from Customers 95,055 102,053 Management Fees 7,141 7,417 Incentive Income 15 16 Total revenue from contracts with customers $ 182,317 $ 207,474

Acquisition (Tables)

Acquisition (Tables)	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Finite-lived Intangible Assets Amortization Expense [Table Text Block]	The estimated amortization expense related to these intangible assets in future periods is as follows: (dollars in thousands) 2019 $ 6,681 2020 8,908 2021 2,608 2022 1,775 2023 — Thereafter — $ 19,972
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 January 2, 2019: (dollars in thousands) Cash and cash equivalents $ 12,236 Fees receivable 7,269 Fixed assets 1,085 Operating lease right-of-use assets 3,200 Intangible assets 22,200 Other assets 667 Compensation payable (637 ) Operating lease liabilities (3,200 ) Due to related parties (4,750 ) Accounts payable, accrued expenses and other liabilities (16,257 ) Total identifiable net assets acquired and liabilities assumed 21,813 Goodwill 81,150 Total estimated purchase price $ 102,963 The allocation of the intangible assets is shown within the following table: Estimated intangible assets acquired Estimated average remaining useful lives (dollars in thousands) (in years) Intangible asset class Trade name $ 900 3 Customer relationships 7,100 4 Backlog 12,600 2 Proprietary software 1,600 3 Total intangible assets $ 22,200
Business Acquisition, Pro Forma Information	Three Months Ended March 31, 2018 (dollars in thousands, except per share data) Revenues $ 236,337 Net income (loss) attributable to Cowen Inc. common stockholders 16,418 Net income (loss) per common share: Basic $ 0.54 Diluted 0.52

Investments of Operating Enti_2

Investments of Operating Entities and Consolidated Funds - (Tables)	3 Months Ended
	Mar. 31, 2019
Investment Holdings [Line Items]
Marketable Securities	As of March 31, 2019 and December 31, 2018 , securities owned, at fair value consisted of the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Common stock (b) $ 428,952 $ 472,299 Preferred stock (b) 11,707 5,617 Warrants and rights (b) 6,787 7,990 Government bonds (a) 93,176 13,398 Corporate bonds (d) 12,012 13,041 Convertible bonds (c) 5,000 3,000 Trade claims 5,487 5,543 $ 563,121 $ 520,888 (a) As of March 31, 2019 , maturities range from April 2019 to February 2041 with an interest rate of 0% to 6.50% . As of December 31, 2018 , maturities ranged from April 2019 to August 2019 with an interest rate of 0% . (b) The Company has elected the fair value option for investments in securities of preferred and common stock with a fair value of $2.9 million and $3.1 million , respectively, at March 31, 2019 and $2.9 million and $7.1 million , respectively, at December 31, 2018 . At December 31, 2018, the Company elected the fair value option for investments in warrants and rights with a fair value of $1.1 million . (c) As of March 31, 2019 , maturities range from June 2020 to March 2022 with an interest rate of 8% . As of December 31, 2018 , the maturity was June 2020 with an interest rate of 8% . (d) As of March 31, 2019 , maturities ranged from April 2019 to March 2026 and interest rates ranged from 0% to 15.5% . As of December 31, 2018 , maturities ranged from April 2019 to April 2049 and interest rates ranged from 2% to 15.50% .
Schedule of Derivative Instruments	The Company's long and short exposure to derivatives is as follows: Receivable on derivative contracts As of March 31, 2019 As of December 31, 2018 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Futures $ — $ — $ 42,288 $ 334 Currency forwards $ 99,791 543 $ 395 1 Swaps $ 141,108 1,915 $ 13,702 917 Options other (a) 325,571 18,971 654,506 23,130 Pay to hold $ — 234 $ — 743 $ 21,663 $ 25,125 (a) Includes index, equity, commodity future and cash conversion options. Payable for derivative contracts As of March 31, 2019 As of December 31, 2018 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Futures $ 12,464 $ 307 $ — $ — Currency forwards $ 6,273 81 $ 96,406 709 Swaps $ 41,031 3,183 $ 52,905 2,162 Options other (a) 140,452 40,012 90,730 13,211 $ 43,583 $ 16,082 (a) Includes index, equity, commodity future and cash conversion options. The following tables present the gross and net derivative positions and the related offsetting amount, as of March 31, 2019 and December 31, 2018 . This table does not include the impact of over-collateralization. Gross amounts not offset in the Condensed Consolidated Statement of Financial Condition Gross amounts recognized Gross amounts offset on the Condensed Consolidated Statements of Financial Condition (a) Net amounts included on the Condensed Consolidated Statements of Financial Condition Financial instruments Cash Collateral pledged (b) Net amounts (dollars in thousands) As of March 31, 2019 Receivable on derivative contracts, at fair value $ 21,663 $ — $ 21,663 $ — $ 2,691 $ 18,972 Payable for derivative contracts, at fair value 43,583 — 43,583 — 3,264 40,319 As of December 31, 2018 Receivable on derivative contracts, at fair value $ 25,125 $ — $ 25,125 $ — $ 1,662 $ 23,463 Payable for derivative contracts, at fair value 16,082 — 16,082 — 2,871 13,211 (a) Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred. (b) Includes the amount of collateral held or posted.
Schedule of Other Investments	As of March 31, 2019 and December 31, 2018 , other investments included the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Portfolio Funds, at fair value (1) $ 145,566 $ 141,236 Equity method investments (2) 54,566 40,171 $ 200,132 $ 181,407
Schedule of Other Investments, Portfolio Funds	The Portfolio Funds, at fair value as of March 31, 2019 and December 31, 2018 , included the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Starboard Value and Opportunity Fund LP (c)(*) $ 36,270 $ 32,579 Formation8 Partners Fund I, L.P. (f) 33,613 34,099 RCG Longview Debt Fund V, L.P. (g)(*) 2,667 4,394 RCG Longview II LP (g) (*) 4,431 4,400 Cowen Healthcare Investments II LP (j) (*) 23,941 21,717 Eclipse Ventures Fund I, L.P. (b) 4,469 4,412 HealthCare Royalty Partners LP (a)(*) 1,825 1,833 Lagunita Biosciences, LLC (d) 4,080 3,833 RCG IO Renergys Sarl (j) (*) 6,329 6,369 Starboard Leaders Fund LP (e)(*) 1,424 1,230 Eclipse SPV I, LP (k)(*) 1,447 1,447 RCG Longview Equity Fund, LP (g) (*) 797 802 RCG Longview Debt Fund VI, LP (g) (*) 1,614 1,586 RCG Park Liberty GP Member LLC (g) (*) 1,129 1,023 HealthCare Royalty Partners II LP (a)(*) 1,106 1,037 RCGL PE MPA, LLC (g)(*) 618 618 RCG LPP2 PNW5 Co-Invest, L.P. (h)(*) 12 296 Other private investment (l)(*) 15,723 15,898 Other affiliated funds (m)(*) 4,071 3,663 $ 145,566 $ 141,236 * 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) Eclipse Ventures Fund I, L.P. is a private equity fund which invests in early stage and growth hardware companies. Distributions will be made when the underlying investments are liquidated. (c) Starboard Value and Opportunity Fund LP 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 investors' 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., RCG Longview II LP, RCG Park Liberty GP Member LLC, RCG Longview Equity Fund, LP, RCGL PE MPA, LLC and RCG Longview Debt Fund VI, LP are real estate private equity structures. The timing of distributions depend on the nature of the underlying investments and therefore will be made either quarterly or when the underlying investments are liquidated. (h) RCG LPP2 PNW5 Co-Invest, L.P. is a single purpose entity formed to participate in a joint venture which acquired five multi-unit residential rental properties located in the Pacific Northwest. RCG LPP2 PNW5 Co-Invest, L.P. is a private equity structure and therefore distributions will be made when the underlying investments are liquidated. (i) Effective January 31, 2018, the Company is no longer affiliated with Quadratic Capital Management LLC. (j) Cowen Healthcare Investments II LP and RCG IO Renergys Sarl are private equity funds. Distributions are made from these funds when cash flows or securities are received from the underlying investments. Investors do not have redemption rights. (k) 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. (l) Other private investment represents the Company's closed end investment in a Portfolio Fund that invests in a wireless broadband communication provider in Italy. (m) 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.
Schedule Equity Method Investments	The following table summarizes equity method investments held by the Company: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Surf House Ocean Views Holdings, LLC $ 8,493 $ 7,589 Starboard Value LP 26,240 12,699 RCG Longview Debt Fund V Partners, LLC 10,362 11,000 RCG Longview Management, LLC 1,167 1,167 RCG Longview Debt Fund VI Partners LLC 1,425 1,254 HealthCare Royalty GP, LLC 149 149 HealthCare Royalty GP II, LLC 187 176 RCG Longview Debt Fund IV Management, LLC 331 331 HealthCare Royalty GP III, LLC 1,645 1,573 Triartisan ES Partners LLC 1,026 1,500 Triartisan PFC Partners LLC 1,000 — RCG Kennedy House, LLC 131 131 RCG Longview Equity Management, LLC 110 114 RCG LPP II GP, LLC 94 272 RCG Park Liberty GP Member Manager, LLC 1,248 1,248 Other 958 968 $ 54,566 $ 40,171 For the period ended March 31, 2019, several equity method investments have met the significance criteria as defined under Regulation S-X Rule 4-08(g) of the SEC guidance ("Reg S-X 4-08(g)"). For the three months ended March 31, 2018 and for the period ended December 31, 2018, no equity method investments have met the significance criteria as defined under Reg S-X 4-08(g). As such, the Company is presenting the following summarized financial information: As of March 31, 2019 (dollars in thousands) Assets Cash $ 3,261 Performance & management fee receivable 73,336 Investments 715,831 Liabilities 20,900 Equity $ 771,528 Three Months Ended March 31, 2019 (dollars in thousands) Revenues $ 68,579 Expenses (18,210 ) Net realized and unrealized gains (losses) 89,560 Net Income $ 139,929
Schedule of Securities Sold, Not yet Purchased	As of March 31, 2019 and December 31, 2018 , securities sold, not yet purchased, at fair value consisted of the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Common stock $ 463,319 $ 194,305 Corporate bonds (a) 3,207 750 Government bonds (b) 84,459 — Preferred stock 3,959 199 Warrants and rights 19,242 53 $ 574,186 $ 195,307 (a) As of March 31, 2019 , the maturities ranged from October 2019 to April 2037 with interest rates ranged from 5.38% to 14.00% . As of December 31, 2018 , the maturities ranged from October 2022 to January 2034 with interest rates ranged from 2.25% to 9.38% .
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 the related offsetting amount as of March 31, 2019 and December 31, 2018 . Gross amounts not offset on the Condensed Consolidated Statement of Financial Condition Gross amounts recognized 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, 2019 Securities borrowed $ 966,857 $ — $ 966,857 $ — $ 957,787 $ — $ 9,070 Securities loaned 852,203 — 852,203 — 858,175 — (5,972 ) As of December 31, 2018 Securities borrowed $ 407,795 $ — $ 407,795 $ — $ 383,593 $ — $ 24,202 Securities loaned 414,852 — 414,852 — 391,310 — 23,542 (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 transactions by remaining contractual maturity and class of collateral pledged as of March 31, 2019 and December 31, 2018 : Open and Overnight Up to 30 days 31 - 90 days Greater than 90 days Total (dollars in thousands) As of March 31, 2019 Securities loaned Common stock $ 710,449 $ — $ — $ — $ 710,449 Corporate bonds 70,565 — — — 70,565 Government bonds 71,189 — — — 71,189 Securities sold, not yet purchased, at fair value - obligation to return securities received as collateral Common stock 79,778 — — — 79,778 As of December 31, 2018 Securities loaned Common stock $ 414,852 $ — $ — $ — $ 414,852
Fair Value, Concentration of Risk	Investment's percentage of the Company's equity Issuer Security Type Country Industry Percentage of Equity Market Value (dollars in thousands) As of March 31, 2019 Linkem Equity Italy Wireless Broadband 8.08 % $ 65,842 As of December 31, 2018 Linkem Equity Italy Wireless Broadband 8.36 % $ 66,439
Consolidated Funds
Investment Holdings [Line Items]
Marketable Securities	As of March 31, 2019 and 2018 , securities owned, at fair value, held by the Consolidated Funds consisted of the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Preferred stock $ 24,322 $ 24,314 Common stock 178,701 95,565 Government bonds (a) 47,034 38,377 Corporate bonds (b) 54,035 24,098 Warrants and rights 4,708 5,279 $ 308,800 $ 187,633 (a) As of March 31, 2019 , maturities ranged from April 2019 to May 2019 and interest rates were 0% . As of December 31, 2018 , maturities ranged from January 2019 to April 2019 and interest rates ranged from 0% . (b) As of March 31, 2019 , maturities ranged from December 2019 to March 2026 and interest rates ranged from 4.90% to 19.00% . As of December 31, 2018 , maturities ranged from August 2020 to March 2026 and interest rates ranged from 5.88% to 7.63% .
Schedule of Derivative Instruments	As of March 31, 2019 and December 31, 2018 , receivable on derivative contracts, at fair value, held by the Consolidated Funds are comprised of: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Currency forwards $ 25 $ 186 Equity swaps 1,196 2,477 Options 1,963 1,753 $ 3,184 $ 4,416 Payable for derivative contracts As of March 31, 2019 and December 31, 2018 , payable for derivative contracts, at fair value, held by the Consolidated Funds are comprised of: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Currency forwards $ 1,327 $ 96 Equity swaps 3,921 713 Options 309 854 $ 5,557 $ 1,663
Schedule of Other Investments, Portfolio Funds	Investments in Portfolio Funds, at fair value As of March 31, 2019 and December 31, 2018 , investments in Portfolio Funds, at fair value, included the following: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Investments of Enterprise LP $ 95,414 $ 97,656 Investments of Merger Fund 91,432 88,739 $ 186,846 $ 186,395
Enterprise Master
Investment Holdings [Line Items]
Marketable Securities	Securities owned by Enterprise Master, at fair value As of December 31, 2018 (dollars in thousands) Common stock $ 469 $ 469
Schedule of Other Investments, Portfolio Funds	Portfolio Funds, owned by Enterprise Master, at fair value As of December 31, 2018 Strategy (dollars in thousands) RCG Special Opportunities Fund, Ltd* Multi-Strategy $ 111,548 Other Private Investments Various 846 $ 112,394 * Affiliates of the Company.
Merger Master
Investment Holdings [Line Items]
Schedule of Derivative Instruments	Receivable on derivative contracts, at fair value, owned by Merger Master As of March 31, 2019 As of December 31, 2018 Description (dollars in thousands) Options $ 1,973 $ 3,450 Equity swaps 219 5,320 $ 2,192 $ 8,770 Payable for derivative contracts, at fair value, owned by Merger Master As of March 31, 2019 As of December 31, 2018 Description (dollars in thousands) Options $ 287 $ 1,430 Currency forwards 22,523 270 Equity swaps 1,547 28 $ 24,357 $ 1,728

