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Stockholder's Equity (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended	9 Months Ended
	Apr. 08, 2019	Oct. 31, 2019	Dec. 31, 2019	Dec. 31, 2019
Subsidiary, Sale of Stock [Line Items]
Weighted Weighted Average Share Price			$ 21.62	$ 21.62
LLC units | October 2019 Follow-On Offering
Subsidiary, Sale of Stock [Line Items]
Stock Repurchased and Retired During Period, Shares		19,835,666
Class A common stock
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock (in shares)				46,000,000
Class A common stock | October 2019 Follow-On Offering
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock (in shares)			19,881,059
Weighted Weighted Average Share Price		$ 42.00
Net proceeds		$ 810.0
Stock Repurchased and Retired During Period, Shares		45,393
Class A common stock | Initial Public Offering
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock (in shares)	46,000,000
Weighted Weighted Average Share Price	$ 27.00
Class A common stock | Over allotment
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock (in shares)	6,000,000	2,593,181
Tradeweb Markets LLC
Subsidiary, Sale of Stock [Line Items]
Weighted Weighted Average Share Price	$ 27.00
Net proceeds	$ 1,200.0

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