Quarterly Results of Operations (Unaudited) - Operating results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended									9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 08, 2019
Revenues
Financial Designation, Predecessor and Successor [Fixed List]				Successor		Successor				Successor	Predecessor	Successor	Successor	Predecessor
Gross revenue						$ 178,637					$ 505,771	$ 775,566		$ 562,968
Contingent consideration											(26,830)			(58,520)
Net revenue						178,637					478,941	775,566		504,448
Expenses
Employee compensation and benefits						80,436					209,053	329,457		248,963
Depreciation and amortization						33,020					48,808	139,330		68,615
Technology and communications						9,907					26,598	39,285		30,013
General and administrative						11,837					23,056	34,960		33,973
Professional fees						8,194					20,360	28,029		19,351
Occupancy						3,308					10,732	14,686		14,441
Total expenses						146,702					338,607	585,747		415,356
Operating income						31,935					140,334	189,819		89,092
Tax receivable agreement liability adjustment	$ 240,817									$ 240,817		240,817			$ 171,400
Net interest income						787					1,726	2,373		685
Income before taxes						32,722					142,060	225,326		89,777
Provision for income taxes						(3,415)					(11,900)	(52,302)		(6,129)
Net income				$ 42,352	$ 29,307	$ 29,307				$ 130,672	$ 130,160	173,024		$ 83,648
Net income attributable to non-controlling interests												46,903
Net income attributable to Tradeweb Markets Inc.												$ 83,769
Earnings per share
Basic										$ 0.57		$ 0.57
Diluted										$ 0.54		$ 0.54
Weighted average shares outstanding
Basic						222,221,628				148,013,274	215,365,920	148,013,274		215,568,635
Diluted						222,243,851				156,540,246	215,365,920	156,540,246		215,568,635
Transaction fees
Revenues
Gross revenue						$ 97,130					$ 273,751	$ 423,583		$ 267,020
Subscription fees
Revenues
Gross revenue						33,052					107,130	138,731		144,409
Commissions
Revenues
Gross revenue						32,840					79,830	149,365		96,745
Refinitiv market data fees
Revenues
Gross revenue						13,467					36,851	55,635		50,125
Other
Revenues
Gross revenue						$ 2,148					8,209	8,252		4,669
Tradeweb Markets Inc
Revenues
Financial Designation, Predecessor and Successor [Fixed List]	Successor	Successor	Successor
Gross revenue	$ 197,308	$ 200,981	$ 190,485
Net revenue	197,308	200,981	190,485
Expenses
Employee compensation and benefits	76,545	79,644	95,995
Depreciation and amortization	36,402	35,133	34,292
Technology and communications	10,199	9,527	9,519
General and administrative	8,999	7,507	9,365
Professional fees	7,048	7,272	6,738
Occupancy	3,786	3,640	3,621
Total expenses	142,979	142,723	159,530
Operating income	54,329	58,258	30,955
Tax receivable agreement liability adjustment	33,134									$ 33,134		33,134
Net interest income	704	636	175
Income before taxes	88,167	58,894	31,130
Provision for income taxes	(30,889)	(10,316)	(6,314)
Net income	57,278	48,578	24,816
Net income attributable to non-controlling interests	15,949	18,966	11,988
Net income attributable to Tradeweb Markets Inc.	$ 41,329	$ 29,612	$ 12,828
Earnings per share
Basic	$ 0.26	$ 0.21	$ 0.09
Diluted	$ 0.25	$ 0.20	$ 0.09
Weighted average shares outstanding
Basic	157,950,550	142,935,206	142,933,192
Diluted	167,323,520	151,362,643	150,847,183
Tradeweb Markets Inc | Transaction fees
Revenues
Gross revenue	$ 104,245	$ 112,746	$ 103,952
Tradeweb Markets Inc | Subscription fees
Revenues
Gross revenue	34,333	35,387	34,566
Tradeweb Markets Inc | Commissions
Revenues
Gross revenue	41,165	37,590	36,413
Tradeweb Markets Inc | Refinitiv market data fees
Revenues
Gross revenue	15,383	13,251	13,385
Tradeweb Markets Inc | Other
Revenues
Gross revenue	$ 2,182	$ 2,007	$ 2,169
Tradeweb Markets LLC
Revenues
Financial Designation, Predecessor and Successor [Fixed List]				Successor		Successor	Predecessor	Predecessor	Predecessor
Gross revenue				$ 186,792		$ 178,637	$ 165,253	$ 171,015	$ 169,503
Contingent consideration							2,537	(19,297)	(10,070)
Net revenue				186,792		178,637	167,790	151,718	159,433
Expenses
Employee compensation and benefits				77,273		80,436	69,076	68,407	71,570
Depreciation and amortization				33,503		33,020	16,362	16,178	16,268
Technology and communications				10,040		9,907	9,112	9,023	8,463
General and administrative				9,089		11,837	9,386	7,153	6,517
Professional fees				6,971		8,194	7,546	7,276	5,538
Occupancy				3,639		3,308	3,491	3,519	3,722
Total expenses				140,515		146,702	114,973	111,556	112,078
Operating income				46,277		31,935	52,817	40,162	47,355
Net interest income				858		787	673	582	471
Income before taxes				47,135		32,722	53,490	40,744	47,826
Provision for income taxes				(4,783)		(3,415)	(7,535)	(1,847)	(2,518)
Net income				$ 42,352		29,307	$ 45,955	$ 38,897	$ 45,308
Net income attributable to Tradeweb Markets Inc.						$ 29,307					$ 130,160	$ 42,352		$ 83,648
Earnings per share
Basic				$ 0.19		$ 0.13	$ 0.21	$ 0.18	$ 0.21		$ 0.60	$ 0.19		$ 0.39
Diluted				$ 0.19		$ 0.13	$ 0.21	$ 0.18	$ 0.21		$ 0.60	$ 0.19		$ 0.39
Weighted average shares outstanding
Basic				222,222,197		222,221,628	219,165,997	213,435,314	213,435,321		215,365,920	222,222,197		212,568,635
Diluted				223,320,457		222,243,851	219,165,997	213,435,314	213,435,321		215,365,920	223,320,457		212,568,635
Tradeweb Markets LLC | Transaction fees
Revenues
Gross revenue				$ 102,640		$ 97,130	$ 92,582	$ 91,030	$ 90,139
Tradeweb Markets LLC | Subscription fees
Revenues
Gross revenue				34,445		33,052	33,157	37,647	36,326
Tradeweb Markets LLC | Commissions
Revenues
Gross revenue				34,197		32,840	24,394	27,553	27,883
Tradeweb Markets LLC | Refinitiv market data fees
Revenues
Gross revenue				13,616		13,467	12,533	12,081	12,237
Tradeweb Markets LLC | Other
Revenues
Gross revenue				$ 1,894		$ 2,148	$ 2,587	$ 2,704	$ 2,918