Fair Value Measurements for O_2

Fair Value Measurements for Operating Entities and Consolidated Funds (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 and December 31, 2018 : Assets at Fair Value as of March 31, 2019 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities owned, at fair value Government bonds $ 13,398 $ 79,778 $ — $ 93,176 Preferred stock 4,550 — 7,157 11,707 Common stock 421,177 2,824 4,951 428,952 Convertible bonds — — 5,000 5,000 Corporate bonds — 11,751 261 12,012 Trade claims — — 5,487 5,487 Warrants and rights 6,333 — 454 6,787 Receivable on derivative contracts, at fair value Currency forwards — 543 — 543 Swaps — 1,915 — 1,915 Options 18,971 — — 18,971 Pay to hold — 234 — 234 Consolidated Funds Securities owned, at fair value Government bonds 47,034 — — 47,034 Preferred stock — — 24,322 24,322 Common stock 177,684 — 1,017 178,701 Corporate bonds — 54,035 — 54,035 Warrants and rights — — 4,708 4,708 Receivable on derivative contracts, at fair value Currency forwards — 25 — 25 Equity swaps — 1,196 — 1,196 Options 1,963 — — 1,963 $ 691,110 $ 152,301 $ 53,357 $ 896,768 Percentage of total assets measured at fair value on a recurring basis 77.1 % 17.0 % 5.9 % Portfolio Funds measured at net asset value (a) 145,566 Consolidated Funds' Portfolio Funds measured at net asset value (a) 186,846 Equity method investments 54,566 Total investments $ 1,283,746 Liabilities at Fair Value as of March 31, 2019 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities sold, not yet purchased, at fair value Government bonds $ — $ 84,459 $ — $ 84,459 Common stock 463,319 — — 463,319 Corporate bonds — 3,207 — 3,207 Preferred stock 3,959 — — 3,959 Warrants and rights 19,242 — — 19,242 Payable for derivative contracts, at fair value Futures 307 — — 307 Currency forwards — 81 — 81 Swaps — 3,183 — 3,183 Options 38,279 — 1,733 40,012 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 29,536 29,536 Consolidated Funds Payable for derivative contracts, at fair value Currency forwards — 1,327 — 1,327 Options 309 — — 309 Equity swaps — 3,921 — 3,921 $ 525,415 $ 96,178 $ 31,269 $ 652,862 Percentage of total liabilities measured at fair value 80.5 % 14.7 % 4.8 % (a) In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table 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 second quarter of 2016 and the first quarter of 2019, 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 2019 and December 2023, respectively. For the acquisition that closed during 2016, the Company estimated the contingent consideration liability using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. For the acquisition that closed during 2019, the Company estimated the contingent consideration liability using the present value of the monte carlo simulated revenue. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts as of March 31, 2019 can range from $1.6 million to $40.0 million . Assets at Fair Value as of December 31, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities owned, at fair value Government bonds $ 13,398 $ — $ — $ 13,398 Preferred stock 449 — 5,168 5,617 Common stock 459,601 2,848 9,850 472,299 Convertible bonds — — 3,000 3,000 Corporate bonds — 13,041 — 13,041 Trade claims — — 5,543 5,543 Warrants and rights 6,324 — 1,666 7,990 Receivable on derivative contracts, at fair value Futures 334 — — 334 Currency forwards — 1 — 1 Swaps — 917 — 917 Options 23,130 — — 23,130 Pay to hold — 743 — 743 Consolidated Funds Securities owned, at fair value Government bonds 38,377 — — 38,377 Preferred stock — — 24,314 24,314 Common stock 95,471 — 94 95,565 Corporate bonds — 24,098 — 24,098 Warrants and rights — — 5,279 5,279 Receivable on derivative contracts, at fair value Currency forwards — 186 — 186 Equity swaps — 2,477 — 2,477 Options 1,753 — — 1,753 $ 638,837 $ 44,311 $ 54,914 $ 738,062 Percentage of total assets measured at fair value on a recurring basis 86.6 % 6.0 % 7.4 % Portfolio Funds measured at net asset value (a) 141,236 Consolidated Funds' Portfolio Funds measured at net asset value (a) 186,395 Equity method investments 40,171 Total investments $ 1,105,864 Liabilities at Fair Value as of December 31, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities sold, not yet purchased, at fair value Common stock $ 194,305 $ — $ — $ 194,305 Corporate bonds — 750 — 750 Preferred stock 199 — — 199 Warrants and rights 53 — — 53 Payable for derivative contracts, at fair value Currency forwards — 709 — 709 Swaps — 2,162 — 2,162 Options 11,115 — 2,096 13,211 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 3,070 3,070 Consolidated Funds Payable for derivative contracts, at fair value Currency forwards — 96 — 96 Options 854 — — 854 Equity swaps — 713 — 713 $ 206,526 $ 4,430 $ 5,166 $ 216,122 Percentage of total liabilities measured at fair value 95.6 % 2.0 % 2.4 % (a) In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table 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 the acquisition that closed during the second quarter of 2016, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired business, if certain targets are achieved through the periods ended December 2020. The Company estimated the contingent consideration liability using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts as of December 31, 2018 can range from $2.8 million to $3.4 million .
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, 2019 and 2018 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, 2019 Balance at December 31, 2018 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at March 31, 2019 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 5,168 $ — $ — $ 2,000 $ — $ (11 ) $ 7,157 $ (11 ) Common stock 9,850 — — 1,262 (5,952 ) (209 ) 4,951 (7 ) Convertible bonds 3,000 — — 5,000 (3,000 ) — 5,000 — Corporate bond — — — 261 — — 261 — Options, liability 2,096 — — — (4 ) (359 ) 1,733 (359 ) Warrants and rights 1,666 — — — (116 ) (1,096 ) 454 (109 ) Trade claims 5,543 — — — (56 ) — 5,487 — Contingent consideration liability 3,070 — — 27,700 (1,234 ) — 29,536 — Consolidated Funds Preferred stock 24,314 — — — — 8 24,322 8 Common stock 94 — — 407 — 516 1,017 516 Warrants and rights 5,279 — — (1,088 ) — 517 4,708 (570 ) Three Months Ended March 31, 2018 Balance at December 31, 2017 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at March 31, 2018 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 8,115 $ — $ — $ 1,415 $ (478 ) $ (235 ) $ 8,817 $ 486 Common stock 7,570 — — 310 (133 ) (347 ) 7,400 412 Convertible bonds 282 — — — (307 ) 25 — — Options, asset 1,455 — — — (1,455 ) — — — Options, liability 22,401 — — — — (1,006 ) 21,395 (1,006 ) Warrants and rights 2,517 — — — — (815 ) 1,702 510 Trade claim 5,950 — — — — 5 5,955 5 Lehman claim 301 — — — — 11 312 12 Contingent consideration liability 3,440 — — — — — 3,440 — Consolidated Funds Preferred stock 50,445 — (38,552 ) (a) — — — 11,893 — Common stock 50 — — — — — 50 — Warrants and rights 3,568 — (20 ) (a) — — 1,706 5,254 1,706 (1) Unrealized gains/losses are reported in other income (loss) in the accompanying condensed consolidated statements of operations. (a) The Company deconsolidated an investment fund.
Fair Value Inputs, Assets, Quantitative Information	The following table includes quantitative information as of March 31, 2019 and December 31, 2018 for financial instruments classified within level 3. The table below quantifies information about the significant unobservable inputs used in the fair value measurement of the Company's level 3 financial instruments. Quantitative Information about Level 3 Fair Value Measurements Fair Value at March 31, 2019 Valuation Techniques Unobservable Inputs Range Level 3 Assets (dollars in thousands) Common and preferred stocks $ 320 Discounted cash flows Discount rate 8% Trade claims 25 Discounted cash flows Discount rate 20% Warrants and rights 5,162 Model based Discounted cash flows Volatility Discount rate 30% 7% to 8% Other level 3 assets (a) 47,850 Total level 3 assets $ 53,357 Level 3 Liabilities Options 1,733 Option pricing models Volatility 35% to 40% Contingent consideration liability 29,536 Discounted cash flows Monte Carlo simulation Discount rate Volatility 14%-22% 14%-15% Total level 3 liabilities $ 31,269 Quantitative Information about Level 3 Fair Value Measurements Fair Value at Valuation Techniques Unobservable Inputs Range Level 3 Assets (dollars in thousands) Common and preferred stocks $ 4,323 Guideline companies/Discounted cash flows Discount rate 8%-14% Trade claims 25 Discounted cash flows Discount rate 20% Warrants and rights 1,666 Model based Discounted cash flows Discount rate 7% to 9% Other level 3 assets (a) 48,900 Total level 3 assets $ 54,914 Level 3 Liabilities Options 2,096 Option pricing models Volatility 35% to 40% Contingent consideration liability 3,070 Discounted cash flows Projected cash flow and discount rate 23% Total level 3 liabilities $ 5,166 (a) The quantitative disclosures exclude financial instruments for which the determination of fair value is based on prices from recent transactions.
Fair Value Measurements, Nonrecurring	The following table presents the carrying values and fair values, at March 31, 2019 and December 31, 2018 , 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 2 . March 31, 2019 December 31, 2018 Fair Value Hierarchy Carrying Amount Fair Value Carrying Amount Fair Value (dollars in thousands) Financial Assets Operating companies Cash and cash equivalents $ 235,838 $ 235,838 $ 259,148 $ 259,148 Level 1 Cash collateral pledged 6,420 6,420 6,318 6,318 Level 2 Segregated cash 136,964 136,964 176,647 176,647 Level 1 Securities borrowed 966,857 $ 957,787 407,795 383,593 Level 2 Loans receivable 34,898 34,898 (d) 36,021 36,021 (d) Level 3 Consolidated Funds Cash and cash equivalents 2,178 2,178 38,118 38,118 Level 1 Financial Liabilities Securities loaned 852,203 858,175 414,852 391,310 Level 2 Convertible debt 115,099 (a) 142,628 (b) 134,489 (a) 157,433 (b) Level 2 Notes payable and other debt 264,273 207,543 (c) 262,965 258,546 (c) Level 2 (a) The carrying amount of the convertible debt includes an unamortized discount of $23.4 million and $24.9 million as of March 31, 2019 and December 31, 2018 , 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.

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, 2019
Receivables from Brokers-Dealers and Clearing Organizations [Abstract]
Schedule of Due to (from) Broker-Dealers and Clearing Organizations	As of March 31, 2019 and December 31, 2018 , amounts receivable from brokers, dealers and clearing organizations include: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Broker-dealers $ 608,841 $ 692,581 Securities failed to deliver 44,037 72,918 Clearing organizations 2,702 15,319 Securities borrowed interest receivable 7,492 5,295 $ 663,072 $ 786,113 As of March 31, 2019 and December 31, 2018 , amounts payable to brokers, dealers and clearing organizations include: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Broker-dealers $ 134,424 $ 159,443 Securities failed to receive 23,619 28,826 Clearing organizations 9,876 36,338 Securities loaned interest payable 6,613 4,124 $ 174,532 $ 228,731

Redeemable Non-Controlling In_2

Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds (Tables)	3 Months Ended
	Mar. 31, 2019
Noncontrolling Interest [Abstract]
Redeemable non-controlling interests in consolidated subsidiaries and funds	Redeemable non-controlling interests in consolidated subsidiaries and investment funds and the related net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds are comprised as follows: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Redeemable non-controlling interests in consolidated subsidiaries and investment funds Operating companies $ 13,568 $ 10,434 Consolidated Funds 404,709 274,346 $ 418,277 $ 284,780
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	Three Months Ended March 31, 2019 2018 (dollars in thousands) Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds Operating companies $ 1,806 $ 1,620 Consolidated Funds 400 9,536 $ 2,206 $ 11,156

Share-Based Compensation and _2

Share-Based Compensation and Employee Ownership Plans (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [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, 2019 and 2018 : Three Months Ended March 31, 2019 Three Months Ended March 31, 2018 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 5,962,295 $ 15.73 5,579,293 $ 16.33 Granted 1,781,949 16.97 2,108,184 14.23 Vested (768,468 ) 16.69 (858,433 ) 16.2 Canceled (233,333 ) 14.12 — — Forfeited (144,346 ) 13.84 (21,412 ) 13.11 Ending balance outstanding 6,598,097 $ 16.05 6,807,632 $ 15.71 Included in the restricted share and restricted stock unit activity are performance linked restricted stock units of 481,438 which were awarded to employees of the Company in December 2013 and January 2014. An additional 700,000 performance linked restricted stock units were awarded in March 2016. Of the awards granted, 130,438 have been forfeited and 233,333 have been canceled, as they did not meet the performance criteria, through March 31, 2019 . The remaining awards, included in the outstanding balance as of March 31, 2019 , will vest between May 2019 and December 2020 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 150% 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.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Operating Lease, Lease Income [Table Text Block]	For the three months ended March 31, 2019 , quantitative information regarding the Company's operating lease obligations reflected in the accompanying condensed consolidated statement of operations were as follows: Three Months Ended March 31, 2019 (dollars in thousands) Lease Cost Operating lease cost $ 6,010 Short-term lease cost 128 Variable lease cost 299 Sublease income (267 ) Total lease costs $ 6,170
Future Minimum Annual Lease and Service Payments	Three Months Ended March 31, 2019 (dollars in thousands) Lease Cost Operating lease cost $ 6,010 Short-term lease cost 128 Variable lease cost 299 Sublease income (267 ) Total lease costs $ 6,170 The following table summarizes the supplemental cash flow information and certain other information related to operating leases for the three months ended March 31, 2019 : Three Months Ended March 31, 2019 (dollars in thousands) Other Information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 7,793 Weighted average remaining lease term - operating leases (in Years) 5.73 Weighted average discount rate - operating leases 4.15 % As of March 31, 2019 , 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) 2019 $ 770 $ 16,967 2020 384 23,828 2021 144 23,270 2022 55 20,023 2023 29 16,950 Thereafter 5 23,552 Total Operating Leases 1,387 124,590 Less discount 365 14,950 Less short term leases — 128 Less not yet commenced leases — 2,165 Total Lease Liability $ 1,022 $ 107,347 (a) The Company has entered into various agreements to sublease certain of its premises. (b) The Company has entered into a new operating real estate lease that is expected to commence during the second quarter of 2019. The Company is currently planning improvements to the leased asset of which the lessor has granted a tenant allowance of $0.4 million . Payments on the lease asset do not begin until five months after the Company completes its leasehold improvements and begins occupying the space. The total rent payment commitments are $2.2 million , which are included in the table.	Prior to the adoption of the new lease accounting guidance, the minimum rental commitments under non-cancelable operating leases at December 31, 2018, were as follows: Equipment Leases (a) Service Payments Real Estate and other Facility Rental (b) (dollars in thousands) 2019 $ 2,434 $ 21,758 $ 24,584 2020 1,492 7,514 22,608 2021 1,382 1,877 22,321 2022 1,123 1,372 19,166 2023 374 735 16,204 Thereafter — 735 21,478 $ 6,805 $ 33,991 $ 126,361 (a) Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 18 for further information on the capital lease minimum payments which are included in the table. (b) The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $1.4 million , $1.1 million , and $2.2 million for the years ended December 31, 2018 , 2017 , and 2016 respectively.
Other Commitments	The following table summarizes unfunded commitments as of March 31, 2019 : Entity Unfunded Commitments Commitment term (dollars in millions) Real estate (a) $ 24.3 (a) HealthCare Royalty Partners funds (b) 5.9 2 years Eclipse Ventures Fund I, L.P. (formerly Formation8 Partners Hardware Fund I, L.P.) 0.1 5 years Lagunita Biosciences, LLC 1.0 3 years Eclipse Fund II, L.P. 0.3 6 years Eclipse Continuity Fund I, L.P. 0.3 7 years Cowen Healthcare Investments II LP 6.9 2 years (a) The Company had unfunded commitments pertaining to capital commitments in five real estate investments held by the Company, all of which pertain to related party investments. Such commitments can be called at any time between two to four years, subject to advance notice. (b) 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_2

