Cowen (COWN) 10-Q 31 Oct 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Cowen Inc.
Entity Central Index Key	1,466,538
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		29,140,689

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 193,066	$ 130,052
Cash collateral pledged	16,092	17,888
Segregated cash	154,191	116,268
Securities owned, at fair value	644,169	673,221
Receivable on derivative contracts, at fair value	32,229	69,177
Securities Borrowed, Gross	713,288	443,148
Securities borrowed	713,288	443,148
Other investments	167,428	141,548
Deposits with clearing organizations, brokers and banks	98,646	93,996
Receivable from brokers, dealers and clearing organizations	644,392	508,178
Receivable from customers, net of allowance of $551 and $1,550, respectively	33,240	49,891
Fees receivable, net of allowance of $2,040 and $1,736, respectively	111,756	111,784
Due from related parties	32,509	34,814
Fixed assets, net of accumulated depreciation and amortization of $33,150 and $28,355, respectively	41,458	40,496
Goodwill	60,678	60,678
Intangible assets, net of accumulated amortization of $37,038 and $33,081, respectively	25,998	29,955
Deferred tax asset, net	101,683	116,323
Other assets	67,118	88,268
Consolidated Funds
Cash and cash equivalents, Consolidated Funds	18,747	21,988
Securities owned, at fair value	108,901	165,916
Receivable on derivative contracts, at fair value	1,911	2,520
Other Investments, Consolidated Funds	183,290	374,111
Receivable from brokers, Consolidated Funds	11,017	5,644
Other assets, Consolidated Funds	355	388
Total Assets	3,462,162	3,296,252
Liabilities
Securities sold, not yet purchased, at fair value	374,518	342,527
Payable for derivative contracts, at fair value	30,002	42,750
Securities Loaned, Gross	548,629	456,831
Securities loaned	548,629	456,831
Payables to brokers, dealers and clearing organizations	210,326	252,153
Payable to customers	470,476	352,467
Commission management payable	90,233	70,451
Compensation payable	189,249	150,206
Notes payable and other debt	271,082	173,458
Convertible debt	133,126	141,502
Fees payable	22,258	8,047
Due to related parties	571	570
Accounts payable, accrued expenses and other liabilities	94,731	96,533
Consolidated Funds
Payable for derivative contracts, at fair value	2,189	7,130
Payable to brokers	1,936	751
Capital withdrawals payable	11,120	11,931
Accounts payable, accrued expenses and other liabilities	260	322
Total Liabilities	2,450,706	2,107,629
Commitments and Contingencies
Redeemable non-controlling interests	203,212	440,604
Stockholders' equity
Additional paid-in capital	1,061,274	1,004,664
(Accumulated deficit) retained earnings	(38,029)	(70,116)
Accumulated other comprehensive income (loss)	(3)	(8)
Less: Class A common stock held in treasury, at cost, 14,092,732 and 12,133,276 shares as of September 30, 2018 and December 31, 2017, respectively.	(215,323)	(186,846)
Total Stockholders' Equity	808,244	748,019
Total Liabilities and Stockholders' Equity	3,462,162	3,296,252
Convertible Preferred Stock
Stockholders' equity
Preferred stock	1	1
Common Stock Class A
Stockholders' equity
Common stock	324	324
Less: Class A common stock held in treasury, at cost, 14,092,732 and 12,133,276 shares as of September 30, 2018 and December 31, 2017, respectively.	(215,323)	(186,846)
Common Stock Class B
Stockholders' equity
Common stock	$ 0	$ 0

Consolidated Statements of Fi_2

Consolidated Statements of Financial Condition (Parenthetical) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Allowance for receivable from brokers	$ 551,000	$ 1,550,000
Allowance for receivable from customers	2,040,000	1,736,000
Assets
Fixed assets, accumulated depreciation and amortization (in dollars)	33,150,000	28,355,000
Intangible assets, accumulated amortization (in dollars)	$ 37,038,000	$ 33,081,000
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	14,092,732	12,133,276
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	43,235,279	41,765,296
Common stock, shares outstanding	29,142,547	29,632,020
Common stock, restricted shares	253,772	191,962
Treasury Stock, Shares	14,092,732	12,133,276
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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Investment banking	$ 81,923	$ 57,383	$ 264,737	$ 158,082
Brokerage	92,035	84,220	301,053	198,599
Management fees	7,546	8,223	22,336	25,587
Incentive income	33	1,945	97	6,217
Interest and dividends	26,448	14,318	77,511	27,324
Reimbursement from affiliates	353	484	1,066	2,631
Aircraft lease revenue	375	934	1,509	3,036
Reinsurance premiums	8,378	7,186	26,251	21,957
Other revenues	1,634	3,402	3,846	6,147
Consolidated Funds
Interest and dividends	2,294	871	8,565	4,253
Other revenues	9	(136)	14	498
Total revenues	221,028	178,830	706,985	454,331
Interest and dividends expense	26,000	15,132	74,846	37,273
Revenue, Net	195,028	163,698	632,139	417,058
Expenses
Employee compensation and benefits	127,303	103,282	394,288	282,066
Floor brokerage and trade execution	23,217	25,817	82,317	48,218
Underwriting expenses	4,412	0	13,260	0
Professional, advisory and other fees	7,698	7,001	20,541	23,344
Service fees	4,880	3,983	14,927	9,927
Communications	7,894	6,423	22,566	17,186
Occupancy and equipment	10,140	9,656	30,385	25,252
Depreciation and amortization	3,139	3,452	9,558	9,612
Client services and business development	6,671	5,551	22,767	20,505
Reinsurance claims, commissions and amortization of deferred acquisition costs	8,773	7,157	27,428	20,610
Restructuring costs	0	222	0	8,763
Other expenses	5,335	4,960	15,007	12,550
Consolidated Funds
Interest and dividends	1,270	1,234	5,660	7,325
Professional, advisory and other fees	191	205	748	901
Floor brokerage and trade execution	39	64	192	278
Other expenses	187	209	667	919
Total expenses	211,149	179,216	660,311	487,456
Other income (loss)
Net gains (losses) on securities, derivatives and other investments	32,040	18,326	64,728	63,101
Bargain purchase gain, net of tax	0	0	0	7,946
Gain (loss) on debt extinguishment	0	0	(556)	0
Consolidated Funds
Net realized and unrealized gains (losses) on investments and other transactions	8,280	9,073	52,284	48,154
Net realized and unrealized gains (losses) on derivatives	1,664	220	6,258	5,405
Net gains (losses) on foreign currency transactions	(2)	8	250	(299)
Total other income (loss)	41,982	27,627	122,964	124,307
Income (loss) before income taxes	25,861	12,109	94,792	53,909
Income tax expense (benefit)	5,083	2,281	15,999	3,407
Net income (loss)	20,778	9,828	78,793	50,502
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	(5,290)	(5,162)	(41,053)	(35,412)
Net income (loss) attributable to Cowen Inc.	15,488	4,666	37,740	15,090
Preferred stock dividends	1,698	1,698	5,094	5,094
Net income (loss) attributable to Cowen Inc. common stockholders	$ 13,790	$ 2,968	$ 32,646	$ 9,996
Weighted average common shares outstanding:
Basic (in shares)	29,610	31,271	29,662	29,004
Diluted (in shares)	30,844	32,246	30,613	30,011
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 0.47	$ 0.09	$ 1.10	$ 0.34
Earnings Per Share, Diluted (in dollars per share)	$ 0.45	$ 0.09	$ 1.07	$ 0.33

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 20,778	$ 9,828	$ 78,793	$ 50,502
Other comprehensive income (loss), net of tax:
Foreign currency translation	4	0	5	(6)
Total other comprehensive income (loss), net of tax	4	0	5	(6)
Comprehensive income (loss)	$ 20,782	$ 9,828	$ 78,798	$ 50,496

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, 2016						26,731,289
Balance, start at Dec. 31, 2016	$ 772,650	$ (153,845)	$ 928,646	$ (2)	$ (2,442)	$ 292	$ 1
Preferred stock, shares outstanding, start at Dec. 31, 2016							120,750
Redeemable Non-controlling Interest, start at Dec. 31, 2016	379,205
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to Cowen Inc.	15,090				15,090
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	35,412
Foreign currency translation	(6)			(6)
Capital contributions	60,322
Capital withdrawals	(53,278)
Deconsolidation of funds	$ 0
Common stock issued during period, shares, acquisitions	3,162,278
Common stock issued during period, value, acquisitions	$ 47,607		47,575			$ 32
Restricted stock awards issued, shares						1,985,618
Purchase of treasury stock, at cost, shares						(791,727)
Purchase of treasury stock, at cost	(11,433)	(11,433)
Preferred stock dividends	(5,094)							$ (5,094)
Embedded Cash Conversion Option	0
Amortization of share based compensation	24,702		24,702
Common stock, shares outstanding, end at Sep. 30, 2017						31,087,458
Balance, end at Sep. 30, 2017	843,516	(165,278)	1,000,923	(8)	7,554	$ 324	$ 1
Preferred stock, shares outstanding, end at Sep. 30, 2017							120,750
Redeemable Non-controlling Interest, end at Sep. 30, 2017	421,661
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						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.	37,740				37,740
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	41,053
Foreign currency translation	5			5
Capital contributions	25,175
Capital withdrawals	(271,061)
Deconsolidation of funds	(32,559)
Common stock issued during period, value, acquisitions	0
Restricted stock awards issued, shares						1,469,983
Purchase of treasury stock, at cost, shares						(1,959,456)
Purchase of treasury stock, at cost	(28,477)	(28,477)
Preferred stock dividends	(5,094)							$ (5,094)
Embedded Cash Conversion Option	28,974		28,974
Amortization of share based compensation	27,636		27,636
Common stock, shares outstanding, end at Sep. 30, 2018						29,142,547
Balance, end at Sep. 30, 2018	$ 808,244	$ (215,323)	$ 1,061,274	$ (3)	$ (38,029)	$ 324	$ 1
Preferred stock, shares outstanding, end at Sep. 30, 2018	120,750						120,750
Redeemable Non-controlling Interest, end at Sep. 30, 2018	$ 203,212

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ 20,778	$ 9,828	$ 78,793	$ 50,502
Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities:
Bargain purchase gain, net of tax			0	(7,946)
Depreciation and amortization	3,139	3,452	9,558	9,612
Amortization of debt issuance costs			990	936
Amortization of debt discount			4,177	5,601
Gain / (loss) on extinguishment of debt			(652)	0
Share-based compensation			27,636	24,702
Deferred tax benefit			14,640	7,039
Deferred rent obligations			(2,532)	(1,503)
Net loss (gain) on disposal of fixed assets			146	(2,362)
Purchases of securities owned, at fair value			(3,137,168)	(3,442,431)
Proceeds from sales of securities owned, at fair value			3,329,707	3,620,347
Proceeds from sales of securities sold, not yet purchased, at fair value			2,132,935	1,809,863
Payments to cover securities sold, not yet purchased, at fair value			(2,233,427)	(1,799,136)
Proceeds from the sale of other investments			7,313	0
Net (gains) losses on securities, derivatives and other investments			(61,927)	(76,325)
Consolidated Funds
Purchases of securities owned, at fair value			(457,293)	(261,863)
Proceeds from sales of securities owned, at fair value			491,427	241,307
Proceeds from sales of securities sold, not yet purchased, at fair value			0	217
Payments to cover securities sold, not yet purchased, at fair value			0	(899)
Purchases of other investments			(1,414)	(26,206)
Proceeds from sales of other investments			230,832	51,709
Net realized and unrealized (gains) losses on investments and other transactions			(58,523)	(43,423)
(Increase) decrease in operating assets:
Cash acquired through acquisition			0	159,587
Securities owned, at fair value, held at broker-dealer			(124,740)	(58,126)
Receivable on derivative contracts, at fair value			36,949	(9,204)
Securities borrowed			(270,140)	(113,046)
Deposits with clearing organizations, brokers and banks			(4,650)	(22,625)
Receivable from brokers, dealers and clearing organizations			(136,214)	(105,255)
Receivable from customers, net of allowance			16,651	(2,040)
Fees receivable, net of allowance			(6,211)	(28,839)
Due from related parties			2,765	2,222
Other assets			16,573	(31,415)
Consolidated Funds
Cash and cash equivalents			(130)	6,605
Receivable on derivative contracts, at fair value			609	(149)
Receivable from brokers			(5,373)	(2,356)
Other assets			(153)	222
Increase (decrease) in operating liabilities:
Securities sold, not yet purchased, at fair value, held at broker dealer			146,853	(100)
Payable for derivative contracts, at fair value			16,225	5,555
Securities loaned			91,798	128,598
Payable to brokers, dealers and clearing organizations			(41,827)	(128,490)
Payable to customers			118,009	190,926
Commission management payable			19,782	(8,457)
Compensation payable			30,500	(38,092)
Fees payable			14,211	2,807
Due to related parties			1	(6)
Accounts payable, accrued expenses and other liabilities			1,527	19,109
Consolidated Funds
Contributions received in advance			0	(2,000)
Payable to brokers			1,185	(2,289)
Payable for derivative contracts, at fair value			(4,941)	1,175
Due to related parties			0	(189)
Accounts payable, accrued expenses and other liabilities			205	(438)
Net cash provided by / (used in) operating activities			295,986
Net Cash Provided by (Used in) Operating Activities			295,986	123,431
Cash flows from investing activities:
Purchases of other investments			(21,355)	(72,834)
Purchase of business			0	(54,017)
Proceeds from sales of other investments			15,730	118,130
Proceeds from loans held for investment			1,410	3,200
Purchase of fixed assets			(6,710)	(3,056)
Sale of fixed assets			0	7,850
Net Cash Provided by (Used in) Investing Activities			(10,925)	(727)
Net cash provided by / (used in) investing activities			(10,925)
Cash flows from financing activities:
Repayments on convertible debt			(13,500)	0
Deferred debt issuance cost			(3,985)	0
Borrowings on notes and other debt			102,382	31,737
Repayments on notes and other debt			(6,561)	(8,845)
Purchase of treasury stock			(16,763)	0
Contingent liability payment			(797)	(393)
Capital contributions by redeemable non-controlling interests in operating entities			581	0
Capital withdrawals to redeemable non-controlling interests in operating entities			(1,685)	(4,628)
Consolidated Funds
Capital contributions by redeemable non-controlling interests in Consolidated Funds			24,594	60,322
Capital withdrawals to redeemable non-controlling interests in Consolidated Funds			(270,186)	(50,778)
Net Cash Provided by (Used in) Financing Activities			(185,920)	27,415
Change in cash and cash equivalents			99,141	150,119
Total cash beginning of period			264,208	125,356	$ 125,356
Cash and cash equivalents	193,066	117,824	193,066	117,824	130,052
Cash collateral pledged	16,092	16,995	16,092	16,995	17,888
Segregated cash	154,191	140,656	154,191	140,656	116,268
Total cash at end of period	$ 363,349	$ 275,475	363,349	275,475	$ 264,208
Supplemental information
Cash paid during the year for interest			62,371	24,528
Cash paid during the year for taxes			4,862	1,944
Purchase of treasury stock, at cost, through net settlement			8,544	11,433
Preferred stock dividends declared			5,094	5,094
Net assets (liabilities) acquired upon acquisition (net of cash)			0	(50,017)
Transfer of investment from consolidated funds, securities owned, fair value to securities owned, fair value			8,820	0
Net decrease in redeemable non-controlling interests in Consolidated Funds due to deconsolidation of consolidated fund			32,559	0
Separately recognized conversion option reclassification from a derivative liability to equity			28,974	0
Common stock issuance upon close of acquisition			0	47,607
Conversion of redeemable non-controlling interest to loan receivable			$ 0	$ 1,299

Organization and Business

Organization and Business	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business	Organization and Business Cowen Inc. (formerly Cowen Group, 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 private funds, managed accounts, real estate funds, private equity structures and listed vehicles . 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 .

Acquisition

Acquisition	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Acquisitions	Acquisition On April 2, 2017, the Company, through its wholly owned subsidiary Cowen CV Acquisition LLC, entered into a securities purchase agreement with, among others, Convergex Holdings LLC to acquire all the outstanding interests in Convergex Group, LLC ("Convergex Group") (subsequently renamed to Cowen Execution Holdco LLC) , a provider of agency based execution services and trading technology to middle market institutional investors and broker-dealers . Convergex Group's operations were primarily conducted through two U.S. Securities Exchange Commission ("SEC") registered broker-dealers, Convergex Execution Solutions LLC (subsequently renamed to Cowen Execution Services LLC) ("Cowen Execution") and Westminster Research Associates LLC ("Westminster") and also Convergex Limited (subsequently renamed to Cowen Execution Services Limited) ("Cowen Execution Ltd"), which is based in the United Kingdom and regulated by the Financial Conduct Authority ("FCA"). The purchase price was paid approximately 50% in cash and 50% in Cowen Inc. Class A common stock. The acquisition was accounted for under the acquisition method of accounting in accordance with accounting principles generally accepted in the United States of America ("US GAAP"). As such, results of operations for Convergex Group 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 Convergex Group were integrated within the Company's existing businesses. The acquisition was consummated effective as of June 1, 2017. The adjusted aggregate estimated purchase price was $98.0 million , which was determined based on closing date tangible book value of Convergex Group, less certain closing adjustments. Based on the closing date purchase price allocation, the fair value of the net identifiable assets acquired and liabilities assumed of $109.6 million exceeded the estimated purchase price of $98.0 million . As a result, the Company recognized a bargain purchase gain of $11.6 million during 2017 related to the acquisition. The bargain purchase gain was shown net of $4.7 million of associated tax. Subsequent to the acquisition, certain of Convergex Group'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 unaudited supplemental pro forma financial information for the nine months ended September 30, 2017 , as if the acquisition were completed as of January 1, 2017. 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, 2017, nor does it purport to be indicative of any future results. Nine Months Ended September 30, 2017 (dollars in thousands, except per share data) (unaudited) Revenues $ 529,294 Net income (loss) attributable to Cowen Inc. stockholders (7,001 ) Net income (loss) per common share: Basic $ (0.23 ) Diluted (0.23 ) In conjunction with the integration of the acquired businesses of Convergex Group, the Company evaluated the combined broker-dealer businesses and operations and, during 2017, incurred approximately $8.8 million of integration and restructuring costs which primarily related to exit and disposal costs, discontinuation of redundant technology services and severance costs. During the nine months ended September 30, 2018 , the Company continued to integrate the businesses acquired through Convergex Group and consolidated certain similar businesses.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies a. Basis of Presentation These unaudited condensed consolidated financial statements are prepared in accordance with US GAAP as promulgated by the Financial Accounting Standards Board ("FASB") through Accounting Standards Codification ("The Accounting Standards") as the source of authoritative accounting principles in the preparation of financial statements, and include the accounts of the Company, its operating and other subsidiaries, and entities in which the Company has a controlling financial interest or a general partner interest. All material intercompany transactions and balances have been eliminated on consolidation. Certain 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 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 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 funds for which it acts (or acted) as the general partner and investment manager. As of and during the three months ended September 30, 2018 , the Company consolidated the following 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") (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 September 30, 2018 and December 31, 2017 , the total net assets of the consolidated VIEs were $254.6 million and $482.8 million , respectively. The decrease is primarily related to other investors' redemptions which reduced 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 September 30, 2018 and December 31, 2017 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 funds and real estate entities for which the Company serves as the general partner, managing member and/or investment manager with decision-making rights. The Company does not consolidate the Unconsolidated Master Funds or real estate entities that are VIEs as it has concluded that it is not the primary beneficiary in each instance. Fund investors are entitled to all of their economics of these VIEs with the exception of the management fee and incentive income, if any, earned by the Company. The Company's involvement with funds and real estate entities that are unconsolidated VIEs is limited to providing investment management services in exchange for management fees and incentive income. Although the Company may advance amounts and pay certain expenses on behalf of the funds and real estate entities that it considers to be VIEs, it does not provide, nor is it required to provide, any type of substantive financial support to these entities outside of regular investment management services (see Note 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 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, Westminster, Cowen Execution Ltd, ATM Execution LLC ("ATM Execution"), Cowen International Limited ("Cowen International Ltd"), Ramius UK Ltd. ("Ramius UK") and Cowen Prime Services LLC ("Cowen Prime") 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 doubtful accounts The allowance for doubtful accounts 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 doubtful accounts. Specifically for prepaid research, the Company reviews clients' historical, current and forecasted trading activity in determining the allowance for doubtful accounts. Expense related to the allowance for doubtful accounts 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 portfolio funds, real estate investments and equity method investments, which are valued as follows : i. Portfolio funds— Portfolio funds (“Portfolio Funds”) include interests in funds and investment companies 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 are estimated based on the price that would be received to sell an asset in an orderly transaction between marketplace participants at the measurement date. Real estate investments without a public market are valued based on assumptions and valuation techniques used by the Company. Such valuation techniques may include discounted cash flow analysis, prevailing market capitalization rates or earnings multiples applied to earnings from the investment, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties, consideration of the amount that currently would be required to replace the asset, as adjusted for obsolescence, as well as independent external appraisals. In general, the Company considers several valuation techniques when measuring the fair value of a real estate investment. However, in certain circumstances, a single valuation technique may be appropriate. Real estate investments are reviewed on a quarterly basis by the Company for significant changes at the property level or a significant change in the overall market which would impact the value of the real estate investment resulting in unrealized appreciation or depreciation. 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 doubtful accounts. An allowance for doubtful accounts is taken 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 doubtful accounts. The Company records this allowance for doubtful accounts 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 funds and are recognized in accordance with the new revenue recognition guidance (see Note 3k). g. Securities borrowed and securities loaned Securities borrowed and securities loaned are carried at the amounts of cash collateral advanced or received on a gross basis. The related rebates are recorded in the 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 collateral from the borrower. The initial collateral advanced or received approximates or is greater than the market value of securities borrowed or loaned. The Company monitors the market value of securities borrowed and loaned on a daily basis, with additional collateral obtained or returned, as necessary. Securities borrowed and loaned may also result in credit exposures for the Company in an event that the counterparties are unable to fulfill their contractual obligations. The Company minimizes its credit risk by continuously monitoring its credit exposure and collateral values by demanding additional or returning excess collateral in accordance with the netting provisions available in the master securities lending contracts in place with the counterparties. Fees and interest received or paid are recorded in interest and 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 September 30, 2018 and December 31, 2017 , 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. Aircraft and related equipment, which are leased out under operating leases, are carried at cost less accumulated depreciation and are depreciated to estimated residual value using the straight-line method over the lease term or estimated useful life of the asset. Any assets received at the end of the lease are marked to the lower of cost or fair value with the adjustment recorded in other income. 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 Capitalized lease asset 5 years Straight-line Aircraft and related equipment 10-20 years Straight-line Modifications to aircraft 4-10 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. Deferred rent Deferred rent primarily consists of step rent, allowances from landlords and valuing the Company's lease properties acquired through business combinations in accordance with US GAAP. Step rent represents the difference between actual operating lease payments due and straight-line rent expense, which is recorded by the Company over the term of the lease, including the build-out period. This amount is recorded as deferred rent in the early years of the lease, when cash payments are generally lower than straight-line rent expense, and reduced in the later years of the lease when payments begin to exceed the straight-line expense. Landlord allowances are generally comprised of amounts received and/or promised to the Company by landlords and may be received in the form of cash or free rent. These allowances are part of the negotiated terms of the lease. The Company records a receivable from the landlord and a deferred rent liability when the allowances are earned. This deferred rent is amortized into income (through lower rent expense) over the term (including the pre-opening build-out period) of the applicable lease, and the receivable is reduced as amounts are received from the landlord. Liabilities resulting from valuing the Company's leased properties acquired through business combinations are quantified by comparing the current fair value of the leased space to the current rental payments on the date of acquisition. Deferred rent, included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition, as of September 30, 2018 and December 31, 2017 is $9.1 million and $12.8 million , respectively. k. Revenue recognition Effective January 1, 2018, the Company adopted ASC Topic 606, Revenue from Contracts with Customers ("ASC Topic 606"). The new revenue recognition guidance 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 guidance requires an entity to follow 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, an entity may include 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. The Company applied the modified retrospective method of adoption which resulted in a cumulative adjustment of $0.6 million to retained earnings as of January 1, 2018. Reported financial results for historic periods were not restated and are reported under The Accounting Standards in effect during the historic period. Refer to the Company's Annual Report on Form 10-K for the year ended December 31, 2017 for discussions related to the Company's previous revenue recognition policies. Our principle sources of revenue are derived from two segments: an investment management segment and an investment bank segment, as more fully described below. The new revenue recognition guidance 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 21 . 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. The investment income was excluded from the new revenue recognition guidance, therefore there were no changes associated with the adoption of the new guidance. Management fees The Company earns management fees from affiliated private funds and certain managed accounts for which it serves as the investment manager; such fees earned are based on assets under management. The management fees are earned as the investment management services are provided and are not subject to reversals. Several management companies of the private 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). While some investors may have separately negotiated fees, in general the management fees are as follows: • Private Hedge Funds. Management fees for the Company's private hedge funds are generally charged at an annual rate of up to 2% of assets under management or notional trading level. Management fees are generally calculated monthly based on assets under management at the end of each month . • Real Estate. Management fees from the Company's r

Cash Collateral Pledged

Cash Collateral Pledged	9 Months Ended
	Sep. 30, 2018
Cash and Cash Equivalents [Abstract]
Cash Collateral Pledged	Cash Collateral Pledged As of September 30, 2018 and December 31, 2017 , the Company pledged cash collateral in the amount of $5.3 million and $6.1 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 $10.8 million , as of September 30, 2018 , and $11.8 million , as of December 31, 2017 , which is anticipated to be due March 2021 (see Note 17 ).

