Recent Accounting Pronouncements	12 Months Ended
Dec. 31, 2017
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements ASU 2014-09 – In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU No. 2014-09, "Revenue from Contracts with Customers" ("ASU 2014-09"). ASU 2014-09 provides amendments to ASC 605, "Revenue Recognition" and creates ASC 606, "Revenue from Contracts with Customers," which changes the requirements for revenue recognition and amends the disclosure requirements. In August 2015, the FASB issued ASU No. 2015-14, "Deferral of the Effective Date," which provides amendments that defer the effective date of ASU 2014-09 by one year. In April 2016, the FASB issued ASU No. 2016-10, "Identifying Performance Obligations and Licensing," which provides clarification to identifying performance obligations and the licensing implementation guidance in ASU 2014-09. In May 2016, the FASB issued ASU No. 2016-12, "Narrow-Scope Improvements and Practical Expedients," which provides clarification on certain issues identified in the guidance on assessing collectability, presentation of sales taxes, noncash consideration, and completed contracts and contract modifications at transition in ASU 2014-09. The amendments in these updates are effective either retrospectively to each prior reporting period presented, or as a cumulative-effect adjustment as of the date of adoption, during interim and annual periods beginning after December 15, 2017, with early adoption permitted beginning after December 15, 2016. The Company adopted ASU 2014-09 on January 1, 2018 using the modified retrospective method of transition, which requires a cumulative-effect adjustment as of the date of adoption. Following the adoption of ASU 2014-09, success related advisory fees, for which payment is generally dependent on the closing of a strategic transaction, a financing arrangement or some other defined outcome, will be considered variable consideration as defined by the standard. ASU 2014-09 requires that revenue be recognized when it is probable that variable consideration will not be reversed in a future period. Accordingly, revenue recognition for such fees could be accelerated under ASU 2014-09 in rare circumstances, which will require careful analysis and judgment. Under legacy U.S. GAAP, the Company recognized such fees upon closing regardless of the probability of the outcome. The effect of the timing of revenue recognition could be material to any given reporting period. Furthermore, legacy U.S. GAAP allows expenses related to underwriting transactions to be reflected net in related revenues. Under ASU 2014-09, those expenses will be presented gross in the results of operations. Interpretive guidance on ASU 2014-09 continues to be issued and vetted, in particular by the AICPA industry task force on Broker-Dealers, the AICPA's Revenue Recognition Working Group and the AICPA's Financial Reporting Executive Committee (FinREC). The Company will continue to monitor and evaluate any additional guidance that is issued. ASU 2016-01 - In January 2016, the FASB issued ASU No. 2016-01, "Recognition and Measurement of Financial Assets and Financial Liabilities" ("ASU 2016-01"). ASU 2016-01 provides amendments to ASC 825, "Financial Instruments," which change the requirements for certain aspects of recognition, measurement and presentation of financial assets and liabilities and amend the disclosure requirements. The amendments in this update are effective during interim and annual periods beginning after December 15, 2017. The amendments in this update should be applied by means of a cumulative-effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption and the amendments related to equity securities without readily determinable fair values should be applied prospectively. The Company holds available-for-sale equity securities of $1,244 within Marketable Securities on the Consolidated Statement of Financial Condition as of December 31, 2017. The Company anticipates that the adoption of this ASU will result in a cumulative effect adjustment of cumulative unrealized losses on available-for-sale equity securities included in Accumulated Other Comprehensive Income (Loss) to Retained Earnings of approximately ($4,100). Going forward, unrealized gains and losses on these securities will be recorded in Other Revenue, Including Interest, on the Consolidated Statements of Operations. The Company also holds equity securities without readily determinable fair values, which were accounted for under the cost method of accounting under legacy U.S. GAAP. Upon adoption of this ASU, the Company elected to continue to measure each of its former cost method investments at its cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. ASU 2016-02 - In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)" ("ASU 2016-02"). ASU 2016-02 supersedes ASC 840, "Leases," and includes requirements for the recognition of a right-of-use asset and lease liability on the balance sheet by lessees for those leases classified as operating leases under previous guidance. The amendments in this update are effective using a modified retrospective approach at the beginning of the earliest period presented, during interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company anticipates adopting ASU 2016-02 on January 1, 2019 using the modified retrospective approach. The adoption will result in the present value of the Company's lease commitments which have a term in excess of one year being reflected on the Company's Statements of Financial Condition as a long-term fixed asset with a corresponding long-term liability. The Company's lease commitments, as discussed in Note 18, primarily relate to office space. The lease-related assets will be amortized to expense over the life of the leases and the liability, and related interest expense, will be reduced as lease payments are made over the life of the lease. The net impact on the Company's earnings is not expected to be materially different from the current expense related to leases as required under legacy U.S. GAAP, which is primarily reflected in Occupancy and Equipment Rental expense on the Consolidated Statements of Operations. ASU 2016-07 - In March 2016, the FASB issued ASU No. 2016-07, "Simplifying the Transition to the Equity Method of Accounting" ("ASU 2016-07"). ASU 2016-07 provides amendments to ASC 323, "Investments - Equity Method and Joint Ventures," which simplify the accounting for equity method investments by eliminating the requirement