Document and Entity Information Statement [Table] Statement [Line Items] Statement Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Entity Emerging Growth Company Entity Ex Transition Period Consolidated Statements of Financial Condition Assets [Abstract] Assets Cash and Cash Equivalents, at Carrying Value Cash Cash and cash equivalents including cash deposited with related parties of $283,790 and $234,107 at December 31, 2018 and December 31, 2017, respectively Restricted Cash. Restricted cash Receivables from Brokers-Dealers and Clearing Organizations Receivable from brokers and dealers and clearing organizations including receivables from related parties of $3,332 at December 31, 2018 Deposits with Clearing Organizations and Others, Securities Deposits with clearing organizations including deposits from related parties of $500 at December 31, 2018 and December 31, 2017 Accounts Receivable, Net Accounts receivable, net of allowance including receivables from related parties of $40,730 and $27,163 at December 31, 2018 and December 31, 2017, respectively Property, Plant and Equipment, Net Furniture, equipment, purchased software and leasehold improvements, net of accumulated depreciation and amortization Furniture, equipment, purchased software and leasehold improvements, net of accumulated depreciation and amortization Capitalized Computer Software, Net Software development costs, net of accumulated amortization Software development costs, net of accumulated amortization Intangible Assets, Net (Excluding Goodwill) Intangible assets, net of accumulated amortization Goodwill Goodwill Goodwill Due from Affiliates Receivable from affiliates Other Assets Other assets including other assets from related parties of $9 and $27 at December 31, 2018 and December 31, 2017, respectively Deferred Income Tax Assets, Net Deferred tax assets Assets Total assets Liabilities and Equity [Abstract] Liabilities and Members' Capital Liabilities [Abstract] Liabilities Payables to Broker-Dealers and Clearing Organizations Payable to brokers and dealers and clearing organizations including payables to related parties of $2,404 at December 31, 2018 Employee-related Liabilities Accrued compensation Contract with Customer, Liability Deferred revenue balance - end of period Deferred revenue balance - beginning of period Deferred revenue including deferred revenue from related parties of $9,151 and $5,106 at December 31, 2018 and December 31, 2017, respectively Amount of liability recognized arising from contingent consideration due to related parties. Contingent Consideration, Liability, Due to Related Parties Contingent consideration payable to related parties Contingent consideration payable Accounts Payable and Accrued Liabilities Accounts payable, accrued expenses and other liabilities including payables to related parties of $2,555 at December 31, 2017 Equity compensation payable to employees. Equity Compensation Payable Employee equity compensation payable Due to Affiliate Payable to affiliates Deferred Income Tax Liabilities, Net Deferred tax liability Liabilities Total liabilities Commitments and Contingencies. Commitments and contingencies (Note 17) Temporary Equity [Abstract] Mezzanine Capital Temporary Equity, Carrying Amount, Attributable to Parent Class C Shares and Class P(C) Shares Members' Equity [Abstract] Members' capital Members' Capital Members' capital Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss Members' Equity Members' capital end of period Members' capital beginning of period Members' equity Total members' capital Liabilities and Equity Total liabilities and members' capital Cash deposited with related parties, included with cash and cash equivalents. Cash And Cash Equivalents Related Parties Cash deposited with related parties Cash and cash equivalents Receivables from related parties, included with receivables from brokers, dealers and clearing organizations. Receivables From Brokers Dealers And Clearing Organizations Related Parties Receivables from related parties Receivables from brokers and dealers and clearing organizations Deposits from related parties, included with deposits with clearing organizations. Deposits Related Parties Deposits from related parties Deposits with clearing organizations Accounts Receivable, Related Parties Accounts receivable Accounts receivable, net of allowance from related parties Other assets from related parties. Other Assets Related Parties Other assets from related parties Other assets Payables to related parties, included with payables to brokers, dealers and clearing organizations. Payables To Broker Dealers And Clearing Organizations Related Parties Payables to related parties, brokers, dealers and clearing organizations Payable to brokers and dealers and clearing organizations Amount of obligation to transfer good or service to related parties for which consideration has been received or is receivable. Contract with Customer, Liability, Related Parties Deferred revenues from related parties Deferred revenue Accounts Payable, Related Parties Accounts payable, accrued expenses and other liabilities Payables to related parties Consolidated Statements of Income Revenues [Abstract] Revenues Revenue from Contract with Customer, Excluding Assessed Tax Gross revenues Gross revenue Contingent consideration to related parties. Contingent Consideration Related Parties Contingent consideration to related parties Contingent consideration recognized Revenues Net revenue Net