Affiliated Entity Affiliated Entity [Member] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Litigation Case [Axis] Litigation Case [Domain] Litigation Case Type [Domain] Customer [Axis] Maximum Maximum [Member] Minimum Minimum [Member] Name Of Major Customer [Domain] Customer [Domain] Ownership [Axis] Ownership [Domain] Ownership [Domain] Parent Company [Member] Tradeweb Markets Inc. only Product and Service [Axis] Products And Services [Domain] Product and Service [Domain] Range [Axis] Range [Member] Range [Domain] Reportable Legal Entities [Member] Reportable Legal Entities Restatement Adjustment [Member] Adjustment Restatement [Axis] Restatement [Domain] Restatement [Domain] Segment Geographical [Domain] Geographical [Domain] Geographical [Axis] Significant Accounting Policies Accounting Standards Update201602 [Member] ASC 842 Accounts payable, accrued expenses and other liabilities including payables to related parties of $2,555 at December 31, 2017 Accounts Payable and Accrued Liabilities Accounts payable, accrued expenses and other liabilities Accounts Payable And Accrued Liabilities [Member] Accounts payable, accrued expenses and other liabilities Accounts Payable, Fair Value Disclosure Contingent consideration payable Accounts Payable, Related Parties Accounts payable, accrued expenses and other liabilities Payables to related parties 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 Accounts Receivable, Net Accounts Receivable, Related Parties Accounts receivable Accounts receivable, net of allowance from related parties Accrued Income Taxes Tax liability Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Accumulated depreciation and amortization Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Loss Additional paid-in capital Additional Paid In Capital [Member] Additional Paid-In Capital Adjustments for New Accounting Pronouncements [Axis] 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: Adjustments to Additional Paid in Capital, Increase in Carrying Amount of Redeemable Preferred Stock Adjustment to Class C Shares and Class P shares in mezzanine capital Adjustment to Class C Shares and Class P(C) Shares in mezzanine capital Adjustments to Additional Paid in Capital, Share-based Compensation, Restricted Stock Unit or Restricted Stock Award, Requisite Service Period Recognition Share-based compensation expense under the PRSU Plan Adjustments to Additional Paid in Capital, Share-based Compensation, Stock Options, Requisite Service Period Recognition Share-based compensation expense under the Option Plan Allocated Share-based Compensation Expense Compensation expense Compensation expense relating to PRSUs, options and shares Allocated Share-based Compensation Expense, Net of Tax Compensation expense, net of taxes Allowance for Credit Losses [Text Block] Credit Risk Allowance for Doubtful Accounts Receivable Allowance for doubtful accounts Amortization of Intangible Assets Amortization expense Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Shares excluded from computation of diluted earnings per share Antidilutive Securities [Axis] Antidilutive Securities Name [Domain] Antidilutive Securities, Name [Domain] Arrangements And Nonarrangement Transactions [Member] Arrangements and Non-arrangement Transactions [Domain] Assets Total assets Assets [Abstract] Assets Assets, Fair Value Disclosure Total assets measured at fair value Award Type [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Base Rate [Member] Base rate Basis of Accounting, Policy [Policy Text Block] Basis of Accounting Business Acquisition Acquiree [Domain] Business Acquisition, Acquiree [Domain] Business Acquisition [Axis] Business Acquisition [Line Items] Pushdown Accounting Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Contingent consideration Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Total assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Cash and cash equivalents Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables Accounts receivable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Deferred Revenue Deferred revenue Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Deferred tax liability Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Intangible assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Total liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Less: fair value of the net assets and liabilities of the Company Fair value of net assets and liabilities of the Company Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets Other assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Furniture, equipment, purchased software and leasehold improvements Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net Fair value of the Company Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract] Net assets and liabilities of the Company at October 1, 2018: Capital Regulatory Capital Capitalized Computer Software, Accumulated Amortization Accumulated amortization Capitalized Computer Software, Additions Software development costs capitalized Capitalized Computer Software, Amortization Amortization expense Capitalized Computer Software, Gross Software development costs Software development costs, net of accumulated amortization Capitalized Computer Software, Net Software development costs, net of accumulated amortization Software Development Cost Capital Required for Capital Adequacy Regulatory Capital Requirement Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Cash Cash and Cash Equivalents [Axis] Cash and Cash Equivalents, Fair Value Disclosure Money market funds Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents 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 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, Period Increase (Decrease), Including Exchange Rate Effect Net decrease in cash and cash equivalents Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Supplemental disclosure of non-cash investing and financing information Shares Class Of Stock [Domain] Class of Stock [Domain] Class of Stock [Line Items] Shares Commitments and contingencies (Note 17) Commitments and Contingencies. Commitments and contingencies (Note 15) Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Common Class A [Member] Class A common stock Common Class B [Member] Class B common stock Common Class C [Member] Class C common stock Common Stock, Dividends, Per Share, Declared Dividends Common Stock, Par or Stated Value Per Share Common stock, par value Common Stock, par value per share Common Stock, Shares Authorized Common Stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Number of shares owned Common Stock, Shares, Outstanding Common stock, shares outstanding Common Stock, shares outstanding Common Stock, Value, Issued Common stock Common Stock, par value $0.01 per share, 1,000 shares authorized, 100 issued and outstanding Common Unit, Issued Number of Vested Shares Issued, Recapitalization Communications and Information Technology Technology and communications 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 Employee Savings Plan Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Regulatory Capital Requirements Components of Deferred Tax Assets and Liabilities [Abstract] Components of deferred tax assets (liabilities) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income attributable to non-controlling interests Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Comprehensive income: Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive income attributable to non-controlling interests Computer Equipment [Member] Computer hardware Concentration Risk Type [Axis] Concentration Risk [Line Items] Credit Risk Concentration Risk [Table] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Consolidation, Policy [Policy Text Block] Basis of Presentation and Consolidation Basis of Consolidation Contract with Customer, Asset and Liability [Table Text Block] Schedule of recognized revenue and remaining deferred revenue balance Contract with Customer, Basis of Pricing [Axis] Contract With Customer Basis Of Pricing [Domain] Contract with Customer, Basis of Pricing [Domain] Deferred revenue including deferred revenue from related parties of $9,151 and $5,106 at December 31, 2018 and December 31, 2017, respectively Contract with Customer, Liability Deferred revenue balance - end of period Deferred revenue balance - beginning of period Deferred revenue Deferred Revenue Contract with Customer, Liability, Revenue Recognized Revenue recognized Convertible Debt [Member] Convertible term note Convertible Debt Securities [Member] Convertible term note Costs and Expenses Operating expenses Total expenses Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Credit Risk [Member] Credit Risk Current