Significant Accounting Policies - Useful Lives of Intangible Assets (Tradeweb Markets LLC and Subsidiaries) (Details) - Tradeweb Markets LLC	3 Months Ended
Mar. 31, 2019
Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets	7 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life of intangible assets	16 years

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.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration