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Commitments and Contingencies - Contingencies (Details) - Tradeweb Markets LLC - Successor	12 Months Ended
	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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The number of actions related to this loss contingency.

+ References

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- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
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