Foreign Tax Expense (Benefit) Foreign Current Income Tax Expense (Benefit) Total current Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Current: Current State and Local Tax Expense (Benefit) State and Local Customer Relationships [Member] Customer relationships Debt Conversion, Converted Instrument, Shares Issued Number of equity shares issued upon conversion of debt Debt Instrument, Basis Spread on Variable Rate Spread (as a percent) Basis spread on variable rate Debt Instrument, Description of Variable Rate Basis Variable interest rate basis Debt Instrument, Face Amount Amount of loan Debt Instrument, Interest Rate, Effective Percentage Effective interest rate percentage Debt Instrument, Term Term of debt Deferred Charges, Policy [Policy Text Block] Deferred IPO costs Deferred Federal Income Tax Expense (Benefit) Deferred - Federal Deferred tax assets Deferred Income Tax Assets, Net Deferred tax asset Deferred Income Tax Expense (Benefit) Deferred taxes Total deferred Deferred Income Tax Liabilities, Net Deferred tax liability Deferred Offering Costs Deferred costs Deferred Rent Credit Deferred rent Deferred Revenue Arrangement, by Type [Table] Deferred Revenue Arrangement [Line Items] Deferred State and Local Income Tax Expense (Benefit) Deferred - state and local Deferred Tax Assets, Net Total deferred tax assets, net Deferred Tax Assets, Operating Loss Carryforwards Net operating losses Deferred Tax Assets, Other Other Deferred Tax Liabilities, Net Deferred Tax Liabilities, Net, Total Deferred Tax Liabilities, Goodwill and Intangible Assets Goodwill and intangible assets Defined Contribution Plan, Cost Expense recognized Defined Contribution Plan Disclosure [Line Items] Employees Savings Plan Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Employer match limit, as a percent of employee's compensation Defined Contribution Plan, Employer Matching Contribution, Percent of Match Company match, as a percent of the employee's contribution Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Employees' voluntary contribution percentage Defined Contribution Plan [Table] Defined Contribution Plan, Tax Status [Extensible List] 401(k) Savings Plan Deposits with Clearing Organizations Deposits with clearing organizations including deposits from related parties of $500 at December 31, 2018 and December 31, 2017 Deposits with Clearing Organizations and Others, Securities Deposits with clearing organizations Depreciation, Depletion and Amortization, Nonproduction Depreciation and amortization Depreciation, Depletion and Amortization Depreciation and amortization expense Disaggregation of Revenue [Abstract] Revenue Recognition Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table Text Block] Breakdown of revenues between fixed and variable revenues Stock-Based Compensation Plans Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock-Based Compensation Plans Share-Based Compensation Plans Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared Capital distributions Cash distribution payable Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid Distribution paid to current owners of the Company Dividends Dividends ($0.08 per share) Dividends, Common Stock, Cash Cash dividend declared Domestic Country [Member] Federal Domestic Plan [Member] Domestic Plan Due from Affiliates Receivable from affiliates Due to Affiliate Payable to affiliates 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 Earnings Per Share Earnings per share Net income per share (Note 18) Earnings Per Share, Basic Earnings per share - Basic Basic Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Net Income Per Share Earnings Per Share, Diluted Earnings per share - Diluted Diluted Earnings Per Share, Policy [Policy Text Block] Earnings Per Share Net Income Per Share Earnings Per Share [Text Block] Earnings Per Share Net Income Per Share Effective Income Tax Rate Reconciliation, Percent Effective tax rate Effective tax rate Effective Income Tax Rate Reconciliation, Percent [Abstract] Reconciliation of the statutory tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Federal statutory income tax rate U.S. federal tax at statutory rate Effective Income Tax Rate Reconciliation, Equity in Earnings (Losses) of Unconsolidated Subsidiary, Percent LLC flow-through structure Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent Foreign taxes Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent State and local taxes - net of federal benefit 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 Employee-related Liabilities Accrued compensation Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Total unrecognized compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Weighted average recognition period Employee Stock Option [Member] Options Stock Options Equity Component [Domain] Equity Component [Domain] Equity Unit Purchase Agreements [Member] Contingent consideration Excess Capital Excess Regulatory Capital Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value of Financial Instruments Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Schedule of fair value measurements Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value of Financial Instruments Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Schedule of inputs in the valuation Fair Value Hierarchy and NAV [Axis] Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Fair Value of Financial Instruments Fair Value Inputs Level1 [Member] Level 1 Fair Value Inputs Level3 [Member] Level 3 Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Schedule of fair value measurements Fair Value Measurement, Policy [Policy Text Block] Fair Value Measurement Fair Value Measurements Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Federal Funds Effective Swap Rate [Member] Federal funds Financial Service Other [Member] Other Finite-Lived Intangible Assets, Accumulated Amortization Accumulated Amortization Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2019 Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year Remainder of 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Five 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2020 Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] Estimated annual future amortization for existing intangibles assets Finite-Lived Intangible Assets, Gross Cost Finite-Lived Intangible Assets [Line Items] Intangible assets that are subject to amortization Intangible Assets Finite Lived Intangible Assets Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Net Net Carrying Amount Finite-Lived Intangible Asset, Useful Life Useful life of intangible assets Amortization Period Fixed Price Contract [Member] Fixed Foreign Currency Transactions and Translations Policy [Policy Text Block] Translation of Foreign Currency Foreign Plan [Member] Foreign Plan Furniture And Fixtures [Member] Furniture Goodwill Goodwill Goodwill Intangible Assets and Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Intangible Assets and Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Goodwill Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] Intangible Assets Goodwill [Line Items] Goodwill Guarantor Obligations [Line Items] Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income before taxes Consolidated Statements of Income Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Income Taxes Income Tax Disclosure [Text Block] Income Taxes Income Taxes Paid Income taxes paid Income Tax Examination, Penalties and Interest Accrued Tax, penalties and interest provision Income Tax Examination, Penalties and Interest Expense Tax, penalties and interest expense Income Tax Expense (Benefit) Provision for income taxes Total Income Tax, Policy [Policy Text Block] Income Tax Increase (Decrease) Due from Affiliates Receivable from affiliates Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable, accrued expenses and other liabilities Increase (Decrease) in Accounts Receivable Accounts receivable Increase (Decrease) in Receivables from Brokers-Dealers and Clearing Organizations Receivable from brokers and dealers and clearing organizations Increase (Decrease) in Deferred Revenue Deferred revenue Increase (Decrease) in Deposit Assets Deposits with clearing organizations Increase (Decrease) in Due to Affiliates Payable to affiliates Increase (Decrease) in Employee Related Liabilities Accrued compensation Increase (Decrease) in Operating Assets [Abstract] (Increase) decrease in operating assets: Increase (Decrease) in Operating Liabilities [Abstract] Increase (decrease) in operating liabilities: Increase (Decrease) in Other Operating Assets Other assets Increase (Decrease) in Payables to Broker-Dealers and Clearing Organizations Payable to brokers and dealers and clearing