Summary Of Significant Accounting Policies (Policy)	9 Months Ended
Summary Of Significant Accounting Policies (Policy)	Sep. 30, 2018
Summary Of Significant Accounting Policies [Abstract]
Adoption Of New Accounting Standards	A. Adoption of New Accounting Standards In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). Subsequent to that date, the FASB has issued additional ASUs clarifying certain aspects of ASU 2014-09 but they did not change the core principal of ASU 2014-09. The new guidance requires entities to recognize revenue in a way that depicts the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company adopted the new guidance on January 1, 2018 using the retrospective transition method. This ASU excludes from its scope revenue recognition related to items the Company records as a component of net trading and principal transactions within its consolidated statements of operations and therefore this ASU had no impact on these items. In terms of asset management and other revenue, the main impact of Topic 606 related to the timing of the recognition of incentive management fees in certain cases. Prior to the adoption of Topic 606, the Company would recognize incentive fees when they were fixed and determinable. Under Topic 606, the Company is required to recognize incentive fees when they are probable and there is not a significant chance of reversal in the future. For the asset management contracts in place at the time of adoption, this change in policy did not result in any actual change in revenue that had already been recognized and therefore there was no transition adjustment necessary. Based on a review of the Company’s asset management contracts in place at the time of adoption, the Company does not believe the actual timing of recognition of incentive fees under future management contracts will be materially impacted in the future. However, the new policy may result in incentive fees being recognized sooner in the future than they would have been under the Company’s revenue recognition policy in place prior to the adoption of Topic 606. In March 2016, the FASB issued ASU 2016-06, Derivatives and Hedging (Topic 815): Contingent Put and Call Options in Debt Instruments. This ASU clarifies what steps are required when assessing whether the economic characteristics and risks of call (put) options are clearly and closely related to the economic characteristics and risks of their debt hosts, which is one of the criteria for bifurcating an embedded derivative. Consequently, when a call (put) option is contingently exercisable, an entity does not have to assess whether the event that triggers the ability to exercise a call (put) option is related to interest rates or credit risks. The Company’s adoption of the provisions of ASU 2016-06 effective January 1, 2017 did not have an effect on the Company’s consolidated financial statements. In March 2016, the FASB issued ASU 2016-07, Investments - Equity Method and Joint Ventures (Topic 323): Simplifying the Transition to the Equity Method of Accounting. This ASU eliminates the requirement that when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence, an investor must adjust the investment, results of operations, and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held. The amendments require that the equity method investor add the cost of acquiring the additional interest in the investee to the current basis of the investor’s previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting. If an entity has an available-for-sale equity security that becomes qualified for the equity method of accounting, it should recognize through earnings the unrealized holding gain or loss in accumulated other comprehensive income at the date the investment becomes qualified for use of the equity method. The Company’s adoption of the provisions of ASU 2016-07 effective January 1, 2017 did not have an effect on the Company’s consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. This ASU simplifies several aspects of the accounting for share-based payment award transactions including (i) income tax consequences, (ii) classification of awards as either equity or liabilities, and (iii) classification on the statement of cash flows. The Company’s adoption of the provisions of ASU 2016-09 effective January 1, 2017 did not have a material impact on the Company’s consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The amendments in this ASU provide cash flow statement classification guidance on eight specific cash flow presentation issues with the objective of reducing existing diversity in practice. The Company’s adoption of the provisions of ASU 2016-15 effective January 1, 2018 did not have a material impact on the Company’s consolidated financial statements. In October 2016, the FASB issued ASU 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other than Inventory. The amendments require an entity to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs. The amendments eliminate the exception of an intra-entity transfer of an asset other than inventory. The Company’s adoption of the provisions of ASU 2016-16 effective January 1, 2018 did not have a material impact on the Company’s consolidated financial statements. In October 2016, the FASB issued ASU 2016-17, Consolidation (Topic 810): Interests Held through Related Parties that are Under Common Control. The amendments change the evaluation of whether a reporting entity is the primary beneficiary of a variable interest entity by changing how a reporting entity that is a single decision maker of a variable interest entity treats indirect interests in the entity held through related parties that are under common control. If a reporting entity satisfies the first characteristic of a primary beneficiary (such that it is the single decision maker of a variable interest entity), the amendments require that reporting entity, in determining whether it satisfies the second characteristic of a primary beneficiary, to include all of its direct variable interests in a variable interest entity and, on a proportionate basis, its indirect variable interests in a variable interest entity held through related parties, including related parties that are under common control with the reporting entity. The Company’s adoption of the provisions of ASU 2016-17 effective January 1, 2017 did not have an effect on the Company’s consolidated financial statements. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The amendments in this ASU clarify the definition of a business and affect all companies and other reporting organizations that must determine whether they have acquired or sold a business. The Company’s adoption of the provisions of ASU 2017-01 effective January 1, 2018 did not have an effect on the Company’s consolidated financial statements. In February 2017, the FASB issued ASU 2017-05, Other Income – Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets. The amendments in this ASU clarify that a financial asset within the scope of this topic may include nonfinancial assets transferred within a legal entity to counterparty. The amendments clarify that an entity should identify each distinct nonfinancial asset or in substance nonfinancial asset promised to counterparty and derecognize each asset when counterparty obtains control of it. The Company’s adoption of the provisions of ASU 2017-05 effective January 1, 2018 did not have an effect on the Company’s consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting. The amendments provide guidance on determining those changes to the terms and conditions of share-based payment awards that require an entity to apply modification accounting. The Company’s adoption of the provisions of ASU 2017-09 effective January 1, 2018 did not have an effect on the Company’s consolidated financial statements. In March 2018, the FASB issued ASU 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118, which updates the income tax accounting in U.S. GAAP to reflect the Securities and Exchange Commission (“SEC”) interpretive guidance released on December 22, 2017 when the Tax Cuts and Jobs Act (the “Tax Act”) was signed into law. The Company’s adoption of the provisions of had a one-time impact on the Company in which a $1,359 tax benefit was recognized in the fourth quarter of 2017. Refer to the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.
Recent Accounting Developments	B. Recent Accounting Developments In February 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10). The amendments in ASU 2016-01, among other things, require equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value with changes in fair value recognized in net income; require public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; require separate presentation of financial assets and liabilities by measurement category and form of financial asset; and eliminate the requirement for public business entities to disclose the methods and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost. The amendments in this ASU are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of these amendments on the presentation of its consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). Under the new guidance, lessees will be required to recognize the following for all leases with the exception of short-term leases: (i) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and (ii) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. Lessor accounting is largely unchanged. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases, to clarify how to apply certain aspects of the new standard and ASU 2018-11, Leases, (Topic 842): Targeted Improvement, allowing for application of the standard at the adoption date, with recognition of a cumulative adjustment to the opening balance of retained earnings in the period of adoption. The amendments in the ASUs are effective for entities for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted. The Company expects to adopt this new guidance effective January 1, 2019. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements. The Company has preliminarily determined that adoption will result in an increase in the Company’s assets and liabilities. The Company expects the cumulative effect adjustment will be immaterial. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in this ASU require the measurement of all expected credit losses for financial assets held at the reporting date to be based on historical experience, current conditions, and reasonable and supportable forecasts. Financial institutions and other organizations will now use forward-looking information to better inform their credit loss estimates. Many of the loss estimation techniques applied today will still be permitted, although the inputs to those techniques will change to reflect the full amount of expected credit losses. In addition, the ASU amends the accounting for credit losses on available-for-sale debt securities and purchased financial assets with credit deterioration. The amendments in this ASU are effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted beginning after December 15, 2018, including interim periods within those fiscal years. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. The amendments in this ASU eliminate Step 2 from the goodwill impairment test. The annual or interim goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized 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. This ASU is effective for fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017 and should be applied on a prospective basis. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements. In March 2017, the FASB issued ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs, Premium Amortization on Purchased Callable Debt Securities (Sub-Topic 310-20). The amendments shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. This ASU is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements. In August 2017, the FASB issued ASU 2017-12, Derivative and Hedging – Targeted Improvements to Accounting for Hedging Activities (Topic 815). This ASU is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. The amendments refine and expand hedge accounting for both financial and commodity risks and it contains provisions to create more transparency and clarify how economic results are presented. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements. In February 2018, the FASB issued ASU 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. The amendments provide the option to reclassify stranded tax effects within accumulated other comprehensive income (“AOCI”) to retained earnings in each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act (or portion thereof) is recorded. This ASU is effective for all organizations for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. The amendments expand the scope of Topic 718, which currently only includes share-based payments to employees, to include share-based payments issued to nonemployees for goods or services. Consequently, the accounting for share-based payments to nonemployees and employees will be substantially aligned. This ASU is effective for all organizations for fiscal years beginning after December 15, 2019 and interim periods within fiscal years beginning after December 15, 2020. Early adoption is permitted. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework –Changes to the Disclosure Requirements for Fair Value Measurement. The ASU modifies the disclosure requirements in Topic 820, by removing certain disclosure requirements related to the fair value hierarchy, modifying existing disclosure requirements related to measurement uncertainty and adding new disclosure requirements such as disclosing the changes in unrealized gains and losses for the period included in other comprehensive income for recurring level 3 fair value measurements held at the end of the reporting period and disclosing the range and weighted average of significant unobservable inputs used to develop level 3 fair value measurements. This ASU is effective for public companies for annual reporting periods and interim periods within those annual periods beginning after December 15, 2019. Early adoption is permitted. The Company is currently evaluating the new guidance to determine the impact it may have on its consolidated financial statements.
