Stockholder's Equity - Recapitalization of Tradeweb Markets LLC (Details) - Tradeweb Markets LLC - shares		9 Months Ended
	Apr. 04, 2019	Sep. 30, 2020
LLC Interests
Class of Stock [Line Items]
Common units exchanged (in shares)	222,222,197
Class A Common Stock
Class of Stock [Line Items]
Common units exchanged (in shares)		146,333
Class C Common Stock
Class of Stock [Line Items]
Common units exchanged (in shares)		447
Class P (A)
Class of Stock [Line Items]
Common units exchanged (in shares)		6,887
Class P (C)
Class of Stock [Line Items]
Common units exchanged (in shares)		2
Class P-1 (A)
Class of Stock [Line Items]
Common units exchanged (in shares)		6,094
Class P-1 (C)
Class of Stock [Line Items]
Common units exchanged (in shares)		232