organizations Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Temporary Equity [Roll Forward] Activity of the Employee Shares Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Dilutive effect Dilutive effect of equity settled PRSUs Indefinite-lived Intangible Assets [Axis] Indefinite-lived Intangible Assets [Line Items] Intangible assets with indefinite useful lives Indefinite-lived Intangible Assets (Excluding Goodwill) Intangible assets which have an indefinite useful life Indefinite Lived Intangible Assets Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indemnification Guarantee [Member] Guaranteed by Refinitiv Intangible Assets, Net (Excluding Goodwill) Intangible assets, net of accumulated amortization Interest Expense, Debt Debt interest expense Interest Expense, Related Party Interest expense from related parties Interest Income, Operating Interest income Interest Income, Related Party Interest income from money market funds invested and savings deposited Interest income from related parties Interest Income, Securities, Operating, by Taxable Status [Abstract] Operating Income Interest Paid, Excluding Capitalized Interest, Operating Activities Interest paid Internal Use Software, Policy [Policy Text Block] Software Development Costs Investment Income, Interest Net interest income 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 I P O [Member] Initial Public Offering Labor and Related Expense Employee compensation and benefits Lease, Cost [Abstract] Activity related to the Company's leases Lease, Cost [Table Text Block] Activity related to the company's leases Leasehold Improvements [Member] Leasehold improvements Lease, Practical Expedients, Package [true false] Package of practical expedients Leases Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Table] Lessee, Operating Lease, Liability, Maturity [Table Text Block] Schedule of maturity of lease liabilities and future minimum lease payments Lessee, Operating Lease, Liability, Payments, Due Total future minimum lease payments Lessee, Operating Lease, Liability, Payments, Due after Year Five Thereafter Lessee, Operating Lease, Liability, Payments, Due Year Five 2023 Lessee, Operating Lease, Liability, Payments, Due Year Four 2022 Lessee, Operating Lease, Liability, Payments, Due Year Three 2021 Lessee, Operating Lease, Liability, Payments, Due Year Two 2020 Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year Remainder of 2019 Lessee, Operating Lease, Liability, Undiscounted Excess Amount Less imputed interest Lessee, Operating Leases [Text Block] Leases Lessee, Operating Lease, Term of Contract Initial term of lease Letter Of Credit [Member] Letter of credit Letters of Credit Outstanding, Amount Letter of credit guaranteed by Refinitiv Liabilities Total liabilities Liabilities [Abstract] Liabilities Liabilities and Equity Total liabilities and stockholders' equity/members' capital Liabilities and Equity [Abstract] Liabilities and Stockholders' Equity/Members' Capital Liabilities and Members' Capital Liabilities Assumed Establishment of liabilities under tax receivable agreement Financial and Nonfinancial Liabilities, Fair Value Disclosure Total Liabilities, at fair value License [Member] Licenses Consolidated Statements of Changes in Equity Limited Liability Company (LLC) Members' Equity, Unit-based Compensation Stock-based compensation Conversion of certain cash-settled PRSUs to equity settled PRSUs Long-term Line of Credit Amount outstanding Line of Credit Facility, Commitment Fee Percentage Commitment fee (as a percent) Line of Credit Facility, Maximum Borrowing Capacity Maximum borrowing capacity Line of credit, maximum borrowing capacity London Interbank Offered Rate L I B O R [Member] LIBOR Long-term Debt, Type [Axis] Longterm Debt Type [Domain] Long-term Debt, Type [Domain] Loss Contingencies [Line Items] Commitments and Contingencies Loss Contingencies [Table] Loss Contingency, Damages Sought, Value Damages sought Measurement Input Default Rate [Member] Discount rate Measurement Input Price Volatility [Member] Standard deviation Measurement Input Revenue Multiple [Member] Revenue multiple Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] Media Content [Member] Content and data Members' Capital Members' capital Members' Equity Members' capital end of period Members' capital beginning of period Members' equity Total members' capital Members' Equity [Abstract] Stockholders' Equity/Members' Capital Members' capital Member Units [Member] Members' Capital Minimum Financial Requirements for Futures Commission Merchants under Commodity Exchange Act [Table Text Block] Schedule of financial resources and liquid financial resources Stockholders' Equity Attributable to Noncontrolling Interest Non-controlling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Distributions to non-controlling interests Noncontrolling Interest Disclosure [Text Block] Non-Controlling Interests Noncontrolling Interest [Line Items] Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Ownership percentage, Continuing LLC Owners Number of LLC Interests held by non-controlling interest holders Noncontrolling Interest, Ownership Percentage by Parent Ownership interest Number of LLC Interests held by Tradeweb Markets Inc Noncontrolling Interest [Table] Money Market Funds [Member] Money market funds Movement in Deferred Revenue [Roll Forward] Changes in deferred revenue Net Capital Excess (Shortage) under Commodity Exchange Act Excess Financial Resources Net Capital under Commodity Exchange Act Computation Financial Resources Net Cash Provided by (Used in) Financing Activities Net cash (used in) financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities Net Cash Provided by (Used in) Investing Activities Net cash (used in) investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from investing activities Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities Net Income (Loss) Attributable to Parent Net income attributable to Tradeweb Markets Net income attributable to Tradeweb Markets Inc. Post-IPO net income attributable to Tradeweb Markets Inc. Net Income (Loss) Attributable to Parent [Abstract] Numerator: Net Income (Loss) Attributable to Noncontrolling Interest Net income attributable to non-controlling interests Less: Net income attributable to non-controlling interests New Accounting Pronouncements, Policy [Policy Text Block] Recent Accounting Pronouncements Noncash Investing and Financing Items [Abstract] Non-cash financing activities - tems arising from the reorganization transactions and IPO Non-Controlling Interests Noncontrolling Interest [Member] Non-Controlling Interests Long-Lived Assets Long-lived assets Non Us [Member] International Occupancy, Net Occupancy 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 Office Equipment [Member] Office equipment Operating Expenses [Abstract] Expenses Operating Income (Loss) Operating income Operating income Operating Lease, Cost Operating lease expense Operating Leased Assets [Line Items] Commitments and Contingencies Maturity of lease liabilities Operating Lease, Liability Lease liability Operating Lease, Payments Cash for amounts included in the measurement of operating liability Operating Lease, Right-of-Use Asset Right-of-use assets Operating Leases, Future Minimum Payments Due Total Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Future minimum rental payments Operating Leases, Future Minimum Payments Due, Next Twelve Months 2019 Operating Leases, Future Minimum Payments, Due in Five Years 2023 Operating Leases, Future Minimum Payments, Due in Four Years 2022 Operating Leases, Future Minimum Payments, Due in Three Years 2021 Operating Leases, Future Minimum Payments, Due in Two Years 2020 Operating Leases, Future Minimum Payments, Due Thereafter Thereafter Operating Leases, Rent Expense, Net Rent expense Operating Lease, Weighted Average Discount Rate, Percent Weighted average borrowing rate Operating Lease, Weighted Average Remaining Lease Term Weighted average remaining lease term (years) Operating Loss Carryforwards Net operating loss carryforwards Organization Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Organization Other assets including other assets from related parties of $9 and $27 at December 31, 2018 and December 31, 2017, respectively Other Assets Other assets Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest Foreign currency translation adjustments attributable to noncontrolling interests Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Foreign currency translation adjustments attributable to non-controlling interests Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Foreign currency translation adjustments Other General and Administrative Expense General and administrative 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 