Fair Value Of Financial Instruments	C. Fair Value of Financial Instruments The following methods and assumptions were used by the Company in estimating the fair value of its financial instruments. These determinations were based on available market information and appropriate valuation methodologies. Considerable judgment is required to interpret market data to develop the estimates and, therefore, these estimates may not necessarily be indicative of the amount the Company could realize in a current market exchange. The use of different market assumptions and/or estimation methodologies may have a material effect on the estimated fair value amounts. Refer to note 9 for a discussion of the fair value hierarchy with respect to investments-trading; other investments, at fair value; and derivatives held by the Company. Cash equivalents: Cash equivalents are carried at historical cost, which is assumed to approximate fair value. The estimated fair value measurement of cash equivalents is classified within level 1 of the fair value hierarchy. Investments-trading: These amounts are carried at fair value. The fair value is based on either quoted market prices of an active exchange, independent broker market quotations, market price quotations from third party pricing services, or valuation models when quotations are not available. Other investments, at fair value: These amounts are carried at fair value. The fair value is based on quoted market prices of an active exchange, independent broker market quotations, or valuation models when quotations are not available. In the case of investments in alternative investment funds, fair value is generally based on the reported net asset value of the underlying fund. Receivables under resale agreements: Receivables under resale agreements are carried at their contracted resale price, have short-term maturities, and are repriced frequently or bear market interest rates and, accordingly, these contracts are at amounts that approximate fair value. The estimated fair value measurements of receivables under resale agreements are based on observations of actual market activity and are generally classified within level 2 of the fair value hierarchy. Trading securities sold, not yet purchased: These amounts are carried at fair value. The fair value is based on quoted market prices of an active exchange, independent market quotations, market price quotations from third party pricing services, or valuation models when quotations are not available. Securities sold under agreements to repurchase: The liabilities for securities sold under agreements to repurchase are carried at their contracted repurchase price, have short-term maturities, and are repriced frequently with amounts normally due in one month or less and, accordingly, these contracts are carried at amounts that approximate fair value. The estimated fair value measurements of securities sold under agreements to repurchase are based on observations of actual market activity and are generally classified within level 2 of the fair value hierarchy. Redeemable financial instruments: The liabilities for redeemable financial instruments are carried at their redemption value, which approximates fair value. The estimated fair value measurement of the redeemable financial instruments is classified within level 3 of the fair value hierarchy. Debt: These amounts are carried at outstanding principal less unamortized discount and deferred financing costs. However, a substantial portion of the debt was assumed in the Merger and recorded at fair value as of that date. As of September 30, 2018 and December 31, 2017, the fair value of the Company’s debt was estimated to be $52,826 and $53,657, respectively. The estimated fair value measurements of the debt are generally based on discounted cash flow models prepared by the Company’s management primarily using discount rates for similar instruments issued to companies with similar credit risks to the Company and are generally classified within level 3 of the value hierarchy. Derivatives: These amounts are carried at fair value. Derivatives may be included as a component of investments-trading; trading securities sold, not yet purchased; and other investments, at fair value. See notes 9 and 10. The fair value is generally based on quoted market prices on an exchange that is deemed to be active for derivative instruments such as foreign currency forward contracts and Eurodollar futures. For derivative instruments, such as TBAs and other extended settlement trades, the fair value is generally based on market price quotations from third party pricing services.