to 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 in this update are effective prospectively to increases in the level of ownership interest or degree of influence that results in the adoption of the equity method, during interim and annual periods beginning after December 15, 2016, with early adoption permitted. The adoption of ASU 2016-07 did not have a material impact on the Company's financial condition, results of operations and cash flows, or disclosures thereto. ASU 2016-09 - In March 2016, the FASB issued ASU 2016-09 which provides amendments to ASC 718, which simplify the accounting for share-based payment transactions, including income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The amendments in this update are effective during interim and annual periods beginning after December 15, 2016, with early adoption permitted. The application of ASU 2016-09 resulted in excess tax benefits from the delivery of Class A Shares under share-based payment arrangements being recognized in the Company's Provision for Income Taxes for year ended December 31, 2017, rather than in Additional Paid-In-Capital under legacy U.S. GAAP. The Company used the retrospective transition method for the presentation of excess tax benefits on the Statements of Cash Flows; as such, the Company classified excess tax benefits as an operating activity within Taxes Payable on the Consolidated Statements of Cash Flows for the years ended December 31, 2017, 2016 and 2015. The application of ASU 2016-09 will result in greater volatility in the effective tax rate and could be material to the results of operations and the classifications of cash flows in future periods depending upon the level of earnings and stock price of the Company, among other things. See Note 20 for further detail, including the impact of the application of ASU 2016-09 on the 2017 results. ASU 2016-13 - In June 2016, the FASB issued ASU No. 2016-13, "Measurement of Credit Losses on Financial Instruments" ("ASU 2016-13"). ASU 2016-13 provides amendments to ASC 326, "Financial Instruments - Credit Losses," which amend the guidance on the impairment of financial instruments and adds an impairment model (the current expected credit loss (CECL) model) that is based on expected losses rather than incurred losses. Entities will recognize an allowance for its estimate of expected credit losses as of the end of each reporting period. The amendments in this update are effective during interim and annual periods beginning after December 15, 2019, with early adoption permitted after December 15, 2018. The Company currently uses the specific identification method for establishing credit provisions and write-offs of its trade accounts receivable. The Company anticipates adopting ASU 2016-13 on January 1, 2020 and does not anticipate a material difference between the current method and the CECL model. ASU 2016-15 - In August 2016, the FASB issued ASU No. 2016-15, "Classification of Certain Cash Receipts and Cash Payments" ("ASU 2016-15"). ASU 2016-15 provides amendments to ASC 230, "Statement of Cash Flows," which provide guidance on the classification of certain cash receipts and payments in the statement of cash flows. The amendments in this update are effective retrospectively, or prospectively, if retrospective application is impracticable, during interim and annual periods beginning after December 15, 2017, with early adoption permitted. The Company is currently assessing the impact of this update on the Company's financial condition, results of operations and cash flows, or disclosures thereto. ASU 2016-18 - In November 2016, the FASB issued ASU No. 2016-18, "Restricted Cash" ("ASU 2016-18"). ASU 2016-18 provides amendments to ASC 230, "Statement of Cash Flows," which require that a statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash and restricted cash equivalents. The amendments in this update are effective retrospectively during interim and annual periods beginning after December 15, 2017, with early adoption permitted. The Company anticipates that the adoption of this ASU will result in expanded disclosure on restricted cash balances. ASU 2017-01 - In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU 2017-01"). ASU 2017-01 provides amendments to ASC 805, "Business Combinations," which clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendments in this update are effective prospectively during interim and annual periods beginning after December 15, 2017, with early adoption permitted. The Company is currently assessing the impact of this update on the Company's financial condition, results of operations and cash flows, or disclosures thereto. ASU 2017-04 - In January 2017, the FASB issued ASU 2017-04. ASU 2017-04 provides amendments to ASC 350, "Intangibles - Goodwill and Other" ("ASC 350"), which eliminate Step 2 from the goodwill impairment test. Entities should perform their goodwill impairment tests by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. The amendments in this update are effective prospectively during interim and annual periods beginning after December 15, 2019, with early adoption permitted. The Company adopted ASU 2017-04 during the second quarter of 2017. See Note 4 for further information. ASU 2017-09 - In May 2017, the FASB issued ASU No. 2017-09, "Scope of Modification Accounting" ("ASU 2017-09"). ASU 2017-09 provides amendments to ASC 718, which provide guidance and clarity around which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The amendments in this update are effective prospectively during interim and annual periods beginning after December 15, 2017, with early adoption permitted. The Company is currently assessing the impact of this update on the Company's financial condition, results of operations and cash flows, or disclosures thereto. ASU 2018-02 - In February 2018, the FASB issued ASU No. 2018-02, "Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" ("ASU 2018-02"). ASU 2018-02 provides amendments to ASC 220, “Income Statement - Reporting Other Comprehensive Income,” which allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. The amendments in this update are effective either in the period of adoption or retrospectively, to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act is recognized, during interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company is currently assessing the impact of this update on the Company's financial condition, results of operations and cash flows, or disclosures thereto.