Segregated Cash

Segregated Cash	9 Months Ended
	Sep. 30, 2018
Segregated Cash [Abstract]
Segregated Cash	Segregated Cash As of September 30, 2018 and December 31, 2017 , cash segregated in compliance with federal regulations and other restricted deposits of $154.2 million and $116.3 million , respectively, consisted of cash deposited in special bank accounts for the 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	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and December 31, 2017 , securities owned, at fair value consisted of the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Common stock (b) $ 576,720 $ 640,065 Preferred stock (b) 6,466 9,604 Warrants and rights (b) 21,403 9,604 U.S. Government securities (a) 2,842 2,807 Corporate bonds (d) 30,992 4,909 Convertible bonds (c) — 282 Trade claims 5,746 5,950 $ 644,169 $ 673,221 (a) As of September 30, 2018 , maturities ranged from October 2018 to August 2019 with an interest rate of 0% . As of December 31, 2017 , maturities ranged from February 2018 to June 2018 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 $6.2 million , respectively, at September 30, 2018 and $6.0 million and $5.2 million , respectively, at December 31, 2017 . At September 30, 2018 and December 31, 2017 , the Company elected the fair value option for investments in warrants and rights with a fair value of $1.1 million and $2.4 million . (c) As of December 31, 2017 , maturities ranged from February 2018 to March 2018 and interest rates ranged from 5% to 12% . (d) As of September 30, 2018 , maturities ranged from October 2018 to April 2049 and interest rates ranged from 0.50% to 14.00% . As of December 31, 2017 , maturities ranged from October 2018 to May 2040 and interest rates ranged from 0.00% to 10.75% . 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. Upon issuance of the Company's 3% cash convertible senior notes due 2019 in March 2014 ("2019 Convertible Notes") (see Note 17 ), the Company recognized the embedded cash conversion option at fair value of $35.7 million which is valued as of September 30, 2018 at $0.2 million and is included in payable for derivative contracts in the accompanying condensed consolidated statement of financial condition. The Company has partially repurchased and extinguished most of the 2019 Convertible Notes (See Note 17 ). Also, on the date of issuance of the 2019 Convertible Notes, the Company entered into a separate cash convertible note economic hedge transaction (the "Hedge Transaction") with a counterparty (the “Option Counterparty”) whereby, the Company purchased a cash settled option contract with terms identical to the conversion option embedded in the 2019 Convertible Notes and simultaneously sold an equity settled warrant with a higher strike price. The Hedge Transaction was expected to reduce the Company’s exposure to potential cash payments in excess of the principal amount of converted notes that the Company may be required to make upon conversion of the 2019 Convertible Notes. The Company paid a premium of $35.7 million for the option under the Hedge Transaction and received a premium of $15.2 million for the equity settled warrant transaction, for a net cost of $20.5 million . During January 2018, the Company terminated the Hedge Transaction for a loss of $0.6 million . The Company's long and short exposure to derivatives is as follows: Receivable on derivative contracts As of September 30, 2018 As of December 31, 2017 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Futures $ — $ — $ 3,819 $ 58 Currency forwards $ 79,310 1,088 $ 233 5 Swaps $ 57,926 1,203 $ 164,664 10,942 Options other (a) 660,776 29,330 283,112 58,172 Pay to hold $ — 608 $ — — $ 32,229 $ 69,177 (a) Includes index, equity, commodity future and cash conversion options. Payable for derivative contracts As of September 30, 2018 As of December 31, 2017 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Futures $ 25,474 $ 71 $ 16,796 $ 242 Currency forwards $ 2,897 4 $ 62,439 874 Swaps $ 77,775 2,743 $ 11,595 71 Options other (a) 96,500 27,184 57,043 41,563 $ 30,002 $ 42,750 (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 September 30, 2018 and December 31, 2017 . 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 September 30, 2018 Receivable on derivative contracts, at fair value $ 32,229 $ — $ 32,229 $ — $ 2,899 $ 29,330 Payable for derivative contracts, at fair value 30,002 — 30,002 — 2,747 27,255 As of December 31, 2017 Receivable on derivative contracts, at fair value $ 69,177 $ — $ 69,177 $ — $ 10,948 $ 58,229 Payable for derivative contracts, at fair value 42,750 — 42,750 — 1,031 41,719 (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 $(7.5) million and $0.5 million for the three months ended September 30, 2018 and 2017 , and $6.4 million and $(4.9) million for the nine months ended September 30, 2018 and 2017 , 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 17 ), exchange traded derivatives, and certain options, the Company is required to post/receive collateral. As of September 30, 2018 and December 31, 2017 , collateral consisting of $9.8 million and $13.5 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 September 30, 2018 and December 31, 2017 all derivative contracts were with multiple major financial institutions. Other investments As of September 30, 2018 and December 31, 2017 , other investments included the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Portfolio Funds, at fair value (1) $ 125,107 $ 100,148 Equity method investments (2) 42,321 41,099 Lehman claims, at fair value — 301 $ 167,428 $ 141,548 (1) Portfolio Funds, at fair value The Portfolio Funds, at fair value as of September 30, 2018 and December 31, 2017 , included the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Starboard Value and Opportunity Fund LP (c)(*) $ 33,321 $ 32,079 Formation8 Partners Fund I, L.P. (f) 28,135 28,243 RCG Longview Debt Fund V, L.P. (g)(*) 4,537 8,892 RCG Longview II LP (g) (*) 4,160 131 Cowen Healthcare Investments II LP (j) (*) 15,875 — Eclipse Ventures Fund I, L.P. (b) 3,575 3,428 HealthCare Royalty Partners LP (a)(*) 2,129 3,452 Lagunita Biosciences, LLC (d) 3,859 2,400 RCG IO Renergys Sarl (j) (*) 1,780 — Starboard Leaders Fund LP (e)(*) 1,405 1,276 Eclipse SPV I, LP (k)(*) 1,447 — RCG Longview Equity Fund, LP (g) (*) 819 — RCG Longview Debt Fund VI, LP (g) (*) 588 1,022 RCG Park Liberty GP Member LLC (g) (*) 908 750 HealthCare Royalty Partners II LP (a)(*) 1,162 873 RCGL PE MPA, LLC (g)(*) 549 — RCG LPP2 PNW5 Co-Invest, L.P. (h)(*) 309 3,493 Quadratic Fund LLC (i)(*) — 906 Other private investment (l)(*) 15,997 10,133 Other affiliated funds (m)(*) 4,552 3,070 $ 125,107 $ 100,148 * 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 16 . (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 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 13% to 56% . The Company holds a majority of the outstanding ownership interest (i.e., more than 50%) in RCG Longview Partners II, LLC and 41% 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 private 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 September 30, 2018 and 2017 , the Company incurred $2.6 million and $0.9 million of these costs, respectively. For the nine months ended September 30, 2018 and 2017 , the Company incurred $6.6 million and $3.5 million of these costs, respectively. During the third quarter of 2018, the Company completed an assessment of the recoverability of the Company's equity method investments and determined that the carrying value of the investment in Surf House Ocean View Holdings, LLC exceeded the estimated fair value of the Company's interest, which was other than temporary. Accordingly, an impairment charge of $7.1 million was recognized to reduce the carrying value of the investment to fair value at September 30, 2018 . The Company recorded no other impairment charges in relation to its equity method investments for the nine months ended September 30, 2018 and 2017 . 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 September 30, 2018 As of December 31, 2017 (dollars in thousands) Surf House Ocean Views Holdings, LLC $ 7,478 $ 14,179 Starboard Value LP 17,842 13,202 RCG Longview Debt Fund V Partners, LLC 10,273 9,284 RCG Longview Management, LLC 1,316 1,149 RCG Longview Debt Fund VI Partners LLC 971 — HealthCare Royalty GP, LLC 174 281 HealthCare Royalty GP II, LLC 197 148 RCG Longview Debt Fund IV Management, LLC 331 331 HealthCare Royalty GP III, LLC 1,562 764 RCG Kennedy House, LLC 119 154 RCG Longview Equity Management, LLC 114 114 RCG LPP II GP, LLC 272 487 RCG Park Liberty GP Member Manager, LLC 1,018 428 Other 654 578 $ 42,321 $ 41,099 As of September 30, 2018 and December 31, 2017 , the Company's share of losses in its equity method investment in RCG Longview Partners II, LLC has exceeded the carrying amount recorded in this investee. These amounts are included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition. RCG Longview Partners II, LLC, as general partner to a real estate fund, has reversed previously recorded incentive income allocations and has recorded a current clawback obligation to the limited partners in the fund. This obligation is due to a change in unrealized value of the fund on which there have previously been distributed carried interest realizations; however, the settlement of a potential obligation is not due until the end of the life of the respective fund. As the Company is obligated to return previous distributions it received from RCG Longview Partners II, LLC, it has continued to record its share of gains/losses in the investee including reflecting its share of the clawback obligation in the amount of $6.2 million as of September 30, 2018 and December 31, 2017 , respectively. The Company's income (loss) from equity method investments was $(4.7) million and $4.1 million for the three months ended September 30, 2018 and 2017, and $7.2 million and $12.1 million for the nine months ended September 30, 2018 and 2017 , 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 September 30, 2018 and December 31, 2017 , securities sold, not yet purchased, at fair value consisted of the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Common stock $ 353,113 $ 342,328 Corporate bonds (a) 20,309 122 Preferred stock 836 77 Warrants and rights 260 — $ 374,518 $ 342,527 (a) As of September 30, 2018 , the maturities ranged from January 2026 to April 2049 with interest rates ranged from 5.00% to 5.55% . As of December 31, 2017 , the maturities ranged from July 2025 to January 2026 with interest rates ranged from 3.78% to 5.55% . 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 September 30, 2018 and December 31, 2017 . 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 September 30, 2018 Securities borrowed $ 713,288 $ — $ 713,288 $ — $ 684,569 $ — $ 28,719 Securities loaned 548,629 — 548,629 — 531,984 — 16,645 As of December 31, 2017 Securities borrowed $ 443,148 $ — $ 443,148 $ — $ 414,778 $ — $ 28,370 Securities loaned 456,831 — 456,831 — 439,228 — 17,603 (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 September 30, 2018 and December 31, 2017 : Open and Overnight Up to 30 days 31 - 90 days Greater than 90 days Total (dollars in thousands) As of September 30, 2018 Common stock $ 548,629 $ — $ — $ — $ 548,629 As of December 31, 2017 Common stock $ 456,831 $ — $ — $ — $ 456,831 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 $5.6 billion and $346.9 million as of September 30, 2018 and $5.2 billion and $445.6 million as of December 31, 2017 , respectively. In addition, the maximum exposure relating to these variable interest entities as of September 30, 2018 was $333.8 million , and as of December 31, 2017 was $471.3 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 Feeder Funds' investment in their Unconsolidated Master Funds and the Company's investment in unconsolidated investment companies. b. Consolidated Funds Securities owned, at fair value As of September 30, 2018 and December 31, 2017 , securities owned, at fair value, held by the Consolidated Funds consisted of the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Preferred stock $ 24,314 $ 50,445 Common stock 55,535 77,702 U.S. Government securities (a) 20,446 34,201 Corporate bonds (b) 3,758 — Warrants and rights 4,848 3,568 $ 108,901 $ 165,916 (a) As of September 30, 2018 , maturities ranged from November 2018 to December 2018 and interest rates were 0% . As of December 31, 2017 , maturities ranged from January 2018 to April 2022 and interest rates ranged from 0% to 5.75% . (b) As of September 30, 2018 , the maturity was December 2023 with an interest rate of 5.88% . Receivable on derivative contracts As of September 30, 2018 and December 31, 2017 , receivable on derivative contracts, at fair value, held by the Consolidated Funds are comprised of: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Currency forwards $ 27 $ 524 Equity swaps 1,584 1,754 Options 300 242 $ 1,911 $ 2,520 Payable for derivative contracts As of September 30, 2018 and December 31, 2017 , payable for derivative contracts, at fair value, held by the Consolidated Funds are comprised of: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Currency forwards $ 539 $ 11 Equity swaps 1,590 7,042 Options 60 77 $ 2,189 $ 7,130 Other investments, at fair value Investments in Portfolio Funds, at fair value As of September 30, 2018 and December 31, 2017 , investments in Portfolio Funds, at fair value, included the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Investments of Enterprise LP $ 97,026 $ 87,221 Investments of Merger Fund 86,264 286,890 $ 183,290 $ 374,111 Consolidated portfolio fund investments of Enterprise LP Enterprise LP operates under a “master-feeder” structure, whereby Enterprise Master's shareholders are Enterprise LP and RCG II Intermediate Fund, L.P. The consolidated investments in Portfolio Funds include Enterprise LP's investment of $97.0 million and $87.2 million in Enterprise Master as of September 30, 2018 and December 31, 2017 , respectively. On May 12, 2010, the Company announced its intention to close Enterprise Master. Prior to this announcement, strategies utilized by Enterprise Master included merger arbitrage and activist investing, investments in distressed securities, convertible hedging, capital structure arbitrage, equity market neutral, investments in private placements of convertible securities, proprietary mortgages, structured credit investments, investments in mortgage backed securities and other structured finance products, investments in real estate and real property interests, structured private placements and other relative value strategies. Enterprise Master had broad investment powers and maximum flexibility in seeking to achieve its investment objective. Enterprise Master was permitted to invest in equity securities, debt instruments, options, futures, swaps, credit default swaps and other derivatives. As Enterprise Master winds down its positions, it will return capital to its investors. 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 $86.3 million and $286.9 million in Merger Master as of September 30, 2018 and December 31, 2017 , 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 September 30, 2018 and December 31, 2017 , 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 September 30, 2018 and one at December 31, 2017 . 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 September 30, 2018 Linkem Equity Italy Wireless Broadband 8.01 % $ 64,754 As of December 31, 2017 Linkem Equity Italy Wireless Broadband 7.52 % $ 56,271 Underlying Investments of Unconsolidated Funds Held by Consolidated Funds Enterprise Master and Merger Master Enterprise LP's investment in Enterprise Master represents Enterprise LP's proportionate share of Enterprise Master's net assets; as a result, the investment balances of Enterprise Master reflected below may exceed the net investment which Enterprise LP has recorded. Merger Fund's investment in Merger Master represents Merger Fund's proportionate share of Merger Master's net assets; as a result, the investment balances of Merger Master reflected below may exceed the net investment which Merger Fund has recorded. The following tables present summarized investment information for the underlying investments and derivatives held by Enterprise Master and Merger Master as of September 30, 2018 and December 31, 2017 : Securities owned by Enterprise Master, at fair value As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Common stock $ 469 $ 608 $ 469 $ 608 Portfolio Funds, owned by Enterprise Master, at fair value As of September 30, 2018 As of December 31, 2017 Strategy (dollars in thousands) RCG Special Opportunities Fund, Ltd* Multi-Strategy $ 109,518 $ 97,345 RCG Longview Equity Fund, LP* Real Estate — 1,266 RCG Longview Debt Fund IV, LP* Real Estate — 99 RCG Longview II, LP* Real Estate — 229 Other Private Investments Various 864 937 $ 110,382 $ 99,876 * Affiliates of the Company. Merger Master As of September 30, 2018 , Merger Master held common stock and corporate bonds, of $342.1 million and $23.8 million , respectively, and common stock, sold not yet purchased, of $128.6 million . As of December 31, 2017 , Merger Master held common stock, securities owned, of $483.2 million and common stock, sold not yet purchased, of $171.2 million , respectively. Receivable on derivative contracts, at fair value, owned by Merger Master As of September 30, 2018 As of December 31, 2017 Description (dollars in thousands) Options $ 1,817 $ 108,063 Equity swaps 1,658 14,488 Currency forwards 200 — $ 3,675 $ 122,551 Payable for derivative contracts, at fair value, owned by Merger Master As of September 30, 2018 As of December 31, 2017 Description (dollars in thousands) Options $ 261 $ 1,256 Currency forwards — 213 Equity swaps 2,005 1,249 $ 2,266 $ 2,718

Fair Value Measurements for Ope

Fair Value Measurements for Operating Entities and Consolidated Funds	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and December 31, 2017 : Assets at Fair Value as of September 30, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities owned US Government securities $ 2,842 $ — $ — $ 2,842 Preferred stock 1,308 — 5,158 6,466 Common stock 564,140 6,906 5,674 576,720 Corporate bonds — 30,992 — 30,992 Trade claims — — 5,746 5,746 Warrants and rights 19,821 — 1,582 21,403 Receivable on derivative contracts, at fair value Currency forwards — 1,088 — 1,088 Swaps — 1,203 — 1,203 Options 29,330 — — 29,330 Pay to hold — 608 — 608 Consolidated Funds Securities owned US Government securities 20,446 — — 20,446 Preferred stock — — 24,314 24,314 Common stock 55,441 — 94 55,535 Corporate bonds — 3,758 — 3,758 Warrants and rights — — 4,848 4,848 Receivable on derivative contracts, at fair value Currency forwards — 27 — 27 Equity swaps — 1,584 — 1,584 Options 300 — — 300 $ 693,628 $ 46,166 $ 47,416 $ 787,210 Percentage of total assets measured at fair value on a recurring basis 88.1 % 5.9 % 6.0 % Portfolio funds measured at net asset value (a) 125,107 Consolidated funds' portfolio funds measured at net asset value (a) 183,290 Equity method investments 42,321 Total investments $ 1,137,928 Liabilities at Fair Value as of September 30, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities sold, not yet purchased Common stock $ 353,113 $ — $ — $ 353,113 Corporate bonds — 20,309 — 20,309 Preferred stock 836 — — 836 Warrants and rights 260 — — 260 Payable for derivative contracts, at fair value Futures 71 — — 71 Currency forwards — 4 — 4 Swaps — 2,743 — 2,743 Options 24,637 — 2,547 27,184 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 2,643 2,643 Consolidated Funds Payable for derivative contracts, at fair value Currency forwards — 539 — 539 Options 60 — — 60 Equity swaps — 1,590 — 1,590 $ 378,977 $ 25,185 $ 5,190 $ 409,352 Percentage of total liabilities measured at fair value 92.6 % 6.2 % 1.3 % (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 third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018, December 2020, and June 2018, respectively. 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 September 30, 2018 can range from $0.1 million to $7.0 million . Assets at Fair Value as of December 31, 2017 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities owned US Government securities $ 2,807 $ — $ — $ 2,807 Preferred stock 571 918 8,115 9,604 Common stock 627,011 5,484 7,570 640,065 Convertible bonds — — 282 282 Corporate bonds — 4,909 — 4,909 Trade claims — — 5,950 5,950 Warrants and rights 7,087 — 2,517 9,604 Receivable on derivative contracts, at fair value Futures 58 — — 58 Currency forwards — 5 — 5 Swaps — 10,942 — 10,942 Options 56,717 — 1,455 58,172 Other investments Lehman claim — — 301 301 Consolidated Funds Securities owned US Government securities 30,552 3,649 — 34,201 Preferred stock — — 50,445 50,445 Common stock 77,652 — 50 77,702 Warrants and rights — — 3,568 3,568 Receivable on derivative contracts, at fair value Currency forwards — 524 — 524 Equity swaps — 1,754 — 1,754 Options 242 — — 242 $ 802,697 $ 28,185 $ 80,253 $ 911,135 Percentage of total assets measured at fair value on a recurring basis 88.1 % 3.1 % 8.8 % Portfolio funds measured at net asset value (a) 100,148 Consolidated funds' portfolio funds measured at net asset value (a) 374,111 Equity method investments 41,099 Total investments $ 1,426,493 Liabilities at Fair Value as of December 31, 2017 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities sold, not yet purchased Common stock $ 342,328 $ — $ — $ 342,328 Corporate bonds — 122 — 122 Preferred stock 77 — — 77 Payable for derivative contracts, at fair value Futures 242 — — 242 Currency forwards — 874 — 874 Swaps — 71 — 71 Options 19,162 — 22,401 41,563 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 3,440 3,440 Consolidated Funds Payable for derivative contracts, at fair value Currency forwards — 11 — 11 Options 77 — — 77 Equity swaps — 7,042 — 7,042 $ 361,886 $ 8,120 $ 25,841 $ 395,847 Percentage of total liabilities measured at fair value 91.4 % 2.1 % 6.5 % (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 third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018 and December 2020, respectively. 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, 2017 can range from $0.1 million to $15.0 million . The following table includes a roll forward of the amounts for the three and nine months ended September 30, 2018 and 2017 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 September 30, 2018 Balance at June 30, 2018 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at September 30, 2018 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 7,422 $ — $ (1,141 ) (c) $ — $ — $ (1,123 ) $ 5,158 $ (1,124 ) Common stock 5,848 — — — — (174 ) 5,674 (174 ) Options, liability 301 — — — — 2,246 2,547 2,246 Warrants and rights 1,544 — — — — 38 1,582 38 Trade claims 5,699 — — 44 — 3 5,746 3 Lehman claim 295 — — — (234 ) (61 ) — — Contingent consideration liability 2,870 — — — (227 ) — 2,643 — Consolidated Funds Preferred stock 24,314 — — — — — 24,314 — Common stock 94 — — — — — 94 — Warrants and rights 4,738 — — — — 110 4,848 110 Three Months Ended September 30, 2017 Balance at June 30, 2017 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at September 30, 2017 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 18,576 $ — $ — $ — $ — $ (587 ) $ 17,989 $ (587 ) Common stock 10,588 — — 3,151 (1,946 ) 297 12,090 297 Convertible bonds 282 — — 250 — (250 ) 282 — Options, asset 9,860 — — — — 499 10,359 499 Options, liability 9,860 — — — — 499 10,359 499 Warrants and rights 3,409 — — — — (1,013 ) 2,396 187 Trade claims 4,648 — — 1,925 (630 ) 3 5,946 3 Lehman claim 309 — — — — 10 319 10 Contingent consideration liability 5,174 — — — (125 ) — 5,049 — Consolidated Funds Preferred stock 18,224 — — 467 — 252 18,943 252 Common stock 848 — — — (848 ) — — — Warrants and rights 3,369 — — — — 9 3,378 9 Term Loan 202 — — — (200 ) (2 ) — — Nine Months Ended September 30, 2018 Balance at December 31, 2017 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at September 30, 2018 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 8,115 $ — $ (1,141 ) (c) $ 1,415 $ (695 ) $ (2,536 ) $ 5,158 $ (2,301 ) Common stock 7,570 — — 531 (1,333 ) (1,094 ) 5,674 (1,128 ) Convertible bonds 282 — — — (307 ) 25 — — Options, asset 1,455 — — — (1,455 ) — — — Options, liability 22,401 — (28,973 ) (e) — (259 ) 9,378 2,547 9,378 Warrants and rights 2,517 — — — (143 ) (792 ) 1,582 (933 ) Trade claims 5,950 — — 44 (334 ) 86 5,746 23 Lehman claim 301 — — — (234 ) (67 ) — — Contingent consideration liability 3,440 — — — (797 ) — 2,643 — Consolidated Funds Preferred stock 50,445 — (38,552 ) (a) 3,066 — 9,355 24,314 9,355 Common stock 50 — — — — 44 94 44 Warrants and rights 3,568 — (20 ) (a) (1,340 ) — 2,640 4,848 1,300 Nine Months Ended September 30, 2017 Balance at December 31, 2016 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at September 30, 2017 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 15,811 $ — $ (3,472 ) (c) $ 9,000 $ (31 ) $ (3,319 ) $ 17,989 $ (1,006 ) Common stock 10,121 — — 3,182 (2,121 ) 908 12,090 908 Convertible bonds 250 — — 282 — (250 ) 282 — Options, asset 14,753 — — — — (4,394 ) 10,359 (4,394 ) Options, liability 14,753 — — — — (4,394 ) 10,359 (4,394 ) Warrants and rights 3,719 3,192 (b) (d) — — (4,367 ) (148 ) 2,396 510 Trade claim 562 — — 5,865 (700 ) 219 5,946 198 Lehman claim 265 — — — — 54 319 54 Contingent consideration liability 5,997 — — — (392 ) (556 ) 5,049 (556 ) Consolidated Funds Preferred stock 36,928 — (13,668 ) (c) 467 (11,853 ) 7,069 18,943 2,958 Common stock 295 — — 476 (848 ) 77 — — Warrants and rights 3 — — — — 3,375 3,378 3,375 Term Loan 657 — — 202 (1,021 ) 162 — — (1) Unrealized gains/losses are reported in other income (loss) in the accompanying condensed consolidated statements of operations. (a) The Company deconsolidated a fund (See note 3) (b) The Company received warrants as consideration as part of an investment banking transaction. (c) The investments were converted to common stock. (d) As part of the preferred stock sale, the sellers received contingent value rights to be paid in the event certain milestones are reached. (e) On June 26, 2018, the Company received shareholder approval which will allow the Company to settle its convertible note (see Note 17 ) entirely in class A common shares. Upon receiving shareholder approval, the Company reclassified the embedded conversion option, associated with the convertible debt, to equity. (See Note 18 ) 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 nine months ended September 30, 2018 and 2017 , there were no transfers between level 1 and level 2 assets and liabilities. The following table includes quantitative information as of September 30, 2018 and December 31, 2017 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 September 30, 2018 Valuation Techniques Unobservable Inputs Range Level 3 Assets (dollars in thousands) Common and preferred stocks $ 2,508 Guideline companies/Discounted cash flows Discount rate 50% Trade claims 25 Discounted cash flows Discount rate 20% Warrants and rights 1,582 Model based Discounted cash flows Discount rate 7% to 9% Other level 3 assets (a) 43,301 Total level 3 assets $ 47,416 Level 3 Liabilities Options 2,547 Option pricing models Volatility 30% to 35% Contingent consideration liability 2,643 Discounted cash flows Projected cash flow and discount rate 23% Total level 3 liabilities $ 5,190 Quantitative Information about Level 3 Fair Value Measurements Fair Value at December 31, 2017 Valuation Techniques Unobservable Inputs Range Level 3 Assets (dollars in thousands) Common and preferred stocks $ 5,642 Guideline companies/transaction price Market multiples 4.8x to 8.5x Trade claims 70 Discounted cash flows Discount rate 20% Warrants and rights 2,516 Model based Discounted cash flows Volatility Discount rate 61% 22% Options 1,455 Option pricing models Volatility 28% Other level 3 assets (a) 70,570 Total level 3 assets $ 80,253 Level 3 Liabilities Options 22,401 Option pricing models Volatility 28% Contingent consideration liability 3,440 Discounted cash flows Projected cash flow and discount rate 8% to 23% Total level 3 liabilities $ 25,841 (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 September 30, 2018 and December 31, 2017 , 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 3 . September 30, 2018 December 31, 2017 Fair Value Hierarchy Carrying Amount Fair Value Carrying Amount Fair Value (dollars in thousands) Financial Assets Operating companies Cash and cash equivalents $ 193,066 $ 193,066 $ 130,052 $ 130,052 Level 1 Cash collateral pledged 16,092 16,092 17,888 17,888 Level 2 Segregated cash 154,191 154,191 116,268 116,268 Level 1 Securities borrowed 713,288 $ 684,569 443,148 414,763 Level 2 Loans receivable 36,009 36,009 (d) 37,993 37,993 (d) Level 3 Consolidated funds Cash and cash equivalents 18,747 18,747 21,988 21,988 Level 1 Financial Liabilities Securities loaned 548,629 531,984 456,831 440,162 Level 2 Convertible debt 133,126 (a) 173,246 (b) 141,502 (a) 172,709 (b) Level 2 Notes payable and other debt 271,082 284,021 (c) 173,458 182,352 (c) Level 2 (a) The carrying amount of the convertible debt includes an unamortized discount of $24.9 million and $25.6 million as of September 30, 2018 and December 31, 2017 , 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	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and December 31, 2017 , the Company had a total of $98.6 million and $94.0 million , respectively, in deposit accounts with clearing organizations, brokers and banks that could be used as collateral to offset losses incurred by the clearing organizations, brokers and banks, on behalf of the Company’s activities, if such losses were to occur.