revenue Operating Expenses [Abstract] Expenses Labor and Related Expense Employee compensation and benefits Depreciation, Depletion and Amortization, Nonproduction Depreciation and amortization Other General and Administrative Expense General and administrative including from related parties of $180, $539, $719 and $740 in the period ended December 31, 2018, September 30, 2018, December 31, 2017 and December 31, 2016, respectively Communications and Information Technology Technology and communications including from related parties of $740, $2,220, $2,960 and $2,960 in the period ended December 31, 2018, September 30, 2018, December 31, 2017 and December 31, 2016, respectively Professional Fees Professional fees Occupancy, Net Occupancy including from related parties of $155, $466, $621 and $600 in the period ended December 31, 2018, September 30, 2018, December 31, 2017 and December 31, 2016, respectively Costs and Expenses Operating expenses Total Expenses Operating Income (Loss) Operating income Operating income Investment Income, Interest Interest income including from related parties of $17, $34, $40 and $80 in the period ended December 31, 2018, September 30, 2018, December 31, 2017 and December 31, 2016, respectively Interest Expense, Related Party Interest expense from related parties Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income before taxes Income Tax Expense (Benefit) Provision for income taxes Total Net Income (Loss) Attributable to Parent Net income Net income Net Income Per Share Net income per share (Note 18) Earnings Per Share, Basic Basic net income per share Basic Earnings Per Share, Diluted Diluted net income per share Diluted Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Weighted average number of shares outstanding Weighted Average Number of Shares Outstanding, Basic Basic Weighted Average Number of Shares Outstanding, Diluted Diluted weighted average shares outstanding Diluted Revenue from Related Parties Related party revenue Revenue from related parties General and administrative expense from related parties. General And Administrative Expense Related Parties General and administrative from related parties Information technology and communication expenses from related parties. Communications And Information Technology Related Parties Technology and communications from related parties Occupancy expense from related parties. Occupancy Related Parties Occupancy from related parties Interest Income, Related Party Interest income from money market funds invested and savings deposited Interest income from related parties Consolidated Statements of Changes in Members' Capital and Accumulated Other Comprehensive Loss Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Comprehensive income: Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Foreign currency translation adjustments Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income Adjustments to Additional Paid in Capital, Increase in Carrying Amount of Redeemable Preferred Stock Adjustment to Class C Shares and Class P(C) Shares in mezzanine capital Stock Issued During Period, Value, Acquisitions Vesting of contingent consideration Vesting of contingent consideration to Class P-1(A) Shares Limited Liability Company (LLC) Members' Equity, Unit-based Compensation Conversion of certain cash-settled PRSUs to equity settled PRSUs Conversion of certain cash-settled PRSUs to equity settled PRSUs Total contributions made by members of a limited liability company. Limited Liability Company Contributions Capital contributions Conversion of convertible term note payable to Thomson Reuters to Class A Shares Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared Capital distributions Consolidated Statements of Cash Flows Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash used in operating activities: Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Contingent consideration Amount of cash outflow for vesting of employee shares, class P-1 C. Vesting of Employee Shares, Class P-1 C Vesting of P-1(C) Shares Deferred Income Tax Expense (Benefit) Total deferred Deferred taxes Increase (Decrease) in Operating Assets [Abstract] (Increase) decrease in operating assets: Increase (Decrease) in Receivables from Brokers-Dealers and Clearing Organizations Receivable from brokers and dealers and clearing organizations Increase (Decrease) in Deposit Assets Deposits with clearing organizations Increase (Decrease) in Accounts Receivable Accounts receivable Increase (Decrease) Due from Affiliates Receivable from affiliates Increase (Decrease) in Other Operating Assets Other assets Increase (Decrease) in Operating Liabilities [Abstract] Increase (decrease) in operating liabilities: Increase (Decrease) in Payables to Broker-Dealers and Clearing Organizations Payable to brokers and dealers and clearing organizations Increase (Decrease) in Employee Related Liabilities Accrued compensation Increase (Decrease) in Deferred Revenue Deferred revenue Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable, accrued expenses and other liabilities The increase (decrease) during the period in equity compensation payable. Increase Decrease In Equity Compensation Payable Employee equity compensation payable Increase (Decrease) in Due to Affiliates Payable to affiliates Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from investing activities Payments to Acquire Property, Plant, and Equipment Purchase of furniture, equipment, software and leasehold improvements