Over Allotment Option [Member] Underwriters option Payable to brokers and dealers and clearing organizations including payables to related parties of $2,404 at December 31, 2018 Payables to Broker-Dealers and Clearing Organizations Payable to brokers and dealers and clearing organizations Payments for (Proceeds from) Businesses and Interest in Affiliates Business acquisitions Payments for Repurchase of Redeemable Noncontrolling Interest Purchase of LLC Interests Payments for Software Capitalized software development costs Payments of Capital Distribution Pre-IPO capital distributions Mezzanine capital distributions Payments of Dividends Capital distributions Payments of Ordinary Dividends Dividends Payments of Stock Issuance Costs Offering costs from issuance of Class A common stock in the IPO Payments to Acquire Investments Purchase of investments Payments to Acquire Property, Plant, and Equipment Purchase of furniture, equipment, software and leasehold improvements Pension and Other Postretirement Benefits Disclosure [Text Block] Employee Savings Plan Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Predecessor [Member] Predecessor Preferred Stock, Par or Stated Value Per Share Preferred stock, par value Preferred Stock, Shares Authorized Preferred stock, shares authorized Preferred Stock, Shares Issued Preferred stock, shares issued Preferred Stock, Shares Outstanding Preferred stock, shares outstanding Proceeds from Contributed Capital Capital contribution Mezzanine capital contributions Proceeds from Issuance Initial Public Offering Net proceeds Proceeds from Issuance of Common Stock Proceeds from issuance of common stock in the IPO, net of underwriting discounts Proceeds from issuance of Class A common stock in the IPO, net of underwriting discounts Proceeds from Issuance or Sale of Equity Investment by employees Professional Fees Professional fees Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Net income Furniture, Equipment, Purchased Software and Leasehold Improvements Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment Disclosure [Text Block] Furniture, Equipment, Purchased Software and Leasehold Improvements Property, Plant and Equipment, Gross Gross amount Property, Plant and Equipment [Line Items] Furniture, Equipment, Purchased Software and Leasehold Improvements Furniture, equipment, purchased software and leasehold improvements, net of accumulated depreciation and amortization Property, Plant and Equipment, Net Furniture, equipment, purchased software and leasehold improvements, net of accumulated depreciation and amortization Property, Plant and Equipment, Policy [Policy Text Block] Furniture, Equipment, Purchased Software and Leasehold Improvements Property, Plant and Equipment [Table Text Block] Components of furniture, equipment, purchased software and leasehold improvements. Property Plant And Equipment Type [Domain] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Useful Life Receivables from Brokers-Dealers and Clearing Organizations Receivable from brokers and dealers and clearing organizations Receivable from brokers and dealers and clearing organizations including receivables from related parties of $3,332 at December 31, 2018 Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block] Allowance for Doubtful Accounts Regulatory Capital Requirements Related Party [Domain] Related Party [Domain] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Related Party Transaction, Expenses from Transactions with Related Party Related party expense Related Party Transaction [Line Items] Related Party Transactions Related Party Transactions Related Party [Axis] Related Party Transactions Disclosure [Text Block] Related Party Transactions Required Net Capital under Commodity Exchange Act Required Financial Resources Research, Development, and Computer Software Disclosure [Text Block] Software Development Cost Restricted Assets Disclosure [Text Block] Restricted Cash Restricted Cash. Restricted cash Restricted Cash And Cash Equivalents Cash And Cash Equivalents [Member] Cash and Cash Equivalents [Domain] Restricted Cash Retained Earnings (Accumulated Deficit) Retained earnings Retained Earnings [Member] Retained Earnings Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location [Domain] Retirement Plan Sponsor Location [Domain] Revenue from Contract with Customer, Excluding Assessed Tax Gross revenues Gross revenue Revenue from Contract with Customer [Policy Text Block] Revenue Recognition Revenue from Related Parties Related party revenue Revenue from related parties Revenues Net revenue Net revenue Revenue Revenues [Abstract] Revenues Revenues from External Customers and Long-Lived Assets [Line Items] Business Segment and Geographic Information Revolving Credit Facility [Member] Revolving credit facility Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Right of use assets obtained in exchange for operating liabilities Credit Risk Sale Of Stock Name Of Transaction [Domain] Sale of Stock [Domain] Scenario Plan [Member] Planned event, contingent on closing of IPO Scenario Unspecified [Domain] Scenario, Unspecified [Domain] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table Text Block] Allocation applying pushdown accounting Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Components of provision for income taxes Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Components of deferred tax assets (Liabilities) Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of basic and Diluted earnings per share Net Income Per Share Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Reconciliation of the statutory tax rate Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Estimated annual future amortization for existing intangible assets Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table Text Block] Intangible assets that are subject to amortization Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of future minimum rental payments Schedule of Goodwill [Table] Schedule of Goodwill [Table Text Block] Summary of goodwill Schedule of Guarantor Obligations [Table] Schedule of Indefinite-Lived Intangible Assets [Table] Schedule of Indefinite-Lived Intangible Assets [Table Text Block] Summary of intangible assets which have an indefinite useful life Schedule of Nonvested Performance-based Units Activity [Table Text Block] Schedule of equity-settled PRSUs issued Schedule of Operating Leased Assets [Table] Property, Plant and Equipment [Table] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions [Table Text Block] Schedule of balances from transactions with affiliates included in the consolidated statements Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Schedule of revenue and long-lived assets by geographic location Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of information regarding revenue by client sector Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation, Stock Appreciation Rights Award Activity [Table Text Block] Schedule of activity for SARs issued Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of options issued Schedule of activity for options issued Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Schedule of significant assumptions used to estimate the fair value of the options Schedule of Stock by Class [Table] Schedule of Stock by Class [Table Text Block] Schedule of class of common stock par value, votes and economic rights Schedule of issued and vested shares Schedule of Unrecognized Compensation Cost, Nonvested Awards [Table Text Block] Schedule of unrecognized compensation expense Schedule of unrecognized compensation cost Business Segment and Geographic Information Segment Reporting Disclosure [Text Block] Business Segment and Geographic Information Segment Reporting Information [Line Items] Business Segment and Geographic Information Series Of Individually Immaterial Business Acquisitions [Member] Other Share-based Compensation Share-based compensation expense Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Forfeited Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Forfeited Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Outstanding, end of period Outstanding, beginning of period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Number of PRSUs Number of SARS Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Weighted-average grant date fair value per unit, PRSUs Outstanding, end of period Outstanding, beginning of period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted Average Fair Value of PRSUs Weighted Average Exercise Price of SARs Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Exercised Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Exercised Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Assumption