Recent Accounting Pronouncements

ASU 2014-09 – In May 2014, the Financial Accounting Standards Board ("FASB") issued ASU No. 2014-09, "Revenue from Contracts with Customers" ("ASU 2014-09"). ASU 2014-09 provides amendments to ASC 605, "Revenue Recognition" and creates ASC 606, "Revenue from Contracts with Customers," which changes the requirements for revenue recognition and amends the disclosure requirements. In August 2015, the FASB issued ASU No. 2015-14, "Deferral of the Effective Date," which provides amendments that defer the effective date of ASU 2014-09 by one year. In April 2016, the FASB issued ASU No. 2016-10, "Identifying Performance Obligations and Licensing," which provides clarification to identifying performance obligations and the licensing implementation guidance in ASU 2014-09. In May 2016, the FASB issued ASU No. 2016-12, "Narrow-Scope Improvements and Practical Expedients," which provides clarification on certain issues identified in the guidance on assessing collectability, presentation of sales taxes, noncash consideration, and completed contracts and contract modifications at transition in ASU 2014-09. The amendments in these updates are effective either retrospectively to each prior reporting period presented, or as a cumulative-effect adjustment as of the date of adoption, during interim and annual periods beginning after December 15, 2017, with early adoption permitted beginning after December 15, 2016.

The Company adopted ASU 2014-09 on January 1, 2018 using the modified retrospective method of transition, which requires a cumulative-effect adjustment as of the date of adoption. Following the adoption of ASU 2014-09, success related advisory fees, for which payment is generally dependent on the closing of a strategic transaction, a financing arrangement or some other defined outcome, will be considered variable consideration as defined by the standard. ASU 2014-09 requires that revenue be recognized when it is probable that variable consideration will not be reversed in a future period. Accordingly, revenue recognition for such fees could be accelerated under ASU 2014-09 in rare circumstances, which will require careful analysis and judgment. Under legacy U.S. GAAP, the Company recognized such fees upon closing regardless of the probability of the outcome. The effect of the timing of revenue recognition could be material to any given reporting period. Furthermore, legacy U.S. GAAP allows expenses related to underwriting transactions to be reflected net in related revenues. Under ASU 2014-09, those expenses will be presented gross in the results of operations.

