The amount of net income (loss) attributable to limited liability company.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Indicates designation of financial information when substantially all business or separately identifiable line of business transfers from one entity to another entity. Acceptable values are "Predecessor" and "Successor".

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- Definition

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended					9 Months Ended		12 Months Ended
	Mar. 31, 2019	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
Net Income Per Share
Financial Designation, Predecessor and Successor [Fixed List]	Successor	Successor				Successor	Predecessor	Successor	Successor	Predecessor
Numerator:
Pre-IPO net income attributable to Tradeweb Markets LLC						$ 83,769
Denominator:
Weighted average outstanding - Basic		222,221,628				148,013,274	215,365,920	148,013,274		215,568,635
Weighted average outstanding - Diluted		222,243,851				156,540,246	215,365,920	156,540,246		215,568,635
Earnings per share - Basic						$ 0.57		$ 0.57
Earnings per share - Diluted						$ 0.54		$ 0.54
Shares excluded from computation of diluted earnings per share							5,444,566
PRSU
Denominator:
Dilutive effect						2,464,137
Options
Net Income Per Share
Financial Designation, Predecessor and Successor [Fixed List]								Successor
Denominator:
Dilutive effect						6,062,835
Potential Dilutive
Denominator:
Shares excluded from computation of diluted earnings per share								59,182,155
Tradeweb Markets LLC
Net Income Per Share
Financial Designation, Predecessor and Successor [Fixed List]	Successor	Successor	Predecessor	Predecessor	Predecessor
Numerator:
Pre-IPO net income attributable to Tradeweb Markets LLC	$ 42,352	$ 29,307					$ 130,160	$ 42,352		$ 83,648
Denominator:
Weighted average 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
Weighted average outstanding - 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
Earnings per share - Basic	$ 0.19	$ 0.13	$ 0.21	$ 0.18	$ 0.21		$ 0.60	$ 0.19		$ 0.39
Earnings per share - Diluted	$ 0.19	$ 0.13	$ 0.21	$ 0.18	$ 0.21		$ 0.60	$ 0.19		$ 0.39
Shares excluded from computation of diluted earnings per share								128,125
Tradeweb Markets LLC \| PRSU
Denominator:
Dilutive effect	1,098,260	22,223