Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net Income Per Share
Financial Designation, Predecessor and Successor [Fixed List]		Predecessor		Predecessor
Numerator:
Pre-IPO net income attributable to Tradeweb Markets LLC			$ 42,352
Denominator:
Weighted average outstanding - Basic	142,935,206		142,934,221	142,934,221
Weighted average outstanding - Diluted	151,362,643		151,158,760	151,158,760
Earnings per share - Basic	$ 0.21		$ 0.30	$ 0.30
Earnings per share - Diluted	$ 0.20		$ 0.28	$ 0.28
Shares excluded from computation of diluted earnings per share		2,798,674		5,444,566
PRSU
Denominator:
Dilutive effect	2,492,381			2,355,938
Options
Net Income Per Share
Financial Designation, Predecessor and Successor [Fixed List]		Predecessor		Predecessor
Denominator:
Dilutive effect	5,935,056			5,868,601
Potential Dilutive
Denominator:
Shares excluded from computation of diluted earnings per share			79,289,005
Tradeweb Markets LLC
Numerator:
Pre-IPO net income attributable to Tradeweb Markets LLC		$ 45,955	$ 42,352	$ 130,160
Denominator:
Weighted average outstanding - Basic		219,165,997	222,222,197	215,365,920
Weighted average outstanding - Diluted		219,165,997	223,320,457	215,365,920
Earnings per share - Basic		$ 0.21	$ 0.19	$ 0.60
Earnings per share - Diluted		$ 0.21	$ 0.19	$ 0.60
Shares excluded from computation of diluted earnings per share	247,491		126,667
Tradeweb Markets LLC | PRSU
Denominator:
Dilutive effect			1,098,260