Interpretive guidance on ASU 2014-09 continues to be issued and vetted, in particular by the AICPA industry task force on Broker-Dealers, the AICPA's Revenue Recognition Working Group and the AICPA's Financial Reporting Executive Committee (FinREC). The Company will continue to monitor and evaluate any additional guidance that is issued.

ASU 2016-01 - In January 2016, the FASB issued ASU No. 2016-01, "Recognition and Measurement of Financial Assets and Financial Liabilities" ("ASU 2016-01"). ASU 2016-01 provides amendments to ASC 825, "Financial Instruments," which change the requirements for certain aspects of recognition, measurement and presentation of financial assets and liabilities and amend the disclosure requirements. The amendments in this update are effective during interim and annual periods beginning after December 15, 2017. The amendments in this update should be applied by means of a cumulative-effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption and the amendments related to equity securities without readily determinable fair values should be applied prospectively. The Company holds available-for-sale equity securities of $1,244 within Marketable Securities on the Consolidated Statement of Financial Condition as of December 31, 2017. The Company anticipates that the adoption of this ASU will result in a cumulative effect adjustment of cumulative unrealized losses on available-for-sale equity securities included in Accumulated Other Comprehensive Income (Loss) to Retained Earnings of approximately ($4,100). Going forward, unrealized gains and losses on these securities will be recorded in Other Revenue, Including Interest, on the Consolidated Statements of Operations. The Company also holds equity securities without readily determinable fair values, which were accounted for under the cost method of accounting under legacy U.S. GAAP. Upon adoption of this ASU, the Company elected to continue to measure each of its former cost method investments at its cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer.

ASU 2016-02 - In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)" ("ASU 2016-02"). ASU 2016-02 supersedes ASC 840, "Leases," and includes requirements for the recognition of a right-of-use asset and lease liability on the balance sheet by lessees for those leases classified as operating leases under previous guidance. The amendments in this update are effective using a modified retrospective approach at the beginning of the earliest period presented, during interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company anticipates adopting ASU 2016-02 on January 1, 2019 using the modified retrospective approach. The adoption will result in the present value of the Company's lease commitments which have a term in excess of one year being reflected on the Company's Statements of Financial Condition as a long-term fixed asset with a corresponding long-term liability. The Company's lease commitments, as discussed in Note 18, primarily relate to office space. The lease-related assets will be amortized to expense over the life of the leases and the liability, and related interest expense, will be reduced as lease payments are made over the life of the lease. The net impact on the Company's earnings is not expected to be materially different from the current expense related to leases as required under legacy U.S. GAAP, which is primarily reflected in Occupancy and Equipment Rental expense on the Consolidated Statements of Operations.

ASU 2016-07 - In March 2016, the FASB issued ASU No. 2016-07, "Simplifying the Transition to the Equity Method of Accounting" ("ASU 2016-07"). ASU 2016-07 provides amendments to ASC 323, "Investments - Equity Method and Joint Ventures," which simplify the accounting for equity method investments by eliminating the requirement to 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 in this update are effective prospectively to increases in the level of ownership interest or degree of influence that results in the adoption of the equity method, during interim and annual periods beginning after December 15, 2016, with early adoption permitted. The adoption of ASU 2016-07 did not have a material impact on the Company's financial condition, results of operations and cash flows, or disclosures thereto.

ASU 2016-09 - In March 2016, the FASB issued ASU 2016-09 which provides amendments to ASC 718, which simplify the accounting for share-based payment transactions, including income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The amendments in this update are effective during interim and annual periods beginning after December 15, 2016, with early adoption permitted. The application of ASU 2016-09 resulted in excess tax benefits from the delivery of Class A Shares under share-based payment arrangements being recognized in the Company's Provision for Income Taxes for year ended December 31, 2017, rather than in Additional Paid-In-Capital under legacy U.S. GAAP. The Company used the retrospective transition method for the presentation of excess tax benefits on the Statements of Cash Flows; as such, the Company classified excess tax benefits as an operating activity within Taxes Payable on the Consolidated Statements of Cash Flows for the years ended December 31, 2017, 2016 and 2015. The application of ASU 2016-09 will result in greater volatility in the effective tax rate and could be material to the results of operations and the classifications of cash flows in future periods depending upon the level of earnings and stock price of the Company, among other things. See Note 20 for further detail, including the impact of the application of ASU 2016-09 on the 2017 results.

