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Fair Value of Financial Instruments - Fair Value Measurements (Details) - Tradeweb Markets LLC - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017
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Predecessor |  |
Fair Value of Financial Instruments |  |
Money market funds |  | $ 101,154
Total assets measured at fair value |  | 101,154
Contingent consideration payable |  | 129,393
Total Liabilities, at fair value |  | 129,393
Predecessor | Level 1 |  |
Fair Value of Financial Instruments |  |
Money market funds |  | 101,154
Total assets measured at fair value |  | 101,154
Predecessor | Level 3 |  |
Fair Value of Financial Instruments |  |
Contingent consideration payable |  | 129,393
Total Liabilities, at fair value |  | $ 129,393
Successor |  |
Fair Value of Financial Instruments |  |
Money market funds | $ 127,927 |
Total assets measured at fair value | 127,927 |
Successor | Level 1 |  |
Fair Value of Financial Instruments |  |
Money market funds | 127,927 |
Total assets measured at fair value | $ 127,927 |

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- Definition Fair value portion of liabilities incurred for goods and services received that are used in an entity's business and related party payables. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611 + Details
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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References No definition available. + Details
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