Convertible Debt and Notes Payable (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Direct Financing Lease, Lease Income [Table Text Block]	As of March 31, 2019 and December 31, 2018, the remaining balance on these finance leases was $4.6 million and $5.0 million , respectively. For the three months ended March 31, 2019 , quantitative information regarding the Company's finance lease obligations reflected in the accompanying condensed consolidated statement of operations, the supplemental cash flow information and certain other information related to finance leases were as follows: Three Months Ended March 31, 2019 2018 (dollars in thousands) Lease Cost Finance Lease Cost: Amortization of finance lease right-of-use assets $ 368 $ 352 Interest on lease liabilities 63 43 Other Information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from finance leases 63 43 Financing cash flows from finance leases $ 394 $ 506
Schedule of Debt and Capital Lease Obligations	As of March 31, 2019 and December 31, 2018 , the Company's outstanding debt was as follows: As of March 31, 2019 As of December 31, 2018 (dollars in thousands) Convertible debt $ 115,099 $ 134,489 Notes payable 229,863 229,740 Term loan 28,200 28,200 Other notes payable 1,579 — Finance lease obligations 4,631 5,025 $ 379,372 $ 397,454
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, 2019 , are as follows: Convertible Debt Notes Payable Term loan Other Notes Payable Finance Lease (dollars in thousands) 2019 $ 4,050 $ 13,420 $ 28,508 $ 2,171 $ 896 2020 4,050 17,893 — — 1,360 2021 4,050 17,893 — — 1,360 2022 139,050 17,893 — — 1,127 2023 — 17,893 — — 374 Thereafter — 352,197 — — — Subtotal 151,200 437,189 28,508 2,171 5,117 Less (a) (36,101 ) (207,326 ) (308 ) (592 ) (486 ) Total $ 115,099 $ 229,863 $ 28,200 $ 1,579 $ 4,631 (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 convertible debt.
Schedule of Line of Credit Facilities	As of March 31, 2019 , the Company has the following seven 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 collateral for reinsurance agreements which amounted to $1.2 million , as of March 31, 2019 , and $1.0 million , as of December 31, 2018 , which is anticipated to be due March 2021 . Location Amount Maturity (dollars in thousands) Boston $ 389 March 2020 New York $ 358 April 2020 New York $ 71 October 2019 New York $ 397 October 2019 New York $ 1,687 October 2019 New York $ 1,611 November 2019 San Francisco $ 708 October 2025

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 : Treasury stock shares Cost Average cost per share Balance outstanding at December 31, 2018 15,336,871 $ 234,142 $ 15.27 Shares purchased for minimum tax withholding under the Equity Plans or other similar transactions 323,227 4,671 14.45 Shares of stock received in respect of indemnification claims 3,331 48 14.41 Purchase of treasury stock 315,400 4,658 14.77 Balance outstanding at March 31, 2019 15,978,829 $ 243,519 $ 15.24

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2019
Accumulated Other Comprehensive Income / (Loss) [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Three Months Ended March 31, 2019 2018 (dollars in thousands) Beginning Balance $ (5 ) $ (8 ) Foreign currency translation — 1 Ending Balance $ (5 ) $ (7 )

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share, Basic and Diluted	The computation of earnings per share is as follows: Three Months Ended March 31, 2019 2018 (dollars in thousands, except share and per share data) Net income (loss) $ 11,989 $ 28,009 Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds 2,206 11,156 Net income (loss) attributable to Cowen Inc. 9,783 16,853 Preferred stock dividends 1,698 1,698 Net income (loss) attributable to Cowen Inc. common stockholders $ 8,085 $ 15,155 Shares for basic and diluted calculations: Weighted average shares used in basic computation 29,750 29,625 Restricted stock 1,875 867 Weighted average shares used in diluted computation 31,625 30,492 Earnings (loss) per share: Basic $ 0.27 $ 0.51 Diluted $ 0.26 $ 0.50

Segment Reporting (Tables)

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2019
Segment Reporting [Abstract]
Segment Reporting Information, by Segment	The following tables set forth operating results for the Company's investment management and investment bank segments and related adjustments necessary to reconcile the Company's Economic Income (Loss) measure to arrive at the Company's consolidated US GAAP net income (loss): Three Months Ended March 31, 2019 Adjustments Investment Investment Bank Total Economic Income (Loss) Funds Consolidation Other Adjustments US GAAP Net Income (Loss) (dollars in thousands) Revenues Investment banking $ — $ 82,991 $ 82,991 $ — $ (2,885 ) (a) $ 80,106 Brokerage — 105,157 105,157 — (7,694 ) (b) 97,463 Management fees 9,633 798 10,431 (501 ) (2,789 ) (c) 7,141 Incentive income (loss) 16,747 — 16,747 (544 ) (16,188 ) (c)(a) 15 Investment income (loss) 7,029 9,955 16,984 — (16,984 ) (d)(e) — Interest and dividends — — — — 29,092 (d) 29,092 Reimbursement from affiliates — — — (34 ) 322 (f) 288 Aircraft lease revenue — — — — — (e) — Reinsurance premiums — — — — 6,591 (g) 6,591 Other revenue 439 720 1,159 — (98 ) (g) 1,061 Consolidated Funds revenues — — — 2,340 — 2,340 Total revenues 33,848 199,621 233,469 1,261 (10,633 ) 224,097 Interest expense (Economic Income/(Loss)) / Interest and dividend expense (US GAAP) 2,806 3,758 6,564 — 22,520 (d) 29,084 Total net revenues 31,042 195,863 226,905 1,261 (33,153 ) 195,013 Expenses Non interest expense 22,023 185,162 207,185 — 12,122 (d)(h)(i) 219,307 Consolidated Funds expenses — — — 1,482 — 1,482 Total expenses 22,023 185,162 207,185 1,482 12,122 220,789 Total other income (loss) — — — 621 40,321 (d)(k)(j) 40,942 Income taxes expense / (benefit) — — — — 3,177 (h) 3,177 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds 2,748 — 2,748 400 (942 ) 2,206 Income (Loss) attributable to Cowen Inc. $ 6,271 $ 10,701 $ 16,972 $ — $ (7,189 ) $ 9,783 Less: Preferred stock dividends 1,698 1,698 Income (Loss) attributable to Cowen Inc. common stockholders 15,274 $ 8,085 Add back: Depreciation and amortization expense 4,956 Economic Operating Income (Loss) attributable to Cowen Inc. common stockholders $ 20,230 Three Months Ended March 31, 2018 Adjustments Investment Investment Bank Total Economic Income (Loss) Funds Consolidation Other Adjustments US GAAP Net Income (Loss) (dollars in thousands) Revenues Investment banking $ — $ 93,924 $ 93,924 $ — $ 4,064 (a) $ 97,988 Brokerage — 114,071 114,071 — (8,338 ) (b) 105,733 Management fees 12,355 771 13,126 (1,203 ) (4,506 ) (c) 7,417 Incentive income (loss) 5,197 — 5,197 (9 ) (5,172 ) (a) (c) 16 Investment income (loss) 11,896 2,405 14,301 — (14,301 ) (d)(e) — Interest and dividends — — — — 25,954 (d) 25,954 Reimbursement from affiliates — — — (68 ) 445 (f) 377 Aircraft lease revenue — — — — 715 (e) 715 Reinsurance premiums — — — — 8,647 (g) 8,647 Other revenue 361 527 888 — 448 (g) 1,336 Consolidated Funds revenues — — — 3,201 — 3,201 Total revenues 29,809 211,698 241,507 1,921 7,956 251,384 Interest expense (Economic Income/(Loss)) / Interest and dividend expense (US GAAP) 3,854 2,104 5,958 — 18,582 (d) 24,540 Total net revenues 25,955 209,594 235,549 1,921 (10,626 ) 226,844 Expenses Non interest expense 22,881 186,452 209,333 — 13,982 (d)(h)(i) 223,315 Consolidated Funds expenses — — — 2,431 — 2,431 Total expenses 22,881 186,452 209,333 2,431 13,982 225,746 Total other income (loss) — — — 10,047 23,787 (d)(j)(k) 33,834 Income taxes expense / (benefit) — — — — 6,923 (h) 6,923 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds 2,158 — 2,158 9,537 (539 ) 11,156 Income (Loss) attributable to Cowen Inc. $ 916 $ 23,142 $ 24,058 $ — $ (7,205 ) $ 16,853 Less: Preferred stock dividends 1,698 1,698 Income (Loss) attributable to Cowen Inc. common stockholders 22,360 $ 15,155 Add back: Depreciation and amortization expense 2,986 Economic Operating Income (Loss) attributable to Cowen Inc. common stockholders $ 25,346 The following is a summary of the adjustments made to US GAAP net income (loss) for the segment to arrive at Economic Income (Loss): Funds Consolidation: The impacts of consolidation and the related elimination entries of the Consolidated Funds are not included in Economic Income (Loss). Adjustments to reconcile to US GAAP net income (loss) included elimination of incentive income and management fees earned from the Consolidated Funds and addition of investment fund expenses excluding management fees paid, investment fund revenues and investment income (loss). Other Adjustments: (a) Economic Income (Loss) presents underwriting expenses net of investment banking revenues, expenses reimbursed from clients within their respective expense category and records income from uncrystallized incentive fees. Economic Income (Loss) also records retainer fees, relating to investment banking activities, collectible during the period that would otherwise be deferred until closing for US GAAP reporting. (b) Economic Income (Loss) brokerage revenues included net securities borrowed and securities loaned activities. (c) Economic Income (Loss) recognizes revenues (i) net of distribution fees paid to agents and (ii) our proportionate share of management and incentive fees of certain real estate operating entities, the healthcare royalty business and the activist business. (d) Economic Income (Loss) recognizes Company income from proprietary trading (including interest and dividends). (e) Aircraft lease revenue is shown net of expenses in investment income for Economic Income (Loss). (f) Reimbursement from affiliates is shown as a reduction of Economic Income expenses, but is included as a part of revenues under US GAAP. (g) Economic Income (Loss) recognizes underwriting income from the Company's insurance related activities, net of expenses, within other revenue. (h) Economic Income (Loss) excludes income taxes and acquisition related adjustments as management does not consider these items when evaluating the performance of the segment. (i) Economic Income (Loss) recognizes the Company's proportionate share of expenses, for certain real estate operating entities and the activist business, for which the investments are recorded under the equity method of accounting for investments. (j) Economic Income (Loss) excludes gain/(loss) on debt extinguishment. (k) Economic Income (Loss) excludes the bargain purchase gain which resulted from the Convergex Group acquisition.

Regulatory Requirements Regulat

Regulatory Requirements Regulatory (Tables)	3 Months Ended
	Mar. 31, 2019
Regulatory [Abstract]
Computation of Net Capital under Securities and Exchange Commission Regulation	As of March 31, 2019 , these regulated broker-dealers had regulatory net capital or financial resources, regulatory net capital requirements or minimum FCA requirement and excess as follows : Subsidiary Net Capital Minimum Net Capital Requirement Excess Net Capital (dollars in millions) Cowen and Company $101.5 $1.0 $100.5 Cowen Execution $116.8 $2.0 $114.8 ATM Execution $3.2 $0.3 $2.9 Cowen Prime $8.4 $0.3 $8.1 Westminster $19.4 $0.3 $19.1 Cowen International Ltd $14.9 $9.9 $5.0 Cowen Execution Ltd $5.0 $3.2 $1.8

Guarantees and Off-Balance Sh_2

Guarantees and Off-Balance Sheet Arrangements Details (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2019 . Lender Contractual Amount Available Amount Maturity Date Description Pledge Lines (dollars in thousands) Texas Capital Bank $ 75,000 $ 75,000 None Secured Depository Trust Company Pledge Line 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 300,000 300,000 Revolving Credit Facility BMO Harris Bank Canadian Imperial Bank of Commerce Texas Capital Bank 70,000 70,000 August 23, 2019 (Syndicated) Unsecured liquidity facility to cover increases in National Securities Clearing Corporation margin deposit requirements Total Credit Lines $ 370,000 $ 370,000

Organization and Business (Deta

Organization and Business (Details)	3 Months Ended
	Mar. 31, 2019segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business segments	2

Significant Accounting Polici_4

Significant Accounting Policies All Other - Quarterly (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)cowenfund	Mar. 31, 2018USD ($)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Operating right of use assets	$ 101,796		$ 103,694	$ 0
Operating Lease, Liability	108,368		$ 110,505	0
Total net assets of consolidated VIEs	571,200			427,500
Cumulative Effect on Retained Earnings, Net of Tax		$ 559
Fees receivable	(130,099)			(111,946)
Other investments	200,132			181,407
Total Stockholders' Equity	814,782			$ 794,407
Investment banking	80,106	97,988
Revenues	224,097	251,384
Underwriting expenses	3,131	4,063
Costs and Expenses	220,789	225,746
Net gains (losses) on securities, derivatives and other investments	39,084	15,969
Net Income (Loss) Available to Common Stockholders, Basic	8,085	15,155
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	11,989	28,009
Gain (Loss) on Investments (excluding broker dealer)	(32,320)	(7,924)
Fees receivable, net of allowance	(10,884)	(30,996)
Payments to Acquire Other Investments	(5,462)	(11,475)
Revenue from Contract with Customer, Excluding Assessed Tax	182,317	207,474
Management Fees	7,141	7,417
Incentive income	$ 15	16
Other investment companies
Number of funds, Consolidated | cowenfund	4
Furniture and Fixtures
Property, Plant and Equipment, Useful Life	5 years
Assets Held under Capital Leases
Property, Plant and Equipment, Useful Life	5 years
Minimum
Redeemable Noncontrolling Interest, Redemption Fee, Percent	1.00%
Minimum | Telephone and computer equipment
Property, Plant and Equipment, Useful Life	3 years
Minimum | Proprietary software
Property, Plant and Equipment, Useful Life	3 years
Maximum
Redeemable Noncontrolling Interest, Redemption Fee, Percent	5.00%
Maximum | Telephone and computer equipment
Property, Plant and Equipment, Useful Life	5 years
Maximum | Proprietary software
Property, Plant and Equipment, Useful Life	8 years
Hedge Funds | Maximum
Asset Management Fees, Percent Fee	2.00%
Real Estate Funds | Minimum
Asset Management Fees, Percent Fee	0.25%
Real Estate Funds | Maximum
Asset Management Fees, Percent Fee	1.50%
Other Healthcare Royalty Partners | Minimum
Asset Management Fees, Percent Fee	0.20%
Other Healthcare Royalty Partners | Maximum
Asset Management Fees, Percent Fee	1.00%
During investment period | Healthcare Royalty Partners | Minimum
Asset Management Fees, Percent Fee	1.00%
During investment period | Healthcare Royalty Partners | Maximum
Asset Management Fees, Percent Fee	2.00%
After investment period | Healthcare Royalty Partners | Minimum
Asset Management Fees, Percent Fee	0.50%
After investment period | Healthcare Royalty Partners | Maximum
Asset Management Fees, Percent Fee	2.00%
Hedge Funds
Incentive Fees, Percent Fee	20.00%
Underwriting fees
Revenue from Contract with Customer, Excluding Assessed Tax	$ 48,036	71,767
Strategic/financial advisory fees
Revenue from Contract with Customer, Excluding Assessed Tax	20,544	14,360
Placement and sales agent fees
Revenue from Contract with Customer, Excluding Assessed Tax	9,498	11,861
Expense reimbursements from clients
Revenue from Contract with Customer, Excluding Assessed Tax	2,028	0
Investment Bank
Revenue from Contract with Customer, Excluding Assessed Tax	80,106	97,988
Commissions
Revenue from Contract with Customer, Excluding Assessed Tax	87,359	94,692
Trade conversion
Revenue from Contract with Customer, Excluding Assessed Tax	4,106	3,522
Equity and credit research fees
Revenue from Contract with Customer, Excluding Assessed Tax	3,590	3,839
Brokerage
Revenue from Contract with Customer, Excluding Assessed Tax	$ 95,055	$ 102,053

