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Employee Savings Plan - 401(k) Plan (Details) - Tradeweb Markets LLC - USD ($) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2018 | Sep. 30, 2018 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Successor | U.S. |  |  |  |  |
Employees Savings Plan |  |  |  |  |
401(k) Savings Plan | us-gaap:QualifiedPlanMember |  | us-gaap:QualifiedPlanMember |  |
Employees' voluntary contribution percentage |  |  | 75.00% |  |
Company match, as a percent of the employee's contribution |  |  | 100.00% |  |
Employer match limit, as a percent of employee's compensation |  |  | 4.00% |  |
Expense recognized | $ 738,000 |  |  |  |
Successor | UK and Asia |  |  |  |  |
Employees Savings Plan |  |  |  |  |
Expense recognized | $ 423,000 |  |  |  |
Predecessor | U.S. |  |  |  |  |
Employees Savings Plan |  |  |  |  |
Expense recognized |  | $ 3,758,000 |  | $ 4,137,000 | $ 4,179,000
Predecessor | UK and Asia |  |  |  |  |
Employees Savings Plan |  |  |  |  |
Expense recognized |  | $ 1,113,000 |  | $ 1,242,000 | $ 1,181,000

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition 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. + References No definition available. + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
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- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. + References No definition available. + Details
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- Definition Indicates tax status of defined contribution plan designed to provide retirement benefits. + References No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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- Details
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