Receivables from and payables t

Receivables from and payables to brokers, dealers and clearing organizations	9 Months Ended
	Sep. 30, 2018
Brokers and Dealers [Abstract]
Receivables From and Payables to Brokers, Dealers and Clearing Organizations	Receivables From and Payables to Brokers, Dealers and Clearing Organizations Receivables 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, 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 receivables from and payables to brokers, dealers and clearing organizations balances are held at multiple financial institutions. As of September 30, 2018 and December 31, 2017 , amounts receivable from brokers, dealers and clearing organizations include: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Broker-dealers $ 569,998 $ 409,499 Securities failed to deliver 47,014 87,820 Clearing organizations 16,541 6,126 Securities borrowed interest receivable 10,839 4,733 $ 644,392 $ 508,178 As of September 30, 2018 and December 31, 2017 , amounts payable to brokers, dealers and clearing organizations include: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Broker-dealers $ 131,358 $ 145,860 Securities failed to receive 54,539 53,540 Clearing organizations 18,202 48,257 Securities loaned interest payable 6,227 4,496 $ 210,326 $ 252,153

Receivable from and Payable to

Receivable from and Payable to Customers	9 Months Ended
	Sep. 30, 2018
Receivables and Payable to Customers [Abstract]
Payable to Customers [Text Block]	Receivable From and Payable To Customers As of September 30, 2018 and December 31, 2017 , receivable from customers of $33.2 million and $49.9 million , respectively, consists of amounts owed by customers relating to securities transactions not completed on settlement date and receivables arising from the prepayment of a Commission Sharing Agreement (“CSA”), net of an allowance for doubtful accounts. A prepaid CSA is established for research-related disbursements in advance of anticipated customer commission volumes. Such receivables may not be evidenced by contractual obligations. As of September 30, 2018 and December 31, 2017 , payable to customers of $470.5 million and $352.5 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.

Commission Management Payable

Commission Management Payable	9 Months Ended
	Sep. 30, 2018
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 $90.2 million as of September 30, 2018 and $70.5 million as of December 31, 2017 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	9 Months Ended
	Sep. 30, 2018
Noncontrolling Interest [Abstract]
Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds	Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds Redeemable non-controlling interests in consolidated subsidiaries and funds and the related net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds are comprised as follows: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Redeemable non-controlling interests in consolidated subsidiaries and funds Operating companies $ 11,069 $ 6,113 Consolidated Funds 192,143 434,491 $ 203,212 $ 440,604 Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (dollars in thousands) (dollars in thousands) Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds Operating companies $ 2,486 $ (266 ) $ 6,060 $ 1,457 Consolidated Funds 2,804 5,428 34,993 33,955 $ 5,290 $ 5,162 $ 41,053 $ 35,412

Reinsurance

Reinsurance	9 Months Ended
	Sep. 30, 2018
Reinsurance [Abstract]
Reinsurance	Reinsurance The Company’s wholly-owned Luxembourg subsidiary, Hollenfels Re SA (“Hollenfels”) provides reinsurance to third party insurance and reinsurance companies. As Hollenfels started its operations during 2016, all claims it experienced (reported or not reported) began in 2016. During the three and nine months ended September 30, 2018 , Hollenfels’s share of incurred and paid claims, as reported to it by the underlying insurance and reinsurance companies, amounted to $1.9 million and $9.6 million , respectively. During the three and nine months ended September 30, 2017 , Hollenfels’ share of incurred and paid claims, as reported to it by the underlying insurance and reinsurance companies, amounted to $1.5 million and $2.6 million , respectively. During the same periods in 2018, Hollenfels’ share of claims incurred but not reported plus expected development on reported claims totaled $0.5 million and $9.0 million , respectively. Hollenfels generally employs an estimation methodology whereby historical average claims ratios over a period of 5 or 10 years, based on availability of data, are utilized. In cases where an event may have occurred that could give rise to claims in excess of the amount calculated using the above-mentioned methodology, then actuarial methods are used to calculate the impact of such an event. During the three and nine months ended September 30, 2018 , Hollenfels did not change its methodology for determining claim liability or claim adjustment expenses and calculated them using the above-mentioned methods. 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 and nine months ended September 30, 2018 and September 30, 2017 .

Share-Based Compensation and Em

Share-Based Compensation and Employee Ownership Plans	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 , there were 0.2 million shares available for future issuance under the Equity Plans. Under the 2010 Equity and Incentive Plan, the Company awarded $39.1 million of deferred cash awards to its employees during the three and nine months ended September 30, 2018 . These awards vest over a four year period and accrue interest at 0.70% per year. As of September 30, 2018 , the Company had unrecognized compensation expense related to the 2010 Equity and Incentive Plan deferred cash awards of $54.8 million . Subsequent to the acquisition of Convergex Group (see Note 2 ) the Company maintained the Convergex Nonqualified Deferred Compensation Plan, which is a deferred cash award plan that is expensed over the 27 month service period. As of September 30, 2018 , the Company had unrecognized compensation expense related to former Convergex Group deferred cash awards of $0.6 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 $8.5 million and $6.8 million for the three months ended September 30, 2018 and 2017 , and $27.6 million and $24.7 million , for the nine months ended September 30, 2018 and 2017 , respectively. The income tax effect recognized for the Equity Plans was a benefit of $2.4 million and $2.7 million for the three months ended September 30, 2018 and 2017 , and $7.2 million and $9.8 million for the nine months ended September 30, 2018 and 2017 , respectively. Stock Appreciation Rights The Company values SARs on grant date using the Black-Scholes valuation model which requires the Company to make assumptions regarding the expected term, volatility, risk-free rate and dividend yield: Expected term . Expected term represents the period of time that awards granted are expected to be outstanding. The Company elected to use the "simplified" calculation method, as applicable to companies that lack extensive historical data. The mid-point between the vesting date and the contractual expiration date is used as the expected term under this method. Expected volatility . The Company bases its expected volatility on its own stock price history. Risk free rate . The risk-free rate for periods within the expected term of the award is based on the interest rate of a traded zero-coupon U.S. Treasury bond with a term equal to the awards' expected term on the date of grant. Dividend yield . The Company has not paid and does not expect to pay dividends in the foreseeable future. Accordingly, the assumed dividend yield is zero . The following table summarizes the Company's SARs for the nine months ended September 30, 2018 : Class A Common Shares Subject Weighted Average Weighted Average Aggregate Intrinsic (in years) (dollars in thousands) Balance outstanding at December 31, 2017 75,000 $ 11.60 0.21 $ 173 SARs vested (75,000 ) 14.21 — — Balance outstanding at September 30, 2018 — $ — 0 $ — SARs exercisable at September 30, 2018 — $ — 0 $ — (1) Based on the Company's closing stock price of $13.65 on December 31, 2017 . As of September 30, 2018 , the Company's SARs were fully expensed. As of December 31, 2017 the unrecognized compensation expense related to the Company's grant of SAR's was an immaterial amount. 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 nine months ended September 30, 2018 : Nonvested Restricted Class A Common Shares and Class A Common Restricted Stock Units Weighted-Average Balance outstanding at December 31, 2017 5,579,293 $ 16.33 Granted 2,255,794 14.27 Vested (1,423,075 ) 16.08 Forfeited (61,997 ) 14.13 Balance outstanding at September 30, 2018 6,350,015 $ 15.68 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, 117,188 have been forfeited through September 30, 2018 . The remaining awards, included in the outstanding balance as of September 30, 2018 , will vest between March 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 September 30, 2018 , there was $62.3 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 2.21 years. Restricted Shares and Restricted Stock Units Granted to Non-employee Board Members There were 88,504 restricted stock units awarded during the three and nine months ended September 30, 2018 . As of September 30, 2018 there were 253,772 restricted stock units outstanding.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
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, 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 16.88% and 6.32% for the nine months ended September 30, 2018 and 2017 , respectively. During the nine months ended September 30, 2018 , the unusual or infrequent items whose tax impact were recorded discretely related primarily to state and foreign taxes, as well as stock compensation. For the nine months ended September 30, 2018 and 2017 , 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, state and foreign taxes, as well as other nondeductible expenses. The Company recorded an uncertain tax position liability of $4.9 million and $5.4 million as of September 30, 2018 and December 31, 2017 , respectively, related to New York State and New York City 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 September 30, 2018 and December 31, 2017 , the Company recorded a valuation allowance against deferred tax assets related to its 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, and Luxembourg. In October, the Company concluded an IRS audit for tax year 2014 with no financial statement impact. The Company continues to permanently reinvest the capital and accumulated earnings of its United Kingdom, Canadian and Hong Kong subsidiaries.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Lease Obligations The Company has entered into leases for office space and equipment. These leases contain rent escalation clauses. The Company records rent expense on a straight-line basis over the lease term, including any rent holiday periods. Rent expense was $6.6 million and $6.3 million for the three months ended September 30, 2018 and 2017 , and $19.5 million and $16.3 million for the nine months ended September 30, 2018 and 2017 , respectively and are included in occupancy and equipment expense in the accompanying condensed consolidated statements of operations. As of September 30, 2018 , future minimum annual lease and service payments for the Company were as follows: Equipment Leases (a) Service Payments Facility Leases (b) (dollars in thousands) 2018 $ 966 $ 6,762 $ 6,453 2019 2,482 19,256 24,508 2020 1,529 5,796 20,907 2021 1,392 1,722 20,640 2022 1,128 1,350 17,464 Thereafter 374 1,470 28,353 $ 7,871 $ 36,356 $ 118,325 (a) Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 17 for further information on the capital lease minimum payments which are included in the table. (b) The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $0.4 million and $0.2 million for the three months ended September 30, 2018 and 2017 , and $1.1 million and $0.8 million for the nine months ended September 30, 2018 and 2017 , respectively. 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 fund's remaining investments and where the fund's general partner has previously received carried interest distributions. The clawback liability, however, is not realized until the end of the fund's life. The life of the real estate funds with a potential clawback obligation is currently in a winding-up phase whereby the remaining assets of the fund are being liquidated as promptly as possible so as to maximize value, however a final date for liquidation has not been set. The fund is currently winding-down and as of both September 30, 2018 and December 31, 2017 , and the clawback obligation was $6.2 million 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 funds. As such, the Company is contingently liable for obligations for those entities. These amounts are not included above as the Company believes that the assets in these funds are sufficient to discharge any liabilities. Unfunded Commitments The following table summarizes unfunded commitments as of September 30, 2018 : Entity Unfunded Commitments Commitment term (dollars in millions) Real estate (a) $ 4.6 (a) HealthCare Royalty Partners funds (b) 1.1 2 years Eclipse Ventures Fund I, L.P. (formerly Formation8 Partners Hardware Fund I, L.P.) 0.4 6 years Lagunita Biosciences, LLC 1.0 3 years Eclipse Fund II, L.P. 0.8 7 years Eclipse Continuity Fund I, L.P. 0.6 8 years Cowen Healthcare Investments II LP 9.6 3 years (a) The Company had unfunded commitments pertaining to capital commitments in four real estate investments held by the Company, all of which pertain to related party investments. Such commitments can be called at any time 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 September 30, 2018 . 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 and October 12, 2018. 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	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Convertible Debt and Notes Payable	Convertible Debt and Notes Payable As of September 30, 2018 and December 31, 2017 , the Company's outstanding debt was as follows: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Convertible debt $ 133,126 $ 141,502 Notes payable 229,581 132,970 Term loan 28,200 28,121 Other notes payable 7,688 8,247 Capital lease obligations 5,613 4,120 $ 404,208 $ 314,960 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 September 30, 2018 , the outstanding balance of the 2022 Convertible Notes was $112.9 million . On June 26, 2018, the Company received Cowen shareholder approval for the Company to settle the 2022 Convertible Note entirely in class A common shares. 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 $3.0 million for the three and nine months ended September 30, 2018 . 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 $1.0 million and $3.0 million for the three and nine months ended September 30, 2018 , based on an effective interest rate of 7.13% . The Company capitalized the debt issuance costs in the amount of $2.2 million , which is a direct deduction from the carrying value of the debt and will be amortized over the life of the 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 are due on March 15, 2019 unless earlier repurchased by the Company or converted by the holder into cash in accordance with their terms prior to such date. The interest on the 2019 Convertible Notes is payable semi-annually on March 15 and September 15 of each year. The 2019 Convertible Notes are senior unsecured obligations of the Company. The 2019 Convertible Notes may be converted into cash, upon the occurrence of certain events, whereby a holder will receive, per $1,000 principal amount of notes being converted, an amount equal to the sum of principal amount outstanding and the conversion amount based on the current conversion price (the "Conversion Option"). The 2019 Convertible Notes were issued with an initial conversion price of $21.32 per share (per share amounts have been retroactively updated to reflect the one-for-four reverse stock split effective as of December 5, 2016). During December 2017, the Company repurchased and extinguished $115.1 million of the outstanding balance of the 2019 Convertible Notes. During June 2018, the Company repurchased and extinguished an additional $13.5 million of the outstanding balance of the 2019 Convertible Notes. As of September 30, 2018 , the outstanding balance of the 2019 Convertible Notes was $20.2 million . The Company recorded interest expense of $0.2 million and $1.1 million for the three months ended September 30, 2018 and 2017 , and $0.9 million and $3.4 million for the nine months ended September 30, 2018 and 2017 , respectively. The initial unamortized discount on the 2019 Convertible Notes was $35.7 million and is shown net in convertible debt in the accompanying condensed consolidated statements of financial condition. Amortization on the discount, included within interest and dividends expense in the accompanying condensed consolidated statements of operations is $0.3 million and $1.9 million for the three months ended September 30, 2018 and 2017 , and $1.2 million and $5.6 million for the nine months ended September 30, 2018 and 2017 , respectively, based on an effective interest rate of 8.89% . Upon issuance of the 2019 Convertible Notes, the Company capitalized the debt issuance costs in the amount of $0.9 million , which is a direct deduction from the carrying value of the debt and will be amortized over the life of the 2019 Convertible Notes. In conjunction with the partial extinguishment of the 2019 Convertible Notes, the Company accelerated the pro-rata unamortized discount and capitalized debt issuance costs. During the nine months ended September 30, 2018 , the Company recognized $0.6 million of loss on debt extinguishment. Of the net proceeds from the sale of the 2019 Convertible Notes, approximately $20.5 million was applied to pay the net cost of a cash convertible note economic hedge and warrant transaction, which increased the effective conversion price to $28.72 (see Note 6 ) (per share amounts have been retroactively updated to reflect the one-for-four reverse stock split effective as of December 5, 2016), and approximately $0.3 million was applied to repurchase shares of Cowen Class A common stock. The remainder of the net proceeds is being used for general corporate purposes. 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 and $2.3 million for the three and nine months ended September 30, 2018 . The Company capitalized debt issuance costs of approximately $3.8 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 $7.6 million for the three and nine months ended September 30, 2018 . 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 funds. The Company has provided a guarantee for this loan. The Company recorded interest expense of $0.4 million and $1.2 million for the three and nine months ended September 30, 2018 and interest expense of $0.4 million and $0.4 million for the three and nine months ended September 30, 2017 . Other Notes Payable During January 2018, the Company borrowed $2.0 million to fund insurance premium payments. This note has an effective interest rate of 2.01% and is due on December 31, 2018, with monthly payment requirements of $0.2 million . As of September 30, 2018 , the outstanding balance on this note payable was $0.6 million . Interest expense for the three and nine months ended September 30, 2018 was insignificant. The Company has entered into various financing for its aircraft. The aircraft financing, net of debt costs, is recorded in notes payable and other debt in the accompanying condensed consolidated statements of financial condition. The debt maturities ranged from January 2019 to April 2021 and interest rates ranged from 4.21% to 7.25% . As of September 30, 2018 and December 31, 2017, the remaining balance on the aircraft financing agreements was $7.1 million and $8.2 million , respectively . Interest expense was $0.1 million and $0.2 million for the three months ended September 30, 2018 and 2017 , and $0.3 million and $0.6 million for the nine months ended September 30, 2018 and 2017, respectively. Capital Lease Obligations The Company has entered into various capital leases for computer equipment, which amounted to $10.1 million and is recorded in fixed assets as capital lease obligations. These capital lease obligations are included in notes payable and other debt in the accompanying condensed consolidated statements of financial condition, and have lease terms that range from 55 to 60 months and interest rates that range from 3.70% to 5.69% . As of September 30, 2018 , t he remaining balance on these capital leases was $5.6 million . Interest expense was $0.1 million and $0.1 million for the three months ended September 30, 2018 and 2017 , and $0.2 million and $0.1 million for the nine months ended September 30, 2018 and 2017 , respectively. Annual scheduled maturities of debt and minimum payments (of principal and interest) for all debt outstanding as of September 30, 2018 , are as follows: Convertible Debt Notes Payable Term loan Other Notes Payable Capital Lease (dollars in thousands) 2018 $ 2,025 $ 4,473 $ — $ 1,106 $ 568 2019 25,223 17,893 29,414 3,410 1,438 2020 4,050 17,893 — 1,363 1,360 2021 4,050 17,893 — 2,512 1,360 2022 139,050 17,893 — — 1,128 Thereafter — 370,090 — — 374 Subtotal 174,398 446,135 29,414 8,391 6,228 Less (a) (41,272 ) (216,554 ) (1,214 ) (703 ) (615 ) Total $ 133,126 $ 229,581 $ 28,200 $ 7,688 $ 5,613 (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 September 30, 2018 , 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 $10.8 million , as of September 30, 2018 , and $11.8 million , as of December 31, 2017 , which is anticipated to be due March 2021 Location Amount Maturity (dollars in thousands) Boston $ 386 March 2019 New York $ 356 April 2019 New York $ 70 May 2019 New York $ 497 October 2018 New York $ 1,686 October 2018 New York $ 1,615 November 2018 San Francisco $ 714 January 2019 To the extent any letter of credit is drawn upon, interest will be assessed at the prime commercial lending rate . As of September 30, 2018 and December 31, 2017 , there were no amounts due related to these letters of credit .

Stockholder's Equity

Stockholder's Equity	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and 2017 , and $5.1 million and $5.1 million for the nine months ended September 30, 2018 and 2017 , 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. Embedded Cash Conversion Option on the 2022 Convertible Notes Upon issuance of the 2022 Convertible Notes (see Note 17 ), the Company recognized the embedded cash conversion option at fair value of $23.4 million which was valued as of June 26, 2018 at $29.0 million. On June 26, 2018, the Company received Cowen shareholder approval for the Company to settle the 2022 Convertible Note entirely in class A common shares. Upon receiving shareholder approval, the Company reclassified the separately recognized conversion option from a derivative liability to equity. Treasury Stock Treasury stock of $215.3 million as of September 30, 2018 , compared to $186.8 million as of December 31, 2017 , resulted from $8.5 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, $3.2 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 $16.8 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 nine months ended September 30, 2018 : Treasury stock shares Cost Average cost per share Balance outstanding at December 31, 2017 12,133,276 $ 186,846 $ 15.40 Shares purchased for minimum tax withholding under the Equity Plans or other similar transactions 578,673 8,544 14.76 Shares of stock received in respect of indemnification claims 220,475 3,171 14.38 Purchase of treasury stock 1,160,308 16,762 14.45 Balance outstanding at September 30, 2018 14,092,732 $ 215,323 $ 15.28

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2018
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 September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (dollars in thousands) Beginning Balance $ (7 ) $ (8 ) $ (8 ) $ (2 ) Foreign currency translation 4 — 5 (6 ) Ending Balance $ (3 ) $ (8 ) $ (3 ) $ (8 )

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 , there were 29,142,547 of Class A common shares outstanding. 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)), unexercised stock options, 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 September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except share and per share data) Net income (loss) $ 20,778 $ 9,828 $ 78,793 $ 50,502 Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 5,290 5,162 41,053 35,412 Net income (loss) attributable to Cowen Inc. 15,488 4,666 37,740 15,090 Preferred stock dividends 1,698 1,698 5,094 5,094 Net income (loss) attributable to Cowen Inc. common stockholders $ 13,790 $ 2,968 $ 32,646 $ 9,996 Shares for basic and diluted calculations: Weighted average shares used in basic computation 29,610 31,271 29,662 29,004 Stock options — — — Stock appreciation rights — 20 — 15 Restricted stock 1,234 955 951 992 Weighted average shares used in diluted computation 30,844 32,246 30,613 30,011 Earnings (loss) per share: Basic $ 0.47 $ 0.09 $ 1.10 $ 0.34 Diluted $ 0.45 $ 0.09 $ 1.07 $ 0.33

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2018
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) 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. 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 funds. For US GAAP purposes, all of these items, are recorded in other income (loss). Economic Income (Loss) recognizes incentive fees during periods when the fees are not yet crystallized 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 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 September 30, 2018 Adjustments Investment Investment Bank Total Economic Income/(Loss) Funds Other US GAAP (dollars in thousands) Revenues Investment banking $ — $ 77,510 $ 77,510 $ — $ 4,413 (i) $ 81,923 Brokerage — 101,672 101,672 — (9,637 ) (h) 92,035 Management fees 11,582 804 12,386 (381 ) (4,459 ) (a) 7,546 Incentive income (loss) 6,910 — 6,910 (20 ) (6,857 ) (a)(i) 33 Investment income (loss) 2,039 25,633 27,672 — (27,672 ) (c)(f) — Interest and dividends — — — — 26,448 (c) 26,448 Reimbursement from affiliates — — — (65 ) 418 (e) 353 Aircraft lease revenue — — — — 375 (f) 375 Reinsurance premiums — — — — 8,378 (g) 8,378 Other revenue (283 ) 366 83 — 1,551 (g) 1,634 Consolidated Funds revenues — — — 2,303 — 2,303 Total revenues 20,248 205,985 226,233 1,837 (7,042 ) 221,028 Interest expense 2,554 3,865 6,419 — 19,581 (c) 26,000 Total net revenues 17,694 202,120 219,814 1,837 (26,623 ) 195,028 Expenses Non interest expense 17,934 177,074 195,008 — 14,454 (b)(c)(d)(i) 209,462 Consolidated Funds expenses — — — 1,687 — 1,687 Total expenses 17,934 177,074 195,008 1,687 14,454 211,149 Total other income (loss) — — — 2,654 39,328 (c)(k) 41,982 Income taxes expense / (benefit) — — — — 5,083 (b) 5,083 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 2,122 — 2,122 2,804 364 5,290 Economic income (loss) / net income (loss) attributable to Cowen Inc. $ (2,362 ) $ 25,046 $ 22,684 $ — $ (7,196 ) $ 15,488 Three Months Ended September 30, 2017 Adjustments Investment Investment Bank Total Funds Other US GAAP (dollars in thousands) Revenues Investment banking $ — $ 57,383 $ 57,383 $ — $ — $ 57,383 Brokerage 19 89,949 89,968 — (5,748 ) (h) 84,220 Management fees 12,983 811 13,794 (640 ) (4,931 ) (a) 8,223 Incentive income (loss) 4,597 — 4,597 (402 ) (2,250 ) (a) 1,945 Investment income (loss) 9,927 6,022 15,949 — (15,949 ) (c)(f) — Interest and dividends — — — — 14,318 (c) 14,318 Reimbursement from affiliates — — — (88 ) 572 (e) 484 Aircraft lease revenue — — — — 934 (f) 934 Reinsurance premiums — — — — 7,186 (g) 7,186 Other revenue 387 552 939 — 2,463 (g) 3,402 Consolidated Funds revenues — — — 735 — 735 Total revenues 27,913 154,717 182,630 (395 ) (3,405 ) 178,830 Interest expense 3,662 1,123 4,785 — 10,347 (c) $ 15,132 Total net revenues 24,251 153,594 177,845 (395 ) (13,752 ) 163,698 Expenses Non interest expense 21,333 147,732 169,065 — 8,439 (b)(c)(d) 177,504 Consolidated Funds expenses — — — 1,712 — 1,712 Total expenses 21,333 147,732 169,065 1,712 8,439 179,216 Total other income (loss) — — — 7,535 20,092 (c)(j) 27,627 Income taxes expense / (benefit) — — — — 2,281 (b) 2,281 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 524 — 524 5,428 (790 ) 5,162 Economic income (loss) / net income (loss) attributable to Cowen Inc. $ 2,394 $ 5,862 $ 8,256 $ — $ (3,590 ) $ 4,666 Nine Months Ended September 30, 2018 Adjustments Investment Investment Bank Total Economic Income/(Loss) Funds Consolidation Other Adjustments US GAAP (dollars in thousands) Revenues Investment banking $ — $ 251,476 $ 251,476 $ — $ 13,261 (i) $ 264,737 Brokerage — 328,929 328,929 — (27,876 ) (h) 301,053 Management fees 35,695 2,303 37,998 (2,197 ) (13,465 ) (a) 22,336 Incentive income (loss) 21,470 — 21,470 (37 ) (21,336 ) (a) 97 Investment income (loss) 30,826 31,101 61,927 — (61,927 ) (c)(f) — Interest and dividends — — — — 77,511 (c) 77,511 Reimbursement from affiliates — — — (198 ) 1,264 (e) 1,066 Aircraft lease revenue — — — — 1,509 (f) 1,509 Reinsurance premiums — — — — 26,251 (g) 26,251 Other revenue (501 ) 751 250 — 3,596 (g) 3,846 Consolidated Funds revenues — — — 8,579 — 8,579 Total revenues 87,490 614,560 702,050 6,147 (1,212 ) 706,985 Interest expense 8,814 7,686 16,500 — 58,346 (c) 74,846 Total net revenues 78,676 606,874 685,550 6,147 (59,558 ) 632,139 Expenses Non interest expense 67,489 542,817 610,306 — 42,738 (b)(d)(i) 653,044 Consolidated Funds expenses — — — 7,267 — 7,267 Total expenses 67,489 542,817 610,306 7,267 42,738 660,311 Total other income (loss) — — — 36,113 86,851 (c)(k) 122,964 Income taxes expense / (benefit) — — — — 15,999 (b) 15,999 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 6,760 — 6,760 34,993 (700 ) 41,053 Economic income (loss) / net income (loss) attributable to Cowen Inc. $ 4,427 $ 64,057 $ 68,484 $ — $ (30,744 ) $ 37,740 Nine Months Ended September 30, 2017 Adjustments Investment Investment Bank Total Economic Income/(Loss) Funds Consolidation Other Adjustments US GAAP (dollars in thousands) Revenues Investment banking $ — $ 158,082 $ 158,082 $ — $ — $ 158,082 Brokerage 38 209,236 209,274 — (10,675 ) (h) 198,599 Management fees 39,730 2,365 42,095 (1,773 ) (14,735 ) (a) 25,587 Incentive income (loss) 18,626 — 18,626 (3,669 ) (8,740 ) (a) 6,217 Investment income (loss) 34,412 17,353 51,765 — (51,765 ) (c)(f) — Interest and dividends — — — — 27,324 (c) 27,324 Reimbursement from affiliates — — — (241 ) 2,872 (e) 2,631 Aircraft lease revenue — — — — 3,036 (f) 3,036 Reinsurance premiums — — — — 21,957 (g) 21,957 Other revenue 2,067 1,247 3,314 — 2,833 (g) 6,147 Consolidated Funds revenues — — — 4,751 — 4,751 Total revenues 94,873 388,283 483,156 (932 ) (27,893 ) 454,331 Interest expense 10,141 3,312 13,453 — 23,820 (c) 37,273 Total net revenues 84,732 384,971 469,703 (932 ) (51,713 ) 417,058 Expenses Non interest expense 68,524 371,792 440,316 (199 ) 37,916 (b)(d) 478,033 Consolidated Funds expenses — — — 9,423 — 9,423 Total expenses 68,524 371,792 440,316 9,224 37,916 487,456 Total other income (loss) — — — 44,111 80,196 (c)(j) 124,307 Income taxes expense / (benefit) — — — — 3,407 (b) 3,407 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 4,129 — 4,129 33,955 (2,672 ) 35,412 Economic income (loss) / net income (loss) attributable to Cowen Inc. $ 12,079 $ 13,179 $ 25,258 $ — $ (10,168 ) $ 15,090 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 fund expenses excluding management fees paid, fund revenues and investment income (loss). Other Adjustments: (a) Economic Income (Loss) recognizes revenues (i) net of distribution fees paid to agents and (ii) our proportionate share of management and incentive fees of certain real estate operating entities, the healthcare royalty business and the activist business. (b) Economic Income (Loss) excludes income taxes and acquisition related adjustments as management does not consider these items when evaluating the performance of the segment. (c) Economic Income (Loss) recognizes Company income from proprietary trading (including interest and dividends). (d) 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. (e) Reimbursement from affiliates is shown as a reduction of Economic Income expenses, but is included as a part of revenues under US GAAP. (f) Aircraft lease revenue is shown net of expenses in investment income for Economic Income (Loss). (g) Economic Income (Loss) recognizes underwriting income from the Company's insurance related activities, net of expenses, within other revenue. (h) Economic Income (Loss) brokerage revenues included net securities borrowed and securities loaned activities. (i) Economic Income (Loss) presents underwriting expenses net of investment banking revenues and records income from uncrystallized incentive fees. (j) Economic Income (Loss) excludes the bargain purchase gain which resulted from the Convergex Group acquisition. (k) Economic Income (Loss) excludes gain/(loss) on debt extinguishment. For the three and nine months ended September 30, 2018 and 2017 , there was no one fund or other customer which represented more than 10% of the Company's total revenues.