Acquisition (Narrative) (Detail

Acquisition (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 02, 2019	Jan. 01, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Purchase of business	$ 48,581	$ 0
Revenues	224,097	251,384
Net income (loss) attributable to Cowen Inc.	9,783	16,853
Operating lease right-of-use assets	101,796			$ 103,694	$ 0
Quarton
Business Acquisition [Line Items]
Total estimated purchase price	103,000
Purchase of business	75,300
Business combination, contingent consideration, liability			$ 40,000
Other payments to acquire businesses	600
Business combination, contingency liability, retention of employee, bonus pool, maximum	$ 10,000
Business combination, contingency liability, retention of employee, bonus pool, period	5 years
Business combination, contingency liability, retention of employee, bonus pool, annual maximum payout	$ 2,500
Intangible assets			22,200
Amortization of Intangible Assets	2,200
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed		$ 1,100
Revenues	5,300
Net income (loss) attributable to Cowen Inc.	$ 1,600
Operating lease right-of-use assets			$ 3,200
Common Stock Class A | Quarton
Business Acquisition [Line Items]
Business acquisition, equity interest issued or issuable, number of shares	1,033,350
Business acquisition, share price			$ 14.52
Fair Value, Measurements, Recurring | Level 3 | Quarton
Business Acquisition [Line Items]
Business combination, contingent consideration, liability			$ 27,700
Minimum | Quarton
Business Acquisition [Line Items]
Business combination, contingent consideration, liability			10,000
Maximum | Quarton
Business Acquisition [Line Items]
Business combination, contingent consideration, liability			$ 40,000

Acquisition (Preliminary Purcha

Acquisition (Preliminary Purchase Price Allocation) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 02, 2019	Jan. 01, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Operating lease right-of-use assets	$ 101,796		$ 103,694	$ 0
Operating lease liabilities	(108,368)		$ (110,505)	$ 0
Quarton
Business Acquisition [Line Items]
Operating lease right-of-use assets		$ 3,200
Intangible assets		22,200
Operating lease liabilities		(3,200)
Total estimated purchase price	103,000
Scenario, Plan | Quarton
Business Acquisition [Line Items]
Cash and cash equivalents		12,236
Fees receivable		7,269
Fixed assets		1,085
Intangible assets		22,200
Other assets		667
Compensation payable		637
Due to related parties		4,750
Accounts payable, accrued expenses and other liabilities		16,257
Total identifiable net assets acquired and liabilities assumed		$ 21,813
Goodwill	81,150
Total estimated purchase price	$ 102,963

Acquisition (Intangible Assets)

Acquisition (Intangible Assets) (Details) - Quarton - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 02, 2019
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross		$ 22,200
Trade name
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross		900
Finite-Lived Intangible Asset, Useful Life	3 years
Customer relationships
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross		7,100
Finite-Lived Intangible Asset, Useful Life	4 years
Backlog
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross		12,600
Finite-Lived Intangible Asset, Useful Life	2 years
Proprietary software
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Gross		$ 1,600
Finite-Lived Intangible Asset, Useful Life	3 years

Acquisition (Pro Forma) (Detail

Acquisition (Pro Forma) (Details) - Quarton $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)$ / shares
Business Acquisition [Line Items]
Revenues | $	$ 236,337
Net income (loss) | $	$ 16,418
Basic (usd per share) | $ / shares	$ 0.54
Diluted (usd per share) | $ / shares	$ 0.52

Acquisition (Amortization Expen

Acquisition (Amortization Expense) (Details) - Scenario, Plan - Quarton $ in Thousands	Mar. 31, 2019USD ($)
Business Acquisition [Line Items]
2019	$ 6,681
2020	8,908
2023	2,608
2024	1,775
2025	0
Thereafter	0
Finite-Lived Intangible Assets, Net	$ 19,972

Cash Collateral Pledged (Detail

Cash Collateral Pledged (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Cash collateral pledged	$ 6,420	$ 6,318	$ 14,786
Facility Leases
Cash collateral pledged	5,200	5,300
Collateral Reinsurance Agreement
Cash collateral pledged	$ 1,200	$ 1,000

Segregated Cash (Details)

Segregated Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Segregated Cash [Abstract]
Segregated cash	$ 136,964	$ 176,647	$ 131,444

Investments of Operating Enti_3

Investments of Operating Entities and Consolidated Funds - Securities Owned at Fair Value (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2019		Mar. 31, 2018	Dec. 31, 2018
Investment Holdings [Line Items]
Securities owned, at fair value		$ 563,121			$ 520,888
Securities owned, at fair value		308,800			187,633
Warrants and Rights
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	6,787			7,990
Securities owned, at fair value		4,708			5,279
Warrants and Rights | Estimate of Fair Value Measurement [Member]
Investment Holdings [Line Items]
Trading Securities, Equity	[1]				1,100
Government Securities
Investment Holdings [Line Items]
Debt Securities, Trading	[2]	93,176			$ 13,398
Investment Interest Rate					0.00%
Securities owned, at fair value	[3]	$ 47,034			$ 38,377
Government Securities | Minimum
Investment Holdings [Line Items]
Investment Interest Rate		0.00%
Government Securities | Maximum
Investment Holdings [Line Items]
Investment Interest Rate		6.50%
Common Stock
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	$ 428,952			472,299
Securities owned, at fair value		178,701			95,565
Common Stock | Estimate of Fair Value Measurement [Member]
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	3,100			7,100
Preferred Stock
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	11,707			5,617
Securities owned, at fair value		24,322			24,314
Preferred Stock | Estimate of Fair Value Measurement [Member]
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	2,900			2,900
Corporate Bonds
Investment Holdings [Line Items]
Debt Securities, Trading	[4]	12,012			13,041
Securities owned, at fair value		$ 54,035	[5]		$ 24,098
Corporate Bonds | Minimum
Investment Holdings [Line Items]
Investment Interest Rate		0.00%			2.00%
Corporate Bonds | Maximum
Investment Holdings [Line Items]
Investment Interest Rate		15.50%			15.50%
Convertible Bonds
Investment Holdings [Line Items]
Debt Securities, Trading	[6]	$ 5,000			$ 3,000
Investment Interest Rate		8.00%		8.00%
Trade Claims
Investment Holdings [Line Items]
Debt Securities, Trading		$ 5,487			$ 5,543
Consolidated Funds | Government Securities
Investment Holdings [Line Items]
Investment Interest Rate		0.00%			0.00%
Consolidated Funds | Corporate Bonds | Minimum
Investment Holdings [Line Items]
Investment Interest Rate		4.90%			5.88%
Consolidated Funds | Corporate Bonds | Maximum
Investment Holdings [Line Items]
Investment Interest Rate		19.00%			7.63%
Enterprise Master
Investment Holdings [Line Items]
Securities owned, at fair value					$ 469
Enterprise Master | Common Stock
Investment Holdings [Line Items]
Securities owned, at fair value					$ 469
[1]	The Company has elected the fair value option for investments in securities of preferred and common stock with a fair value of $2.9 million and $3.1 million, respectively, at March 31, 2019 and $2.9 million and $7.1 million, respectively, at December 31, 2018. At December 31, 2018, the Company elected the fair value option for investments in warrants and rights with a fair value of $1.1 million.
[2]	As of March 31, 2019, maturities range from April 2019 to February 2041 with an interest rate of 0% to 6.50%. As of December 31, 2018, maturities ranged from April 2019 to August 2019 with an interest rate of 0%.
[3]	As of March 31, 2019, maturities ranged from April 2019 to May 2019 and interest rates were 0%. As of December 31, 2018, maturities ranged from January 2019 to April 2019 and interest rates ranged from 0%.
[4]	As of March 31, 2019, maturities ranged from April 2019 to March 2026 and interest rates ranged from 0% to 15.5%. As of December 31, 2018, maturities ranged from April 2019 to April 2049 and interest rates ranged from 2% to 15.50%.
[5]	As of December 31, 2018, maturities ranged from August 2020 to March 2026 and interest rates ranged from 5.88% to 7.63%.
[6]	As of March 31, 2019, maturities range from June 2020 to March 2022 with an interest rate of 8%. As of December 31, 2018, the maturity was June 2020 with an interest rate of 8%

Investments of Operating Enti_4

Investments of Operating Entities and Consolidated Funds - Derivatives (Details)		Dec. 05, 2016	Mar. 31, 2019USD ($)contract	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)contract
Derivative [Line Items]
Stockholders' Equity Note, Stock Split, Conversion Ratio		0.25
Receivable on derivative contracts, at fair value			$ 21,663,000		$ 25,125,000
Payable for derivative contracts, at fair value			43,583,000		16,082,000
Receivable on derivative contracts, at fair value			3,184,000		4,416,000
Payable for derivative contracts, at fair value, Consolidated Funds			5,557,000		1,663,000
Equity Swap
Derivative [Line Items]
Receivable on derivative contracts, at fair value			1,196,000		2,477,000
Payable for derivative contracts, at fair value, Consolidated Funds			3,921,000		713,000
Futures
Derivative [Line Items]
Derivative Asset, Notional Amount			0		42,288,209
Receivable on derivative contracts, at fair value			0		334,000
Derivative Liability, Notional Amount			12,464,000		0
Payable for derivative contracts, at fair value			307,000		0
Currency Forwards
Derivative [Line Items]
Derivative Asset, Notional Amount			99,790,897		394,875
Receivable on derivative contracts, at fair value			543,000		1,000
Derivative Liability, Notional Amount			6,273,000		96,406,000
Payable for derivative contracts, at fair value			81,000		709,000
Receivable on derivative contracts, at fair value			25,000		186,000
Payable for derivative contracts, at fair value, Consolidated Funds			1,327,000		96,000
Swaps
Derivative [Line Items]
Derivative Asset, Notional Amount			141,108,170		13,702,458
Receivable on derivative contracts, at fair value			1,915,000		917,000
Derivative Liability, Notional Amount			41,031,000		52,905,000
Payable for derivative contracts, at fair value			$ 3,183,000		$ 2,162,000
Options
Derivative [Line Items]
Derivative Asset, Number of Instruments Held | contract	[1]		325,571		654,506
Receivable on derivative contracts, at fair value	[1]		$ 18,971,000		$ 23,130,000
Receivable on derivative contracts, at fair value			1,963,000		1,753,000
Payable for derivative contracts, at fair value, Consolidated Funds			$ 309,000		$ 854,000
Option
Derivative [Line Items]
Derivative Liability, Number of Instruments Held | contract	[2]		140,452		90,730
Payable for derivative contracts, at fair value	[2]		$ 40,012,000		$ 13,211,000
Pay to hold
Derivative [Line Items]
Derivative Asset, Number of Instruments Held | contract			0		0
Receivable on derivative contracts, at fair value			$ 234,000		$ 743,000
Receivable on derivatives contracts, at fair value [Member]
Derivative [Line Items]
Receivable on derivative contracts, at fair value			21,663,000		25,125,000
Derivative Asset, Fair Value, Gross Asset			21,663,000		25,125,000
Derivative Asset, Fair Value, Amount Offset Against Collateral	[3]		0		0
Financial Instruments, Owned and Pledged as Collateral, at Fair Value			0		0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	[4]		2,691,000		1,662,000
Derivative asset, net of offset			18,972,000		23,463,000
Payable for derivatives contracts, at fair value [Member]
Derivative [Line Items]
Payable for derivative contracts, at fair value			43,583,000		16,082,000
Financial Instruments, Owned and Pledged as Collateral, at Fair Value			0		0
Derivative Liability, Fair Value, Gross Liability			43,583,000		16,082,000
Derivative Liability, Fair Value, Amount Offset Against Collateral	[3]		0		0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	[4]		3,264,000		2,871,000
Derivative Liability, net of offset			40,319,000		13,211,000
Receivables from Brokers-Dealers and Clearing Organizations
Derivative [Line Items]
Collateral posted			6,700,000		$ 11,200,000
Other Income [Member]
Derivative [Line Items]
Realized and unrealized gains/(losses) related to derivatives trading activities			$ (2,200,000)	$ 7,900,000
[1]	Includes index, equity, commodity future and cash conversion options.
[2]	Includes index, equity, commodity future and cash conversion options.
[3]	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
[4]	Includes the amount of collateral held or posted.