ASU 2016-13 - In June 2016, the FASB issued ASU No. 2016-13, "Measurement of Credit Losses on Financial Instruments" ("ASU 2016-13"). ASU 2016-13 provides amendments to ASC 326, "Financial Instruments - Credit Losses," which amend the guidance on the impairment of financial instruments and adds an impairment model (the current expected credit loss (CECL) model) that is based on expected losses rather than incurred losses. Entities will recognize an allowance for its estimate of expected credit losses as of the end of each reporting period. The amendments in this update are effective during interim and annual periods beginning after December 15, 2019, with early adoption permitted after December 15, 2018. The Company currently uses the specific identification method for establishing credit provisions and write-offs of its trade accounts receivable. The Company anticipates adopting ASU 2016-13 on January 1, 2020 and does not anticipate a material difference between the current method and the CECL model.

ASU 2016-15 - In August 2016, the FASB issued ASU No. 2016-15, "Classification of Certain Cash Receipts and Cash Payments" ("ASU 2016-15"). ASU 2016-15 provides amendments to ASC 230, "Statement of Cash Flows," which provide guidance on the classification of certain cash receipts and payments in the statement of cash flows. The amendments in this update are effective retrospectively, or prospectively, if retrospective application is impracticable, during interim and annual periods beginning after December 15, 2017, with early adoption permitted. The Company is currently assessing the impact of this update on the Company's financial condition, results of operations and cash flows, or disclosures thereto.

ASU 2016-18 - In November 2016, the FASB issued ASU No. 2016-18, "Restricted Cash" ("ASU 2016-18"). ASU 2016-18 provides amendments to ASC 230, "Statement of Cash Flows," which require that a statement of cash flows explain the change during the period in the total of cash, cash equivalents and amounts generally described as restricted cash and restricted cash equivalents. The amendments in this update are effective retrospectively during interim and annual periods beginning after December 15, 2017, with early adoption permitted. The Company anticipates that the adoption of this ASU will result in expanded disclosure on restricted cash balances.

ASU 2017-01 - In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU 2017-01"). ASU 2017-01 provides amendments to ASC 805, "Business Combinations," which clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendments in this update are effective prospectively during interim and annual periods beginning after December 15, 2017, with early adoption permitted. The Company is currently assessing the impact of this update on the Company's financial condition, results of operations and cash flows, or disclosures thereto.

ASU 2017-04 - In January 2017, the FASB issued ASU 2017-04. ASU 2017-04 provides amendments to ASC 350, "Intangibles - Goodwill and Other" ("ASC 350"), which eliminate Step 2 from the goodwill impairment test. Entities should perform their goodwill impairment tests by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value. The amendments in this update are effective prospectively during interim and annual periods beginning after December 15, 2019, with early adoption permitted. The Company adopted ASU 2017-04 during the second quarter of 2017. See Note 4 for further information.

ASU 2017-09 - In May 2017, the FASB issued ASU No. 2017-09, "Scope of Modification Accounting" ("ASU 2017-09"). ASU 2017-09 provides amendments to ASC 718, which provide guidance and clarity around which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. The amendments in this update are effective prospectively during interim and annual periods beginning after December 15, 2017, with early adoption permitted. The Company is currently assessing the impact of this update on the Company's financial condition, results of operations and cash flows, or disclosures thereto.

ASU 2018-02 - In February 2018, the FASB issued ASU No. 2018-02, "Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income" ("ASU 2018-02"). ASU 2018-02 provides amendments to ASC 220, “Income Statement - Reporting Other Comprehensive Income,” which allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act. The amendments in this update are effective either in the period of adoption or retrospectively, to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act is recognized, during interim and annual periods beginning after December 15, 2018, with early adoption permitted. The Company is currently assessing the impact of this update on the Company's financial condition, results of operations and cash flows, or disclosures thereto.