Regulatory Requirements

Regulatory Requirements	9 Months Ended
	Sep. 30, 2018
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. 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. 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 September 30, 2018 , Cowen Execution had $111.8 million of net capital in excess of this minimum requirement. Ramius UK, Cowen International Ltd and Cowen Execution Ltd are subject to the capital requirements of the FCA of the U.K. Financial Resources, as defined, must exceed the requirement of 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 of its permissions because it was no longer conducting or expecting to conduct regulated activities in the United Kingdom. As of September 30, 2018 , 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 $161.5 $1.0 $160.5 Cowen Execution $114.2 $2.4 $111.8 ATM Execution $1.7 $0.3 $1.4 Cowen Prime $16.6 $0.3 $16.3 Westminster $16.6 $0.3 $16.3 Cowen International Ltd $13.2 $9.1 $4.1 Cowen Execution Ltd $5.0 $3.2 $1.8 Certain transactions cleared on a fully disclosed basis, which promptly transmit customer funds and securities to the clearing broker-dealer that carries the introduced accounts, allow Cowen and Company, Cowen Prime and Cowen Execution Services, in addition to all security transactions executed by ATM Executions, to claim exemption from the SEC's Customer Protection Rule 15c3-3 ("SEC Rule 15c3-3") subparagraph (k)(2)(ii) of the Securities Exchange Act of 1934. Cowen and Company, Cowen Prime and Westminster claim exemption from SEC Rule 15c3-3 subparagraph (k)(2)(i) of the Securities Exchange Act of 1934 since Cowen and Company and Cowen Prime conduct certain of their securities transactions with their customers and Westminster conducts primarily all of its financial transactions with its customers through a bank account designated as Special Account for the Exclusive Benefit of Customers. 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 September 30, 2018 , Co wen Execution had segregated approximately $39.1 million of cash, while its required deposit was $12.0 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 September 30, 2018 , Cowen Execution had $24.3 million of cash on deposit in PAB Reserve Bank Accounts, which was more than its required deposit of $16.9 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 (“Vianden”) and Hollenfels, are required to maintain a solvency capital ratio as calculated by relevant European Commission directives and local regulatory rules in Luxembourg. Each company’s solvency capital ratio as of September 30, 2018 was 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 September 30, 2018 . RCG Insurance Company’s capital and surplus as of September 30, 2018 totaled approximately $28.6 million .

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2018
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 management products and certain managed accounts. Management fees and incentive income are primarily earned from affiliated entities. As of September 30, 2018 and December 31, 2017 , $19.4 million and $13.5 million , respectively, included in fees receivable are earned from related parties. The Company may, at its discretion, reimburse certain fees charged to the funds that it manages to avoid duplication of fees when such funds have an underlying investment in another affiliated investment fund. For the three and nine months ended September 30, 2018 , these amounts are 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 September 30, 2018 and December 31, 2017 , loans to employees of $14.8 million and $11.1 million , respectively, were included in due from related parties on the accompanying condensed consolidated statements of financial condition. Of these amounts $7.1 million and $4.8 million , respectively, are related to forgivable loans. These forgivable loans provide for a cash payment up-front to employees, with the amount due back to the Company forgiven over a vesting period. An employee that voluntarily ceases employment, or is terminated with cause, is generally required to pay back to the Company any unvested forgivable loans granted to them. The forgivable loans are recorded as an asset to the Company on the date of grant and payment, and then amortized to compensation expense on a straight-line basis over the vesting period. The vesting period on forgivable loans is generally one to three years. The Company recorded compensation expense of $0.8 million and $0.6 million for the three months ended September 30, 2018 and 2017 , and $2.2 million and $1.6 million for the nine months ended September 30, 2018 and 2017 , respectively. This expense is included in employee compensation and benefits in the accompanying condensed consolidated statement of operations. For the three and nine months ended September 30, 2018 and 2017, the interest income was insignificant for these related party loans and advances. As of September 30, 2018 and December 31, 2017 , included in due from related parties is $7.8 million and $14.0 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 September 30, 2018 and 2017 , was $0.1 million and $0.2 million and for the nine months ended September 30, 2018 and 2017 , was $0.3 million and $0.6 million , respectively. The remaining balance included in due from related parties of $9.7 million and $9.7 million as of September 30, 2018 and December 31, 2017 , respectively, relates to amounts due to the Company from affiliated 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 as of September 30, 2018 and December 31, 2017 , 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 September 30, 2018 and December 31, 2017 , such investments aggregated $ 27.7 million and $ 28.2 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 funds aggregated $4.5 million and $1.6 million for the three months ended September 30, 2018 and 2017 , and $ 8.9 million and $ 7.2 million for the nine months ended September 30, 2018 and 2017 , respectively.

Guarantees and Off-Balance Shee

Guarantees and Off-Balance Sheet Arrangements	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and December 31, 2017 . 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 September 30, 2018 . 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	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events 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 subsequent events requiring adjustment or disclosure in the condensed consolidated financial statements.

Significant Accounting Polici_2

Significant Accounting Policies - Quarterly (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of presentation	Basis of Presentation These unaudited condensed consolidated financial statements are prepared in accordance with US GAAP as promulgated by the Financial Accounting Standards Board ("FASB") through Accounting Standards Codification ("The Accounting Standards") as the source of authoritative accounting principles in the preparation of financial statements, and include the accounts of the Company, its operating and other subsidiaries, and entities in which the Company has a controlling financial interest or a general partner interest. All material intercompany transactions and balances have been eliminated on consolidation. Certain 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 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 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 funds for which it acts (or acted) as the general partner and investment manager. As of and during the three months ended September 30, 2018 , the Company consolidated the following 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") (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 September 30, 2018 and December 31, 2017 , the total net assets of the consolidated VIEs were $254.6 million and $482.8 million , respectively. The decrease is primarily related to other investors' redemptions which reduced 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 September 30, 2018 and December 31, 2017 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 funds and real estate entities for which the Company serves as the general partner, managing member and/or investment manager with decision-making rights. The Company does not consolidate the Unconsolidated Master Funds or real estate entities that are VIEs as it has concluded that it is not the primary beneficiary in each instance. Fund investors are entitled to all of their economics of these VIEs with the exception of the management fee and incentive income, if any, earned by the Company. The Company's involvement with funds and real estate entities that are unconsolidated VIEs is limited to providing investment management services in exchange for management fees and incentive income. Although the Company may advance amounts and pay certain expenses on behalf of the funds and real estate entities that it considers to be VIEs, it does not provide, nor is it required to provide, any type of substantive financial support to these entities outside of regular investment management services (see Note 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 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, Westminster, Cowen Execution Ltd, ATM Execution LLC ("ATM Execution"), Cowen International Limited ("Cowen International Ltd"), Ramius UK Ltd. ("Ramius UK") and Cowen Prime Services LLC ("Cowen Prime") 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 doubtful accounts The allowance for doubtful accounts 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 doubtful accounts. Specifically for prepaid research, the Company reviews clients' historical, current and forecasted trading activity in determining the allowance for doubtful accounts. Expense related to the allowance for doubtful accounts 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 portfolio funds, real estate investments and equity method investments, which are valued as follows : i. Portfolio funds— Portfolio funds (“Portfolio Funds”) include interests in funds and investment companies 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 are estimated based on the price that would be received to sell an asset in an orderly transaction between marketplace participants at the measurement date. Real estate investments without a public market are valued based on assumptions and valuation techniques used by the Company. Such valuation techniques may include discounted cash flow analysis, prevailing market capitalization rates or earnings multiples applied to earnings from the investment, analysis of recent comparable sales transactions, actual sale negotiations and bona fide purchase offers received from third parties, consideration of the amount that currently would be required to replace the asset, as adjusted for obsolescence, as well as independent external appraisals. In general, the Company considers several valuation techniques when measuring the fair value of a real estate investment. However, in certain circumstances, a single valuation technique may be appropriate. Real estate investments are reviewed on a quarterly basis by the Company for significant changes at the property level or a significant change in the overall market which would impact the value of the real estate investment resulting in unrealized appreciation or depreciation. 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 doubtful accounts. An allowance for doubtful accounts is taken 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 doubtful accounts. The Company records this allowance for doubtful accounts 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 funds and are recognized in accordance with the new revenue recognition guidance (see Note 3k).
Securities borrowed and securities loaned	Securities borrowed and securities loaned Securities borrowed and securities loaned are carried at the amounts of cash collateral advanced or received on a gross basis. The related rebates are recorded in the 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 collateral from the borrower. The initial collateral advanced or received approximates or is greater than the market value of securities borrowed or loaned. The Company monitors the market value of securities borrowed and loaned on a daily basis, with additional collateral obtained or returned, as necessary. Securities borrowed and loaned may also result in credit exposures for the Company in an event that the counterparties are unable to fulfill their contractual obligations. The Company minimizes its credit risk by continuously monitoring its credit exposure and collateral values by demanding additional or returning excess collateral in accordance with the netting provisions available in the master securities lending contracts in place with the counterparties. Fees and interest received or paid are recorded in interest and 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 September 30, 2018 and December 31, 2017 , 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. Aircraft and related equipment, which are leased out under operating leases, are carried at cost less accumulated depreciation and are depreciated to estimated residual value using the straight-line method over the lease term or estimated useful life of the asset. Any assets received at the end of the lease are marked to the lower of cost or fair value with the adjustment recorded in other income. 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 Capitalized lease asset 5 years Straight-line Aircraft and related equipment 10-20 years Straight-line Modifications to aircraft 4-10 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.
Deferred rent	Deferred rent Deferred rent primarily consists of step rent, allowances from landlords and valuing the Company's lease properties acquired through business combinations in accordance with US GAAP. Step rent represents the difference between actual operating lease payments due and straight-line rent expense, which is recorded by the Company over the term of the lease, including the build-out period. This amount is recorded as deferred rent in the early years of the lease, when cash payments are generally lower than straight-line rent expense, and reduced in the later years of the lease when payments begin to exceed the straight-line expense. Landlord allowances are generally comprised of amounts received and/or promised to the Company by landlords and may be received in the form of cash or free rent. These allowances are part of the negotiated terms of the lease. The Company records a receivable from the landlord and a deferred rent liability when the allowances are earned. This deferred rent is amortized into income (through lower rent expense) over the term (including the pre-opening build-out period) of the applicable lease, and the receivable is reduced as amounts are received from the landlord. Liabilities resulting from valuing the Company's leased properties acquired through business combinations are quantified by comparing the current fair value of the leased space to the current rental payments on the date of acquisition. Deferred rent, included in accounts payable, accrued expenses and other liabilities in the accompanying condensed consolidated statements of financial condition, as of September 30, 2018 and December 31, 2017 is $9.1 million and $12.8 million , respectively.
Revenue recognition	Revenue recognition Effective January 1, 2018, the Company adopted ASC Topic 606, Revenue from Contracts with Customers ("ASC Topic 606"). The new revenue recognition guidance 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 guidance requires an entity to follow 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, an entity may include 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. The Company applied the modified retrospective method of adoption which resulted in a cumulative adjustment of $0.6 million to retained earnings as of January 1, 2018. Reported financial results for historic periods were not restated and are reported under The Accounting Standards in effect during the historic period. Refer to the Company's Annual Report on Form 10-K for the year ended December 31, 2017 for discussions related to the Company's previous revenue recognition policies. Our principle sources of revenue are derived from two segments: an investment management segment and an investment bank segment, as more fully described below. The new revenue recognition guidance 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 21 . 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. The investment income was excluded from the new revenue recognition guidance, therefore there were no changes associated with the adoption of the new guidance. Management fees The Company earns management fees from affiliated private funds and certain managed accounts for which it serves as the investment manager; such fees earned are based on assets under management. The management fees are earned as the investment management services are provided and are not subject to reversals. Several management companies of the private 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). While some investors may have separately negotiated fees, in general the management fees are as follows: • Private Hedge Funds. Management fees for the Company's private hedge funds are generally charged at an annual rate of up to 2% of assets under management or notional trading level. Management fees are generally calculated monthly based on assets under management 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 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 funds are generally charged at an annual rate of 0.5% to 2% o f the net asset value or the aggregate cost basis of the unrealized investments held by the funds. For certain other 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 assets under management, 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 funds and managed accounts. The incentive income is either allocated to the Company or is charged to the funds in accordance with their respective investment management or partnership agreements. For the private hedge fund products 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. With the adoption of ASC Topic 606, the Company applied 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. This accounting change did not change the timing or amount of revenue recognized. 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 funds. The Company recognizes incentive income charged to the Company's private hedge funds based on the net profits of the funds. The Company recognizes such incentive income when the fees are no longer subject to reversal or are crystalized. For a majority of the private hedge funds, the incentive fee crystallizes annually when the high-water mark for such 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.” The management companies and general partners of the Company's private equity and debt funds (including the real estate funds, the private healthcare investing funds and HealthCare Royalty Partners funds) are private companies and therefore have not adopted the new revenue recognition guidance. Generally, incentive income or carried interest on real estate funds is earned after the investor has received a full return of their invested capital, plus a preferred return. However, for certain real estate funds, 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 funds are generally subject to a potential clawback of these incentive fees upon the liquidation of the fund 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 and the Company's private healthcare investing funds is generally earned only after investors receive a full return of their capital plus a preferred return. With the adoption of ASC Topic 606, the Company recognizes incentive income at the end of the performance period. Several general partners of the Company's private funds are jointly owned by the Company and third parties. Accordingly, the incentive fees generated by these 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 small- and mid-capitalization companies within the Company's Target Sectors. Investment banking revenue consists of underwriting fees, strategic/financial advisory fees 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; and (iii) the Company has been informed of the number of securities that it has been allotted. 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. The Company records strategic advisory revenues at the point in time, gross of related expenses, when the services for the transactions are completed 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. 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. These fees are recognized on a trade-date basis. 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". Commissions on soft dollar brokerage are recorded net of the related expenditures on an accrual basis. The costs of commission recapture arrangements are recorded on an accrual basis for each eligible trade and shown net of commission revenue. The Company recognizes the soft dollar and commission recapture revenue on a net basis where the Company acts as an agent and on a gross basis where the Company is deemed to be the principal. Commission revenues also includes fees from making algorithms available to clients. • 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 warrants 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 and access to research has been provided. • 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 an d 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 private fund and real estate businesses. These expenses relate to the administration of such subsidiaries and assets that the Company manages for its funds. In addition, pursuant to the funds' offering documents, the Company charges certain allowable expenses to the 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 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. Aircraft lease revenue Aircraft lease revenue associated with the Company's aircraft leasing business is recorded on a straight-line basis over the term of the lease, net of deferred rent and/or prepaid initial direct costs. 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. The following tables summarize the impacts of adopting ASC Topic 606 on the Company’s condensed consolidated financial statements. Condensed Consolidated Statements of Financial Condition As of September 30, 2018 As reported ASC 606 Impact Adjusted (a) (dollars in thousands) Assets Fees receivable, net of allowance $ 111,756 $ 11,739 $ 123,495 Other investments 167,428 (11,739 ) 155,689 Stockholders' equity $ 808,244 $ 3,493 $ 811,737 Condensed Consolidated Statements of Operations Three Months Ended September 30, 2018 Nine Months Ended September 30, 2018 As reported ASC 606 Impact Adjusted (a) As reported ASC 606 Impact Adjusted (a) (dollars in thousands) Revenues Investment banking $ 81,923 $ (4,412 ) $ 77,511 $ 264,737 $ (13,260 ) $ 251,477 Incentive income 33 7,776 7,809 97 11,186 11,283 Total revenues 221,028 3,364 224,392 706,985 (2,074 ) 704,911 Expenses Underwriting expenses 4,412 (4,412 ) — 13,260 (13,260 ) — Total expenses 211,149 (4,412 ) 206,737 660,311 (13,260 ) 647,051 Net gains (losses) on securities, derivatives and other investments 32,040 6,822 38,862 64,728 8,252 72,980 Net income (loss) attributable to Cowen Inc. common stockholders $ 13,790 $ 954 $ 14,744 $ 32,646 $ 2,934 $ 35,580 Condensed Consolidated Statements of Cash Flows Nine Months Ended September 30, 2018 As reported ASC 606 Impact Adjusted (a) (dollars in thousands) Cash flows from operating activities: Net income (loss) $ 78,793 $ 2,934 $ 81,727 Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities: Net (gains) losses on securities, derivatives, and other investments (61,927 ) 6,075 (55,852 ) (Increase) decrease in operating assets: Fees receivable, net of allowance (6,211 ) (8,197 ) (14,408 ) Net cash provided by / (used in) operating activities 295,986 812 296,798 Cash flows from investing activities: Purchase of other investments (21,355 ) (812 ) (22,167 ) Net cash provided by / (used in) investing activities $ (10,925 ) $ (812 ) $ (11,737 ) (a) The amounts reflected above represent items as they would have been reported prior to adoption of the new revenue standard. Refer to Note 21, Segment Reporting, for revenues from contracts with customers disaggregated by major business activity.
Recently issued accounting pronouncements	Recently issued accounting pronouncements 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 condensed consolidated financial statements and does not expect this guidance to have a material impact on its condensed consolidated statements of financial condition or its condensed 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 condensed consolidated statements of financial condition or its condensed consolidated statements of operations. In February 2018, the FASB issued guidance to permit entities to reclassify certain tax effects from accumulated comprehensive income as a result of recent tax reforms. The amendments in this guidance are effective for public business entities for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The Company is currently evaluating the impact of this guidance on the Company’s condensed consolidated financial statements and does not expect this guidance to have a material impact as the Company does not hold any material components of deferred taxes in accumulated other comprehensive income (loss). In March 2017, the FASB issued guidance to amend the amortization period for certain purchased callable debt securities held at a premium. Under current guidance, entities generally amortize 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. The amendments in this guidance are effective for public business entities for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. The Company is currently evaluating the impact of this guidance on the Company’s condensed consolidated financial statements and does not expect this guidance to have a material impact on its condensed consolidated statement of financial condition or its statement of operations as the Company does not hold any material callable debt securities. 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 condensed consolidated financial statements. The Company expects this guidance to simplify its goodwill impairment analysis. In February 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, and present them in its statement 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. For public business entities, the guidance is effective for reporting periods beginning after December 15, 2018. As of September 30, 2018, the Company has identified its arrangements that are within the scope of the new guidance and has evaluated its portfolio of leases, which is primarily comprised of operating real estate leases for its respective offices. The Company will elect the package of practical expedients and, upon adoption, will recognize the right to use lease assets and related lease liabilities as of the adoption date using FASB's modified retrospective approach. Prior period information will not be restated.
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)), unexercised stock options, 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	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) 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. 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 funds. For US GAAP purposes, all of these items, are recorded in other income (loss). Economic Income (Loss) recognizes incentive fees during periods when the fees are not yet crystallized 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 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.

Acquisition (Tables)

Acquisition (Tables)	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Business Acquisition, Pro Forma Information	Nine Months Ended September 30, 2017 (dollars in thousands, except per share data) (unaudited) Revenues $ 529,294 Net income (loss) attributable to Cowen Inc. stockholders (7,001 ) Net income (loss) per common share: Basic $ (0.23 ) Diluted (0.23 )

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
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 Capitalized lease asset 5 years Straight-line Aircraft and related equipment 10-20 years Straight-line Modifications to aircraft 4-10 years Straight-line
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following tables summarize the impacts of adopting ASC Topic 606 on the Company’s condensed consolidated financial statements. Condensed Consolidated Statements of Financial Condition As of September 30, 2018 As reported ASC 606 Impact Adjusted (a) (dollars in thousands) Assets Fees receivable, net of allowance $ 111,756 $ 11,739 $ 123,495 Other investments 167,428 (11,739 ) 155,689 Stockholders' equity $ 808,244 $ 3,493 $ 811,737 Condensed Consolidated Statements of Operations Three Months Ended September 30, 2018 Nine Months Ended September 30, 2018 As reported ASC 606 Impact Adjusted (a) As reported ASC 606 Impact Adjusted (a) (dollars in thousands) Revenues Investment banking $ 81,923 $ (4,412 ) $ 77,511 $ 264,737 $ (13,260 ) $ 251,477 Incentive income 33 7,776 7,809 97 11,186 11,283 Total revenues 221,028 3,364 224,392 706,985 (2,074 ) 704,911 Expenses Underwriting expenses 4,412 (4,412 ) — 13,260 (13,260 ) — Total expenses 211,149 (4,412 ) 206,737 660,311 (13,260 ) 647,051 Net gains (losses) on securities, derivatives and other investments 32,040 6,822 38,862 64,728 8,252 72,980 Net income (loss) attributable to Cowen Inc. common stockholders $ 13,790 $ 954 $ 14,744 $ 32,646 $ 2,934 $ 35,580 Condensed Consolidated Statements of Cash Flows Nine Months Ended September 30, 2018 As reported ASC 606 Impact Adjusted (a) (dollars in thousands) Cash flows from operating activities: Net income (loss) $ 78,793 $ 2,934 $ 81,727 Adjustments to reconcile net income (loss) to net cash provided by / (used in) operating activities: Net (gains) losses on securities, derivatives, and other investments (61,927 ) 6,075 (55,852 ) (Increase) decrease in operating assets: Fees receivable, net of allowance (6,211 ) (8,197 ) (14,408 ) Net cash provided by / (used in) operating activities 295,986 812 296,798 Cash flows from investing activities: Purchase of other investments (21,355 ) (812 ) (22,167 ) Net cash provided by / (used in) investing activities $ (10,925 ) $ (812 ) $ (11,737 ) (a) The amounts reflected above represent items as they would have been reported prior to adoption of the new revenue standard.