Investments of Operating Enti_5

Investments of Operating Entities and Consolidated Funds - Other Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019		Dec. 31, 2018
Investment Holdings [Line Items]
Other investments	$ 200,132		$ 181,407
Portfolio Funds, Consolidated Funds	186,846		186,395
Portfolio Funds, at fair value
Investment Holdings [Line Items]
Other investments	145,566	[1]	141,236	[2]
Equity Method Investments
Investment Holdings [Line Items]
Other investments	54,566		40,171
Enterprise LP [Member]
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	95,414		97,656
Merger Fund [Member]
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	$ 91,432		$ 88,739
[1]	In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.
[2]	In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table 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_6

Investments of Operating Entities and Consolidated Funds - Portfolio Funds - (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019		Dec. 31, 2018
Investment Holdings [Line Items]
Other investments		$ 200,132		$ 181,407
Portfolio Funds
Investment Holdings [Line Items]
Other investments		145,566	[1]	141,236	[2]
Portfolio Funds | Starboard Value and Opportunity Fund LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[4]	$ 36,270		32,579
Required notice period, withdrawal		90 days
Portfolio Funds | Formation 8 Partners Fund I LP
Investment Holdings [Line Items]
Other investments	[5]	$ 33,613		34,099
Portfolio Funds | RCGLongview Debt Fund V, L.P. | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	2,667		4,394
Portfolio Funds | RCG Longview II, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	4,431		4,400
Portfolio Funds | Cowen Healthcare Investments II LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments		23,941	[4],[7]	21,717
Portfolio Funds | Eclipse Ventures Fund I, L.P.
Investment Holdings [Line Items]
Other investments	[8]	4,469		4,412
Portfolio Funds | Healthcare Royalty Partners | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[9]	1,825		1,833
Portfolio Funds | Lagunita Biosciences, LLC
Investment Holdings [Line Items]
Other investments	[10]	4,080		3,833
Portfolio Funds | RCG IO Renergys Sarl | Affiliated Entity
Investment Holdings [Line Items]
Other investments		6,329	[4],[7]	6,369
Portfolio Funds | Starboard Leaders Fund LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[11]	$ 1,424		1,230
Unfunded Commitment cancellation		30 days
Portfolio Funds | Elipse SPV I,LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments		$ 1,447	[4],[12]	1,447
Portfolio Funds | RCG Longview Equity Fund, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments		797	[4],[6]	802
Portfolio Funds | RCG Longview Debt Fund VI, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	1,614		1,586
Portfolio Funds | RCG Park Liberty GP Member LLC | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	1,129		1,023
Portfolio Funds | Healthcare Royalty Partners II | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[9]	1,106		1,037
Portfolio Funds | RCGL PE MPA LLC | Affiliated Entity
Investment Holdings [Line Items]
Other investments		618	[4],[6]	618
Portfolio Funds | RCG LPP2 PNW5 Co-Invest, L.P. | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[13]	12		296
Portfolio Funds | Other Private Investment | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[14]	15,723		15,898
Portfolio Funds | Other Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[15]	$ 4,071		3,663
Enterprise Master | Portfolio Funds
Investment Holdings [Line Items]
Other investments				112,394
Multi-strategy | Enterprise Master | Portfolio Funds | RCG Special Opportunities Fund, Ltd | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[16]			111,548
Various Strategies | Enterprise Master | Portfolio Funds | Other Private Investment
Investment Holdings [Line Items]
Other investments				$ 846
[1]	In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.
[2]	In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.
[3]	Starboard Value and Opportunity Fund LP permits quarterly withdrawals upon 90 days' notice.
[4]	These Portfolio Funds are affiliates of the Company.
[5]	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.
[6]	RCG Longview Debt Fund V, L.P., RCG Longview II LP, RCG Park Liberty GP Member LLC, RCG Longview Equity Fund, LP, RCGL PE MPA, LLC and RCG Longview Debt Fund VI, LP are real estate private equity structures. The timing of distributions depend on the nature of the underlying investments and therefore will be made either quarterly or when the underlying investments are liquidated.
[7]	Cowen Healthcare Investments II LP and RCG IO Renergys Sarl are private equity funds. Distributions are made from these funds when cash flows or securities are received from the underlying investments. Investors do not have redemption rights
[8]	Eclipse Ventures Fund I, L.P. is a private equity fund which invests in early stage and growth hardware companies. Distributions will be made when the underlying investments are liquidated.
[9]	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.
[10]	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.
[11]	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 investors' initial capital contribution.
[12]	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.
[13]	RCG LPP2 PNW5 Co-Invest, L.P. is a single purpose entity formed to participate in a joint venture which acquired five multi-unit residential rental properties located in the Pacific Northwest. RCG LPP2 PNW5 Co-Invest, L.P. is a private equity structure and therefore distributions will be made when the underlying investments are liquidated.
[14]	Other private investment represents the Company's closed end investment in a Portfolio Fund that invests in a wireless broadband communication provider in Italy.
[15]	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.
[16]	Affiliates of the Company.

Investments of Operating Enti_7

Investments of Operating Entities and Consolidated Funds - Equity Method Investments - (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Cash	$ 3,261
Expense, equity method investments	2,700	$ 1,900
Equity method investments	54,566		$ 40,171
Liabilities	20,900
Equity	771,528
Revenue	68,579
Expenses	(18,210)
Net realized and unrealized gain (loss)	89,560
Net Income	139,929
Equity Method Investment, Summarized Financial Information, Performance And Management Fee Receivable	73,336
Equity Method Investment, Summarized Financial Information, Investments in Portfolio Funds	715,831
Surf House Ocean Views Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	8,493		7,589
Starboard Value LP
Schedule of Equity Method Investments [Line Items]
Equity method investments	26,240		12,699
RCG Longview Debt Fund V Partners, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	10,362		11,000
RCG Longview Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,167		1,167
RCG Longview Debt Fund VI, LP
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,425		1,254
Healthcare Royalty GP, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	149		149
Healthcare Royalty GP II, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	187		176
RCG Longview Debt Fund IV Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	331		331
Healthcare Royalty GP III, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,645		1,573
Triartisan ES Partners, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,026		1,500
Triartisan PFC Partners, LLC [Member] [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,000		0
RCG Kennedy House, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	131		131
RCG Longview Equity Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	110		114
RCG LPP II GP, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	94		272
RCG Park Liberty GP Member Manager, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,248		1,248
Equity Method Investee, Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	958		968
Net Gains (Losses) on Securities, Derivatives and Other Investments
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Equity Method Investments	$ 16,300	$ 3,900
Minimum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	1.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	56.00%
Clawback Obligation
Schedule of Equity Method Investments [Line Items]
Contractual obligation			6,200
Clawback Obligation | RCG Longview Partners II, LLC
Schedule of Equity Method Investments [Line Items]
Contractual obligation	$ 6,500		$ 6,500

Investments of Operating Enti_8

Investments of Operating Entities and Consolidated Funds - Securities Sold, Not Yet Purchased (Details) - USD ($)		Mar. 31, 2019	Dec. 31, 2018
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value		$ 574,186,000	$ 195,307,000
Common Stock
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value		463,319,000	194,305,000
Corporate Bonds
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	[1]	$ 3,207,000	$ 750,000
Corporate Bonds | Minimum
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, interest rate		5.38%	2.25%
Corporate Bonds | Maximum
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, interest rate		14.00%	9.38%
Government Securities | Minimum
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, interest rate		5.38%
Government Securities | Maximum
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, interest rate		8.25%
US Government Debt Securities
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	[2]	$ 84,459,000	$ 0
Preferred Stock
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value		3,959,000	199,000
Warrants and Rights
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value		$ 19,242,000	$ 53,000
[1]	As of March 31, 2019, the maturities ranged from October 2019 to April 2037 with interest rates ranged from 5.38% to 14.00%. As of December 31, 2018, the maturities ranged from October 2022 to January 2034 with interest rates ranged from 2.25% to 9.38%.
[2]	As of March 31, 2019, the maturities ranged from October 2019 to February 2041 with interest rates ranged from 5.38% to 8.25%.

Investments of Operating Enti_9

Investments of Operating Entities and Consolidated Funds - Securities borrowed and securities loaned (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Securities Borrowed, Gross		$ 966,857	$ 407,795
Securities borrowed, gross amounts offset on the condensed consolidated statements of financial condition	[1]	0	0
Securities borrowed, net amounts included on the condensed consolidated statements of financial condition		966,857	407,795
Securities borrowed, additional amounts, asset		0	0
Securities borrowed, financial instruments			383,593
Securities borrowed, net amounts		9,070	24,202
Securities Loaned, Gross		852,203	414,852
Securities Loaned, Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	[1]	0	0
Securities Loaned, Gross amounts recognized		852,203	414,852
Securities Loaned, Additional Amounts Available		0	0
Securities Loaned, Financial instruments			391,310
Securities Loaned, Net amounts		$ (5,972)	$ 23,542
[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.

Investments of Operating Ent_10

Investments of Operating Entities and Consolidated Funds - Securities loaned transactions by remaining contractual maturity and class of collateral pledged (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	$ 852,203,000	$ 414,852,000
Securities sold, not yet purchased, at fair value	574,186,000	195,307,000
Common stock
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	710,449,000	414,852,000
Securities sold, not yet purchased, at fair value	79,778,000
Common stock | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	710,449,000	414,852,000
Securities sold, not yet purchased, at fair value	79,778,000
Common stock | 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
Common stock | 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	0
Common stock | 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
Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	70,565,000
Corporate Bonds | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	70,565,000
Corporate Bonds | Up to 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0
Corporate Bonds | 31 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0
Corporate Bonds | Greater than 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0
US Government Debt Securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	71,189,000
US Government Debt Securities | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	71,189,000
US Government Debt Securities | Up to 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0
US Government Debt Securities | 31 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0
US Government Debt Securities | Greater than 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	$ 0

Investments of Operating Ent_11

Investments of Operating Entities and Consolidated Funds - Variable Interest Entities (Details) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Total assets of nonconsolidated variable interest entities	$ 5,400	$ 5,100
Total liabilities of nonconsolidated variable interest entities	282	157.6
Variable Interest Entity, Nonconsolidated, Comparison of Carrying Amount of Assets and Liabilities to Maximum Loss Exposure	231.6	301.4
Maximum exposure regarding nonconsolidated variable interest entities	$ 263.3	$ 332.4

Investments of Operating Ent_12

Investments of Operating Entities and Consolidated Funds - Indirect Concentration of the Underlying Investments Held by Consolidated Funds (Details) $ in Thousands	Mar. 31, 2019USD ($)investments	Dec. 31, 2018USD ($)investments
Investment [Line Items]
Concentration of risk, number of investments | investments	1	1
Equity Securities | Linkem | ITALY | 517210 Wireless Telecommunications Carriers (except Satellite)
Investment [Line Items]
Percentage of Equity	8.08%	8.36%
Market Value | $	$ 65,842	$ 66,439

Investments of Operating Ent_13

Investments of Operating Entities and Consolidated Funds - Merger Master Narrative (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Investment [Line Items]
Trading securities		$ 563,121	$ 520,888
Securities sold, not yet purchased, at fair value		574,186	195,307
Common Stock
Investment [Line Items]
Securities sold, not yet purchased, at fair value		463,319	194,305
Common Stock | Merger Master
Investment [Line Items]
Trading securities		249,700	162,800
Securities sold, not yet purchased, at fair value		104,200	9,600
Corporate Bonds
Investment [Line Items]
Securities sold, not yet purchased, at fair value	[1]	3,207	750
Corporate Bonds | Merger Master
Investment [Line Items]
Trading securities		$ 74,200	$ 116,500
[1]	As of March 31, 2019, the maturities ranged from October 2019 to April 2037 with interest rates ranged from 5.38% to 14.00%. As of December 31, 2018, the maturities ranged from October 2022 to January 2034 with interest rates ranged from 2.25% to 9.38%.

Investments of Operating Ent_14

Investments of Operating Entities and Consolidated Funds - Merger Master Derivatives (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Asset		$ 21,663	$ 25,125
Derivative Liability		43,583	16,082
Merger Master
Derivative [Line Items]
Derivative Asset		2,192	8,770
Derivative Liability		24,357	1,728
Option
Derivative [Line Items]
Derivative Liability	[1]	40,012	13,211
Option | Merger Master
Derivative [Line Items]
Derivative Liability		287	1,430
Options
Derivative [Line Items]
Derivative Asset	[2]	18,971	23,130
Options | Merger Master
Derivative [Line Items]
Derivative Asset		1,973	3,450
Swaps
Derivative [Line Items]
Derivative Asset		1,915	917
Derivative Liability		3,183	2,162
Swaps | Merger Master
Derivative [Line Items]
Derivative Asset		219	5,320
Derivative Liability		1,547	28
Currency Forwards
Derivative [Line Items]
Derivative Asset		543	1
Derivative Liability		81	709
Currency Forwards | Merger Master
Derivative [Line Items]
Derivative Liability		$ 22,523	$ 270
[1]	Includes index, equity, commodity future and cash conversion options.
[2]	Includes index, equity, commodity future and cash conversion options.

