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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

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