Investments of Operating Enti_2

Investments of Operating Entities and Consolidated Funds - (Tables)	9 Months Ended
	Sep. 30, 2018
Investment Holdings [Line Items]
Marketable Securities	As of September 30, 2018 and December 31, 2017 , securities owned, at fair value consisted of the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Common stock (b) $ 576,720 $ 640,065 Preferred stock (b) 6,466 9,604 Warrants and rights (b) 21,403 9,604 U.S. Government securities (a) 2,842 2,807 Corporate bonds (d) 30,992 4,909 Convertible bonds (c) — 282 Trade claims 5,746 5,950 $ 644,169 $ 673,221 (a) As of September 30, 2018 , maturities ranged from October 2018 to August 2019 with an interest rate of 0% . As of December 31, 2017 , maturities ranged from February 2018 to June 2018 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 $6.2 million , respectively, at September 30, 2018 and $6.0 million and $5.2 million , respectively, at December 31, 2017 . At September 30, 2018 and December 31, 2017 , the Company elected the fair value option for investments in warrants and rights with a fair value of $1.1 million and $2.4 million . (c) As of December 31, 2017 , maturities ranged from February 2018 to March 2018 and interest rates ranged from 5% to 12% . (d) As of September 30, 2018 , maturities ranged from October 2018 to April 2049 and interest rates ranged from 0.50% to 14.00% . As of December 31, 2017 , maturities ranged from October 2018 to May 2040 and interest rates ranged from 0.00% to 10.75% .
Schedule of Derivative Instruments	The Company's long and short exposure to derivatives is as follows: Receivable on derivative contracts As of September 30, 2018 As of December 31, 2017 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Futures $ — $ — $ 3,819 $ 58 Currency forwards $ 79,310 1,088 $ 233 5 Swaps $ 57,926 1,203 $ 164,664 10,942 Options other (a) 660,776 29,330 283,112 58,172 Pay to hold $ — 608 $ — — $ 32,229 $ 69,177 (a) Includes index, equity, commodity future and cash conversion options. Payable for derivative contracts As of September 30, 2018 As of December 31, 2017 Number of contracts / Notional Value Fair value Number of contracts / Notional Value Fair value (dollars in thousands) Futures $ 25,474 $ 71 $ 16,796 $ 242 Currency forwards $ 2,897 4 $ 62,439 874 Swaps $ 77,775 2,743 $ 11,595 71 Options other (a) 96,500 27,184 57,043 41,563 $ 30,002 $ 42,750 (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 September 30, 2018 and December 31, 2017 . 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 September 30, 2018 Receivable on derivative contracts, at fair value $ 32,229 $ — $ 32,229 $ — $ 2,899 $ 29,330 Payable for derivative contracts, at fair value 30,002 — 30,002 — 2,747 27,255 As of December 31, 2017 Receivable on derivative contracts, at fair value $ 69,177 $ — $ 69,177 $ — $ 10,948 $ 58,229 Payable for derivative contracts, at fair value 42,750 — 42,750 — 1,031 41,719 (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 Equity Method Investments	The following table summarizes equity method investments held by the Company: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Surf House Ocean Views Holdings, LLC $ 7,478 $ 14,179 Starboard Value LP 17,842 13,202 RCG Longview Debt Fund V Partners, LLC 10,273 9,284 RCG Longview Management, LLC 1,316 1,149 RCG Longview Debt Fund VI Partners LLC 971 — HealthCare Royalty GP, LLC 174 281 HealthCare Royalty GP II, LLC 197 148 RCG Longview Debt Fund IV Management, LLC 331 331 HealthCare Royalty GP III, LLC 1,562 764 RCG Kennedy House, LLC 119 154 RCG Longview Equity Management, LLC 114 114 RCG LPP II GP, LLC 272 487 RCG Park Liberty GP Member Manager, LLC 1,018 428 Other 654 578 $ 42,321 $ 41,099
Schedule of Securities Sold, Not yet Purchased	As of September 30, 2018 and December 31, 2017 , securities sold, not yet purchased, at fair value consisted of the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Common stock $ 353,113 $ 342,328 Corporate bonds (a) 20,309 122 Preferred stock 836 77 Warrants and rights 260 — $ 374,518 $ 342,527 (a) As of September 30, 2018 , the maturities ranged from January 2026 to April 2049 with interest rates ranged from 5.00% to 5.55% . As of December 31, 2017 , the maturities ranged from July 2025 to January 2026 with interest rates ranged from 3.78% to 5.55% .
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 September 30, 2018 and December 31, 2017 . 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 September 30, 2018 Securities borrowed $ 713,288 $ — $ 713,288 $ — $ 684,569 $ — $ 28,719 Securities loaned 548,629 — 548,629 — 531,984 — 16,645 As of December 31, 2017 Securities borrowed $ 443,148 $ — $ 443,148 $ — $ 414,778 $ — $ 28,370 Securities loaned 456,831 — 456,831 — 439,228 — 17,603 (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 September 30, 2018 and December 31, 2017 : Open and Overnight Up to 30 days 31 - 90 days Greater than 90 days Total (dollars in thousands) As of September 30, 2018 Common stock $ 548,629 $ — $ — $ — $ 548,629 As of December 31, 2017 Common stock $ 456,831 $ — $ — $ — $ 456,831
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 September 30, 2018 Linkem Equity Italy Wireless Broadband 8.01 % $ 64,754 As of December 31, 2017 Linkem Equity Italy Wireless Broadband 7.52 % $ 56,271
Schedule of Other Investments	As of September 30, 2018 and December 31, 2017 , other investments included the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Portfolio Funds, at fair value (1) $ 125,107 $ 100,148 Equity method investments (2) 42,321 41,099 Lehman claims, at fair value — 301 $ 167,428 $ 141,548
Schedule of Other Investments, Portfolio Funds	The Portfolio Funds, at fair value as of September 30, 2018 and December 31, 2017 , included the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Starboard Value and Opportunity Fund LP (c)(*) $ 33,321 $ 32,079 Formation8 Partners Fund I, L.P. (f) 28,135 28,243 RCG Longview Debt Fund V, L.P. (g)(*) 4,537 8,892 RCG Longview II LP (g) (*) 4,160 131 Cowen Healthcare Investments II LP (j) (*) 15,875 — Eclipse Ventures Fund I, L.P. (b) 3,575 3,428 HealthCare Royalty Partners LP (a)(*) 2,129 3,452 Lagunita Biosciences, LLC (d) 3,859 2,400 RCG IO Renergys Sarl (j) (*) 1,780 — Starboard Leaders Fund LP (e)(*) 1,405 1,276 Eclipse SPV I, LP (k)(*) 1,447 — RCG Longview Equity Fund, LP (g) (*) 819 — RCG Longview Debt Fund VI, LP (g) (*) 588 1,022 RCG Park Liberty GP Member LLC (g) (*) 908 750 HealthCare Royalty Partners II LP (a)(*) 1,162 873 RCGL PE MPA, LLC (g)(*) 549 — RCG LPP2 PNW5 Co-Invest, L.P. (h)(*) 309 3,493 Quadratic Fund LLC (i)(*) — 906 Other private investment (l)(*) 15,997 10,133 Other affiliated funds (m)(*) 4,552 3,070 $ 125,107 $ 100,148 * 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 16 . (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 funds are affiliates of the Company or are managed by the Company and the investors can redeem from these funds as investments are liquidated.
Consolidated Funds
Investment Holdings [Line Items]
Marketable Securities	As of September 30, 2018 and December 31, 2017 , securities owned, at fair value, held by the Consolidated Funds consisted of the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Preferred stock $ 24,314 $ 50,445 Common stock 55,535 77,702 U.S. Government securities (a) 20,446 34,201 Corporate bonds (b) 3,758 — Warrants and rights 4,848 3,568 $ 108,901 $ 165,916 (a) As of September 30, 2018 , maturities ranged from November 2018 to December 2018 and interest rates were 0% . As of December 31, 2017 , maturities ranged from January 2018 to April 2022 and interest rates ranged from 0% to 5.75% . (b) As of September 30, 2018 , the maturity was December 2023 with an interest rate of 5.88% .
Schedule of Derivative Instruments	As of September 30, 2018 and December 31, 2017 , receivable on derivative contracts, at fair value, held by the Consolidated Funds are comprised of: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Currency forwards $ 27 $ 524 Equity swaps 1,584 1,754 Options 300 242 $ 1,911 $ 2,520 Payable for derivative contracts As of September 30, 2018 and December 31, 2017 , payable for derivative contracts, at fair value, held by the Consolidated Funds are comprised of: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Currency forwards $ 539 $ 11 Equity swaps 1,590 7,042 Options 60 77 $ 2,189 $ 7,130
Schedule of Other Investments, Portfolio Funds	Investments in Portfolio Funds, at fair value As of September 30, 2018 and December 31, 2017 , investments in Portfolio Funds, at fair value, included the following: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Investments of Enterprise LP $ 97,026 $ 87,221 Investments of Merger Fund 86,264 286,890 $ 183,290 $ 374,111
Enterprise Master
Investment Holdings [Line Items]
Marketable Securities	Securities owned by Enterprise Master, at fair value As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Common stock $ 469 $ 608 $ 469 $ 608
Schedule of Other Investments, Portfolio Funds	Portfolio Funds, owned by Enterprise Master, at fair value As of September 30, 2018 As of December 31, 2017 Strategy (dollars in thousands) RCG Special Opportunities Fund, Ltd* Multi-Strategy $ 109,518 $ 97,345 RCG Longview Equity Fund, LP* Real Estate — 1,266 RCG Longview Debt Fund IV, LP* Real Estate — 99 RCG Longview II, LP* Real Estate — 229 Other Private Investments Various 864 937 $ 110,382 $ 99,876 * 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 September 30, 2018 As of December 31, 2017 Description (dollars in thousands) Options $ 1,817 $ 108,063 Equity swaps 1,658 14,488 Currency forwards 200 — $ 3,675 $ 122,551 Payable for derivative contracts, at fair value, owned by Merger Master As of September 30, 2018 As of December 31, 2017 Description (dollars in thousands) Options $ 261 $ 1,256 Currency forwards — 213 Equity swaps 2,005 1,249 $ 2,266 $ 2,718

Fair Value Measurements for O_2

Fair Value Measurements for Operating Entities and Consolidated Funds (Tables)	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and December 31, 2017 : Assets at Fair Value as of September 30, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities owned US Government securities $ 2,842 $ — $ — $ 2,842 Preferred stock 1,308 — 5,158 6,466 Common stock 564,140 6,906 5,674 576,720 Corporate bonds — 30,992 — 30,992 Trade claims — — 5,746 5,746 Warrants and rights 19,821 — 1,582 21,403 Receivable on derivative contracts, at fair value Currency forwards — 1,088 — 1,088 Swaps — 1,203 — 1,203 Options 29,330 — — 29,330 Pay to hold — 608 — 608 Consolidated Funds Securities owned US Government securities 20,446 — — 20,446 Preferred stock — — 24,314 24,314 Common stock 55,441 — 94 55,535 Corporate bonds — 3,758 — 3,758 Warrants and rights — — 4,848 4,848 Receivable on derivative contracts, at fair value Currency forwards — 27 — 27 Equity swaps — 1,584 — 1,584 Options 300 — — 300 $ 693,628 $ 46,166 $ 47,416 $ 787,210 Percentage of total assets measured at fair value on a recurring basis 88.1 % 5.9 % 6.0 % Portfolio funds measured at net asset value (a) 125,107 Consolidated funds' portfolio funds measured at net asset value (a) 183,290 Equity method investments 42,321 Total investments $ 1,137,928 Liabilities at Fair Value as of September 30, 2018 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities sold, not yet purchased Common stock $ 353,113 $ — $ — $ 353,113 Corporate bonds — 20,309 — 20,309 Preferred stock 836 — — 836 Warrants and rights 260 — — 260 Payable for derivative contracts, at fair value Futures 71 — — 71 Currency forwards — 4 — 4 Swaps — 2,743 — 2,743 Options 24,637 — 2,547 27,184 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 2,643 2,643 Consolidated Funds Payable for derivative contracts, at fair value Currency forwards — 539 — 539 Options 60 — — 60 Equity swaps — 1,590 — 1,590 $ 378,977 $ 25,185 $ 5,190 $ 409,352 Percentage of total liabilities measured at fair value 92.6 % 6.2 % 1.3 % (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 third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018, December 2020, and June 2018, respectively. 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 September 30, 2018 can range from $0.1 million to $7.0 million . Assets at Fair Value as of December 31, 2017 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities owned US Government securities $ 2,807 $ — $ — $ 2,807 Preferred stock 571 918 8,115 9,604 Common stock 627,011 5,484 7,570 640,065 Convertible bonds — — 282 282 Corporate bonds — 4,909 — 4,909 Trade claims — — 5,950 5,950 Warrants and rights 7,087 — 2,517 9,604 Receivable on derivative contracts, at fair value Futures 58 — — 58 Currency forwards — 5 — 5 Swaps — 10,942 — 10,942 Options 56,717 — 1,455 58,172 Other investments Lehman claim — — 301 301 Consolidated Funds Securities owned US Government securities 30,552 3,649 — 34,201 Preferred stock — — 50,445 50,445 Common stock 77,652 — 50 77,702 Warrants and rights — — 3,568 3,568 Receivable on derivative contracts, at fair value Currency forwards — 524 — 524 Equity swaps — 1,754 — 1,754 Options 242 — — 242 $ 802,697 $ 28,185 $ 80,253 $ 911,135 Percentage of total assets measured at fair value on a recurring basis 88.1 % 3.1 % 8.8 % Portfolio funds measured at net asset value (a) 100,148 Consolidated funds' portfolio funds measured at net asset value (a) 374,111 Equity method investments 41,099 Total investments $ 1,426,493 Liabilities at Fair Value as of December 31, 2017 Level 1 Level 2 Level 3 Total (dollars in thousands) Operating Entities Securities sold, not yet purchased Common stock $ 342,328 $ — $ — $ 342,328 Corporate bonds — 122 — 122 Preferred stock 77 — — 77 Payable for derivative contracts, at fair value Futures 242 — — 242 Currency forwards — 874 — 874 Swaps — 71 — 71 Options 19,162 — 22,401 41,563 Accounts payable, accrued expenses and other liabilities Contingent consideration liability (b) — — 3,440 3,440 Consolidated Funds Payable for derivative contracts, at fair value Currency forwards — 11 — 11 Options 77 — — 77 Equity swaps — 7,042 — 7,042 $ 361,886 $ 8,120 $ 25,841 $ 395,847 Percentage of total liabilities measured at fair value 91.4 % 2.1 % 6.5 % (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 third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018 and December 2020, respectively. 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, 2017 can range from $0.1 million to $15.0 million .
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation	The following table includes a roll forward of the amounts for the three and nine months ended September 30, 2018 and 2017 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 September 30, 2018 Balance at June 30, 2018 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at September 30, 2018 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 7,422 $ — $ (1,141 ) (c) $ — $ — $ (1,123 ) $ 5,158 $ (1,124 ) Common stock 5,848 — — — — (174 ) 5,674 (174 ) Options, liability 301 — — — — 2,246 2,547 2,246 Warrants and rights 1,544 — — — — 38 1,582 38 Trade claims 5,699 — — 44 — 3 5,746 3 Lehman claim 295 — — — (234 ) (61 ) — — Contingent consideration liability 2,870 — — — (227 ) — 2,643 — Consolidated Funds Preferred stock 24,314 — — — — — 24,314 — Common stock 94 — — — — — 94 — Warrants and rights 4,738 — — — — 110 4,848 110 Three Months Ended September 30, 2017 Balance at June 30, 2017 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at September 30, 2017 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 18,576 $ — $ — $ — $ — $ (587 ) $ 17,989 $ (587 ) Common stock 10,588 — — 3,151 (1,946 ) 297 12,090 297 Convertible bonds 282 — — 250 — (250 ) 282 — Options, asset 9,860 — — — — 499 10,359 499 Options, liability 9,860 — — — — 499 10,359 499 Warrants and rights 3,409 — — — — (1,013 ) 2,396 187 Trade claims 4,648 — — 1,925 (630 ) 3 5,946 3 Lehman claim 309 — — — — 10 319 10 Contingent consideration liability 5,174 — — — (125 ) — 5,049 — Consolidated Funds Preferred stock 18,224 — — 467 — 252 18,943 252 Common stock 848 — — — (848 ) — — — Warrants and rights 3,369 — — — — 9 3,378 9 Term Loan 202 — — — (200 ) (2 ) — — Nine Months Ended September 30, 2018 Balance at December 31, 2017 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at September 30, 2018 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 8,115 $ — $ (1,141 ) (c) $ 1,415 $ (695 ) $ (2,536 ) $ 5,158 $ (2,301 ) Common stock 7,570 — — 531 (1,333 ) (1,094 ) 5,674 (1,128 ) Convertible bonds 282 — — — (307 ) 25 — — Options, asset 1,455 — — — (1,455 ) — — — Options, liability 22,401 — (28,973 ) (e) — (259 ) 9,378 2,547 9,378 Warrants and rights 2,517 — — — (143 ) (792 ) 1,582 (933 ) Trade claims 5,950 — — 44 (334 ) 86 5,746 23 Lehman claim 301 — — — (234 ) (67 ) — — Contingent consideration liability 3,440 — — — (797 ) — 2,643 — Consolidated Funds Preferred stock 50,445 — (38,552 ) (a) 3,066 — 9,355 24,314 9,355 Common stock 50 — — — — 44 94 44 Warrants and rights 3,568 — (20 ) (a) (1,340 ) — 2,640 4,848 1,300 Nine Months Ended September 30, 2017 Balance at December 31, 2016 Transfers in Transfers out Purchases/(covers) (Sales)/shorts Realized and Unrealized gains/losses Balance at September 30, 2017 Change in unrealized gains/losses relating to instruments still held (1) (dollars in thousands) Operating Entities Preferred stock $ 15,811 $ — $ (3,472 ) (c) $ 9,000 $ (31 ) $ (3,319 ) $ 17,989 $ (1,006 ) Common stock 10,121 — — 3,182 (2,121 ) 908 12,090 908 Convertible bonds 250 — — 282 — (250 ) 282 — Options, asset 14,753 — — — — (4,394 ) 10,359 (4,394 ) Options, liability 14,753 — — — — (4,394 ) 10,359 (4,394 ) Warrants and rights 3,719 3,192 (b) (d) — — (4,367 ) (148 ) 2,396 510 Trade claim 562 — — 5,865 (700 ) 219 5,946 198 Lehman claim 265 — — — — 54 319 54 Contingent consideration liability 5,997 — — — (392 ) (556 ) 5,049 (556 ) Consolidated Funds Preferred stock 36,928 — (13,668 ) (c) 467 (11,853 ) 7,069 18,943 2,958 Common stock 295 — — 476 (848 ) 77 — — Warrants and rights 3 — — — — 3,375 3,378 3,375 Term Loan 657 — — 202 (1,021 ) 162 — — (1) Unrealized gains/losses are reported in other income (loss) in the accompanying condensed consolidated statements of operations. (a) The Company deconsolidated a fund (See note 3) (b) The Company received warrants as consideration as part of an investment banking transaction. (c) The investments were converted to common stock. (d) As part of the preferred stock sale, the sellers received contingent value rights to be paid in the event certain milestones are reached. (e) On June 26, 2018, the Company received shareholder approval which will allow the Company to settle its convertible note (see Note 17 ) entirely in class A common shares. Upon receiving shareholder approval, the Company reclassified the embedded conversion option, associated with the convertible debt, to equity. (See Note 18 )
Fair Value Inputs, Assets, Quantitative Information	The following table includes quantitative information as of September 30, 2018 and December 31, 2017 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 September 30, 2018 Valuation Techniques Unobservable Inputs Range Level 3 Assets (dollars in thousands) Common and preferred stocks $ 2,508 Guideline companies/Discounted cash flows Discount rate 50% Trade claims 25 Discounted cash flows Discount rate 20% Warrants and rights 1,582 Model based Discounted cash flows Discount rate 7% to 9% Other level 3 assets (a) 43,301 Total level 3 assets $ 47,416 Level 3 Liabilities Options 2,547 Option pricing models Volatility 30% to 35% Contingent consideration liability 2,643 Discounted cash flows Projected cash flow and discount rate 23% Total level 3 liabilities $ 5,190 Quantitative Information about Level 3 Fair Value Measurements Fair Value at December 31, 2017 Valuation Techniques Unobservable Inputs Range Level 3 Assets (dollars in thousands) Common and preferred stocks $ 5,642 Guideline companies/transaction price Market multiples 4.8x to 8.5x Trade claims 70 Discounted cash flows Discount rate 20% Warrants and rights 2,516 Model based Discounted cash flows Volatility Discount rate 61% 22% Options 1,455 Option pricing models Volatility 28% Other level 3 assets (a) 70,570 Total level 3 assets $ 80,253 Level 3 Liabilities Options 22,401 Option pricing models Volatility 28% Contingent consideration liability 3,440 Discounted cash flows Projected cash flow and discount rate 8% to 23% Total level 3 liabilities $ 25,841 (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 September 30, 2018 and December 31, 2017 , 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 3 . September 30, 2018 December 31, 2017 Fair Value Hierarchy Carrying Amount Fair Value Carrying Amount Fair Value (dollars in thousands) Financial Assets Operating companies Cash and cash equivalents $ 193,066 $ 193,066 $ 130,052 $ 130,052 Level 1 Cash collateral pledged 16,092 16,092 17,888 17,888 Level 2 Segregated cash 154,191 154,191 116,268 116,268 Level 1 Securities borrowed 713,288 $ 684,569 443,148 414,763 Level 2 Loans receivable 36,009 36,009 (d) 37,993 37,993 (d) Level 3 Consolidated funds Cash and cash equivalents 18,747 18,747 21,988 21,988 Level 1 Financial Liabilities Securities loaned 548,629 531,984 456,831 440,162 Level 2 Convertible debt 133,126 (a) 173,246 (b) 141,502 (a) 172,709 (b) Level 2 Notes payable and other debt 271,082 284,021 (c) 173,458 182,352 (c) Level 2 (a) The carrying amount of the convertible debt includes an unamortized discount of $24.9 million and $25.6 million as of September 30, 2018 and December 31, 2017 , 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)	9 Months Ended
	Sep. 30, 2018
Receivables from Brokers-Dealers and Clearing Organizations [Abstract]
Schedule of Due to (from) Broker-Dealers and Clearing Organizations	As of September 30, 2018 and December 31, 2017 , amounts receivable from brokers, dealers and clearing organizations include: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Broker-dealers $ 569,998 $ 409,499 Securities failed to deliver 47,014 87,820 Clearing organizations 16,541 6,126 Securities borrowed interest receivable 10,839 4,733 $ 644,392 $ 508,178 As of September 30, 2018 and December 31, 2017 , amounts payable to brokers, dealers and clearing organizations include: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Broker-dealers $ 131,358 $ 145,860 Securities failed to receive 54,539 53,540 Clearing organizations 18,202 48,257 Securities loaned interest payable 6,227 4,496 $ 210,326 $ 252,153

Redeemable Non-Controlling In_2

Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds (Tables)	9 Months Ended
	Sep. 30, 2018
Noncontrolling Interest [Abstract]
Redeemable non-controlling interests in consolidated subsidiaries and funds	Redeemable non-controlling interests in consolidated subsidiaries and funds and the related net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds are comprised as follows: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Redeemable non-controlling interests in consolidated subsidiaries and funds Operating companies $ 11,069 $ 6,113 Consolidated Funds 192,143 434,491 $ 203,212 $ 440,604
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (dollars in thousands) (dollars in thousands) Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds Operating companies $ 2,486 $ (266 ) $ 6,060 $ 1,457 Consolidated Funds 2,804 5,428 34,993 33,955 $ 5,290 $ 5,162 $ 41,053 $ 35,412

Share-Based Compensation and _2

Share-Based Compensation and Employee Ownership Plans (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation, Stock Appreciation Rights, Activity	The following table summarizes the Company's SARs for the nine months ended September 30, 2018 : Class A Common Shares Subject Weighted Average Weighted Average Aggregate Intrinsic (in years) (dollars in thousands) Balance outstanding at December 31, 2017 75,000 $ 11.60 0.21 $ 173 SARs vested (75,000 ) 14.21 — — Balance outstanding at September 30, 2018 — $ — 0 $ — SARs exercisable at September 30, 2018 — $ — 0 $ — (1) Based on the Company's closing stock price of $13.65 on December 31, 2017 .
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 nine months ended September 30, 2018 : Nonvested Restricted Class A Common Shares and Class A Common Restricted Stock Units Weighted-Average Balance outstanding at December 31, 2017 5,579,293 $ 16.33 Granted 2,255,794 14.27 Vested (1,423,075 ) 16.08 Forfeited (61,997 ) 14.13 Balance outstanding at September 30, 2018 6,350,015 $ 15.68 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, 117,188 have been forfeited through September 30, 2018 . The remaining awards, included in the outstanding balance as of September 30, 2018 , will vest between March 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)	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Annual Lease and Service Payments	As of September 30, 2018 , future minimum annual lease and service payments for the Company were as follows: Equipment Leases (a) Service Payments Facility Leases (b) (dollars in thousands) 2018 $ 966 $ 6,762 $ 6,453 2019 2,482 19,256 24,508 2020 1,529 5,796 20,907 2021 1,392 1,722 20,640 2022 1,128 1,350 17,464 Thereafter 374 1,470 28,353 $ 7,871 $ 36,356 $ 118,325 (a) Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 17 for further information on the capital lease minimum payments which are included in the table. (b) The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $0.4 million and $0.2 million for the three months ended September 30, 2018 and 2017 , and $1.1 million and $0.8 million for the nine months ended September 30, 2018 and 2017 , respectively.
Other Commitments	The following table summarizes unfunded commitments as of September 30, 2018 : Entity Unfunded Commitments Commitment term (dollars in millions) Real estate (a) $ 4.6 (a) HealthCare Royalty Partners funds (b) 1.1 2 years Eclipse Ventures Fund I, L.P. (formerly Formation8 Partners Hardware Fund I, L.P.) 0.4 6 years Lagunita Biosciences, LLC 1.0 3 years Eclipse Fund II, L.P. 0.8 7 years Eclipse Continuity Fund I, L.P. 0.6 8 years Cowen Healthcare Investments II LP 9.6 3 years (a) The Company had unfunded commitments pertaining to capital commitments in four real estate investments held by the Company, all of which pertain to related party investments. Such commitments can be called at any time 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)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Debt and Capital Lease Obligations	As of September 30, 2018 and December 31, 2017 , the Company's outstanding debt was as follows: As of September 30, 2018 As of December 31, 2017 (dollars in thousands) Convertible debt $ 133,126 $ 141,502 Notes payable 229,581 132,970 Term loan 28,200 28,121 Other notes payable 7,688 8,247 Capital lease obligations 5,613 4,120 $ 404,208 $ 314,960
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 September 30, 2018 , are as follows: Convertible Debt Notes Payable Term loan Other Notes Payable Capital Lease (dollars in thousands) 2018 $ 2,025 $ 4,473 $ — $ 1,106 $ 568 2019 25,223 17,893 29,414 3,410 1,438 2020 4,050 17,893 — 1,363 1,360 2021 4,050 17,893 — 2,512 1,360 2022 139,050 17,893 — — 1,128 Thereafter — 370,090 — — 374 Subtotal 174,398 446,135 29,414 8,391 6,228 Less (a) (41,272 ) (216,554 ) (1,214 ) (703 ) (615 ) Total $ 133,126 $ 229,581 $ 28,200 $ 7,688 $ 5,613 (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 September 30, 2018 , 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 $10.8 million , as of September 30, 2018 , and $11.8 million , as of December 31, 2017 , which is anticipated to be due March 2021 Location Amount Maturity (dollars in thousands) Boston $ 386 March 2019 New York $ 356 April 2019 New York $ 70 May 2019 New York $ 497 October 2018 New York $ 1,686 October 2018 New York $ 1,615 November 2018 San Francisco $ 714 January 2019

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Treasury Stock Activity	The following represents the activity relating to the treasury stock held by the Company during the nine months ended September 30, 2018 : Treasury stock shares Cost Average cost per share Balance outstanding at December 31, 2017 12,133,276 $ 186,846 $ 15.40 Shares purchased for minimum tax withholding under the Equity Plans or other similar transactions 578,673 8,544 14.76 Shares of stock received in respect of indemnification claims 220,475 3,171 14.38 Purchase of treasury stock 1,160,308 16,762 14.45 Balance outstanding at September 30, 2018 14,092,732 $ 215,323 $ 15.28

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2018
Accumulated Other Comprehensive Income / (Loss) [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (dollars in thousands) Beginning Balance $ (7 ) $ (8 ) $ (8 ) $ (2 ) Foreign currency translation 4 — 5 (6 ) Ending Balance $ (3 ) $ (8 ) $ (3 ) $ (8 )

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share, Basic and Diluted	The computation of earnings per share is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except share and per share data) Net income (loss) $ 20,778 $ 9,828 $ 78,793 $ 50,502 Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 5,290 5,162 41,053 35,412 Net income (loss) attributable to Cowen Inc. 15,488 4,666 37,740 15,090 Preferred stock dividends 1,698 1,698 5,094 5,094 Net income (loss) attributable to Cowen Inc. common stockholders $ 13,790 $ 2,968 $ 32,646 $ 9,996 Shares for basic and diluted calculations: Weighted average shares used in basic computation 29,610 31,271 29,662 29,004 Stock options — — — Stock appreciation rights — 20 — 15 Restricted stock 1,234 955 951 992 Weighted average shares used in diluted computation 30,844 32,246 30,613 30,011 Earnings (loss) per share: Basic $ 0.47 $ 0.09 $ 1.10 $ 0.34 Diluted $ 0.45 $ 0.09 $ 1.07 $ 0.33