used in the Black-Scholes model Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Weighted Average Expected Dividend Yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Weighted Average Expected Life (years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Weighted Average Expected Volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Weighted Average Risk Free Interest Rate Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-Based Compensation Plans Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Additional disclosures Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Weighted Average Remaining Contractual Life (years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Granted Share-based Compensation Arrangement by Share-based Payment Award, Option, Nonvested, Weighted Average Exercise Price Weighted-average fair value per unit, options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Intrinsic value, options outstanding, end of period Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Outstanding, end of period Outstanding, beginning of period Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Number of Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Outstanding, end of period Outstanding, beginning of period Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Weighted Average Grant Date Fair Value of Options Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Number of Employees Affected Number of employees impacted by modification Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Equity Award [Domain] Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Granted Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Share-Based Compensation Share Price Share Price Share Price (per share) Shares, Outstanding Equity at end of period (in shares) Equity at beginning of period ( in shares) Significant Accounting Policies [Text Block] Significant Accounting Policies SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Software Development [Member] Software Development Costs Special Mention [Member] Special Mention Class of Stock [Axis] Equity Components [Axis] Statement [Line Items] Statement Consolidated Statements of Cash Flows Consolidated Statements of Financial Condition Scenario [Axis] Statement [Table] Stock Appreciation Rights S A R S [Member] SARs Stockholders' Equity Attributable to Parent Total stockholders' equity attributable to Tradeweb Markets Inc./members' equity Stockholders' Equity Attributable to Parent [Abstract] Stockholders' Equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total equity Equity at end of period Equity at beginning of period Stockholder's Equity Stockholders' Equity Note Disclosure [Text Block] Shares Stockholders' Equity Stock Issued During Period, Shares, Acquisitions Shares issued to acquire TWM LLC Stock Issued During Period, Shares, New Issues Issuance of common stock, net of offering costs and cancellations (in shares) Shares issued Stock Issued During Period, Value, Acquisitions Vesting of contingent consideration Vesting of contingent consideration to Class P-1(A) Shares Stock Issued During Period, Value, New Issues Issuance of common stock, net of offering costs and cancellations Subsequent Event [Line Items] Subsequent Events Subsequent Event [Member] Subsequent Event Subsequent Events Subsequent Events [Text Block] Subsequent Events SUBSEQUENT EVENTS Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Sale of Stock [Axis] Subsidiary, Sale of Stock [Line Items] Supplemental Cash Flow Information [Abstract] Supplemental disclosure of cash flow information Tax Period [Axis] Tax Period [Domain] Tax Period [Domain] Temporary Equity [Abstract] Mezzanine Capital Temporary Equity, Carrying Amount, Attributable to Parent Class C Shares and Class P(C) Shares Temporary Equity, Shares Outstanding Classes shares outstanding Outstanding, end of period Outstanding, beginning of period Number of Vested Shares Issued Trade Names [Member] Tradenames Type Of Adoption [Member] Type of Adoption [Domain] Type of Arrangement and Non-arrangement Transactions [Axis] Underlying Asset Class [Axis] Underlying Asset Class [Domain] Underlying Asset Class [Domain] Use of Estimates, Policy [Policy Text Block] Use of Estimates Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Weighted Average Number of Shares Outstanding, Diluted Diluted Weighted average outstanding - Diluted Weighted Average Number of Shares Issued, Basic Basic weighted average shares outstanding Weighted Average Number of Shares Outstanding, Basic Weighted average outstanding - Basic Basic Weighted Average Number of Shares Outstanding, Basic [Abstract] Denominator: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Weighted average interests outstanding Weighted average number of shares outstanding U [S] U.S. Amendment Flag Document Period End Date Document Type Entities [Table] Entity Central Index Key Entity [Domain] Entity [Domain] Entity Emerging Growth Company Entity Ex Transition Period Entity Information [Line Items] Entity Registrant Name Legal Entity [Axis] Account receivable excluding receivable from brokers and dealers and clearing organizations, net of allowance Account receivable, net of allowance Account receivable excluding receivable from brokers and dealers and clearing organizations, net of allowance. Accounts Payable Accrued Expenses And Other Liabilities [Member] Accounts payable, accrued expenses and other liabilities Represents the information pertaining to accounts payable, accrued expenses and other liabilities. Adjusted For Refinitiv Transaction [Member] Successor Reflects a new basis of accounting resulting from the Refinitiv transaction. Adjustments to Additional Paid in Capital Tax Receivable Agreement Liability and Deferred Taxes Reorganization Transaction and IPO Tax receivable agreement liability and deferred taxes arising from the reorganization transactions and IPO Amount of decrease to additional paid in capital (APIC) resulting from tax receivable agreement liability and deferred taxes arising from the reorganization transactions and IPO. Amortization Period Pushdown Accounting Adjustment Amortization of pushdown accounting allocation Amortization period for pushdown accounting adjustments. Antitrust Actions Related To Trading Practices And Interest Rate Swaps [Member] Antitrust Actions Related To Trading Practices and Interest Rate Swaps Represents information pertaining to litigation of antitrust actions related to trading practices in United States Treasury securities auctions, and separately, interest rate swaps. Antitrust Actions Related To Trading Practices [Member] Antitrust Actions Related To Trading Practices NA. Banks [Member] Banks Group of investment and commercial banks that own a minority interest in the reporting entity. Bond Desk Group L L C And Subsidiaries [Member] BondDesk The acquisition of assets of Bond Desk Group LLC and subsidiaries ("BondDesk") on November 1, 2013. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Accounts Payable Accrued Expenses And Other Liabilities Accounts payable, accrued expenses and other liabilities Amount of accounts payable, accrued expenses and other liabilities at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Deposits With Clearing Organizations Deposits with clearing organizations Amount of deposits with clearing organizations at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Due To Affiliate Payable to affiliates Amount due to affiliates at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Employee Equity Compensation Payable Employee equity compensation payable Amount of accounts payable, accrued expenses and other liabilities at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Employee-Related Liabilities Accrued compensation Amount of accrued compensation at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Leasehold Interests Leasehold interests Amount of leasehold interests at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Receivables From Affiliates Receivables from affiliates Amount of receivables from affiliates at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Receivables From Brokers Dealers And Clearing Organizations Receivable from brokers and dealers and clearing organizations Amount of receivables from brokers and dealers and clearing organizations at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Restricted Cash Restricted cash Amount of restricted cash acquired at the acquisition date. Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Software Development Costs Software development costs Fair value assigned to software development costs as a result of the Refinitiv Transaction Amount of software development costs at the acquisition date. Capital Contributions From Related Parties [Member] Capital contribution Represents information pertaining to capital contributions from related parties. Cash deposited with related parties Cash And Cash Equivalents Related Parties Cash and cash equivalents Cash deposited with related parties, included with cash and cash equivalents. Commissions Revenue Commissions Revenue [Member] Commissions Commission revenue from electronic and voice brokerage services on a riskless principal basis recorded on a trade-date basis. Common Class C And Or Class D [Member] Class C and/or D common stock The aggregation of Common Class C and or Common Class D stock, representing ownership interest in a corporation. Common Class D [Member] Class D common stock Classification of common stock that has different rights than provided to other classes of common stock, representing interest in a corporation. Common Class P1a Shares [Member] Class P-1(A) Shares Class P-1(A) shares. Common Class P1c Shares [Member] Class P-1(C) Shares Class P-1(C) shares. Common Class Pa Shares [Member] Class P(A) Shares Class P(A) shares. Common Class Pc Shares [Member] Class P(C) Shares Class P(C) shares. Common Stock Cancellation Ratio Cancellation ratio Represents the ratio for cancellation of common stock. Common Stock Conversion Ratio Conversion ratio Represents the ratio for conversion of common stock. Common Stock, Shares, Retired Number of shares canceled Number of shares of common stock canceled during the period. Common Unit Exchanged Number Common units exchanged The number of common units exchanged. Communications And Information Technology Related Parties Technology and communications from related parties Information technology and communication expenses from related parties. Contingent Consideration, Liability, Due to Related Parties Contingent consideration payable to related parties Contingent consideration payable Amount of liability recognized arising from contingent consideration due to related parties. Contingent Consideration, Liability, Due to Related Parties, Measurement Input Contingent consideration, measurement input Value of input used to measure contingent consideration liability due to related parties. Contingent consideration to related parties Contingent Consideration Related Parties Contingent consideration Contingent consideration recognized Contingent consideration to related parties. Continuing L L C Owners [Member] Continuing LLC Owners Represents information pertaining to Continuing LLC Owners. Contract With Customer Liability, New Billings New billings Amount of deferred revenue recognized for new billing arising during the current reporting period. Deferred revenues from related parties Contract with Customer, Liability, Related Parties Deferred revenue Amount of obligation to transfer good or service to related parties for which consideration has been received or is receivable. Contract With Customer Liability [Text Block] Deferred Revenue The entire disclosure about the contract with customer liability. Conversion of Awards, Awards Converted Converted to equity settled PRSUs The number of awards converted in a noncash transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. Conversion of Awards, Awards Issued Converted to equity settled PRSUs The number of new awards issued in the modification of the share-based incentive plan. Dealerweb [Member] DW Dealerweb Inc. (DW) is a registered broker-dealer under the Securities Exchange Act of 1934, a member of the Financial Industry Regulatory Authority, a registered independent introducing broker with the Commodities Future Trading Commission and a member of the National Futures Association. Debt Instrument Floor Rate Floor (as a percent) The Percentage of floor rate under debt instrument. Debt Instrument, Variable Rate Adjustment Variable rate additional adjustment Percentage points adjustment to the variable rate of the debt instrument. Deposits from related parties Deposits Related Parties Deposits with clearing organizations Deposits from related parties, included with deposits with clearing organizations. Deposits With Clearing Organizations [Text Block] Deposits with Clearing Organizations The entire disclosure of deposits with clearing organizations. Document and Entity Information Dw Sef Llc [Member] DW SEF DW SEF LLC (DW SEF) is a swap execution facility regulated by the Commodities Future Trading Commission. Effective Income Tax Rate Reconciliation, Tax Cuts And Jobs Act Of 2017, Percent Tax Cuts and Jobs Act provisional tax charge Percentage of reported income tax expense (benefit) in excess of (less than) expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to increase (decrease) in income tax rate and transition tax on accumulated earnings of controlled foreign corporation deemed repatriated pursuant to Tax Cuts and Jobs Act of 2017. Effect of Reorganization Transactions Effect of the reorganization transactions Represents the effect of reorganization transasctions. Employees [Member] Employees Employees of the reporting entity that invested in the company. Equity Compensation Payable Employee equity compensation payable Equity compensation payable to employees. Equity Settled Performance Based Restricted Stock Units [Member] PRSU Equity Settled Performance Based Restricted Stock Units [Member] Excess Liquid Financial Assets Excess Liquid Financial Assets The amount by which actual liquid financial assets exceeds (does not exceed) required liquid financial assets under the Commodity Exchange Act Excess Regulatory Capital Excess Regulatory Capital Amount by which the entity's regulatory capital (as defined) exceeds the requirement. Fixed Income Business [Member] Fixed Income Business Represents information pertaining to relationships with customers with fixed pricing agreements. Furniture And Office Equipment [Member] Furniture and office equipment Furniture and office equipment Furniture Equipment And Purchased Software [Member] Furniture, Equipment, Purchased Software and Leasehold Improvements Furniture, equipment and purchased software. Furniture Equipment Purchased Software And Leasehold Improvements [Member] Furniture, equipment, purchased software and leasehold improvements Furniture, equipment, purchased software and leasehold improvements. General And Administrative Expense Related Parties General and administrative from related parties General and administrative expense from related parties. Income Taxes Income Tax Disclosure [Line Items] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Income Tax Disclosure [Table] Disclosure of information pertaining to income taxes. Increase Decrease In Equity Compensation Payable Employee equity compensation payable The increase (decrease) during the period in equity compensation payable. Institutional Client Sector [Member] Institutional The institutional client sector. Limited Liability Company Agreement Recapitalization [Member] Recapitalization Represents information pertaining to the Company's limited liability company agreement ("LLC Agreement") amended and restated o April 4, 2019. Limited Liability Company Contributions Capital contributions Conversion of convertible term note payable to Thomson Reuters to Class A Shares Total contributions made by members of a limited liability company. Liquid Financial Assets Liquid Financial Assets Liquid financial assets calculated under the Commodity Exchange Act. Liquidity Contracts [Member] Liquidity contracts Represents information pertaining to liquidity contracts. Litigation Relating To Distribution Of Financial Strength Ratings [Member] Litigation relating to distribution of financial strength ratings Litigation relating to distribution of financial strength ratings Llc Interests [Member] LLC Interests Information pertaining to LLC Interests. Local Jurisdiction [Member] New York City Designated tax department of a local government entitled to levy and collect income taxes from the entity. Loss Contingency Number Of Actions Number of actions The number of actions related to this loss contingency. Market Data Client Sector [Member] Market Data The market data client sector. Market Data License Agreements [Member] Market Data License Agreements Market data license agreement in which the reporting entity earns license fees or royalties for market data feeds from the counterparty. Refinitiv Market Data Fees Market Data Revenue [Member] Refinitiv market data fees Market data revenue earned from the sale of market data to Refinitiv, which redistributes the data. Includes real-time market data fees and historical data sets. Merger Transaction [Member] Merger The merger in 2010 of the Company with Tradeweb NewMarkets LLC ("NewMarkets"), which was a company owned by the Banks and Thomson Reuters. Minority