Stockholder's Equity - Redemptions and Exchange of LLC Interests (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 08, 2019	Oct. 31, 2019	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2019
Subsidiary, Sale of Stock [Line Items]
Weighted Weighted Average Share Price			$ 21.62	$ 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
LLC units | Redemptions and Exchanges of LLC Interests [Member]
Subsidiary, Sale of Stock [Line Items]
Number of LLC Units received from the exchange transaction					271,184
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 | Redemptions and Exchanges of LLC Interests [Member]
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock (in shares)					271,184
Class D common stock
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock (in shares)				69,282,736
Class D common stock | Redemptions and Exchanges of LLC Interests [Member]
Subsidiary, Sale of Stock [Line Items]
Stock Repurchased and Retired During Period, Shares					271,184
Class B common stock
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock (in shares)	96,933,192			96,933,192
Class C common stock
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock (in shares)				10,006,269
Tradeweb Markets LLC
Subsidiary, Sale of Stock [Line Items]
Weighted Weighted Average Share Price	$ 27.00
Net proceeds	$ 1,200.0
Ownership interest	64.30%		73.40%	73.40%	73.40%
Equity interest of noncontrolling shareholders in consolidated entity			26.60%	26.60%	26.60%
Tradeweb Markets LLC | Public Investors
Subsidiary, Sale of Stock [Line Items]
Equity interest of noncontrolling shareholders in consolidated entity			29.80%	29.80%	29.80%
Tradeweb Markets LLC | Bank Stockholders
Subsidiary, Sale of Stock [Line Items]
Equity interest of noncontrolling shareholders in consolidated entity			16.20%	16.20%	16.20%
Tradeweb Markets Inc | Public Investors
Subsidiary, Sale of Stock [Line Items]
Voting power percentage			4.30%	4.30%	4.30%
Tradeweb Markets Inc | Bank Stockholders
Subsidiary, Sale of Stock [Line Items]
Voting power percentage			18.40%	18.40%	18.40%
Tradeweb Markets Inc | Class A common stock | Public Investors
Subsidiary, Sale of Stock [Line Items]
Number of share owned			66,408,328	66,408,328	66,408,328
Tradeweb Markets Inc | Class D common stock | Bank Stockholders
Subsidiary, Sale of Stock [Line Items]
Number of share owned			27,662,354	27,662,354	27,662,354
Tradeweb Markets Inc | Class C common stock | Bank Stockholders
Subsidiary, Sale of Stock [Line Items]
Number of share owned			8,328,983	8,328,983	8,328,983
Tradeweb Markets LLC
Subsidiary, Sale of Stock [Line Items]
Weighted Weighted Average Share Price	$ 27.00
Net proceeds	$ 1,200.0
Refinitiv | Tradeweb Markets LLC
Subsidiary, Sale of Stock [Line Items]
Ownership interest			53.90%	53.90%	53.90%
Refinitiv | Tradeweb Markets Inc
Subsidiary, Sale of Stock [Line Items]
Ownership interest			77.20%	77.20%	77.20%
Refinitiv | Tradeweb Markets Inc | Class D common stock
Subsidiary, Sale of Stock [Line Items]
Number of share owned			22,988,329	22,988,329	22,988,329
Refinitiv | Tradeweb Markets Inc | Class B common stock
Subsidiary, Sale of Stock [Line Items]
Number of share owned			96,933,192	96,933,192	96,933,192