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 Adjustments Investment Investment Bank Total Economic Income/(Loss) Funds Other US GAAP (dollars in thousands) Revenues Investment banking $ — $ 77,510 $ 77,510 $ — $ 4,413 (i) $ 81,923 Brokerage — 101,672 101,672 — (9,637 ) (h) 92,035 Management fees 11,582 804 12,386 (381 ) (4,459 ) (a) 7,546 Incentive income (loss) 6,910 — 6,910 (20 ) (6,857 ) (a)(i) 33 Investment income (loss) 2,039 25,633 27,672 — (27,672 ) (c)(f) — Interest and dividends — — — — 26,448 (c) 26,448 Reimbursement from affiliates — — — (65 ) 418 (e) 353 Aircraft lease revenue — — — — 375 (f) 375 Reinsurance premiums — — — — 8,378 (g) 8,378 Other revenue (283 ) 366 83 — 1,551 (g) 1,634 Consolidated Funds revenues — — — 2,303 — 2,303 Total revenues 20,248 205,985 226,233 1,837 (7,042 ) 221,028 Interest expense 2,554 3,865 6,419 — 19,581 (c) 26,000 Total net revenues 17,694 202,120 219,814 1,837 (26,623 ) 195,028 Expenses Non interest expense 17,934 177,074 195,008 — 14,454 (b)(c)(d)(i) 209,462 Consolidated Funds expenses — — — 1,687 — 1,687 Total expenses 17,934 177,074 195,008 1,687 14,454 211,149 Total other income (loss) — — — 2,654 39,328 (c)(k) 41,982 Income taxes expense / (benefit) — — — — 5,083 (b) 5,083 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 2,122 — 2,122 2,804 364 5,290 Economic income (loss) / net income (loss) attributable to Cowen Inc. $ (2,362 ) $ 25,046 $ 22,684 $ — $ (7,196 ) $ 15,488 Three Months Ended September 30, 2017 Adjustments Investment Investment Bank Total Funds Other US GAAP (dollars in thousands) Revenues Investment banking $ — $ 57,383 $ 57,383 $ — $ — $ 57,383 Brokerage 19 89,949 89,968 — (5,748 ) (h) 84,220 Management fees 12,983 811 13,794 (640 ) (4,931 ) (a) 8,223 Incentive income (loss) 4,597 — 4,597 (402 ) (2,250 ) (a) 1,945 Investment income (loss) 9,927 6,022 15,949 — (15,949 ) (c)(f) — Interest and dividends — — — — 14,318 (c) 14,318 Reimbursement from affiliates — — — (88 ) 572 (e) 484 Aircraft lease revenue — — — — 934 (f) 934 Reinsurance premiums — — — — 7,186 (g) 7,186 Other revenue 387 552 939 — 2,463 (g) 3,402 Consolidated Funds revenues — — — 735 — 735 Total revenues 27,913 154,717 182,630 (395 ) (3,405 ) 178,830 Interest expense 3,662 1,123 4,785 — 10,347 (c) $ 15,132 Total net revenues 24,251 153,594 177,845 (395 ) (13,752 ) 163,698 Expenses Non interest expense 21,333 147,732 169,065 — 8,439 (b)(c)(d) 177,504 Consolidated Funds expenses — — — 1,712 — 1,712 Total expenses 21,333 147,732 169,065 1,712 8,439 179,216 Total other income (loss) — — — 7,535 20,092 (c)(j) 27,627 Income taxes expense / (benefit) — — — — 2,281 (b) 2,281 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 524 — 524 5,428 (790 ) 5,162 Economic income (loss) / net income (loss) attributable to Cowen Inc. $ 2,394 $ 5,862 $ 8,256 $ — $ (3,590 ) $ 4,666 Nine Months Ended September 30, 2018 Adjustments Investment Investment Bank Total Economic Income/(Loss) Funds Consolidation Other Adjustments US GAAP (dollars in thousands) Revenues Investment banking $ — $ 251,476 $ 251,476 $ — $ 13,261 (i) $ 264,737 Brokerage — 328,929 328,929 — (27,876 ) (h) 301,053 Management fees 35,695 2,303 37,998 (2,197 ) (13,465 ) (a) 22,336 Incentive income (loss) 21,470 — 21,470 (37 ) (21,336 ) (a) 97 Investment income (loss) 30,826 31,101 61,927 — (61,927 ) (c)(f) — Interest and dividends — — — — 77,511 (c) 77,511 Reimbursement from affiliates — — — (198 ) 1,264 (e) 1,066 Aircraft lease revenue — — — — 1,509 (f) 1,509 Reinsurance premiums — — — — 26,251 (g) 26,251 Other revenue (501 ) 751 250 — 3,596 (g) 3,846 Consolidated Funds revenues — — — 8,579 — 8,579 Total revenues 87,490 614,560 702,050 6,147 (1,212 ) 706,985 Interest expense 8,814 7,686 16,500 — 58,346 (c) 74,846 Total net revenues 78,676 606,874 685,550 6,147 (59,558 ) 632,139 Expenses Non interest expense 67,489 542,817 610,306 — 42,738 (b)(d)(i) 653,044 Consolidated Funds expenses — — — 7,267 — 7,267 Total expenses 67,489 542,817 610,306 7,267 42,738 660,311 Total other income (loss) — — — 36,113 86,851 (c)(k) 122,964 Income taxes expense / (benefit) — — — — 15,999 (b) 15,999 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 6,760 — 6,760 34,993 (700 ) 41,053 Economic income (loss) / net income (loss) attributable to Cowen Inc. $ 4,427 $ 64,057 $ 68,484 $ — $ (30,744 ) $ 37,740 Nine Months Ended September 30, 2017 Adjustments Investment Investment Bank Total Economic Income/(Loss) Funds Consolidation Other Adjustments US GAAP (dollars in thousands) Revenues Investment banking $ — $ 158,082 $ 158,082 $ — $ — $ 158,082 Brokerage 38 209,236 209,274 — (10,675 ) (h) 198,599 Management fees 39,730 2,365 42,095 (1,773 ) (14,735 ) (a) 25,587 Incentive income (loss) 18,626 — 18,626 (3,669 ) (8,740 ) (a) 6,217 Investment income (loss) 34,412 17,353 51,765 — (51,765 ) (c)(f) — Interest and dividends — — — — 27,324 (c) 27,324 Reimbursement from affiliates — — — (241 ) 2,872 (e) 2,631 Aircraft lease revenue — — — — 3,036 (f) 3,036 Reinsurance premiums — — — — 21,957 (g) 21,957 Other revenue 2,067 1,247 3,314 — 2,833 (g) 6,147 Consolidated Funds revenues — — — 4,751 — 4,751 Total revenues 94,873 388,283 483,156 (932 ) (27,893 ) 454,331 Interest expense 10,141 3,312 13,453 — 23,820 (c) 37,273 Total net revenues 84,732 384,971 469,703 (932 ) (51,713 ) 417,058 Expenses Non interest expense 68,524 371,792 440,316 (199 ) 37,916 (b)(d) 478,033 Consolidated Funds expenses — — — 9,423 — 9,423 Total expenses 68,524 371,792 440,316 9,224 37,916 487,456 Total other income (loss) — — — 44,111 80,196 (c)(j) 124,307 Income taxes expense / (benefit) — — — — 3,407 (b) 3,407 Income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds 4,129 — 4,129 33,955 (2,672 ) 35,412 Economic income (loss) / net income (loss) attributable to Cowen Inc. $ 12,079 $ 13,179 $ 25,258 $ — $ (10,168 ) $ 15,090 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 fund expenses excluding management fees paid, fund revenues and investment income (loss). Other Adjustments: (a) Economic Income (Loss) recognizes revenues (i) net of distribution fees paid to agents and (ii) our proportionate share of management and incentive fees of certain real estate operating entities, the healthcare royalty business and the activist business. (b) Economic Income (Loss) excludes income taxes and acquisition related adjustments as management does not consider these items when evaluating the performance of the segment. (c) Economic Income (Loss) recognizes Company income from proprietary trading (including interest and dividends). (d) 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. (e) Reimbursement from affiliates is shown as a reduction of Economic Income expenses, but is included as a part of revenues under US GAAP. (f) Aircraft lease revenue is shown net of expenses in investment income for Economic Income (Loss). (g) Economic Income (Loss) recognizes underwriting income from the Company's insurance related activities, net of expenses, within other revenue. (h) Economic Income (Loss) brokerage revenues included net securities borrowed and securities loaned activities. (i) Economic Income (Loss) presents underwriting expenses net of investment banking revenues and records income from uncrystallized incentive fees. (j) Economic Income (Loss) excludes the bargain purchase gain which resulted from the Convergex Group acquisition. (k) Economic Income (Loss) excludes gain/(loss) on debt extinguishment.

Regulatory Requirements Regulat

Regulatory Requirements Regulatory (Tables)	9 Months Ended
	Sep. 30, 2018
Regulatory [Abstract]
Computation of Net Capital under Securities and Exchange Commission Regulation	Subsidiary Net Capital Minimum Net Capital Requirement Excess Net Capital (dollars in millions) Cowen and Company $161.5 $1.0 $160.5 Cowen Execution $114.2 $2.4 $111.8 ATM Execution $1.7 $0.3 $1.4 Cowen Prime $16.6 $0.3 $16.3 Westminster $16.6 $0.3 $16.3 Cowen International Ltd $13.2 $9.1 $4.1 Cowen Execution Ltd $5.0 $3.2 $1.8

Guarantees and Off-Balance Sh_2

Guarantees and Off-Balance Sheet Arrangements Details (Tables)	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 . 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)	9 Months Ended
	Sep. 30, 2018segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business segments	2

Acquisition (Narrative) (Detail

Acquisition (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jun. 01, 2017
Business Acquisition [Line Items]
Goodwill/(Bargain purchase gain)			$ 0	$ 7,946
Restructuring costs	$ 0	$ 222	$ 0	8,763
Convergex Group
Business Acquisition [Line Items]
Total estimated purchase price					$ 98,000
Business combination, recognized identifiable assets acquired and liabilities assumed, net						$ 109,600
Goodwill/(Bargain purchase gain)					11,600
Other tax expense (benefit)				$ 4,700
Restructuring costs					$ 8,800

Acquisition (Pro Forma) (Detail

Acquisition (Pro Forma) (Details) - Convergex Group $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)$ / shares
Business Acquisition [Line Items]
Revenues | $	$ 529,294
Net income (loss) | $	$ (7,001)
Basic (usd per share) | $ / shares	$ (0.23)
Diluted (usd per share) | $ / shares	$ (0.23)

Significant Accounting Polici_4

Significant Accounting Policies All Other - Quarterly (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)cowenfund	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)cowenfund	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Total net assets of consolidated VIEs	$ 254,600		$ 254,600		$ 482,800
Deferred rent	9,100		9,100		12,800
Cumulative Effect on Retained Earnings, Net of Tax	600		559
Fees receivable	111,756		111,756		111,784
Other investments	167,428		167,428		141,548
Total Stockholders' Equity	808,244		808,244		$ 748,019
Investment banking	81,923	$ 57,383	264,737	$ 158,082
Incentive income	33	1,945	97	6,217
Revenues	221,028	178,830	706,985	454,331
Underwriting expenses	4,412	0	13,260	0
Costs and Expenses	211,149	179,216	660,311	487,456
Net gains (losses) on securities, derivatives and other investments	32,040	18,326	64,728	63,101
Net Income (Loss) Available to Common Stockholders, Basic	13,790	2,968	32,646	9,996
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 20,778	$ 9,828	78,793	50,502
Gain (Loss) on Investments (excluding broker dealer)			(61,927)	(76,325)
Fees receivable, net of allowance			(6,211)	(28,839)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations			295,986
Payments to Acquire Other Investments			(21,355)	$ (72,834)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations			$ (10,925)
Other investment companies
Number of funds, Consolidated | cowenfund	4		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 | Telephone and computer equipment
Property, Plant and Equipment, Useful Life			3 years
Minimum | Computer Software, Intangible Asset
Property, Plant and Equipment, Useful Life			3 years
Minimum | Aircraft
Property, Plant and Equipment, Useful Life			10 years
Minimum | Flight Equipment
Property, Plant and Equipment, Useful Life			4 years
Maximum | Telephone and computer equipment
Property, Plant and Equipment, Useful Life			5 years
Maximum | Computer Software, Intangible Asset
Property, Plant and Equipment, Useful Life			8 years
Maximum | Aircraft
Property, Plant and Equipment, Useful Life			20 years
Maximum | Flight Equipment
Property, Plant and Equipment, Useful Life			10 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%
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Fees receivable	$ 123,495		$ 123,495
Other investments	155,689		155,689
Total Stockholders' Equity	811,737		811,737
Investment banking	77,511		251,477
Incentive income	7,809		11,283
Revenues	224,392		704,911
Underwriting expenses	0		0
Costs and Expenses	206,737		647,051
Net gains (losses) on securities, derivatives and other investments	38,862		72,980
Net Income (Loss) Available to Common Stockholders, Basic	14,744		35,580
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest			81,727
Gain (Loss) on Investments (excluding broker dealer)			55,852
Fees receivable, net of allowance			14,408
Net Cash Provided by (Used in) Operating Activities, Continuing Operations			296,798
Payments to Acquire Other Investments			(22,167)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations			(11,737)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Fees receivable	11,739		11,739
Other investments	(11,739)		(11,739)
Total Stockholders' Equity	3,493		3,493
Investment banking	(4,412)		(13,260)
Incentive income	7,776		11,186
Revenues	3,364		(2,074)
Underwriting expenses	(4,412)		(13,260)
Costs and Expenses	(4,412)		(13,260)
Net gains (losses) on securities, derivatives and other investments	6,822		8,252
Net Income (Loss) Available to Common Stockholders, Basic	$ 954		2,934
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest			2,934
Gain (Loss) on Investments (excluding broker dealer)			(6,075)
Fees receivable, net of allowance			8,197
Net Cash Provided by (Used in) Operating Activities, Continuing Operations			812
Payments to Acquire Other Investments			812
Net Cash Provided by (Used in) Investing Activities, Continuing Operations			$ (812)

Cash Collateral Pledged (Detail

Cash Collateral Pledged (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Cash collateral pledged	$ 16,092	$ 17,888	$ 16,995
Facility Leases
Cash collateral pledged	5,300	6,100
Collateral Reinsurance Agreement
Cash collateral pledged	$ 10,800	$ 11,800

Segregated Cash (Details)

Segregated Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Segregated Cash [Abstract]
Segregated cash	$ 154,191	$ 116,268	$ 140,656

Investments of Operating Enti_3

Investments of Operating Entities and Consolidated Funds - Securities Owned at Fair Value (Details) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2018		Dec. 31, 2017
Investment Holdings [Line Items]
Securities owned, at fair value		$ 644,169		$ 673,221
Securities owned, at fair value		108,901		165,916
Common Stock
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	576,720		640,065
Securities owned, at fair value		55,535		77,702
Preferred Stock
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	6,466		9,604
Securities owned, at fair value		24,314		50,445
Warrants and Rights
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	21,403		9,604
Securities owned, at fair value		4,848		3,568
US Government Securities
Investment Holdings [Line Items]
Trading Securities, Debt	[2]	$ 2,842		$ 2,807
Investment Interest Rate		0.00%		0.00%
Securities owned, at fair value	[3]	$ 20,446		$ 34,201
Corporate Bonds
Investment Holdings [Line Items]
Trading Securities, Debt	[4]	30,992		4,909
Securities owned, at fair value		$ 3,758	[5]	$ 0
Corporate Bonds | Minimum
Investment Holdings [Line Items]
Investment Interest Rate		0.50%		0.00%
Corporate Bonds | Maximum
Investment Holdings [Line Items]
Investment Interest Rate		14.00%		10.75%
Convertible Bonds
Investment Holdings [Line Items]
Trading Securities, Debt	[6]	$ 0		$ 282
Convertible Bonds | Minimum
Investment Holdings [Line Items]
Investment Interest Rate				5.00%
Convertible Bonds | Maximum
Investment Holdings [Line Items]
Investment Interest Rate				12.00%
Trade Claims
Investment Holdings [Line Items]
Trading Securities, Debt		5,746		$ 5,950
Warrants and Rights | Estimate of Fair Value Measurement [Member]
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	1,100		2,400
Common Stock | Estimate of Fair Value Measurement [Member]
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	6,200		5,200
Preferred Stock | Estimate of Fair Value Measurement [Member]
Investment Holdings [Line Items]
Trading Securities, Equity	[1]	$ 2,900		$ 6,000
Consolidated Funds | US Government Securities
Investment Holdings [Line Items]
Investment Interest Rate		0.00%
Consolidated Funds | US Government Securities | Minimum
Investment Holdings [Line Items]
Investment Interest Rate				0.00%
Consolidated Funds | US Government Securities | Maximum
Investment Holdings [Line Items]
Investment Interest Rate				5.75%
Consolidated Funds | Corporate Bonds
Investment Holdings [Line Items]
Investment Interest Rate				5.88%
Enterprise Master
Investment Holdings [Line Items]
Securities owned, at fair value		$ 469		$ 608
Enterprise Master | Common Stock
Investment Holdings [Line Items]
Securities owned, at fair value		$ 469		$ 608
[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 $6.2 million, respectively, at September 30, 2018 and $6.0 million and $5.2 million, respectively, at December 31, 2017. At September 30, 2018 and December 31, 2017, the Company elected the fair value option for investments in warrants and rights with a fair value of $1.1 million and $2.4 million.
[2]	As of September 30, 2018, maturities ranged from October 2018 to August 2019 with an interest rate of 0%. As of December 31, 2017, maturities ranged from February 2018 to June 2018 with an interest rate of 0%.
[3]	As of September 30, 2018, maturities ranged from November 2018 to December 2018 and interest rates were 0%. As of December 31, 2017, maturities ranged from January 2018 to April 2022 and interest rates ranged from 0% to 5.75%.
[4]	As of September 30, 2018, maturities ranged from October 2018 to April 2049 and interest rates ranged from 0.50% to 14.00%. As of December 31, 2017, maturities ranged from October 2018 to May 2040 and interest rates ranged from 0.00% to 10.75%.
[5]	As of September 30, 2018, the maturity was December 2023 with an interest rate of 5.88%.
[6]	As of December 31, 2017, maturities ranged from February 2018 to March 2018 and interest rates ranged from 5% to 12%.

Investments of Operating Enti_4

Investments of Operating Entities and Consolidated Funds - Derivatives (Details)		Dec. 05, 2016	Sep. 30, 2018USD ($)contract	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)contract	Sep. 30, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)contract	Mar. 10, 2014USD ($)
Derivative [Line Items]
Warrants issued							$ 15,200,000
Cost of hedge transaction and warrant, net									$ 20,500,000
Stockholders' Equity Note, Stock Split, Conversion Ratio		0.25
Receivable on derivative contracts, at fair value			$ 32,229,000		$ 32,229,000			$ 69,177,000
Payable for derivative contracts, at fair value			30,002,000		30,002,000			42,750,000
Receivable on derivative contracts, at fair value			1,911,000		1,911,000			2,520,000
Payable for derivative contracts, at fair value, Consolidated Funds			2,189,000		2,189,000			7,130,000
Equity Swap
Derivative [Line Items]
Receivable on derivative contracts, at fair value			1,584,000		1,584,000			1,754,000
Payable for derivative contracts, at fair value, Consolidated Funds			1,590,000		1,590,000			7,042,000
Futures
Derivative [Line Items]
Derivative Asset, Notional Amount			0		0			3,819,350
Receivable on derivative contracts, at fair value			0		0			58,000
Derivative Liability, Notional Amount			25,474,000		25,474,000			16,796,000
Payable for derivative contracts, at fair value			71,000		71,000			242,000
Currency Forwards
Derivative [Line Items]
Derivative Asset, Notional Amount			79,309,515		79,309,515			233,136
Receivable on derivative contracts, at fair value			1,088,000		1,088,000			5,000
Derivative Liability, Notional Amount			2,897,000		2,897,000			62,439,000
Payable for derivative contracts, at fair value			4,000		4,000			874,000
Receivable on derivative contracts, at fair value			27,000		27,000			524,000
Payable for derivative contracts, at fair value, Consolidated Funds			539,000		539,000			11,000
Swaps
Derivative [Line Items]
Derivative Asset, Notional Amount			57,925,887		57,925,887			164,664,203
Receivable on derivative contracts, at fair value			1,203,000		1,203,000			10,942,000
Derivative Liability, Notional Amount			77,775,000		77,775,000			11,595,000
Payable for derivative contracts, at fair value			$ 2,743,000		$ 2,743,000			$ 71,000
Options
Derivative [Line Items]
Derivative Asset, Number of Instruments Held | contract	[1]		660,776		660,776			283,112
Receivable on derivative contracts, at fair value	[1]		$ 29,330,000		$ 29,330,000			$ 58,172,000
Receivable on derivative contracts, at fair value			300,000		300,000			242,000
Payable for derivative contracts, at fair value, Consolidated Funds			$ 60,000		$ 60,000			$ 77,000
Option
Derivative [Line Items]
Derivative Liability, Number of Instruments Held | contract	[2]		96,500		96,500			57,043
Payable for derivative contracts, at fair value	[2]		$ 27,184,000		$ 27,184,000			$ 41,563,000
Pay to hold
Derivative [Line Items]
Derivative Asset, Number of Instruments Held | contract			0		0			0
Receivable on derivative contracts, at fair value			$ 608,000		$ 608,000			$ 0
Receivable on derivatives contracts, at fair value [Member]
Derivative [Line Items]
Receivable on derivative contracts, at fair value			32,229,000		32,229,000			69,177,000
Derivative Asset, Fair Value, Gross Asset			32,229,000		32,229,000			69,177,000
Derivative Asset, Fair Value, Amount Offset Against Collateral	[3]		0		0			0
Financial Instruments, Owned and Pledged as Collateral, at Fair Value			0		0			0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	[4]		2,899,000		2,899,000			10,948,000
Derivative asset, net of offset			29,330,000		29,330,000			58,229,000
Payable for derivatives contracts, at fair value [Member]
Derivative [Line Items]
Payable for derivative contracts, at fair value			30,002,000		30,002,000			42,750,000
Financial Instruments, Owned and Pledged as Collateral, at Fair Value			0		0			0
Derivative Liability, Fair Value, Gross Liability			30,002,000		30,002,000			42,750,000
Derivative Liability, Fair Value, Amount Offset Against Collateral	[3]		0		0			0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	[4]		2,747,000		2,747,000			1,031,000
Derivative Liability, net of offset			27,255,000		27,255,000			41,719,000
Receivables from Brokers-Dealers and Clearing Organizations
Derivative [Line Items]
Collateral posted			9,800,000		9,800,000			$ 13,500,000
Other Income [Member]
Derivative [Line Items]
Realized and unrealized gains/(losses) related to derivatives trading activities			(7,500,000)	$ 500,000	6,400,000	$ (4,900,000)
2019 convertible note | Convertible Debt
Derivative [Line Items]
Call Option, Fair Value									$ 35,700,000
Open Option Contracts Written, at Fair Value			200,000		$ 200,000
Derivative, Loss on Derivative			$ 600,000
[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	Sep. 30, 2018		Dec. 31, 2017
Investment Holdings [Line Items]
Other investments	$ 167,428		$ 141,548
Portfolio Funds, Consolidated Funds	183,290		374,111
Portfolio Funds, at fair value
Investment Holdings [Line Items]
Other investments	125,107	[1]	100,148	[2]
Equity Method Investments
Investment Holdings [Line Items]
Other investments	42,321		41,099
Lehman claims, at fair value
Investment Holdings [Line Items]
Other investments	0		301
Enterprise LP [Member]
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	97,026		87,221
Merger Fund [Member]
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	$ 86,264		$ 286,890
[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		9 Months Ended
		Sep. 30, 2018		Dec. 31, 2017
Investment Holdings [Line Items]
Other investments		$ 167,428		$ 141,548
Portfolio Funds
Investment Holdings [Line Items]
Other investments		125,107	[1]	100,148	[2]
Portfolio Funds | Starboard Value and Opportunity Fund LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[3],[4]	$ 33,321		32,079
Required notice period, withdrawal		90 days
Portfolio Funds | Formation 8 Partners Fund I LP
Investment Holdings [Line Items]
Other investments	[5]	$ 28,135		28,243
Portfolio Funds | RCGLongview Debt Fund V, L.P. | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	4,537		8,892
Portfolio Funds | RCG Longview II, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	4,160		131
Portfolio Funds | Cowen Healthcare Investments II LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[7]	15,875		0
Portfolio Funds | Eclipse Ventures Fund I, L.P.
Investment Holdings [Line Items]
Other investments	[8]	3,575		3,428
Portfolio Funds | Healthcare Royalty Partners | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[9]	2,129		3,452
Portfolio Funds | Lagunita Biosciences, LLC
Investment Holdings [Line Items]
Other investments	[10]	3,859		2,400
Portfolio Funds | RCG IO Renergys Sarl | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[7]	1,780		0
Portfolio Funds | Starboard Leaders Fund LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[11]	$ 1,405		1,276
Unfunded Commitment cancellation		30 days
Portfolio Funds | Elipse SPV I,LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[12]	$ 1,447		0
Portfolio Funds | RCG Longview Equity Fund, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	819		0
Portfolio Funds | RCG Longview Debt Fund VI, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	588		1,022
Portfolio Funds | RCG Park Liberty GP Member LLC | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	908		750
Portfolio Funds | Healthcare Royalty Partners II | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[9]	1,162		873
Portfolio Funds | RCGL PE MPA LLC | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[6]	549		0
Portfolio Funds | RCG LPP2 PNW5 Co-Invest, L.P. | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[13]	309		3,493
Portfolio Funds | Quadratic Fund LLC | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[14]	$ 0		906
Required notice period, withdrawal		30 days
Portfolio Funds | Other Private Investment | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[15]	$ 15,997		10,133
Portfolio Funds | Other Funds | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[4],[16]	4,552		3,070
Enterprise Master | Portfolio Funds
Investment Holdings [Line Items]
Other investments		110,382		99,876
Multi-strategy | Enterprise Master | Portfolio Funds | RCG Special Opportunities Fund, Ltd | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[17]	109,518		97,345
Real Estate Funds | Enterprise Master | Portfolio Funds | RCG Longview II, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[17]	0		229
Real Estate Funds | Enterprise Master | Portfolio Funds | RCG Longview Equity Fund, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[17]	0		1,266
Real Estate Funds | Enterprise Master | Portfolio Funds | RCG Longview Debt Fund IV, LP | Affiliated Entity
Investment Holdings [Line Items]
Other investments	[17]	0		99
Various Strategies | Enterprise Master | Portfolio Funds | Other Private Investment
Investment Holdings [Line Items]
Other investments		$ 864		$ 937
[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]	Effective January 31, 2018, the Company is no longer affiliated with Quadratic Capital Management LLC.
[15]	Other private investment represents the Company's closed end investment in a portfolio fund that invests in a wireless broadband communication provider in Italy.
[16]	The majority of these funds are affiliates of the Company or are managed by the Company and the investors can redeem from these funds as investments are liquidated.
[17]	Affiliates of the Company.

