Non-Controlling Interests (Details) $ in Thousands		3 Months Ended	9 Months Ended
	Apr. 08, 2019 shares	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) shares	Sep. 30, 2018 USD ($)
Noncontrolling Interest [Line Items]
Net income attributable to Tradeweb Markets		$ 29,612	$ 42,440	$ 42,440
Allocation of equity to non-controlling interests arising from the reorganization transactions and IPO			(1,607,529)
Change in ownership percentage resulting from issuance of common stock from equity incentive plans		73	73
Net transfers (to) from non-controlling interest		73	(1,607,456)
Change from net income attributable to Tradeweb Markets Inc. and transfers (to) from non-controlling interest		$ 29,685	$ (1,565,016)
Class A common stock
Noncontrolling Interest [Line Items]
Conversion ratio			1
Class B common stock
Noncontrolling Interest [Line Items]
Conversion ratio			1
Tradeweb Markets LLC
Noncontrolling Interest [Line Items]
Number of LLC Interests held by Tradeweb Markets Inc | shares	142,933,192		142,942,945
Number of LLC Interests held by non-controlling interest | shares			79,289,005
Total LLC Interests outstanding | shares			222,231,950
Number of LLC Interests held by Tradeweb Markets Inc	64.30%	64.30%	64.30%
Number of LLC Interests held by non-controlling interest holders		35.70%	35.70%
Total LLC Interests outstanding		100.00%	100.00%