Stockholder's Equity - Common Units Outstanding (Details) - Tradeweb Markets LLC - shares		12 Months Ended
	Apr. 04, 2019	Dec. 31, 2019
LLC Interests
Class of Stock [Line Items]
Common units exchanged	222,222,197
Class A common stock
Class of Stock [Line Items]
Common units exchanged		146,333
Class C common stock
Class of Stock [Line Items]
Common units exchanged		447
Class P(A) Shares
Class of Stock [Line Items]
Common units exchanged		6,887
Class P(C) Shares
Class of Stock [Line Items]
Common units exchanged		2
Class P-1(A) Shares
Class of Stock [Line Items]
Common units exchanged		6,094
Class P-1(C) Shares
Class of Stock [Line Items]
Common units exchanged		232