Interest Increase From Allocation of Equity Allocation of equity to non-controlling interests Amount of increase in noncontrolling interest from allocation of equity to noncontrolling interest holders. Minority interest Number Of Interests Held By Noncontrolling Owners Number of LLC Interests held by non-controlling interest Number of LLC Interest The equity interest of noncontrolling shareholders. Minority Interest Number Of Interests Held By Parent Number of LLC Interests held by Tradeweb Markets Inc Number of LLC Interest held by parent The parent entity's interest in the subsidiary. Minority Interest Total Number Of Interests Total LLC Interests outstanding The total number of shares of the subsidiary. Minority Interest Total Ownership Percentage Total LLC Interests outstanding The total ownership interest on noncontrolling interest expressed as a percentage. Net Income Attributable To Parent And Transfers (To) From Noncontrolling Interest Change from net income attributable to Tradeweb Markets Inc. and transfers (to) from non-controlling interest The amount of net income (loss) attributable to parent and transfers (to) from noncontrolling interests. Net Income (Loss) Attributable To Limited Liability Company Pre-IPO net income attributable to Tradeweb Markets LLC Less: Pre-IPO net income attributable to Tradeweb Markets LLC The amount of net income (loss) attributable to limited liability company. Net Income (Loss) Including Portion Attributable To Non Controlling Interest Net Of Tax Post-IPO net income attributable to Tradeweb Markets Inc. and non-controlling interests The amount of net income (loss) attributable to non-controlling interest adjusted for corporate tax. Noncontrolling Interest, Conversion Ratio Conversion ratio The conversion ratio of shares of non-controlling interests. Number of votes per common stock Number Of Votes Per Common Stock Number Of votes per common stock. Occupancy Related Parties Occupancy from related parties Occupancy expense from related parties. One Month London Inter Bank Offered Rate [Member] One-month LIBOR One Month London Inter Bank Offered Rate. Operating Expense Reimbursement [Member] Operating Expense Reimbursement Operating expense reimbursement arrangement in which the reporting entity reimburses affiliates of the counterparty for various services including salaries and bonuses, marketing, professional fees, communications, data costs and certain other administrative services. Operating Leases, Future Minimum Lease Payments, Remainder of Fiscal Year Remainder of 2019 Amount of required payments for operating leases in excess of one year due in the remainder of the fiscal year following the latest fiscal year. Operating Leases, Future Minimum Payments [Abstract] future minimum lease payments n/a Operating Leases, Future Minimum Payments, After Year Five Thereafter Amount of required payments for operating leases in excess of one year due after the fifth fiscal year following the latest fiscal year. Operating Leases, Future Minimum Payments, Year Five 2023 Amount of required payments for operating leases in excess of one year due in the fifth fiscal year following the latest fiscal year. Operating Leases, Future Minimum Payments, Year Four 2022 Amount of required payments for operating leases in excess of one year due in the fourth fiscal year following the latest fiscal year. Operating Leases, Future Minimum Payments, Year Three 2021 Amount of required payments for operating leases in excess of one year due in the third fiscal year following the latest fiscal year. Operating Leases, Future Minimum Payments, Year Two 2020 Amount of required payments for operating leases in excess of one year due in the second fiscal year following the latest fiscal year. Option Plan [Member] Option Plan Represents information pertaining to the Option Plan. Other assets from related parties Other Assets Related Parties Other assets Other assets from related parties. Other Customer [Member] Other Customer classified as other. Payables to related parties, brokers, dealers and clearing organizations Payables To Broker Dealers And Clearing Organizations Related Parties Payable to brokers and dealers and clearing organizations Payables to related parties, included with payables to brokers, dealers and clearing organizations. Payments Of Capital Distribution To Noncontrolling Interest Capital distributions to non-controlling interests Amount of cash outflow in the form of capital distribution to noncontrolling interests. Percentage of Combined Voting Power of Common Stock Percentage of combined voting power The percentage of combined voting power of common stock. Percentage of Economic Interest Percentage of economic interest The percentage of economic interest. Percentage of Economic Interest in Limited Liability Company Percentage of economic interest The percentage of economic interest in limited liability company. Performance Shares Settled With Cash [Member] Cash-settled PRSUs Performance restricted share units settled with cash. Performance Shares Settled With Equity [Member] Equity-settled PRSUs Performance restricted share units settled with equity. Potential Dilutive Securities [Member] Potential Dilutive Potential dilutive securities. Profit Loss After Pre IPO Net income attributable to Tradeweb Markets Inc. and non-controlling interests Represents the amount of profit loss after pre-IPO. Provision For Income Taxes [Member] Provision for income taxes Primary financial statement caption encompassing provision for income taxes. Purchased Software [Member] Purchased software Purchased software applications. Pushdown Accounting No definition available. Pushdown Accounting [Text Block] Pushdown Accounting The entire disclosure for reporting pushdown accounting. Raff Cap Business [Member] RaffCap The acquisition of assets of the RaffCap business on October 7, 2011. Recapitalization [Policy Text Block] Recapitalization Disclosure of accounting policy for the recapitalization in the preparation of financial statements in conformity with generally accepted accounting principles. Receivables from related parties Receivables From Brokers Dealers And Clearing Organizations Related Parties Receivables from brokers and dealers and clearing organizations Receivables from related parties, included with receivables from brokers, dealers and clearing organizations. Refinitiv Direct Owner [Member] Refinitiv Direct Owner [Member] Represents information pertaining to Refinitiv Direct Owner. Refinitiv Llc Owner [Member] Refinitiv LLC Owner [Member] Represents information pertaining to Refinitiv LLC Owner. Refinitiv [Member] Refinitiv Refinitiv, formerly the Thomson Reuters Financial & Risk Business. This entity owns a majority interest in the reporting entity, but is accounted for using pushdown accounting. Regulatory Capital Regulatory Capital Regulatory capital as calculated for each entity under applicable regulations. Regulatory Capital Requirement Regulatory Capital Requirement Amount of regulatory capital required to be maintained for each entity under applicable regulations. Regulatory Capital Requirements [Text Block] Regulatory Capital Requirements The entire disclosure of capital requirements and required financial resources under applicable regulations. Required Liquid Financial Assets Required Liquid Financial Assets Amount of liquid financial assets required to be maintained under the Commodity Exchange Act. Retail Client Sector [Member] Retail The retail client sector. Schedule Of Capitalized Computer Software [Table Text Block] Components of software development costs Tabular disclosure of the components of capitalized computer software. Schedule Of Cash Settled Performance Based Units Activity [Table Text Block] Schedule of cash-settled PRSUs issued Tabular disclosure of activity for cash-settled performance-based restricted stock units (PRSUs) issued by the reporting entity. Schedule of Common Units Outstanding [Table Text Block] Schedule of common units outstanding Tabular disclosure of common units outstanding. ScheduleOfEmployee Shares Classified As Mezzanine Capital [Table Text Block] Schedule of Employee Shares Tabular disclosure of employee shares which are classified as mezzanine capital due to the right of employees to sell the shares back to the reporting entity upon termination of employment. Schedule Of Impact On Equity Due To Changes In The Company'S Ownership Interest In Noncontrolling Interest [Table Text Block] Summary of the impact on equity due to changes in the Company's ownership interest in noncontrolling interest Tabular disclosure of impact on equity due to changes in the Company's ownership interest in noncontrolling interest. Schedule Of Ownership Interest In Noncontrolling