Investments of Operating Enti_7

Investments of Operating Entities and Consolidated Funds - Equity Method Investments - (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Schedule of Equity Method Investments [Line Items]
Expense, equity method investments	$ 2,600	$ 900	$ 6,600	$ 3,500
Equity method investments	42,321		42,321		$ 41,099
Other than Temporary Impairment Losses, Investments			7,100
Net Gains (Losses) on Securities, Derivatives and Other Investments
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Equity Method Investments	(4,700)	$ 4,100	7,200	$ 12,100
Surf House Ocean Views Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	7,478		7,478		14,179
Starboard Value LP
Schedule of Equity Method Investments [Line Items]
Equity method investments	17,842		17,842		13,202
RCG Longview Debt Fund V Partners, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	10,273		10,273		9,284
RCG Longview Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,316		1,316		1,149
RCG Longview Debt Fund VI, LP
Schedule of Equity Method Investments [Line Items]
Equity method investments	971		971		0
Healthcare Royalty GP, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	174		174		281
Healthcare Royalty GP II, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	197		197		148
RCG Longview Debt Fund IV Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	331		331		331
Healthcare Royalty GP III, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,562		1,562		764
RCG Kennedy House, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	119		119		154
RCG Longview Equity Management, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	114		114		114
RCG LPP II GP, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	272		272		487
RCG Park Liberty GP Member Manager, LLC
Schedule of Equity Method Investments [Line Items]
Equity method investments	1,018		1,018		428
Equity Method Investee, Other
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 654		$ 654		578
Equity Method Investee, Exceeded Threshold for Income Test [Member]
Schedule of Equity Method Investments [Line Items]
Number of investments			1
Minimum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	13.00%		13.00%
Maximum
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	56.00%		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	$ 6,200		$ 6,200		$ 6,200

Investments of Operating Enti_8

Investments of Operating Entities and Consolidated Funds - Securities Sold, Not Yet Purchased (Details) - USD ($)		Sep. 30, 2018	Dec. 31, 2017
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value		$ 374,518,000	$ 342,527,000
Common Stock
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value		353,113,000	342,328,000
Corporate Bonds
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value	[1]	$ 20,309,000	$ 122,000
Corporate Bonds | Minimum
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, interest rate		5.00%	3.78%
Corporate Bonds | Maximum
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, interest rate		5.55%	5.55%
Preferred Stock
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value		$ 836,000	$ 77,000
Warrants and Rights
Investments Sold, Not yet Purchased [Line Items]
Securities sold, not yet purchased, at fair value		$ 260,000	$ 0
[1]	As of September 30, 2018, the maturities ranged from January 2026 to April 2049 with interest rates ranged from 5.00% to 5.55%. As of December 31, 2017, the maturities ranged from July 2025 to January 2026 with interest rates ranged from 3.78% to 5.55%.

Investments of Operating Enti_9

Investments of Operating Entities and Consolidated Funds - Securities borrowed and securities loaned (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Securities Borrowed, Gross		$ 713,288	$ 443,148
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		713,288	443,148
Securities borrowed, additional amounts, asset		0	0
Securities borrowed, financial instruments		684,569	414,778
Securities borrowed, cash collateral pledged	[2]	0	0
Securities borrowed, net amounts		28,719	28,370
Securities Loaned, Gross		548,629	456,831
Securities Loaned, Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	[1]	0	0
Securities Loaned, Gross amounts recognized		548,629	456,831
Securities Loaned, Additional Amounts Available		0	0
Securities Loaned, Financial instruments		531,984	439,228
Securities Loaned, Cash Collateral pledged	[2]	0	0
Securities Loaned, Net amounts		$ 16,645	$ 17,603
[1]	Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.
[2]	Includes the amount of cash collateral held/posted.

Investments of Operating Ent_10

Investments of Operating Entities and Consolidated Funds - Securities loaned transactions by remaining contractual maturity and class of collateral pledged (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	$ 548,629	$ 456,831
Common stock
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	548,629	456,831
Common stock | Open and Overnight
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	548,629	456,831
Common stock | Up to 30 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Common stock | 31 - 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	0	0
Common stock | Greater than 90 days
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Common stock	$ 0	$ 0

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	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Total assets of nonconsolidated variable interest entities	$ 5,600	$ 5,200
Total liabilities of nonconsolidated variable interest entities	346.9	445.6
Maximum exposure regarding nonconsolidated variable interest entities	$ 333.8	$ 471.3

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	Sep. 30, 2018USD ($)investments	Dec. 31, 2017USD ($)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	8.01%	7.52%
Market Value | $	$ 64,754	$ 56,271

Investments of Operating Ent_13

Investments of Operating Entities and Consolidated Funds - Merger Master Narrative (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Investment [Line Items]
Trading securities		$ 644,169	$ 673,221
Securities sold, not yet purchased, at fair value		374,518	342,527
Common Stock
Investment [Line Items]
Securities sold, not yet purchased, at fair value		353,113	342,328
Common Stock | Merger Master
Investment [Line Items]
Trading securities		342,100	483,200
Securities sold, not yet purchased, at fair value		128,600	171,200
Corporate Bonds
Investment [Line Items]
Securities sold, not yet purchased, at fair value	[1]	20,309	$ 122
Corporate Bonds | Merger Master
Investment [Line Items]
Trading securities		$ 23,800
[1]	As of September 30, 2018, the maturities ranged from January 2026 to April 2049 with interest rates ranged from 5.00% to 5.55%. As of December 31, 2017, the maturities ranged from July 2025 to January 2026 with interest rates ranged from 3.78% to 5.55%.

Investments of Operating Ent_14

Investments of Operating Entities and Consolidated Funds - Merger Master Derivatives (Details) - USD ($) $ in Thousands		Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative Asset		$ 32,229	$ 69,177
Derivative Liability		30,002	42,750
Merger Master
Derivative [Line Items]
Derivative Asset		3,675	122,551
Derivative Liability		2,266	2,718
Option
Derivative [Line Items]
Derivative Liability	[1]	27,184	41,563
Option | Merger Master
Derivative [Line Items]
Derivative Liability		261	1,256
Options
Derivative [Line Items]
Derivative Asset	[2]	29,330	58,172
Options | Merger Master
Derivative [Line Items]
Derivative Asset		1,817	108,063
Swaps
Derivative [Line Items]
Derivative Asset		1,203	10,942
Derivative Liability		2,743	71
Swaps | Merger Master
Derivative [Line Items]
Derivative Asset		1,658	14,488
Derivative Liability		2,005	1,249
Currency Forwards
Derivative [Line Items]
Derivative Asset		1,088	5
Derivative Liability		4	874
Currency Forwards | Merger Master
Derivative [Line Items]
Derivative Asset		200	0
Derivative Liability		$ 0	$ 213
[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	Sep. 30, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	$ 787,210		$ 911,135
Financial Liabilities Fair Value Disclosure	409,352		395,847
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, Low	100		100
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	7,000		15,000
Other investments	167,428		141,548
Other Investments, Consolidated Funds	183,290		374,111
Investments	1,137,928		1,426,493
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	$ 693,628		$ 802,697
Percentage of Total Assets at Fair Value	88.10%		88.10%
Percentage of Total Liabilities at Fair Value	92.60%		91.40%
Financial Liabilities Fair Value Disclosure	$ 378,977		$ 361,886
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	$ 46,166		$ 28,185
Percentage of Total Assets at Fair Value	5.90%		3.10%
Percentage of Total Liabilities at Fair Value	6.20%		2.10%
Financial Liabilities Fair Value Disclosure	$ 25,185		$ 8,120
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	$ 47,416		$ 80,253
Percentage of Total Assets at Fair Value	6.00%		8.80%
Percentage of Total Liabilities at Fair Value	1.30%		6.50%
Financial Liabilities Fair Value Disclosure	$ 5,190		$ 25,841
Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	836		77
Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	836		77
Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	353,113		342,328
Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	353,113		342,328
Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	20,309		122
Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	20,309		122
Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	260
Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	260
Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0
Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0
Contingent liability payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	2,643	[1]	3,440
Contingent liability payable | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0	[1]	0	[2]
Contingent liability payable | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0	[1]	0	[2]
Contingent liability payable | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	2,643	[1]	3,440	[2]
Futures | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	71		242
Futures | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	71		242
Futures | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Futures | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Currency forward | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	4		874
Currency forward | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Currency forward | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	4		874
Currency forward | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Swaps | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	2,743		71
Swaps | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Swaps | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	2,743		71
Swaps | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Options | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	27,184		41,563
Options | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	24,637		19,162
Options | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Options | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	2,547		22,401
US Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	2,842		2,807
US Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	2,842		2,807
US Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
US Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	6,466		9,604
Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1,308		571
Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		918
Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	5,158		8,115
Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	576,720		640,065
Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	564,140		627,011
Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	6,906		5,484
Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	5,674		7,570
Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	30,992		4,909
Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	30,992		4,909
Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Trade Claims
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	5,746		5,950
Trade Claims | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Trade Claims | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Trade Claims | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	5,746		5,950
Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	21,403		9,604
Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	19,821		7,087
Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1,582		2,517
Convertible Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			282
Convertible Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			0
Convertible Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			0
Convertible Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			282
Derivative Assets | Futures
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			58
Derivative Assets | Futures | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			58
Derivative Assets | Futures | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			0
Derivative Assets | Futures | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			0
Derivative Assets | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1,088		5
Derivative Assets | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Derivative Assets | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1,088		5
Derivative Assets | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Derivative Assets | Swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1,203		10,942
Derivative Assets | Swaps | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Derivative Assets | Swaps | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1,203		10,942
Derivative Assets | Swaps | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Derivative Assets | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	29,330		58,172
Derivative Assets | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	29,330		56,717
Derivative Assets | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Derivative Assets | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		1,455
Derivative Assets | Pay to hold
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	608
Derivative Assets | Pay to hold | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Derivative Assets | Pay to hold | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	608
Derivative Assets | Pay to hold | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Lehman claims, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			301
Other investments	0		301
Lehman claims, at fair value | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			0
Lehman claims, at fair value | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			0
Lehman claims, at fair value | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring			301
Portfolio Funds, at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	125,107	[3]	100,148	[4]
Other Investments, Consolidated Funds	183,290	[3]	374,111	[4]
Equity Method Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	42,321		41,099
Consolidated Funds | Currency forward | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	539		11
Consolidated Funds | Currency forward | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Consolidated Funds | Currency forward | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	539		11
Consolidated Funds | Currency forward | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Consolidated Funds | Equity Swap | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	1,590		7,042
Consolidated Funds | Equity Swap | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Consolidated Funds | Equity Swap | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	1,590		7,042
Consolidated Funds | Equity Swap | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Consolidated Funds | Options | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	60		77
Consolidated Funds | Options | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	60		77
Consolidated Funds | Options | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Consolidated Funds | Options | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Liabilities Fair Value Disclosure	0		0
Consolidated Funds | US Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	20,446		34,201
Consolidated Funds | US Government Securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	20,446		30,552
Consolidated Funds | US Government Securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		3,649
Consolidated Funds | US Government Securities | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	24,314		50,445
Consolidated Funds | Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	24,314		50,445
Consolidated Funds | Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	55,535		77,702
Consolidated Funds | Common Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	55,441		77,652
Consolidated Funds | Common Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Common Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	94		50
Consolidated Funds | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	3,758
Consolidated Funds | Corporate Bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Consolidated Funds | Corporate Bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	3,758
Consolidated Funds | Corporate Bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0
Consolidated Funds | Warrants and Rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	4,848		3,568
Consolidated Funds | Warrants and Rights | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Warrants and Rights | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Warrants and Rights | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	4,848		3,568
Consolidated Funds | Derivative Assets | Currency forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	27		524
Consolidated Funds | Derivative Assets | Currency forward | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Derivative Assets | Currency forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	27		524
Consolidated Funds | Derivative Assets | Currency forward | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Derivative Assets | Equity Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1,584		1,754
Consolidated Funds | Derivative Assets | Equity Swap | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Derivative Assets | Equity Swap | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	1,584		1,754
Consolidated Funds | Derivative Assets | Equity Swap | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Derivative Assets | Options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	300		242
Consolidated Funds | Derivative Assets | Options | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	300		242
Consolidated Funds | Derivative Assets | Options | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	0		0
Consolidated Funds | Derivative Assets | Options | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Recurring	$ 0		$ 0
[1]	In accordance with the terms of the purchase agreements for acquisitions that closed during the third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018, December 2020, and June 2018, respectively. 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 September 30, 2018 can range from $0.1 million to $7.0 million.
[2]	In accordance with the terms of the purchase agreements for acquisitions that closed during the third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018 and December 2020, respectively. 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, 2017 can range from $0.1 million to $15.0 million.
[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 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.

Fair Value Measurements for O_4

Fair Value Measurements for Operating Entities and Consolidated Funds Unobservable Input Roll Forward (Details) - USD ($)		3 Months Ended			9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		$ 7,422,000		$ 18,576,000	$ 8,115,000		$ 15,811,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		1,141,000	[1]	0	1,141,000		3,472,000	[1]
Purchases/(covers)		0		0	1,415,000		9,000,000
(Sales)/short buys		0		0	(695,000)		(31,000)
Realized and unrealized gains (losses), asset		(1,123,000)		(587,000)	(2,536,000)		(3,319,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(1,124,000)		(587,000)	(2,301,000)		(1,006,000)
Balance Asset Value		5,158,000		17,989,000	5,158,000		17,989,000
Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,848,000		10,588,000	7,570,000		10,121,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	0		0
Purchases/(covers)		0		3,151,000	531,000		3,182,000
(Sales)/short buys		0		(1,946,000)	(1,333,000)		(2,121,000)
Realized and unrealized gains (losses), asset		(174,000)		297,000	(1,094,000)		908,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	(174,000)		297,000	(1,128,000)		908,000
Balance Asset Value		5,674,000		12,090,000	5,674,000		12,090,000
Convertible Bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				282,000	282,000		250,000
Asset, Transfers In				0	0		0
Asset, Transfers Out				0	0		0
Purchases/(covers)				250,000	0		282,000
(Sales)/short buys				0	(307,000)		0
Realized and unrealized gains (losses), asset				(250,000)	25,000		(250,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]			0	0		0
Balance Asset Value		0		282,000	0		282,000
Options
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				9,860,000	1,455,000		14,753,000
Asset, Transfers In				0	0		0
Asset, Transfers Out				0	0		0
Purchases/(covers)				0	0		0
(Sales)/short buys				0	(1,455,000)		0
Realized and unrealized gains (losses), asset				499,000	0		(4,394,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]			499,000	0		(4,394,000)
Balance Asset Value		0		10,359,000	0		10,359,000
Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		1,544,000		3,409,000	2,517,000		3,719,000
Asset, Transfers In		0		0	0		3,192,000	[3],[4]
Asset, Transfers Out		0	[1]	0	0		0
Purchases/(covers)		0		0	0		0
(Sales)/short buys		0		0	(143,000)		(4,367,000)
Realized and unrealized gains (losses), asset		38,000		(1,013,000)	(792,000)		(148,000)
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	38,000		187,000	(933,000)		510,000
Balance Asset Value		1,582,000		2,396,000	1,582,000		2,396,000
Trade Claims
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		5,699,000		4,648,000	5,950,000		562,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	0		0
Purchases/(covers)		44,000		1,925,000	44,000		5,865,000
(Sales)/short buys		0		(630,000)	(334,000)		(700,000)
Realized and unrealized gains (losses), asset		3,000		3,000	86,000		219,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	3,000		3,000	23,000		198,000
Balance Asset Value		5,746,000		5,946,000	5,746,000		5,946,000
Lehman claims, at fair value
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		295,000		309,000	301,000		265,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	0		0
Purchases/(covers)		0		0	0		0
(Sales)/short buys		(234,000)		0	(234,000)		0
Realized and unrealized gains (losses), asset		(61,000)		10,000	(67,000)		54,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	0		10,000	0		54,000
Balance Asset Value		0		319,000	0		319,000
Consolidated Funds | Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		24,314,000		18,224,000	50,445,000		36,928,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	38,552,000	[5]	13,668,000	[1]
Purchases/(covers)		0		467,000	3,066,000		467,000
(Sales)/short buys		0		0	0		(11,853,000)
Realized and unrealized gains (losses), asset		0		252,000	9,355,000		7,069,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	0		252,000	9,355,000		2,958,000
Balance Asset Value		24,314,000		18,943,000	24,314,000		18,943,000
Consolidated Funds | Common Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		94,000		848,000	50,000		295,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	0		0
Purchases/(covers)		0		0	0		476,000
(Sales)/short buys		0		848,000	0		(848,000)
Realized and unrealized gains (losses), asset		0		0	44,000		77,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	0		0	44,000		0
Balance Asset Value		94,000		0	94,000		0
Consolidated Funds | Warrants and Rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value		4,738,000		3,369,000	3,568,000		3,000
Asset, Transfers In		0		0	0		0
Asset, Transfers Out		0		0	20,000	[5]	0
Purchases/(covers)		0		0	(1,340,000)		0
(Sales)/short buys		0		0	0		0
Realized and unrealized gains (losses), asset		110,000		9,000	2,640,000		3,375,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]	110,000		9,000	1,300,000		3,375,000
Balance Asset Value		4,848,000		3,378,000	4,848,000		3,378,000
Consolidated Funds | Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Asset Value				202,000			657,000
Asset, Transfers In				0			0
Asset, Transfers Out				0			0
Purchases/(covers)				0			202,000
(Sales)/short buys				200,000			(1,021,000)
Realized and unrealized gains (losses), asset				(2,000)			162,000
Change in Unrealized Gain (Loss), instruments still held, asset	[2]			0			0
Balance Asset Value				0			0
Options, liability
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		301,000		9,860,000	22,401,000		14,753,000
Liability, Transfers In		0		0	0		0
Liability, Transfers Out		0		0	(28,973,000)	[6]	0
Liability, Purchases		0		0	0		0
Liability, Sales		0		0	(259,000)		0
Realized and unrealized gains (losses), liability		2,246,000		499,000	9,378,000		(4,394,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[2]	2,246,000		499,000	9,378,000		(4,394,000)
Balance Liability Value		2,547,000		10,359,000	2,547,000		10,359,000
Contingent liability payable
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance Liability Value		2,870,000		5,174,000	3,440,000		5,997,000
Liability, Transfers In		0		0	0		0
Liability, Transfers Out		0		0	0		0
Liability, Purchases		0		0	0		0
Liability, Sales		(227,000)		(125,000)	(797,000)		(392,000)
Realized and unrealized gains (losses), liability		0		0	0		(556,000)
Change in Unrealized Gain (Loss), instruments still held, liabilities	[2]	0		0	0		(556,000)
Balance Liability Value		$ 2,643,000		$ 5,049,000	$ 2,643,000		$ 5,049,000
[1]	The investments were converted to common stock.
[2]	Unrealized gains/losses are reported in other income (loss) in the accompanying condensed consolidated statements of operations.
[3]	As part of the preferred stock sale, the sellers received contingent value rights to be paid in the event certain milestones are reached.
[4]	The Company received warrants as consideration as part of an investment banking transaction.
[5]	The Company deconsolidated a fund (See note 3)
[6]	On June 26, 2018, the Company received shareholder approval which will allow the Company to settle its convertible note (see Note 17) entirely in class A common shares. Upon receiving shareholder approval, the Company reclassified the embedded conversion option, associated with the convertible debt, to equity. (See Note 18)

Fair Value Measurements for O_5

Fair Value Measurements for Operating Entities and Consolidated Funds Fair Value Inputs, Unobservable Inputs, Quantitative Information (Details) $ in Thousands		9 Months Ended
		Sep. 30, 2018USD ($)		Sep. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2017USD ($)		Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		$ 409,352				$ 395,847
Contingent liability payable
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		2,643	[1]			3,440
Balance Liability Value		2,643		$ 5,049	$ 2,870	3,440		$ 5,174	$ 5,997
Trade Claims
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		5,746		5,946	5,699	5,950		4,648	562
Warrants and Rights
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		1,582		2,396	$ 1,544	2,517		3,409	3,719
Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		0		$ 10,359		1,455		$ 9,860	$ 14,753
Options | Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		27,184				41,563
Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		47,416				80,253
Financial Liabilities Fair Value Disclosure		5,190				25,841
Balance Liability Value		$ 5,190				25,841
Level 3 | Options | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility				28.00%
Level 3 | Options | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility		30.00%
Level 3 | Options | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility		35.00%
Level 3 | Contingent liability payable
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		$ 2,643	[1]			3,440	[2]
Level 3 | Contingent liability payable | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate		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]
DCF discount rate				8.00%
Level 3 | Contingent liability payable | Income Approach and Market Approach Valuation Techniques | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate				23.00%
Level 3 | Contingent liability payable | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Assumptions, Weighted Average Volatility Rate				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						3,440
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		$ 2,508				5,642
DCF discount rate		50.00%
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]
Market multiple		4.5		4.8
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]
Market multiple		9		8.5
Level 3 | Trade Claims | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate		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				70
Level 3 | Warrants and Rights | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value		$ 1,582
Level 3 | Warrants and Rights | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate		22.00%
Volatility				61.00%
Level 3 | Warrants and Rights | Market Approach Valuation Technique | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate		7.00%
Level 3 | Warrants and Rights | Market Approach Valuation Technique | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
DCF discount rate		9.00%
Level 3 | Warrants and Rights | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value						2,516
Level 3 | Other Investments | Income Approach and Market Approach Valuation Techniques
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value	[3]	$ 43,301
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	[3]					70,570
Level 3 | Options | Market Approach Valuation Technique
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Volatility				28.00%
Level 3 | Options | Options
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Financial Liabilities Fair Value Disclosure		$ 2,547				22,401
Level 3 | Options | Derivative Assets | Market Approach, Income Approach and Replacement Cost Valuation Techniques [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Balance Asset Value						1,455
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						$ 22,401
[1]	In accordance with the terms of the purchase agreements for acquisitions that closed during the third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018, December 2020, and June 2018, respectively. 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 September 30, 2018 can range from $0.1 million to $7.0 million.
[2]	In accordance with the terms of the purchase agreements for acquisitions that closed during the third and fourth quarter of 2015 and 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 businesses, if certain targets are achieved through the periods ended December 2018 and December 2020, respectively. 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, 2017 can range from $0.1 million to $15.0 million.
[3]	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		Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Cash and cash equivalents		$ 193,066	$ 130,052	$ 117,824
Cash collateral pledged		16,092	17,888	16,995
Segregated cash		154,191	116,268	$ 140,656
Securities Borrowed, Gross		713,288	443,148
Securities borrowed		713,288	443,148
Loans Receivable, Net		36,009	37,993
Cash and cash equivalents, Consolidated Funds		18,747	21,988
Securities Loaned, Gross		548,629	456,831
Securities loaned		548,629	456,831
Convertible debt		133,126	141,502
Notes payable and other debt		271,082	173,458
Convertible Debt
Convertible debt, unamortized discount		24,900	25,600
Level 1
Cash and cash equivalents, Fair Value		193,066	130,052
Segregated cash fair value disclosures		154,191	116,268
Cash and cash equivalents, Consolidated Funds, Fair Value		18,747	21,988
Level 2
Cash collateral pledged, Fair Value		16,092	17,888
Securities Borrowed, Fair Value Disclosure		684,569	414,763
Securities loaned, fair value disclosure		531,984	440,162
Convertible debt, Fair Value	[1]	173,246	172,709
Notes payable and other debt, Fair Value	[2]	284,021	182,352
Level 3
Loans Receivable, Fair Value Disclosure	[3]	$ 36,009	$ 37,993
[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	Sep. 30, 2018	Dec. 31, 2017
Deposits with Clearing Organizations, Brokers and Banks [Abstract]
Deposits with clearing organizations, brokers and banks	$ 98,646	$ 93,996

Receivables from and payables_3

Receivables from and payables to brokers, dealers and clearing organizations (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Brokers and Dealers [Abstract]
Receivable from Broker-dealers	$ 569,998	$ 409,499
Securities Failed-to-Deliver	47,014	87,820
Receivable from Clearing organizations	16,541	6,126
Stock borrow interest receivable	10,839	4,733
Receivable from brokers, dealers and clearing organizations	644,392	508,178
Payable to Broker-Dealers	131,358	145,860
Securities Failed-to-Receive	54,539	53,540
Payable to clearing organizations	18,202	48,257
Stock loan interest payable	6,227	4,496
Payables to brokers, dealers and clearing organizations	$ 210,326	$ 252,153

Receivable from and Payable t_2

Receivable from and Payable to Customers (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Receivables and Payable to Customers [Abstract]
Receivable from customers	$ 33,240	$ 49,891
Payable to customers	$ 470,476	$ 352,467

Commission Management Payable (

Commission Management Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commission Management Payable [Abstract]
Commission management payable	$ 90,233	$ 70,451

Redeemable Non-Controlling In_3

Redeemable Non-Controlling Interests in Consolidated Subsidiaries and Funds (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	$ 203,212		$ 203,212		$ 440,604
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	5,290	$ 5,162	41,053	$ 35,412
Operating Entities
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	11,069		11,069		6,113
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	2,486	(266)	6,060	1,457
Consolidated Funds
Noncontrolling Interest [Line Items]
Redeemable non-controlling interests in consolidated subsidiaries and funds	192,143		192,143		$ 434,491
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	$ 2,804	$ 5,428	$ 34,993	$ 33,955

Reinsurance (Details)

Reinsurance (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Historical Average Claims Ratios, Period, Minimum			5 years
Historical Average Claims Ratios, Period, Maximum			10 years
Hollenfels
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Share of incurred and paid claims	$ 1.9	$ 1.5	$ 9.6	$ 2.6
Share of claims incurred but not reported	$ 0.5		$ 9

Share-Based Compensation and _3

Share-Based Compensation and Employee Ownership Plans Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for issuance under compensation plan, in shares	200,000		200,000
Stock-compensation expense recognized in connection with compensation plan	$ 8.5	$ 6.8	$ 27.6	$ 24.7
Tax benefit of stock-compensation expense recognized in connection with compensation plan	2.4	$ 2.7	$ 7.2	$ 9.8
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	62.3		$ 62.3
Vested, shares			1,423,075
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 | Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
SAR's, initial term			5 years
Vested, shares			75,000
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	39.1		$ 39.1
Stock compensation award, vesting period			4 years
Convergex Group | Deferred Cash Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred cash awards granted	$ 0.6		$ 0.6

Share-Based Compensation and _4

Share-Based Compensation and Employee Ownership Plans Deferred Cash (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Cowen Group, Inc. 2010 Equity and Incentive Plan | Deferred Cash Award
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred cash awards granted	$ 39.1
Deferred cash awards, vesting period	4 years
Deferred cash award, interest rate	0.70%
Deferred cash awards, unrecognized compensation expense	$ 54.8
Convergex Group
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred Compensation Arrangement with Individual, Requisite Service Period	27 months
Convergex Group | Deferred Cash Award
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred cash awards granted	$ 0.6

Share-Based Compensation and _5

Share-Based Compensation and Employee Ownership Plans Stock Options (Details) - $ / shares	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0.00%
Closing stock price, in dollars per share		$ 13.65

Share-Based Compensation and _6

Share-Based Compensation and Employee Ownership Plans SARs (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2018	Dec. 31, 2017
Weighted Average Exercise Price/Share
Closing stock price, in dollars per share			$ 13.65
Stock Appreciation Rights
Weighted Average Exercise Price/Share
Exercisable, weighted remaining contractual term		0 years
Equity Plans | Stock Appreciation Rights
Shares Subject to Option
Balance outstanding, beginning of period, shares		75,000
Acquired, shares		(75,000)
Balance outstanding, end of period, shares		0	75,000
Balance exercisable, shares		0
Weighted Average Exercise Price/Share
Balance outstanding, beginning of period, in dollars per share		$ 11.60
Acquired, in dollars per share		14.21
Balance outstanding, end of period, in dollars per share			$ 11.60
Balance exercisable, weighted shares		$ 0
Weighted Average Remaining Term Outstanding		0 years	2 months 16 days
Aggregate intrinsic value, outstanding	[1]	$ 0	$ 173
[1]	Based on the Company's closing stock price of $13.65 on December 31, 2017.

