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Commitments and Contingencies - Contingencies (Details) - Tradeweb Markets LLC - Successor | 12 Months Ended
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Dec. 31, 2018 USD ($) item
Antitrust Actions Related To Trading Practices and Interest Rate Swaps |
Commitments and Contingencies |
Number of actions | item | 2
Litigation relating to distribution of financial strength ratings |
Commitments and Contingencies |
Damages sought | $ | $ 80,000,000

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