Interest [Table Text Block] Summary of the ownership interest in noncontrolling interest Tabular disclosure of ownership interest in noncontrolling interest. Schedule Of Regulatory Capital Requirements [Table Text Block]` Schedule of regulatory capital requirements Tabular disclosure of the regulatory capital requirements and regulatory capital for entities subject to regulation. Schedule Of Related Party Transactions Affiliates [Table Text Block] Schedule of affiliates were included in the consolidated statements of income Schedule Of Related Party Transactions Affiliates. Secured Operating Lease [Member] US lease secured by letter of credit Lease secured by letter of credit Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Converted, Weighted Average Grant Date Fair Value Converted to equity settled PRSUs The weighted average fair value at conversion date for nonvested equity-based awards converted during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Issued Upon Conversion, Weighted Average Grant Date Fair Value Converted to equity settled PRSUs The weighted average fair value at issue date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Share Based Compensation Arrangement By Share Based Payment, Award Options Vested In Period Total Fair Value Total fair value of vested options Represents the total fair value of options vested during the reporting period. Share Based Compensation Arrangements By Share Based Payment Award Exercise Period Following Change In Control Exercise period following a change in control Share Based Compensation Arrangements By Share Based Payment Award Exercise Period Following Change In Control Shared Services Agreement [Member] Shared Services Shared services agreement in which the counterparty provides the reporting entity with certain real estate, payroll, benefits administration, insurance, content, financial reporting and tax support. Software Development Costs [Abstract] Software Development Cost n/a State Jurisdiction [Member] New York state Designated tax department of a state government entitled to levy and collect income taxes from the entity. Stock Compensation Expense Allocation Term Allocation term The Stock compensation expense allocation term. Stock Contributed During Period Acquiree Majority Owner Shares contributed by Refinitiv Owner The number of shares contributed by the majority owner of the acquiree in the exchange transaction. Subscription Fee And Market Data Revenue [Member] Subscription Fees including Refinitiv market data Subscription fee revenue from granting access to institutional investors to the entity's electronic marketplaces and fees from the sale of market data to Refinitiv. Subscription Fee Revenue Subscription Fee Revenue [Member] Subscription fees Subscription fee revenue from granting access to institutional investors to the entity's electronic marketplaces. Tax Amortization Period Tax amortization period Represents the tax amortization period. Tax Benefit Assumed Due To Increase In Amortizable Tax Basis Tax benefit assumed due to increase in amortizable tax basis The amount of tax benefit assumed as a result of initial public offering, due to an increase in amortizable tax basis that will be amortized. Tax Cuts and Jobs Act of 2017, Change in Tax Rate, Deferred Tax Asset, Income Tax Expense Remeasurement of deferred tax asset Amount of income tax expense for remeasurement of deferred tax asset from change in tax rate pursuant to Tax Cuts and Jobs Act of 2017. Tax Cuts and Jobs Act of 2017, Income Tax Expense (Benefit) Adjustment to previously recorded provisional tax expense Amount of income tax expense (benefit) from effect of Tax Cuts and Jobs Act of 2017. Tax Receivable Agreement Liability Tax receivable agreement liability The carrying amount as on the balance sheet date of tax receivable agreement liability. Tax receivable agreement liability No definition available. Tax Receivable Agreement Liability Disclosure [Text Block] Tax receivable agreement liability The entire disclosure of tax receivable agreement liability. Tax Receivable Agreement, Percentage Of Amount Of Federal, State And Local Income Or Franchise Tax Savings Percentage of amount of U.S. federal, state and local income or franchise tax savings The percentage of amount of U.S. federal, state and local income or franchise tax savings under the tax receivable agreement. Tax Receivable Agreement Remaining Percentage of Amount of Federal State and Local Income or Franchise Tax Savings Remaining percentage of tax benefits The remaining percentage of amount of U.S. federal, state and local income or franchise tax savings under the tax receivable agreement. Tax Years2009 To2013 [Member] Tax periods from 2009 - 2013 Identified as tax years 2009 through 2013. Tax Years2012 To2016 [Member] Tax periods from 2012 - 2016 Identified as tax years 2012 through 2016. Temporary Equity, Capital Shares Reserved for Future Issuance Shares reserved for future issuance Aggregate number of temporary equity capital shares reserved for future issuance. Temporary Equity Compensation Payable Employee Shares compensation payable The value of compensation payable attributable to temporary equity. Temporary Equity Shares Classified As Compensation Payable Duration Period of time to determine classification as compensation payable The maximum period of time used to determine classification of temporary equity shares as compensation payable. Temporary Equity, Shares Purchased Purchased The number of securities classified as temporary equity that have been purchased during the reporting period. Temporary Equity, Shares Sold Sold The number of securities classified as temporary equity that have been sold (or granted) during the reporting period. Thomson Reuters Acquisition [Member] TR Thomson Reuters Acquisition Threshold Percentage of Economic Interest for Conversion Threshold percentage of economic interest for conversion Threshold percentage of economic interest for conversion. Total Enterprise Value Total Enterprise Value Represents the amount of enterprise value. Tradeweb Direct Llc [Member] TWD Tradeweb Direct LLC (TWD) is a registered broker-dealer under the Securities Exchange Act of 1934, and a member of the Financial Industry Regulatory Authority. Tradeweb Eu Bv [Member] TWEU Tradeweb EU B.V. (TWEU) is a trading venue and approved publication arrangement regulated by the Netherlands Authority for the Financial Markets. Tradeweb Europe Limited [Member] TEL Tradeweb Europe Limited (TEL) is a Multilateral Trading Facility regulated by the Financial Conduct Authority in the UK, which maintains branches in Asia which are regulated by certain Asian securities regulators. Tradeweb Japan Kk [Member] TWJ Tradeweb Japan K.K. (TWJ) is a security house regulated by the Japanese Financial Services Agency and the Japan Securities Dealers Association. Tradeweb Llc [Member] TWL Tradeweb LLC (TWL) is a registered broker-dealer under the Securities Exchange Act of 1934, a member of the Financial Industry Regulatory Authority, a registered independent introducing broker with the Commodities Future Trading Commission and a member of the National Futures Association. Tradeweb Markets Llc [Member] Tradeweb Markets LLC Tradeweb Markets LLC. Transaction Fee Revenue Transaction Fee Revenue [Member] Transaction fees Transaction fee revenues, both variable and fixed, recorded at a point in time when the trade occurs. Transaction Subscription And Other Fees [Member] Transaction, subscription and other fees Transaction, subscription and other fees. Transfers From (To) Noncontrolling Interests, Allocation of Equity to N C I Arising From Reorganization And IPO Allocation of equity to non-controlling interests arising from the reorganization transactions and IPO The amount of transfers from (to) noncontrolling interest due to allocation of equity to noncontrolling interest arising from reorganization and initial public offering. Tw Sef Llc [Member] TW SEF TW SEF LLC (TW SEF) is a swap execution facility regulated by the Commodities Future Trading Commission. United Kingdom And Asia [Member] UK and Asia United Kingdom and the continent of Asia. Variable Pricing [Member] Variable Contract with customer in which amount of consideration is based on variable components such as transaction based fees. Vesting of Employee Shares, Class P-1 C Vesting of P-1(C) Shares Amount of cash outflow for vesting of employee shares, class P-1 C. Voting Power Threshold Percentage To Require Conversion of Shares Voting power threshold percentage to require conversion of shares The voting power threshold percentage to require conversion of shares. Wholesale Client Sector [Member] Wholesale The wholesale client sector. Entity Filer Category Entity Small Business