Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Organization and Basis of Presentation (Details)			3 Months Ended	6 Months Ended
Organization and Basis of Presentation (Details)	Oct. 24, 2017 segment	Jul. 19, 2017 item	Sep. 30, 2017 segment	Jun. 30, 2017 item segment	Dec. 31, 2017	Jul. 27, 2016
Ownership interest (as a percent)						29.40%
Number of businesses Company is managed and operated as \| item		1		1
Number of reportable segments		1		1
Number of operating segments \| segment	3		3
Virtu Financial
Ownership interest (as a percent)					48.30%