Share-Based Compensation and _7

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	9 Months Ended
	Mar. 31, 2016	Jan. 31, 2014	Sep. 30, 2018
Equity Plans | Restricted Shares and Restricted Stock Units (RSUs)
Nonvested Restricted Shares and Restricted Stock Units
Balance outstanding, beginning of period, shares			5,579,293
Granted, shares			2,255,794
Vested, shares			(1,423,075)
Forfeited, shares			(61,997)
Balance outstanding, end of period, shares			6,350,015
Weighted-Average Grant Date Fair Value
Balance outstanding, beginning of period, in dollars per share			$ 16.33
Granted, in dollars per share			14.27
Vested, in dollars per share			16.08
Forfeited, in dollars per share			14.13
Balance outstanding, end of period, in dollars per share			$ 15.68
Unrecognized compensation expense			$ 62.3
Weighted-average recognition period for unrecognized compensation expense			2 years 2 months 16 days
Equity Plans | Performance based restricted stock
Nonvested Restricted Shares and Restricted Stock Units
Granted, shares	700,000	481,438
Forfeited, shares			(117,188)
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			88,504
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	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Contingency [Line Items]
Effective income tax rate, percent	16.88%	6.32%
Statutory rate, percent	21.00%
Convergex Group
Income Tax Contingency [Line Items]
Taxes payable	$ 4.9		$ 5.4

Commitments and Contingencies_2

Commitments and Contingencies (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Lease Obligations
Net rent expense		$ 6,600,000	$ 6,300,000	$ 19,500,000	$ 16,300,000
Future minimum annual lease and service payments
Sublease income related to operating leases		400,000	$ 200,000	1,100,000	$ 800,000
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		6,200,000		6,200,000		$ 6,200,000
Equipment Leases
Future minimum annual lease and service payments
2,018	[1]	966,000		966,000
2,019	[1]	2,482,000		2,482,000
2,020	[1]	1,529,000		1,529,000
2,021	[1]	1,392,000		1,392,000
2,022	[1]	1,128,000		1,128,000
Thereafter	[1]	374,000		374,000
Future minimum annual lease and service payments	[1]	7,871,000		7,871,000
Service Payments
Future minimum annual lease and service payments
2,018		6,762,000		6,762,000
2,019		19,256,000		19,256,000
2,020		5,796,000		5,796,000
2,021		1,722,000		1,722,000
2,022		1,350,000		1,350,000
Thereafter		1,470,000		1,470,000
Future minimum annual lease and service payments		36,356,000		36,356,000
Facility Leases
Future minimum annual lease and service payments
2,018	[2]	6,453,000		6,453,000
2,019	[2]	24,508,000		24,508,000
2,020	[2]	20,907,000		20,907,000
2,021	[2]	20,640,000		20,640,000
2,022	[2]	17,464,000		17,464,000
Thereafter	[2]	28,353,000		28,353,000
Future minimum annual lease and service payments	[2]	$ 118,325,000		$ 118,325,000
[1]	Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 17 for further information on the capital lease minimum payments which are included in the table.
[2]	The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $0.4 million and $0.2 million for the three months ended September 30, 2018 and 2017, and $1.1 million and $0.8 million for the nine months ended September 30, 2018 and 2017, respectively.

Commitments and Contingencies S

Commitments and Contingencies Schedules of Unfunded Commitments (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)cowenfund
Unfunded Commitments
Other Commitments [Line Items]
Number of real estate investments | cowenfund	4
Real Estate Funds
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 4.6	[1]
Healthcare Royalty Partners
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 1.1	[2]
Healthcare Royalty Partners | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment	2 years
Formation 8 Partners Hardware Fund I, L.P.
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 0.4
Formation 8 Partners Hardware Fund I, L.P. | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment	6 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	$ 0.8
Eclipse Fund II, L.P. | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment	7 years
Eclipse Continuity Fund I, L.P.
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 0.6
Eclipse Continuity Fund I, L.P. | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment	8 years
Cowen Healthcare Investments II LP
Other Commitments [Line Items]
Other commitments, unfunded amount	$ 9.6
Cowen Healthcare Investments II LP | Commitment to Invest
Other Commitments [Line Items]
Term of capital commitment	3 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 four real estate investments held by the Company, all of which pertain to related party investments.
[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	Sep. 30, 2018USD ($)letters_of_credit	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)letters_of_credit	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)	Jan. 31, 2014USD ($)	Dec. 14, 2017USD ($)$ / shares	Dec. 08, 2017USD ($)	Jan. 31, 2016	Mar. 10, 2014USD ($)$ / shares
Components of short-term borrowings and other debt
Convertible debt			$ 133,126,000		$ 133,126,000		$ 141,502,000
Note payable			229,581,000		229,581,000		132,970,000
Loans Payable to Bank			28,200,000		28,200,000		28,121,000
Other Notes Payable			7,688,000		7,688,000		8,247,000
Capital lease obligations			5,613,000		5,613,000		4,120,000
Debt, Long-term and Short-term, Combined Amount			404,208,000		404,208,000		314,960,000
Purchase of treasury stock, cost					16,762,000
Amortization of debt discount					4,177,000	$ 5,601,000
Stockholders' Equity Note, Stock Split, Conversion Ratio		0.25
Letter of credit, borrowing capacity			370,000,000		370,000,000
Capital Lease Obligations Incurred								$ 10,100,000
Capital Leases, Income Statement, Interest Expense			100,000	$ 100,000	200,000	100,000
Future minimum lease payments for capital lease obligations
2,018			568,000		568,000
2,019			1,438,000		1,438,000
2,020			1,360,000		1,360,000
2,021			1,360,000		1,360,000
2,022			1,128,000		1,128,000
Thereafter			374,000		374,000
Subtotal			6,228,000		6,228,000
Less: Amount representing interest	[1]		(615,000)		(615,000)
Capital lease obligations			$ 5,613,000		$ 5,613,000		4,120,000
Number of letters of credit | letters_of_credit			7		7
Cash collateral pledged			$ 16,092,000	16,995,000	$ 16,092,000	16,995,000	17,888,000
Minimum
Components of short-term borrowings and other debt
Capital Lease Obligation, Initial Term					55 months
Capital leases, interest rate			3.70%		3.70%
Maximum
Components of short-term borrowings and other debt
Capital Lease Obligation, Initial Term					60 months
Capital leases, interest rate			5.69%		5.69%
Letter of Credit, San Francisco Office, Expires January 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			$ 713,781		$ 713,781
Letter of Credit, Boston Office, Expires March 2019 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			386,022		386,022
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			355,818		355,818
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			70,406		70,406
Letter of Credit, NY Office 3, Expires October 2018 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			496,563		496,563
Letter of Credit, NY Office 4, Expires October 2018 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			1,686,297		1,686,297
Letter of Credit, NY Office 5, Expires November 2018 | Letter of Credit
Components of short-term borrowings and other debt
Letter of credit, borrowing capacity			1,615,204		1,615,204
Convertible Debt
Components of short-term borrowings and other debt
Convertible debt, unamortized discount			24,900,000		24,900,000		25,600,000
Repayments on long-term and short-term borrowings
2,018			2,025,000		2,025,000
2,019			25,223,000		25,223,000
2,020			4,050,000		4,050,000
2,021			4,050,000		4,050,000
2,022			139,050,000		139,050,000
Thereafter			0		0
Subtotal			174,398,000		174,398,000
Less: Amount representing interest	[1]		(41,272,000)		(41,272,000)
Senior Notes
Components of short-term borrowings and other debt
Note payable			229,581,000		229,581,000
Repayments on long-term and short-term borrowings
2,018			4,473,000		4,473,000
2,019			17,893,000		17,893,000
2,020			17,893,000		17,893,000
2,021			17,893,000		17,893,000
2,022			17,893,000		17,893,000
Thereafter			370,090,000		370,090,000
Subtotal			446,135,000		446,135,000
Less: Amount representing interest	[1]		(216,554,000)		(216,554,000)
Notes Payable to Banks
Components of short-term borrowings and other debt
Debt Instrument, Face Amount			28,200,000		28,200,000
Interest Expense, Debt, Excluding Amortization			$ 400,000	400,000	$ 1,200,000	400,000
Short-term Debt, Percentage Bearing Variable Interest Rate			3.75%		3.75%
Insurance Note
Components of short-term borrowings and other debt
Other Notes Payable			$ 600,000		$ 600,000
Interest rate											2.01%
Short-term Debt, Maximum Amount Outstanding During Period					2,000,000
Debt Instrument, Periodic Payment, Principal					200,000
Loans
Repayments on long-term and short-term borrowings
2,018			0		0
2,019			29,414,000		29,414,000
2,020			0		0
2,021			0		0
2,022			0		0
Thereafter			0		0
Subtotal			29,414,000		29,414,000
Less: Amount representing interest	[1]		(1,214,000)		(1,214,000)
Insurance Note and Aircraft
Repayments on long-term and short-term borrowings
2,018			1,106,000		1,106,000
2,019			3,410,000		3,410,000
2,020			1,363,000		1,363,000
2,021			2,512,000		2,512,000
2,022			0		0
Thereafter			0		0
Subtotal			8,391,000		8,391,000
Less: Amount representing interest	[1]		(703,000)		(703,000)
Aircraft and related equipment
Components of short-term borrowings and other debt
Other Notes Payable			7,100,000		7,100,000		8,200,000
Interest Expense, Debt			100,000	200,000	300,000	600,000
Aircraft and related equipment | Minimum
Components of short-term borrowings and other debt
Interest rate											4.21%
Aircraft and related equipment | Maximum
Components of short-term borrowings and other debt
Interest rate											7.25%
2022 convertible note | Convertible Debt
Components of short-term borrowings and other debt
Convertible debt			112,900,000		112,900,000
Debt Instrument, Face Amount									$ 135,000,000
Debt Instrument, Convertible, Conversion Price | $ / shares									$ 17.375
Interest on Convertible Debt, Net of Tax			1,000,000		3,000,000
Convertible debt, unamortized discount												$ 23,400,000
Amortization of debt discount			1,000,000		3,000,000
Debt Instrument, Interest Rate, Effective Percentage												7.13%
Debt Issuance Costs, Gross												$ 2,200,000
2019 convertible note
Components of short-term borrowings and other debt
Purchase of treasury stock, cost					19,500,000
2019 convertible note | Convertible Debt
Components of short-term borrowings and other debt
Convertible debt			20,200,000		20,200,000
Debt Instrument, Face Amount												$ 149,500,000
Debt Instrument, Convertible, Conversion Price | $ / shares												$ 21.32
Debt Instrument, Repurchase Amount			13,500,000		13,500,000		115,100,000					$ 115,100,000
Purchase of treasury stock, cost							300,000
Interest on Convertible Debt, Net of Tax			200,000	1,100,000	900,000	3,400,000
Convertible debt, unamortized discount												$ 35,700,000
Amortization of debt discount			300,000	$ 1,900,000	1,200,000	5,600,000
Debt Instrument, Interest Rate, Effective Percentage												8.89%
Debt Issuance Costs, Gross												$ 900,000
Interest rate												3.00%
Principal amount of notes being converted												$ 1,000
Extinguishment of Debt, Amount					600,000
Cash convertible note hedge transaction						$ 20,500,000
Class of Warrant, Exercise Price of Warrants or Rights | $ / shares												$ 28.72
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										$ 3,800,000
Interest rate										7.75%
Interest Expense, Debt, Excluding Amortization			1,900,000		2,300,000
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		7,600,000
Collateral Reinsurance Agreement
Future minimum lease payments for capital lease obligations
Cash collateral pledged			$ 10,800,000		$ 10,800,000		$ 11,800,000
[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	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity, Class of Stock [Line Items]
Preferred stock dividends declared				$ 5,094	$ 5,094
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				12,133,276
Purchase of treasury stock, shares				1,160,308
Treasury stock, shares, end of period		14,092,732		14,092,732
Treasury stock, cost, beginning of period				$ 186,846
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions				8,544	11,433
Purchase of treasury stock, cost				16,762
Treasury stock, cost, end of period		$ 215,323		$ 215,323
Treasury stock, average cost per share, beginning of period, in dollars per share				$ 15.40
Purchase of treasury stock, average cost per share, in dollars per share				14.45
Treasury stock, average cost per share, end of period, in dollars per share		$ 15.28		$ 15.28
Treasury Stock
Treasury Stock, Shares [Roll Forward]
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions				578,673
Treasury stock shares received, other				220,475
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions				$ 8,544
Treasury stock received, value, other				$ 3,171
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions, Average Cost Per Share				$ 14.76
Treasury stock received, per share, other				$ 14.38
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		$ 1,700	$ 1,700	$ 5,094	$ 5,094

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income / (Loss) [Abstract]
Beginning Balance	$ (7)	$ (8)	$ (8)	$ (2)
Foreign currency translation	4	0	5	(6)
Ending Balance	$ (3)	$ (8)	$ (3)	$ (8)

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Computation of earnings per share:
Net income (loss)	$ 20,778	$ 9,828	$ 78,793	$ 50,502
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	5,290	5,162	41,053	35,412
Net income (loss) attributable to Cowen Inc.	15,488	4,666	37,740	15,090
Preferred stock dividends	1,698	1,698	5,094	5,094
Net income (loss) attributable to Cowen Inc. common stockholders	$ 13,790	$ 2,968	$ 32,646	$ 9,996
Shares for basic and diluted calculations:
Weighted average shares used in basic computation, shares	29,610,000	31,271,000	29,662,000	29,004,000
Weighted average shares used in diluted computation, shares	30,844,000	32,246,000	30,613,000	30,011,000
Earnings (loss) per share:
Earnings Per Share, Basic (in dollars per share)	$ 0.47	$ 0.09	$ 1.10	$ 0.34
Earnings Per Share, Diluted (in dollars per share)	$ 0.45	$ 0.09	$ 1.07	$ 0.33
Stock Options
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares		0	0	0
Stock Appreciation Rights
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares	0	20,000	0	15,000
Restricted Stock
Shares for basic and diluted calculations:
Shares attributable to share-based payment awards, shares	1,234,000	955,000	951,000	992,000
Common Stock Class A
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Common stock, shares outstanding, shares	29,142,547	31,087,458	29,142,547	31,087,458	29,632,020	26,731,289
Common stock, restricted shares, shares	253,772		253,772		191,962

Segment Reporting (Details)

Segment Reporting (Details)		3 Months Ended				9 Months Ended
		Sep. 30, 2018USD ($)		Sep. 30, 2017USD ($)		Sep. 30, 2018USD ($)segmentcustomer		Sep. 30, 2017USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment						2
Entity-wide revenue, major customer, number | customer						0
Revenues
Investment banking		$ 81,923,000		$ 57,383,000		$ 264,737,000		$ 158,082,000
Brokerage		92,035,000		84,220,000		301,053,000		198,599,000
Management fees		7,546,000		8,223,000		22,336,000		25,587,000
Incentive income		33,000		1,945,000		97,000		6,217,000
Investment Income		0		0		0		0
Interest and dividends		26,448,000		14,318,000		77,511,000		27,324,000
Reimbursement from affiliates		353,000		484,000		1,066,000		2,631,000
Aircraft lease revenue		375,000		934,000		1,509,000		3,036,000
Reinsurance premiums		8,378,000		7,186,000		26,251,000		21,957,000
Other revenues		1,634,000		3,402,000		3,846,000		6,147,000
Total revenues		221,028,000		178,830,000		706,985,000		454,331,000
Interest expense		26,000,000		15,132,000		74,846,000		37,273,000
Revenue, Net		195,028,000		163,698,000		632,139,000		417,058,000
Expenses
Non-interest expense		209,462,000		177,504,000		653,044,000		478,033,000
Total expenses		211,149,000		179,216,000		660,311,000		487,456,000
Other income (loss)
Total other income (loss)		41,982,000		27,627,000		122,964,000		124,307,000
Income tax expense (benefit)		5,083,000		2,281,000		15,999,000		3,407,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		5,290,000		5,162,000		41,053,000		35,412,000
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		15,488,000		4,666,000		37,740,000		15,090,000
Consolidated Funds
Revenues
Total revenues		2,303,000		735,000		8,579,000		4,751,000
Expenses
Total expenses		1,687,000		1,712,000		7,267,000		9,423,000
Operating Segments
Revenues
Investment banking		77,510,000		57,383,000		251,476,000		158,082,000
Brokerage		101,672,000		89,968,000		328,929,000		209,274,000
Management fees		12,386,000		13,794,000		37,998,000		42,095,000
Incentive income		6,910,000		4,597,000		21,470,000		18,626,000
Investment Income		27,672,000		15,949,000		61,927,000		51,765,000
Interest and dividends		0		0		0		0
Reimbursement from affiliates		0		0		0		0
Aircraft lease revenue		0		0		0		0
Reinsurance premiums		0		0		0		0
Other revenues		83,000		939,000		250,000		3,314,000
Total revenues		226,233,000		182,630,000		702,050,000		483,156,000
Interest expense		6,419,000		4,785,000		16,500,000		13,453,000
Revenue, Net		219,814,000		177,845,000		685,550,000		469,703,000
Expenses
Non-interest expense		195,008,000		169,065,000		610,306,000		440,316,000
Total expenses		195,008,000		169,065,000		610,306,000		440,316,000
Other income (loss)
Total other income (loss)		0		0		0		0
Income tax expense (benefit)		0		0		0		0
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		2,122,000		524,000		6,760,000		4,129,000
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		22,684,000		8,256,000		68,484,000		25,258,000
Operating Segments | Consolidated Funds
Revenues
Total revenues		0		0		0		0
Expenses
Total expenses		0		0		0		0
Operating Segments | Investment Management
Revenues
Investment banking		0		0		0		0
Brokerage		0		19,000		0		38,000
Management fees		11,582,000		12,983,000		35,695,000		39,730,000
Incentive income		6,910,000		4,597,000		21,470,000		18,626,000
Investment Income		2,039,000		9,927,000		30,826,000		34,412,000
Interest and dividends		0		0		0		0
Reimbursement from affiliates		0		0		0		0
Aircraft lease revenue		0		0		0		0
Reinsurance premiums		0		0		0		0
Other revenues		(283,000)		387,000		(501,000)		2,067,000
Total revenues		20,248,000		27,913,000		87,490,000		94,873,000
Interest expense		2,554,000		3,662,000		8,814,000		10,141,000
Revenue, Net		17,694,000		24,251,000		78,676,000		84,732,000
Expenses
Non-interest expense		17,934,000		21,333,000		67,489,000		68,524,000
Total expenses		17,934,000		21,333,000		67,489,000		68,524,000
Other income (loss)
Total other income (loss)		0		0		0		0
Income tax expense (benefit)		0		0		0		0
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		2,122,000		524,000		6,760,000		4,129,000
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		(2,362,000)		2,394,000		4,427,000		12,079,000
Operating Segments | Investment Management | Consolidated Funds
Revenues
Total revenues		0		0		0		0
Expenses
Total expenses		0		0		0		0
Operating Segments | Investment Bank
Revenues
Investment banking		77,510,000		57,383,000		251,476,000		158,082,000
Brokerage		101,672,000		89,949,000		328,929,000		209,236,000
Management fees		804,000		811,000		2,303,000		2,365,000
Incentive income		0		0		0		0
Investment Income		25,633,000		6,022,000		31,101,000		17,353,000
Interest and dividends		0		0		0		0
Reimbursement from affiliates		0		0		0		0
Aircraft lease revenue		0		0		0		0
Reinsurance premiums		0		0		0		0
Other revenues		366,000		552,000		751,000		1,247,000
Total revenues		205,985,000		154,717,000		614,560,000		388,283,000
Interest expense		3,865,000		1,123,000		7,686,000		3,312,000
Revenue, Net		202,120,000		153,594,000		606,874,000		384,971,000
Expenses
Non-interest expense		177,074,000		147,732,000		542,817,000		371,792,000
Total expenses		177,074,000		147,732,000		542,817,000		371,792,000
Other income (loss)
Total other income (loss)		0		0		0		0
Income tax expense (benefit)		0		0		0		0
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		0		0		0		0
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		25,046,000		5,862,000		64,057,000		13,179,000
Operating Segments | Investment Bank | Consolidated Funds
Revenues
Total revenues		0		0		0		0
Expenses
Total expenses		0		0		0		0
Adjustments | Funds Consolidation
Revenues
Investment banking		0		0		0		0
Brokerage		0		0		0		0
Management fees		(381,000)		(640,000)		(2,197,000)		(1,773,000)
Incentive income		(20,000)		(402,000)		(37,000)		(3,669,000)
Investment Income		0		0		0		0
Interest and dividends		0		0		0		0
Reimbursement from affiliates		(65,000)		(88,000)		(198,000)		(241,000)
Aircraft lease revenue		0		0		0		0
Reinsurance premiums		0		0		0		0
Other revenues		0		0		0		0
Total revenues		1,837,000		(395,000)		6,147,000		(932,000)
Interest expense		0		0		0		0
Revenue, Net		1,837,000		(395,000)		6,147,000		(932,000)
Expenses
Non-interest expense		0		0		0		(199,000)
Total expenses		1,687,000		1,712,000		7,267,000		9,224,000
Other income (loss)
Total other income (loss)		2,654,000		7,535,000		36,113,000		44,111,000
Income tax expense (benefit)		0		0		0		0
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		2,804,000		5,428,000		34,993,000		33,955,000
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		0		0		0		0
Adjustments | Funds Consolidation | Consolidated Funds
Revenues
Total revenues		2,303,000		735,000		8,579,000		4,751,000
Expenses
Total expenses		1,687,000		1,712,000		7,267,000		9,423,000
Adjustments | Other Adjustments
Revenues
Investment banking		4,413,000	[1]	0		13,261,000	[1]	0
Brokerage	[2]	(9,637,000)		(5,748,000)		(27,876,000)		(10,675,000)
Management fees	[3]	(4,459,000)		(4,931,000)		(13,465,000)		(14,735,000)
Incentive income	[3]	(6,857,000)	[1]	(2,250,000)		(21,336,000)		(8,740,000)
Investment Income	[4],[5]	(27,672,000)		(15,949,000)		(61,927,000)		(51,765,000)
Interest and dividends	[5]	26,448,000		14,318,000		77,511,000		27,324,000
Reimbursement from affiliates	[6]	418,000		572,000		1,264,000		2,872,000
Aircraft lease revenue	[4]	375,000		934,000		1,509,000		3,036,000
Reinsurance premiums	[7]	8,378,000		7,186,000		26,251,000		21,957,000
Other revenues	[7]	1,551,000		2,463,000		3,596,000		2,833,000
Total revenues		(7,042,000)		(3,405,000)		(1,212,000)	[5]	(27,893,000)
Interest expense	[5]	19,581,000		10,347,000		58,346,000		23,820,000
Revenue, Net		(26,623,000)		(13,752,000)		(59,558,000)		(51,713,000)
Expenses
Non-interest expense	[8],[9]	14,454,000	[1],[5]	8,439,000	[5]	42,738,000	[1]	37,916,000
Total expenses		14,454,000		8,439,000		42,738,000		37,916,000
Other income (loss)
Total other income (loss)	[5]	39,328,000	[10]	20,092,000	[11]	86,851,000	[10]	80,196,000	[11]
Income tax expense (benefit)	[8]	5,083,000		2,281,000		15,999,000		3,407,000
(Income) loss attributable to redeemable non-controlling interests in consolidated subsidiaries and funds		364,000		(790,000)		(700,000)		(2,672,000)
Economic Income (Loss) / Net income (loss) attributable to Cowen Group, Inc.		(7,196,000)		(3,590,000)		(30,744,000)		(10,168,000)
Adjustments | Other Adjustments | Consolidated Funds
Revenues
Total revenues		0		0		0		0
Expenses
Total expenses		$ 0		$ 0		$ 0		$ 0
[1]	Economic Income (Loss) presents underwriting expenses net of investment banking revenues and records income from uncrystallized incentive fees.
[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)	9 Months Ended
	Sep. 30, 2018USD ($)
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	161,500,000
Excess capital	160,500,000
Cowen Execution
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	39,100,000
Net capital requirement under alternative method	2,400,000
Required net capital under commodity exchange act	111,800,000
Net capital	114,200,000
Excess capital	111,800,000
ATM Execution LLC
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	300,000
Net capital	1,700,000
Excess capital	1,400,000
Cowen Prime
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	300,000
Net capital	16,600,000
Excess capital	16,300,000
Westminster Research
Regulatory Requirements for Broker-Dealers [Line Items]
Net capital requirement under alternative method	300,000
Net capital	16,600,000
Excess capital	16,300,000
RCG Insurance Company
Regulatory Requirements for Broker-Dealers [Line Items]
Minimum net capital required	300,000
Net capital	28,600,000
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	$ 13,200,000
Financial resources requirement	9,100,000
Excess financial resources	4,100,000
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	12,000,000
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	24,300,000
Special Reserve Accounts | Minimum | Cowen Execution
Regulatory Requirements for Broker-Dealers [Line Items]
Cash and securities segregated under securities exchange commission regulation	$ 16,900,000

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Fees receivable	$ 111,756		$ 111,756		$ 111,784
Due from related parties	32,509		32,509		34,814
Redeemable non-controlling interests, Related Party	203,212		203,212		440,604
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	(5,290)	$ (5,162)	(41,053)	$ (35,412)
Employees
Related Party Transaction [Line Items]
Redeemable non-controlling interests, Related Party	27,700		27,700		28,200
Net income (loss) attributable to redeemable non-controlling interests in consolidated subsidiaries and funds	(4,500)	(1,600)	(8,900)	(7,200)
Employee Loans
Related Party Transaction [Line Items]
Due from employees	14,800		14,800		11,100
Forgivable Loan Balances	7,100		7,100		4,800
Amortization on Forgivable Loans	800	600	$ 2,200	$ 1,600
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	19,400		$ 19,400		13,500
Investor
Related Party Transaction [Line Items]
Due to Affiliate	600		600		600
Other Funds
Related Party Transaction [Line Items]
Due from related parties	9,700		9,700		9,700
Starboard Value LP
Related Party Transaction [Line Items]
Effective interest rate				5.00%
Interest Income, Related Party	100	$ 200	300	$ 600
Due from related parties	$ 7,800		$ 7,800		$ 14,000
Finance Period			5 years

Guarantees and Off-Balance Sh_3

Guarantees and Off-Balance Sheet Arrangements (Details)	Sep. 30, 2018USD ($)
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