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, 2019		Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		$ 574,186		$ 195,307
Securities sold, not yet purchased, at fair value		574,186		195,307
Derivative Liability		43,583		16,082
Derivative Asset		21,663		25,125
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low		1,600		2,800
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High		40,000		3,400
Other investments		200,132		181,407
Other Investments, Consolidated Funds		186,846		186,395
Investments		$ 1,283,746		$ 1,105,864
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of Total Assets at Fair Value		77.10%		86.60%
Percentage of Total Liabilities at Fair Value		80.50%		95.60%
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of Total Assets at Fair Value		17.00%		6.00%
Percentage of Total Liabilities at Fair Value		14.70%		2.00%
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of Total Assets at Fair Value		5.90%		7.40%
Percentage of Total Liabilities at Fair Value		4.80%		2.40%
Futures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		$ 307		$ 0
Derivative Asset		0		334
Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		3,183		2,162
Derivative Asset		1,915		917
Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset	[1]	18,971		23,130
Pay to hold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		234		743
Portfolio Funds, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		145,566	[2]	141,236	[3]
Other Investments, Consolidated Funds		186,846	[2]	186,395	[3]
Equity Method Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments		54,566		40,171
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		652,862		216,122
Assets, Fair Value Disclosure, Recurring (Deprecated 2018-01-31)		896,768		738,062
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		525,415		206,526
Assets, Fair Value Disclosure, Recurring (Deprecated 2018-01-31)		691,110		638,837
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		96,178		4,430
Assets, Fair Value Disclosure, Recurring (Deprecated 2018-01-31)		152,301		44,311
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment Sold, Not yet Purchased and Derivative Liability, at Fair Value		31,269		5,166
Assets, Fair Value Disclosure, Recurring (Deprecated 2018-01-31)		53,357		54,914
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		3,959		199
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		3,959		199
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 | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		463,319		194,305
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		463,319		194,305
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		3,207		750
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		3,207		750
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		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		19,242		53
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		19,242		53
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]
Business Combination, Contingent Consideration, Liability		29,536	[4]	3,070
Fair Value, Measurements, Recurring | Contingent liability payable | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		0	[4]	0	[5]
Fair Value, Measurements, Recurring | Contingent liability payable | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		0	[4]	0	[5]
Fair Value, Measurements, Recurring | Contingent liability payable | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability		29,536	[4]	3,070	[5]
Fair Value, Measurements, Recurring | Futures | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		307
Fair Value, Measurements, Recurring | Futures | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		307
Fair Value, Measurements, Recurring | Futures | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0
Fair Value, Measurements, Recurring | Futures | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0
Fair Value, Measurements, Recurring | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		543
Fair Value, Measurements, Recurring | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		543
Fair Value, Measurements, Recurring | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Currency forward | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		81		709
Fair Value, Measurements, Recurring | Currency forward | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Currency forward | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		81		709
Fair Value, Measurements, Recurring | Currency forward | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		1,915
Fair Value, Measurements, Recurring | Swaps | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Swaps | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		1,915
Fair Value, Measurements, Recurring | Swaps | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Swaps | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		3,183		2,162
Fair Value, Measurements, Recurring | Swaps | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Swaps | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		3,183		2,162
Fair Value, Measurements, Recurring | Swaps | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		18,971
Fair Value, Measurements, Recurring | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		18,971
Fair Value, Measurements, Recurring | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0
Fair Value, Measurements, Recurring | Options | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		40,012		13,211
Fair Value, Measurements, Recurring | Options | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		38,279		11,115
Fair Value, Measurements, Recurring | Options | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Options | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability				2,096
Financial Liabilities Fair Value Disclosure		1,733
Fair Value, Measurements, Recurring | Pay to hold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		234		743
Fair Value, Measurements, Recurring | Pay to hold | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Pay to hold | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		234		743
Fair Value, Measurements, Recurring | Pay to hold | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		93,176		13,398
Fair Value, Measurements, Recurring | Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		13,398		13,398
Fair Value, Measurements, Recurring | Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		79,778		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		11,707		5,617
Fair Value, Measurements, Recurring | Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		4,550		449
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		7,157		5,168
Fair Value, Measurements, Recurring | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		428,952		472,299
Fair Value, Measurements, Recurring | Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		421,177		459,601
Fair Value, Measurements, Recurring | Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		2,824		2,848
Fair Value, Measurements, Recurring | Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		4,951		9,850
Fair Value, Measurements, Recurring | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		12,012		13,041
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		11,751		13,041
Fair Value, Measurements, Recurring | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		261		0
Fair Value, Measurements, Recurring | Convertible Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading				3,000
Trading Securities, Equity		5,000
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
Trading Securities, Equity		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
Trading Securities, Equity		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				3,000
Trading Securities, Equity		5,000
Fair Value, Measurements, Recurring | Trade Claims
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		5,487		5,543
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		5,487		5,543
Fair Value, Measurements, Recurring | Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		6,787		7,990
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		6,333		6,324
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		454		1,666
Fair Value, Measurements, Recurring | Derivative Assets | Futures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				334
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				334
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Futures | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				1
Fair Value, Measurements, Recurring | Derivative Assets | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				1
Fair Value, Measurements, Recurring | Derivative Assets | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				917
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				917
Fair Value, Measurements, Recurring | Derivative Assets | Swaps | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				23,130
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				23,130
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Derivative Assets | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset				0
Fair Value, Measurements, Recurring | Operating Companies [Member] | US Government Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		84,459
Fair Value, Measurements, Recurring | Operating Companies [Member] | US Government Debt 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
Fair Value, Measurements, Recurring | Operating Companies [Member] | US Government Debt Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		84,459
Fair Value, Measurements, Recurring | Operating Companies [Member] | US Government Debt Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities sold, not yet purchased, at fair value		0
Fair Value, Measurements, Recurring | Consolidated Funds | Currency forward | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		1,327		96
Fair Value, Measurements, Recurring | Consolidated Funds | Currency forward | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Currency forward | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		1,327		96
Fair Value, Measurements, Recurring | Consolidated Funds | Currency forward | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Equity Swap | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		3,921		713
Fair Value, Measurements, Recurring | Consolidated Funds | Equity Swap | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Equity Swap | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		3,921		713
Fair Value, Measurements, Recurring | Consolidated Funds | Equity Swap | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Options | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		309		854
Fair Value, Measurements, Recurring | Consolidated Funds | Options | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		309		854
Fair Value, Measurements, Recurring | Consolidated Funds | Options | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Options | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		47,034		38,377
Fair Value, Measurements, Recurring | Consolidated Funds | Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		47,034		38,377
Fair Value, Measurements, Recurring | Consolidated Funds | 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 | Consolidated Funds | 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 | Consolidated Funds | Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		24,322		24,314
Fair Value, Measurements, Recurring | Consolidated Funds | Preferred Stock | 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 | 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 | Consolidated Funds | Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		24,322		24,314
Fair Value, Measurements, Recurring | Consolidated Funds | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities, Equity		178,701		95,565
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		177,684		95,471
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		1,017		94
Fair Value, Measurements, Recurring | Consolidated Funds | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		54,035
Fair Value, Measurements, Recurring | Consolidated Funds | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0
Fair Value, Measurements, Recurring | Consolidated Funds | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		54,035
Fair Value, Measurements, Recurring | Consolidated Funds | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Trading		0
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		4,708		5,279
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		4,708		5,279
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		25		186
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		25		186
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Equity Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		1,196		2,477
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Equity Swap | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Equity Swap | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		1,196		2,477
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Equity Swap | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		1,963		1,753
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		1,963		1,753
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		0		0
Fair Value, Measurements, Recurring | Consolidated Funds | Derivative Assets | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset		$ 0		$ 0
[1]	Includes index, equity, commodity future and cash conversion options.
[2]	In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table 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 US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.
[4]	In accordance with the terms of the purchase agreements for acquisitions that closed during the second quarter of 2016 and the first quarter of 2019, 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 2019 and December 2023, respectively. For the acquisition that closed during 2016, the Company estimated the contingent consideration liability using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. For the acquisition that closed during 2019, the Company estimated the contingent consideration liability using the present value of the monte carlo simulated revenue. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts as of March 31, 2019 can range from $1.6 million to $40.0 million.
[5]	In accordance with the terms of the purchase agreements for the acquisition that closed during the second quarter of 2016, the Company is required to pay to the sellers a portion of future net income and/or revenues of the acquired business, if certain targets are achieved through the periods ended December 2020. The Company estimated the contingent consideration liability using the income approach (discounted cash flow method) which requires the Company to make estimates and assumptions regarding the future cash flows and profits. Changes in these estimates and assumptions could have a significant impact on the amounts recognized. The undiscounted amounts as of December 31, 2018 can range from $2.8 million to $3.4 million.

Fair Value Measurements for O_4

Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) - USD ($)		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 5,168,000	$ 8,115,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	0
Purchases/(covers)		2,000,000	1,415,000
(Sales)/short buys		0	(478,000)
Realized and unrealized gains (losses), asset		(11,000)	(235,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(11,000)	486,000
Balance Asset Value		7,157,000	8,817,000
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		9,850,000	7,570,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	0
Purchases/(covers)		1,262,000	310,000
(Sales)/short buys		(5,952,000)	(133,000)
Realized and unrealized gains (losses), asset		(209,000)	(347,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(7,000)	412,000
Balance Asset Value		4,951,000	7,400,000
Corporate Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		0
Asset, Transfers In		0
Asset, Transfers Out		0
Purchases/(covers)		261,000
(Sales)/short buys		0
Realized and unrealized gains (losses), asset		0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	0
Balance Asset Value		261,000
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		3,000,000	282,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	0
Purchases/(covers)		5,000,000	0
(Sales)/short buys		(3,000,000)	(307,000)
Realized and unrealized gains (losses), asset		0	25,000
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	0	0
Balance Asset Value		5,000,000	0
Options
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value			1,455,000
Asset, Transfers In			0
Asset, Transfers Out			0
Purchases/(covers)			0
(Sales)/short buys			1,455,000
Realized and unrealized gains (losses), asset			0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]		0
Balance Asset Value			0
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		1,666,000	2,517,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	0
Purchases/(covers)		0	0
(Sales)/short buys		(116,000)	0
Realized and unrealized gains (losses), asset		(1,096,000)	(815,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(109,000)	510,000
Balance Asset Value		454,000	1,702,000
Trade Claims
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,543,000	5,950,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	0
Purchases/(covers)		0	0
(Sales)/short buys		(56,000)	0
Realized and unrealized gains (losses), asset		0	5,000
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	0	5,000
Balance Asset Value		5,487,000	5,955,000
Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value			301,000
Asset, Transfers In			0
Asset, Transfers Out			0
Purchases/(covers)			0
(Sales)/short buys			0
Realized and unrealized gains (losses), asset			11,000
Change in Unrealized Gain (Loss), instruments still held, asset	[1]		12,000
Balance Asset Value			312,000
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		24,314,000	50,445,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	(38,552,000)	[2]
Purchases/(covers)		0	0
(Sales)/short buys		0	0
Realized and unrealized gains (losses), asset		8,000	0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	8,000	0
Balance Asset Value		24,322,000	11,893,000
Consolidated Funds | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		94,000	50,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	0
Purchases/(covers)		407,000	0
(Sales)/short buys		0	0
Realized and unrealized gains (losses), asset		516,000	0
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	516,000	0
Balance Asset Value		1,017,000	50,000
Consolidated Funds | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,279,000	3,568,000
Asset, Transfers In		0	0
Asset, Transfers Out		0	(20,000)	[2]
Purchases/(covers)		(1,088,000)	0
(Sales)/short buys		0	0
Realized and unrealized gains (losses), asset		517,000	1,706,000
Change in Unrealized Gain (Loss), instruments still held, asset	[1]	(570,000)	1,706,000
Balance Asset Value		4,708,000	5,254,000
Options, liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		2,096,000	22,401,000
Liability, Transfers In		0	0
Liability, Transfers Out		0	0
Liability, Purchases		0	0
Liability, Sales		(4,000)	0
Realized and unrealized gains (losses), liability		(359,000)	(1,006,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[1]	(359,000)	(1,006,000)
Balance Liability Value		1,733,000	21,395,000
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		3,070,000	3,440,000
Liability, Transfers In		0	0
Liability, Transfers Out		0	0
Liability, Purchases		27,700,000	0
Liability, Sales		(1,234,000)	0
Realized and unrealized gains (losses), liability		0	0
Change in Unrealized Gain (Loss), instruments still held, liabilities	[1]	0	0
Balance Liability Value		$ 29,536,000	$ 3,440,000
[1]	Unrealized gains/losses are reported in other income (loss) in the accompanying condensed consolidated statements of operations.
[2]	The Company deconsolidated an investment fund.

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, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Contingent liability payable
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Liability Value		$ 29,536	$ 3,070	$ 3,440	$ 3,440
Trade Claims
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		5,487	5,543	5,955	5,950
Warrants and Rights [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		454	1,666	1,702	2,517
Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value				$ 0	$ 1,455
Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		53,357	54,914
Balance Liability Value		$ 31,269	$ 5,166
Level 3 | Contingent liability payable | Monte Carlo [Member] | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		14.00%
Level 3 | Contingent liability payable | Monte Carlo [Member] | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		15.00%
Level 3 | Contingent liability payable | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs			23.00%
Level 3 | Contingent liability payable | Income Approach and Market Approach Valuation Techniques | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		14.00%
Level 3 | Contingent liability payable | Income Approach and Market Approach Valuation Techniques | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		22.00%
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			$ 3,070
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		$ 320	$ 4,323
Level 3 | Common and Preferred Stock | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member] | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs			650.00%
Level 3 | Common and Preferred Stock | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member] | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs			700.00%
Level 3 | Trade Claims | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		20.00%	20.00%
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		$ 25	$ 25
Level 3 | Warrants and Rights [Member] | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		5,162
Level 3 | Warrants and Rights [Member] | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value			1,666
Level 3 | Other Investments | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	[1]	47,850
Level 3 | Other Investments | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	[1]		$ 48,900
Level 3 | Options | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs
Fair Value, Measurements, Recurring | Level 3 | Options | Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		$ 1,733
Fair Value, Measurements, Recurring | Level 3 | Option | Options | 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			$ 2,096
Discount rate | 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]
Fair value inputs		8.00%
Discount rate | Level 3 | Common and Preferred Stock | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member] | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs			8.00%
Discount rate | Level 3 | Common and Preferred Stock | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member] | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs			14.00%
Discount rate | Level 3 | Warrants and Rights [Member] | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		7.00%	7.00%
Discount rate | Level 3 | Warrants and Rights [Member] | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		8.00%	9.00%
Volatility | Level 3 | Warrants and Rights [Member] | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs
Volatility | Level 3 | Warrants and Rights [Member] | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		30.00%
Volatility | Level 3 | Options | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		35.00%	35.00%
Volatility | Level 3 | Options | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value inputs		40.00%	40.00%
[1]	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 ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Cash and cash equivalents		$ 235,838	$ 259,148	$ 117,680
Cash collateral pledged		6,420	6,318	14,786
Segregated cash		136,964	176,647	$ 131,444
Securities Borrowed, Gross		966,857	407,795
Securities borrowed, financial instruments			383,593
Securities borrowed		966,857	407,795
Loans Receivable, Net		34,898	36,021
Cash and cash equivalents, Consolidated Funds		2,178	38,118
Securities Loaned, Gross		852,203	414,852
Securities Loaned, Financial instruments			391,310
Convertible debt		115,099	134,489
Notes payable and other debt		264,273	262,965
Convertible Debt
Convertible debt, unamortized discount		23,400	24,900
Level 1
Cash and cash equivalents, Fair Value		235,838	259,148
Segregated cash fair value disclosures		136,964	176,647
Cash and cash equivalents, Consolidated Funds, Fair Value		2,178	38,118
Level 2
Cash collateral pledged, Fair Value		6,420	6,318
Securities borrowed, financial instruments		957,787
Securities Borrowed, Fair Value Disclosure			383,593
Securities Loaned, Financial instruments		858,175
Securities loaned, fair value disclosure			391,310
Convertible debt, Fair Value	[1]	142,628	157,433
Notes payable and other debt, Fair Value	[2]	207,543	258,546
Level 3
Loans Receivable, Fair Value Disclosure	[3]	$ 34,898	$ 36,021
[1]	The convertible debt includes the conversion option and is based on the last broker quote available.
[2]	Notes payable and other debt are based on the last broker quote available.
[3]	The fair market value of level 3 loans is calculated using discounted cash flows.

Deposits with Clearing Organi_2

Deposits with Clearing Organizations, Brokers and Banks (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Deposits with Clearing Organizations, Brokers and Banks [Abstract]
Deposits with clearing organizations, brokers and banks	$ 109,310	$ 89,423

Receivables from and payables_3

Receivables from and payables to brokers, dealers and clearing organizations (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Brokers and Dealers [Abstract]
Receivable from Broker-dealers	$ 608,841	$ 692,581
Securities Failed-to-Deliver	44,037	72,918
Receivable from Clearing organizations	2,702	15,319
Stock borrow interest receivable	7,492	5,295
Receivable from brokers, dealers and clearing organizations	663,072	786,113
Payable to Broker-Dealers	134,424	159,443
Securities Failed-to-Receive	23,619	28,826
Payable to clearing organizations	9,876	36,338
Stock loan interest payable	6,613	4,124
Payables to brokers, dealers and clearing organizations	$ 174,532	$ 228,731

Receivable from and Payable t_2

Receivable from and Payable to Customers (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Receivables and Payable to Customers [Abstract]
Receivable from customers	$ 36,719	$ 37,858
Payable to customers	$ 413,050	$ 525,153

Goodwill and Intangibles Qtlry

Goodwill and Intangibles Qtlry (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 02, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, Impairment Loss	$ 0	$ 0
Quarton
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired	22,200,000
Goodwill, Acquired During Period	$ 81,200,000
Intangible assets			$ 22,200,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	2 years 9 months 18 days
Amortization of Intangible Assets	$ 2,200,000
Minimum | Quarton
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years
Maximum | Quarton
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life	4 years

Commission Management Payable (

Commission Management Payable (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commission Management Payable [Abstract]
Commission management payable	$ 103,634	$ 95,270

Redeemable Non-Controlling In_3

Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	$ 418,277		$ 284,780
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	2,206	$ 11,156
Operating Entities
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	13,568		10,434
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	1,806	1,620
Consolidated Funds
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	404,709		$ 274,346
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	$ 400	$ 9,536

Reinsurance (Details)

Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Historical Average Claims Ratios, Period, Maximum	10 years
Hollenfels
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Share of incurred and paid claims	$ 2.9	$ 3.6
Share of claims incurred but not reported	$ 10.1	$ 8.3

Share-Based Compensation and _3

Share-Based Compensation and Employee Ownership Plans Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares		0
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	500,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number			253,772
Equity Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-compensation expense recognized in connection with compensation plan	$ 7.8	$ 10.2
Tax benefit of stock-compensation expense recognized in connection with compensation plan	$ 2.1	$ 2.4
Equity Plans | Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, initial term	7 years
Equity Plans | Employee Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation award, vesting period	2 years
Equity Plans | Employee Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation award, vesting period	5 years
Equity Plans | Restricted Shares and Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense	$ 76.7
Vested, shares	768,468	858,433
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	6,598,097	6,807,632	5,962,295	5,579,293
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 | Restricted Stock Units (RSUs) | Non-employee Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	253,772
Equity Plans | Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
SAR's, initial term	5 years
Deferred Cash Award | Cowen Group, Inc. 2010 Equity and Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred cash awards granted	$ 41.8
Stock compensation award, vesting period	4 years
Deferred cash award, interest rate	0.70%
Deferred cash awards, unrecognized compensation expense	$ 82.2
Convergex Group
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred Compensation Arrangement with Individual, Requisite Service Period	27 months
Convergex Group | Deferred Cash Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred cash awards granted	$ 0.1

