Non-Controlling Interests (Details) $ in Thousands		3 Months Ended		9 Months Ended
	Apr. 08, 2019 shares	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares
Non-Controlling Interests
Net income attributable to Tradeweb Markets Inc.		$ 36,812	$ 29,612	$ 111,236	$ 42,440
Change in non-controlling interests as a result of ownership changes		(1,478)	73	423,339	(1,607,456)
Net transfers (to) from non-controlling interests		(1,478)	73	423,339	(1,607,456)
Change from net income attributable to Tradeweb Markets Inc. and transfers (to) from non-controlling interests		$ 35,334	$ 29,685	$ 534,575	$ (1,565,016)
Class A Common Stock
Non-Controlling Interests
Conversion ratio				1
Class B Common Stock
Non-Controlling Interests
Conversion ratio				1
Tradeweb Markets LLC
Non-Controlling Interests
Number of LLC Interests held by Tradeweb Markets Inc. (in shares) | shares	142,933,192			187,918,774	142,942,945
Number of LLC Interests held by non-controlling interests (in shares) | shares				39,513,246	79,289,005
Total LLC Interests outstanding (in shares) | shares				227,432,020	222,231,950
Number of LLC Interests held by Tradeweb Markets Inc.	64.30%	82.60%	64.30%	82.60%	64.30%
Number of LLC Interests held by Tradeweb Markets Inc.		17.40%	35.70%	17.40%	35.70%
Total LLC Interests outstanding		100.00%	100.00%	100.00%	100.00%