Payments for Software Capitalized software development costs Payments for (Proceeds from) Businesses and Interest in Affiliates Business acquisitions Payments to Acquire Investments Purchase of investments Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities Payments of Dividends Capital distributions Proceeds from Contributed Capital Capital contribution Mezzanine capital contributions Payments of Capital Distribution Mezzanine capital distributions Net Cash Provided by (Used in) Financing Activities Net cash used in financing activities Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations Effect of exchange rate changes on cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Net decrease in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations [Abstract] Cash and cash equivalents and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents End of period Beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Total Supplemental Cash Flow Information [Abstract] Supplemental disclosure of cash flow information Interest Paid, Excluding Capitalized Interest, Operating Activities Interest paid Income Taxes Paid Income taxes paid Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Supplemental disclosure of non-cash investing and financing information Organization Entities [Table] Entity Information [Line Items] Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Organization Significant Accounting Policies Significant Accounting Policies [Text Block] Significant Accounting Policies No definition available. Pushdown Accounting The entire disclosure for reporting pushdown accounting. Pushdown Accounting [Text Block] Pushdown Accounting Restricted Cash Restricted Assets Disclosure [Text Block] Restricted Cash Receivable from and Payable to Brokers and Dealers and Clearing Organizations Due to and from Broker-Dealers and Clearing Organizations Disclosure [Text Block] Receivable from and Payable to Brokers and Dealers and Clearing Organizations Deposits with Clearing Organizations The entire disclosure of deposits with clearing organizations. Deposits With Clearing Organizations [Text Block] Deposits with Clearing Organizations Furniture, Equipment, Purchased Software and Leasehold Improvements Property, Plant and Equipment Disclosure [Text Block] Furniture, Equipment, Purchased Software and Leasehold Improvements Software Development Cost Research, Development, and Computer Software Disclosure [Text Block] Software Development Cost Intangible Assets and Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Intangible Assets and Goodwill Deferred Revenue The entire disclosure about the contract with customer liability. Contract With Customer Liability [Text Block] Deferred Revenue Income Taxes Income Tax Disclosure [Text Block] Income Taxes Shares Stockholders' Equity Note Disclosure [Text Block] Shares Share-Based Compensation Plans Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Share-Based Compensation Plans Related Party Transactions Related Party Transactions Disclosure [Text Block] Related Party Transactions Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Fair Value of Financial Instruments Credit Risk Allowance for Credit Losses [Text Block] Credit Risk Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Earnings Per Share [Text Block] Net Income Per Share Regulatory Capital Requirements The entire disclosure of capital requirements and required financial resources under applicable regulations. Regulatory Capital Requirements [Text Block] Regulatory Capital Requirements Employee Savings Plan Pension and Other Postretirement Benefits Disclosure [Text Block] Employee Savings Plan Business Segment and Geographic Information Segment Reporting Disclosure [Text Block] Business Segment and Geographic Information Subsequent Events Subsequent Events [Text Block] Subsequent Events Basis of Accounting, Policy [Policy Text Block] Basis of Accounting Use of Estimates, Policy [Policy Text Block] Use of Estimates Consolidation, Policy [Policy Text Block] Basis of Consolidation Disclosure of accounting policy for the recapitalization in the preparation of financial statements in conformity with generally accepted accounting principles. Recapitalization [Policy Text Block] Recapitalization Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block] Allowance for Doubtful Accounts Property, Plant and Equipment, Policy [Policy Text Block] Furniture, Equipment, Purchased Software and Leasehold Improvements Internal Use Software, Policy [Policy Text Block] Software Development Costs Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Intangible Assets Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Goodwill Deferred Charges, Policy [Policy Text Block] Deferred IPO costs Foreign Currency Transactions and Translations Policy [Policy Text Block] Translation of Foreign Currency Income Tax, Policy [Policy Text Block] Income Tax Revenue from Contract with Customer [Policy Text Block] Revenue Recognition Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Share-Based Compensation Earnings Per Share, Policy [Policy Text Block] Net Income Per Share Fair Value Measurement, Policy [Policy Text Block] Fair Value Measurement New Accounting Pronouncements, Policy [Policy Text Block] Recent Accounting Pronouncements Disaggregation of Revenue [Table Text Block] Breakdown of revenues between fixed and variable revenues Schedule of Business Acquisitions, by Acquisition [Table Text Block] Allocation applying pushdown accounting