Share-Based Compensation and _4

Share-Based Compensation and Employee Ownership Plans Restricted Shares and Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended
	Mar. 31, 2016	Jan. 31, 2014	Mar. 31, 2019	Mar. 31, 2018
Nonvested Restricted Shares and Restricted Stock Units
Balance outstanding, beginning of period, shares			253,772
Weighted-Average Grant Date Fair Value
Granted, shares				0
Equity Plans | Restricted Shares and Restricted Stock Units (RSUs)
Nonvested Restricted Shares and Restricted Stock Units
Balance outstanding, beginning of period, shares			5,962,295	5,579,293
Granted, shares			1,781,949	2,108,184
Vested, shares			(768,468)	(858,433)
Canceled, shares			(233,333)	0
Forfeited, shares			(144,346)	(21,412)
Balance outstanding, end of period, shares			6,598,097	6,807,632
Weighted-Average Grant Date Fair Value
Balance outstanding, beginning of period, in dollars per share			$ 15.73	$ 16.33
Granted, in dollars per share			16.97	14.23
Vested, in dollars per share			16.69	16.20
Canceled, in dollars per share			14.12	0
Forfeited, in dollars per share			13.84	13.11
Balance outstanding, end of period, in dollars per share			$ 16.05	$ 15.71
Unrecognized compensation expense			$ 76.7
Weighted-average recognition period for unrecognized compensation expense			2 years 6 months 18 days
Equity Plans | Performance based restricted stock
Nonvested Restricted Shares and Restricted Stock Units
Granted, shares	700,000	481,438
Vested, shares			(233,333)
Forfeited, shares			(130,438)
Non-employee Director | Equity Plans | Restricted Stock Units (RSUs)
Nonvested Restricted Shares and Restricted Stock Units
Balance outstanding, end of period, shares			253,772
Weighted-Average Grant Date Fair Value
Granted, shares			0
Maximum
Nonvested Restricted Shares and Restricted Stock Units
Percent of RSU's earned			150.00%
Minimum
Nonvested Restricted Shares and Restricted Stock Units
Percent of RSU's earned			0.00%

Income Taxes - Quarterly (Detai

Income Taxes - Quarterly (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Income Tax Contingency [Line Items]
Effective income tax rate, percent	20.95%	19.82%
Statutory rate, percent	21.00%	21.00%
Convergex Group
Income Tax Contingency [Line Items]
Taxes payable	$ 0.3		$ 4.9

Commitments and Contingencies_2

Commitments and Contingencies (Details) - USD ($)		3 Months Ended	12 Months Ended
		Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
Contractual Commitments, Commitment [Line Items]
Payments for Tenant Improvements		$ 400,000
Lessor, Operating Lease, Lease Not yet Commenced, Assumption and Judgment, Value of Underlying Asset, Amount		2,200,000
Operating Lease, Payments		7,793
Lease Cost		6,010,000
Short-term lease cost		128,000
Variable lease cost		299,000
Sublease income		(267,000)
Total lease costs		$ 6,170,000
Weighted average remaining lease term - operating leases (in Years)		5 years 8 months 23 days
Weighted average discount rate -operating leases		4.15%
Future minimum annual lease and service payments
Total Lease Liability		$ 108,368,000	$ 0			$ 110,505,000
Sublease income related to operating leases			1,400,000	$ 1,100,000	$ 2,200,000
Clawback Obligation
Future minimum annual lease and service payments
Contractual obligation			6,200,000
RCG Longview Partners II, LLC | Clawback Obligation
Future minimum annual lease and service payments
Contractual obligation		6,500,000	6,500,000
Equipment Leases
Contractual Commitments, Commitment [Line Items]
Contractual Obligation, Due in Next Fiscal Year			2,434,000
Contractual Obligation, Due in Second Year			1,492,000
Contractual Obligation, Due in Third Year			1,382,000
Contractual Obligation, Due in Fourth Year			1,123,000
Contractual Obligation, Due in Fifth Year			374,000
Contractual Obligation, Due after Fifth Year			0
Contractual Obligation			6,805,000
Short-term lease cost		0
Future minimum annual lease and service payments
2019		770,000
2020		384,000
2021		144,000
2022		55,000
2023		29,000
Thereafter		5,000
Future minimum annual lease and service payments		1,387,000
Less discount		365,000
Uncommenced leases		0
Total Lease Liability		1,022,000
Service Payments
Contractual Commitments, Commitment [Line Items]
Contractual Obligation, Due in Next Fiscal Year		16,420,000	21,758,000
Contractual Obligation, Due in Second Year		9,082,000	7,514,000
Contractual Obligation, Due in Third Year		4,675,000	1,877,000
Contractual Obligation, Due in Fourth Year		5,031,000	1,372,000
Contractual Obligation, Due in Fifth Year		3,573,000	735,000
Contractual Obligation, Due after Fifth Year		6,331,000	735,000
Contractual Obligation		45,112,000	33,991,000
Facility Leases
Contractual Commitments, Commitment [Line Items]
Contractual Obligation, Due in Next Fiscal Year			24,584,000
Contractual Obligation, Due in Second Year			22,608,000
Contractual Obligation, Due in Third Year			22,321,000
Contractual Obligation, Due in Fourth Year			19,166,000
Contractual Obligation, Due in Fifth Year			16,204,000
Contractual Obligation, Due after Fifth Year			21,478,000
Contractual Obligation			$ 126,361,000
Future minimum annual lease and service payments
2019	[1],[2]	16,967,000
2020	[1],[2]	23,828,000
2021	[1],[2]	23,270,000
2022	[1],[2]	20,023,000
2023	[1],[2]	16,950,000
Thereafter	[1],[2]	23,552,000
Future minimum annual lease and service payments	[1],[2]	124,590,000
Less discount		14,950,000
Uncommenced leases		2,165,000
Total Lease Liability		$ 107,347,000
[1]	The Company has entered into a new operating real estate lease that is expected to commence during the second quarter of 2019. The Company is currently planning improvements to the leased asset of which the lessor has granted a tenant allowance of $0.4 million. Payments on the lease asset do not begin until five months after the Company completes its leasehold improvements and begins occupying the space. The total rent payment commitments are $2.2 million, which are included in the table.
[2]	The Company has entered into various agreements to sublease certain of its premises.

Commitments and Contingencies S

Commitments and Contingencies Service Payments (Details) - Service Payments - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Other Commitments [Line Items]
Contractual Obligation, Due in Next Fiscal Year	$ 16,420,000	$ 21,758,000
Contractual Obligation, Due in Second Year	9,082,000	7,514,000
Contractual Obligation, Due in Third Year	4,675,000	1,877,000
Contractual Obligation, Due in Fourth Year	5,031,000	1,372,000
Contractual Obligation, Due in Fifth Year	3,573,000	735,000
Thereafter	6,331,000	735,000
Total Operating Leases	$ 45,112,000	$ 33,991,000

Commitments and Contingencies_3

Commitments and Contingencies Schedules of Unfunded Commitments (Details) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2019USD ($)cowenfund	Dec. 31, 2018
Unfunded Commitments
Other Commitments [Line Items]
Number of real estate investments | cowenfund		5
Real Estate Funds
Other Commitments [Line Items]
Other commitments, unfunded amount	[1]	$ 24.3
Healthcare Royalty Partners
Other Commitments [Line Items]
Other commitments, unfunded amount	[2]	$ 5.9
Healthcare Royalty Partners | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment		2 years
Eclipse Ventures Fund I, L.P.
Other Commitments [Line Items]
Other commitments, unfunded amount		$ 0.1
Eclipse Ventures Fund I, L.P. | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment		5 years
Lagunita Biosciences, LLC
Other Commitments [Line Items]
Other commitments, unfunded amount		$ 1
Lagunita Biosciences, LLC | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment		3 years
Eclipse Fund II, L.P.
Other Commitments [Line Items]
Other commitments, unfunded amount		$ 0.3
Eclipse Fund II, L.P. | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment		6 years
Eclipse Continuity Fund I, L.P.
Other Commitments [Line Items]
Other commitments, unfunded amount		$ 0.3
Eclipse Continuity Fund I, L.P. | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment		7 years
Cowen Healthcare Investments II LP
Other Commitments [Line Items]
Other commitments, unfunded amount		$ 6.9
Cowen Healthcare Investments II LP | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment		2 years
Minimum | Real Estate Funds | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment			2 years
Maximum | Real Estate Funds | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment		4 years
[1]	The Company had unfunded commitments pertaining to capital commitments in five real estate investments held by the Company, all of which pertain to related party investments. Such commitments can be called at any time between
[2]	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 (Details)		Dec. 05, 2016	Mar. 31, 2019USD ($)letters_of_credit$ / sharesshares	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)$ / sharesshares	Dec. 14, 2017USD ($)$ / shares	Dec. 08, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 10, 2014USD ($)
Debt and Capital Lease Obligations [Line Items]
Finance Lease, Right-of-Use Asset, Amortization			$ 368,000	$ 352,000
Finance Lease, Interest Expense			63,000	43,000
Finance Lease, Interest Payment on Liability			63,000	43,000
Finance Lease, Principal Payments			394,000	506,000
Preferred stock dividends			(1,698,000)	(1,698,000)
Components of short-term borrowings and other debt
Convertible debt			115,099,000		$ 134,489,000
Note payable			229,863,000		229,740,000
Loans Payable to Bank			28,200,000		28,200,000
Other Notes Payable			1,579,000		0
Capital lease obligations			4,631,000		5,025,000
Debt, Long-term and Short-term, Combined Amount			379,372,000		397,454,000
Purchase of treasury stock, cost			4,658,000
Interest on Convertible Debt, Net of Tax				1,000,000
Amortization of debt discount			1,349,000	1,442,000
Stockholders' Equity Note, Stock Split, Conversion Ratio		0.25
Letter of credit, borrowing capacity			370,000,000
Capital Lease Obligations Incurred			6,000,000
Future minimum lease payments for capital lease obligations
2019			896,000
2020			1,360,000
2021			1,360,000
2022			1,127,000
2023			374,000
Thereafter			0
Subtotal			5,117,000
Less: Amount representing interest	[1]		(486,000)
Capital lease obligations			$ 4,631,000		5,025,000
Number of letters of credit | letters_of_credit			7
Cash collateral pledged			$ 6,420,000	14,786,000	$ 6,318,000
Preferred stock, shares authorized | shares			10,000,000		10,000,000
Preferred stock, par value (in dollars per share) | $ / shares			$ 0.01		$ 0.01
Finance Lease, Weighted Average Remaining Lease Term			3 years 10 months 24 days
Finance Lease, Weighted Average Discount Rate, Percent			4.93%
Letter of Credit, Boston Office, Expires March 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			$ 389,007
Letter of Credit, NY Office 1, Expires April 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			358,468
Letter of Credit, NY Office 2, Expires May 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			70,881
Letter of Credit, NY Office 3, Expires October 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			397,451
Letter of Credit, NY Office 4, Expires October 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			1,686,697
Letter of Credit, NY Office 5, Expires November 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			1,611,291
Letter of Credit, San Francisco Office, Expires January 2020 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			708,090
Convertible Debt
Components of short-term borrowings and other debt
Convertible debt, unamortized discount			23,400,000		$ 24,900,000
Repayments on long-term and short-term borrowings
2019			4,050,000
2020			4,050,000
2021			4,050,000
2022			139,050,000
2023			0
Thereafter			0
Subtotal			151,200,000
Less: Amount representing interest	[1]		(36,101,000)
Senior Notes
Components of short-term borrowings and other debt
Note payable			229,863,000
Repayments on long-term and short-term borrowings
2019			13,420,000
2020			17,893,000
2021			17,893,000
2022			17,893,000
2023			17,893,000
Thereafter			352,197,000
Subtotal			437,189,000
Less: Amount representing interest	[1]		(207,326,000)
Notes Payable to Banks
Components of short-term borrowings and other debt
Debt Instrument, Face Amount								$ 28,200,000
Interest Expense, Debt, Excluding Amortization			$ 400,000	400,000
Short-term Debt, Percentage Bearing Variable Interest Rate			3.75%
Insurance Note
Components of short-term borrowings and other debt
Interest rate			2.51%
Short-term Debt, Maximum Amount Outstanding During Period			$ 2,200,000
Debt Instrument, Periodic Payment, Principal			200,000
Loans
Repayments on long-term and short-term borrowings
2019			28,508,000
2020			0
2021			0
2022			0
2023			0
Thereafter			0
Subtotal			28,508,000
Less: Amount representing interest	[1]		(308,000)
Insurance Note and Aircraft [Member]
Repayments on long-term and short-term borrowings
2019			2,171,000
2020			0
2021			0
2022			0
2023			0
Thereafter			0
Subtotal			2,171,000
Less: Amount representing interest	[1]		$ (592,000)
Common Stock Class A
Debt and Capital Lease Obligations [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
2022 convertible note | Convertible Debt
Components of short-term borrowings and other debt
Convertible debt			$ 135,000,000
Debt Instrument, Face Amount						$ 135,000,000
Debt Instrument, Convertible, Conversion Price | $ / shares						$ 17.375
Purchase of treasury stock, cost			19,500,000
Interest on Convertible Debt, Net of Tax			1,000,000
Convertible debt, unamortized discount									$ 23,400,000
Amortization of debt discount			1,100,000	1,000,000
Debt Instrument, Interest Rate, Effective Percentage									7.57%
Debt Issuance Costs, Gross									$ 2,200,000
2019 convertible note | Convertible Debt
Components of short-term borrowings and other debt
Debt Instrument, Face Amount									149,500,000
Debt Instrument, Repurchase Amount									$ 115,100,000
Interest on Convertible Debt, Net of Tax			100,000	500,000
Amortization of debt discount			300,000	500,000
Debt Instrument, Interest Rate, Effective Percentage									8.89%
Interest rate									3.00%
2033 Notes | Senior Notes
Components of short-term borrowings and other debt
Debt Instrument, Face Amount						$ 10,000,000	$ 90,000,000
Debt Issuance Costs, Gross							$ 3,600,000
Interest rate							7.75%
Interest Expense, Debt, Excluding Amortization			1,900,000
2027 Notes | Senior Notes
Components of short-term borrowings and other debt
Debt Instrument, Face Amount						$ 18,000,000	$ 120,000,000
Debt Issuance Costs, Gross							$ 5,000,000
Interest rate							7.35%
Interest Expense, Debt, Excluding Amortization			2,500,000	2,500,000
Collateral Reinsurance Agreement
Future minimum lease payments for capital lease obligations
Cash collateral pledged			1,200,000		$ 1,000,000
Retained Earnings/(Accumulated deficit) | Convertible Preferred Stock
Debt and Capital Lease Obligations [Line Items]
Preferred stock dividends			$ (1,698,000)	$ (1,698,000)
[1]	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 convertible debt.

