Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net income attributable to Tradeweb Markets Inc.	$ 67,859	$ 43,928
Denominator:
Weighted average shares of Class A and Class B common stock outstanding - Basic (in shares)	199,064,607	166,234,749
Dilutive effect (in shares)	5,964,110
Weighted average shares of Class A and Class B common stock outstanding - Diluted (in shares)	205,028,717	174,517,244
Earnings per share - Basic (in dollars per share)	$ 0.34	$ 0.26
Earnings per share - Diluted (in dollars per share)	$ 0.33	$ 0.25
Weighted-average shares (in shares)		378,124
PRSU
Denominator:
Dilutive effect (in shares)	1,832,308	2,038,422
Weighted-average shares (in shares)	77,692
Options
Denominator:
Dilutive effect (in shares)	3,851,594	6,221,549
RSU
Denominator:
Dilutive effect (in shares)	280,208	22,524
Weighted-average shares (in shares)	60,315
Potential Dilutive
Denominator:
Weighted-average shares (in shares)	31,214,407	57,644,547