Stockholder's Equity - Quarterl

Stockholder's Equity - Quarterly (Details) - USD ($) $ / shares in Units, $ in Thousands	May 19, 2015	Mar. 31, 2019	Mar. 31, 2018
Equity, Class of Stock [Line Items]
Preferred stock dividends declared		$ 1,698	$ 1,698
Convertible Preferred Stock, Shares Issued upon Conversion	38.0619
Convertible Preferred Stock, Threshold Percentage of Stock Price Trigger		150.00%
Treasury Stock, Shares [Roll Forward]
Treasury stock, shares, beginning of period		15,336,871
Purchase of treasury stock, shares		315,400
Treasury stock, shares, end of period		15,978,829
Treasury stock, cost, beginning of period		$ 234,142
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions		4,671	4,910
Purchase of treasury stock, cost		4,658
Treasury stock, cost, end of period		$ 243,519
Treasury stock, average cost per share, beginning of period, in dollars per share		$ 15.27
Purchase of treasury stock, average cost per share, in dollars per share		14.77
Treasury stock, average cost per share, end of period, in dollars per share		$ 15.24
Treasury Stock
Treasury Stock, Shares [Roll Forward]
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions		323,227
Treasury stock shares received, other		3,331
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions		$ 4,671
Treasury stock received, value, other		$ 48
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions, Average Cost Per Share		$ 14.45
Treasury stock received, per share, other		$ 14.41
Call Option
Equity, Class of Stock [Line Items]
Option indexed to Issuer's Equity, Value	$ 15,900
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		$ 26.27
Maximum
Equity, Class of Stock [Line Items]
Convertible Preferred Stock, Threshold Consecutive Trading Days		30 days
Maximum | Call Option
Equity, Class of Stock [Line Items]
Option Indexed to Issuer's Equity, Strike Price		$ 33.54
Convertible Preferred Stock
Equity, Class of Stock [Line Items]
Preferred stock issuance, net of issuance costs, 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	$ 1,000
Convertible Preferred Stock | Retained Earnings/(Accumulated deficit)
Equity, Class of Stock [Line Items]
Preferred stock dividends declared		1,698	$ 1,698
2022 convertible note | Convertible Debt
Treasury Stock, Shares [Roll Forward]
Purchase of treasury stock, cost		$ 19,500

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income / (Loss) [Abstract]
Beginning Balance	$ (5)	$ (8)
Foreign currency translation	0	1
Ending Balance	$ (5)	$ (7)

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Computation of earnings per share:
Net income (loss)	$ 11,989	$ 28,009
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	2,206	11,156
Net income (loss) attributable to Cowen Inc.	9,783	16,853
Preferred stock dividends	1,698	1,698
Net income (loss) attributable to Cowen Inc. common stockholders	$ 8,085	$ 15,155
Shares for basic and diluted calculations:
Weighted average shares used in basic computation, shares	29,750,000	29,625,000
Weighted average shares used in diluted computation, shares	31,625,000	30,492,000
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 0.27	$ 0.51
Earnings Per Share, Diluted (in dollars per share)	$ 0.26	$ 0.50
Restricted Stock
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares	1,875,000	867,000
Common Stock Class A
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares outstanding, shares	29,580,687	29,517,218	28,437,860	29,632,020
Common stock, restricted shares, shares	253,772		253,772

Segment Reporting (Details)

Segment Reporting (Details)		3 Months Ended
		Mar. 31, 2019USD ($)segmentcustomer		Mar. 31, 2018USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment		2
Entity-wide revenue, major customer, number | customer		0
Revenues
Investment banking		$ 80,106,000		$ 97,988,000
Brokerage		97,463,000		105,733,000
Management fees		7,141,000		7,417,000
Incentive income		15,000		16,000
Investment Income		0		0
Interest and dividends		29,092,000		25,954,000
Reimbursement from affiliates		288,000		377,000
Aircraft lease revenue		0		715,000
Reinsurance premiums		6,591,000		8,647,000
Other revenues		1,061,000		1,336,000
Total revenues		224,097,000		251,384,000
Interest expense		29,084,000		24,540,000
Total net revenues		195,013,000		226,844,000
Expenses
Non-interest expense		219,307,000		223,315,000
Total expenses		220,789,000		225,746,000
Other income (loss)
Total other income (loss)		40,942,000		33,834,000
Income tax expense (benefit)		3,177,000		6,923,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		2,206,000		11,156,000
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		9,783,000		16,853,000
Preferred stock dividends		1,698,000		1,698,000
Net income (loss) attributable to Cowen Inc. common stockholders		8,085,000		15,155,000
Consolidated Funds
Revenues
Total revenues		2,340,000		3,201,000
Expenses
Total expenses		1,482,000		2,431,000
Operating Segments
Revenues
Investment banking		82,991,000		93,924,000
Brokerage		105,157,000		114,071,000
Management fees		10,431,000		13,126,000
Incentive income		16,747,000		5,197,000
Investment Income		16,984,000		14,301,000
Interest and dividends		0		0
Reimbursement from affiliates		0		0
Aircraft lease revenue		0		0
Reinsurance premiums		0		0
Other revenues		1,159,000		888,000
Total revenues		233,469,000		241,507,000
Interest expense		6,564,000		5,958,000
Total net revenues		226,905,000		235,549,000
Expenses
Non-interest expense		207,185,000		209,333,000
Total expenses		207,185,000		209,333,000
Other income (loss)
Total other income (loss)		0		0
Income tax expense (benefit)		0		0
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		2,748,000		2,158,000
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		16,972,000		24,058,000
Preferred stock dividends		1,698,000		1,698,000
Net income (loss) attributable to Cowen Inc. common stockholders		15,274,000		22,360,000
Other Depreciation and Amortization		4,956,000		2,986,000
Operating Segments | Consolidated Funds
Revenues
Total revenues		0		0
Expenses
Total expenses		0		0
Operating Segments | Investment Management
Revenues
Investment banking		0		0
Brokerage		0		0
Management fees		9,633,000		12,355,000
Incentive income		16,747,000		5,197,000
Investment Income		7,029,000		11,896,000
Interest and dividends		0		0
Reimbursement from affiliates		0		0
Aircraft lease revenue		0		0
Reinsurance premiums		0		0
Other revenues		439,000		361,000
Total revenues		33,848,000		29,809,000
Interest expense		2,806,000		3,854,000
Total net revenues		31,042,000		25,955,000
Expenses
Non-interest expense		22,023,000		22,881,000
Total expenses		22,023,000		22,881,000
Other income (loss)
Total other income (loss)		0		0
Income tax expense (benefit)		0		0
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		2,748,000		2,158,000
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		6,271,000		916,000
Operating Segments | Investment Management | Consolidated Funds
Revenues
Total revenues		0		0
Expenses
Total expenses		0		0
Operating Segments | Investment Bank
Revenues
Investment banking		82,991,000		93,924,000
Brokerage		105,157,000		114,071,000
Management fees		798,000		771,000
Incentive income		0		0
Investment Income		9,955,000		2,405,000
Interest and dividends		0		0
Reimbursement from affiliates		0		0
Aircraft lease revenue		0		0
Reinsurance premiums		0		0
Other revenues		720,000		527,000
Total revenues		199,621,000		211,698,000
Interest expense		3,758,000		2,104,000
Total net revenues		195,863,000		209,594,000
Expenses
Non-interest expense		185,162,000		186,452,000
Total expenses		185,162,000		186,452,000
Other income (loss)
Total other income (loss)		0		0
Income tax expense (benefit)		0		0
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		0		0
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		10,701,000		23,142,000
Operating Segments | Investment Bank | Consolidated Funds
Revenues
Total revenues		0		0
Expenses
Total expenses		0		0
Adjustments | Funds Consolidation
Revenues
Investment banking		0		0
Brokerage		0		0
Management fees		(501,000)		(1,203,000)
Incentive income		(544,000)		(9,000)
Investment Income		0		0
Interest and dividends		0		0
Reimbursement from affiliates		(34,000)		(68,000)
Aircraft lease revenue		0		0
Reinsurance premiums		0		0
Other revenues		0		0
Total revenues		1,261,000		1,921,000
Interest expense		0		0
Total net revenues		1,261,000		1,921,000
Expenses
Non-interest expense		0		0
Total expenses		1,482,000		2,431,000
Other income (loss)
Total other income (loss)		621,000		10,047,000
Income tax expense (benefit)		0		0
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		400,000		9,537,000
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		0		0
Adjustments | Funds Consolidation | Consolidated Funds
Revenues
Total revenues		2,340,000		3,201,000
Expenses
Total expenses		1,482,000		2,431,000
Adjustments | Other Adjustments
Revenues
Investment banking		(2,885,000)	[1]	4,064,000
Brokerage	[2]	(7,694,000)		(8,338,000)
Management fees	[3]	(2,789,000)		(4,506,000)
Incentive income	[3]	(16,188,000)	[1]	(5,172,000)
Investment Income	[4],[5]	(16,984,000)		(14,301,000)
Interest and dividends	[5]	29,092,000		25,954,000
Reimbursement from affiliates	[6]	322,000		445,000
Aircraft lease revenue	[4]	0		715,000
Reinsurance premiums	[7]	6,591,000		8,647,000
Other revenues	[7]	(98,000)		448,000
Total revenues		(10,633,000)		7,956,000
Interest expense	[5]	22,520,000		18,582,000
Total net revenues		(33,153,000)		(10,626,000)
Expenses
Non-interest expense	[5],[8],[9]	12,122,000		13,982,000
Total expenses		12,122,000		13,982,000
Other income (loss)
Total other income (loss)	[5],[10],[11]	40,321,000		23,787,000
Income tax expense (benefit)	[8]	3,177,000		6,923,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		(942,000)		(539,000)
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		(7,189,000)		(7,205,000)
Adjustments | Other Adjustments | Consolidated Funds
Revenues
Total revenues		0		0
Expenses
Total expenses		0		0
Other Adjustments | Operating Segments
Other income (loss)
Net income (loss) attributable to Cowen Inc. common stockholders		$ 20,230,000		$ 25,346,000
[1]	Economic Income (Loss) presents underwriting expenses net of investment banking revenues, expenses reimbursedfrom clients within their respective expense category and records income from uncrystallized incentive fees. Economic Income (Loss) also records retainer fees, relating to investment banking activities, collectible during the period that would otherwise be deferred until closing for US GAAP reporting
[2]	Economic Income (Loss) brokerage revenues included net securities borrowed and securities loaned activities.
[3]	Economic Income (Loss) recognizes revenues (i) net of distribution fees paid to agents and (ii) our proportionate share of management and incentive fees of certain real estate operating entities, the healthcare royalty business and the activist business.
[4]	Aircraft lease revenue is shown net of expenses in investment income for Economic Income (Loss).
[5]	Economic Income (Loss) recognizes Company income from proprietary trading (including interest and dividends).
[6]	Reimbursement from affiliates is shown as a reduction of Economic Income expenses, but is included as a part of revenues under US GAAP.
[7]	Economic Income (Loss) recognizes underwriting income from the Company's insurance related activities, net of expenses, within other revenue.
[8]	Economic Income (Loss) excludes income taxes and acquisition related adjustments as management does not consider these items when evaluating the performance of the segment.
[9]	Economic Income (Loss) recognizes the Company's proportionate share of expenses, for certain real estate operating entities and the activist business, for which the investments are recorded under the equity method of accounting for investments.
[10]	Economic Income (Loss) excludes gain/(loss) on debt extinguishment.
[11]	Economic Income (Loss) excludes the bargain purchase gain which resulted from the Convergex Group acquisition.

Regulatory Requirements (Detail

Regulatory Requirements (Details)	3 Months Ended
	Mar. 31, 2019USD ($)
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	1,000,000
Net capital	101,500,000
Excess capital	100,500,000
Cowen Securities [Member]
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	5,000
Excess capital	100,000
Cowen Execution
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	15,100,000
Net capital requirement under alternative method	2,000,000
Required net capital under commodity exchange act	114,800,000
Net capital	116,800,000
Excess capital	114,800,000
ATM Execution LLC
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	300,000
Net capital	3,200,000
Excess capital	2,900,000
Cowen Prime
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	300,000
Net capital	8,400,000
Excess capital	8,100,000
Westminster Research
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	300,000
Net capital	19,400,000
Excess capital	19,100,000
RCG Insurance Company
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	300,000
Net capital	32,100,000
Options Clearing Corporation | Cowen Execution
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	$ 14,900,000
Financial resources requirement	9,900,000
Excess financial resources	5,000,000
U.K. Financial Services Authority | Cowen Execution Services Ltd
Regulatory Requirements for Broker-Dealers [Line Items]
Financial resources	5,000,000
Financial resources requirement	3,200,000
Excess financial resources	1,800,000
Minimum | Cowen Execution
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	3,000,000
Required net capital under commodity exchange act	45,000
Special Reserve Accounts | Cowen Execution
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	25,600,000
Special Reserve Accounts | Minimum | Cowen Execution
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	$ 16,300,000

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Fees receivable	$ (130,099)		$ (111,946)
Due from related parties	28,841		33,870
Redeemable non-controlling interests, Related Party	418,277		284,780
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds	(2,206)	$ (11,156)
Employees
Related Party Transaction [Line Items]
Redeemable non-controlling interests, Related Party	27,300		25,100
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and investment funds	(1,500)	(2,900)
Employee Loans
Related Party Transaction [Line Items]
Due from employees	14,500		17,000
Forgivable Loan Balances	7,900		8,800
Amortization on Forgivable Loans	$ 900	$ 600
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	$ (20,000)		(19,400)
Investor
Related Party Transaction [Line Items]
Due to Affiliate	600		600
Other Funds
Related Party Transaction [Line Items]
Due from related parties	7,500		8,900
Starboard Value LP
Related Party Transaction [Line Items]
Effective interest rate		5.00%
Interest Income, Related Party	100	$ 100
Due from related parties	$ 6,700		$ 7,700
Finance Period	5 years

Guarantees and Off-Balance Sh_3

Guarantees and Off-Balance Sheet Arrangements (Details)	Mar. 31, 2019USD ($)
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	$ 370,000,000
Line of credit facility, remaining borrowing capacity	370,000,000
Pledge Lines
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	300,000,000
Line of credit facility, remaining borrowing capacity	300,000,000
Texas Capital Bank | Pledge Lines
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	75,000,000
Line of credit facility, remaining borrowing capacity	75,000,000
BMO Harris Bank | Pledge Lines
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	150,000,000
Line of credit facility, remaining borrowing capacity	150,000,000
BMO Harris Bank | Tri-Party Pledge Line
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	75,000,000
Line of credit facility, remaining borrowing capacity	75,000,000
BMO Harris Bank | Revolving Credit Facility
Debt Instrument [Line Items]
Letter of credit, borrowing capacity	70,000,000
Line of credit facility, remaining borrowing capacity	$ 70,000,000

Subsequent Events - Narrative (

Subsequent Events - Narrative (Details) - Subsequent Event - USD ($)	Apr. 25, 2019	Apr. 23, 2019
Subsequent Event [Line Items]
Stock Repurchase Program Additional Authorized Amount		$ 19,700,000
Stock Repurchase Program, Authorized Amount		$ 25,000,000
2027 Notes [Member] | Senior Notes
Subsequent Event [Line Items]
Debt Instrument, Face Amount	$ 45,000,000
Interest rate	7.25%