Capital Structure - Prior to Reorganization and IPO (Details) $ / shares in Units, $ in Thousands				3 Months Ended		9 Months Ended		12 Months Ended			48 Months Ended
	Dec. 31, 2014 USD ($) shares	Nov. 04, 2014 USD ($) shares	Jul. 08, 2011 USD ($) item shares	Sep. 30, 2015 shares	Sep. 30, 2014 shares	Sep. 30, 2015 shares	Sep. 30, 2014 shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 shares	Jul. 08, 2015	Nov. 30, 2015 $ / shares shares	Apr. 15, 2015 USD ($) item
Class A
Common stock offered for sale (in shares)												397,534
Virtu Financial Inc And Silver Lake Partners | Class A
Common stock offered for sale (in shares)												6,473,371
Price of stock (in dollars per share) | $ / shares												$ 22.15
Silver Lake Post-IPO | Class A
Common stock offered for sale (in shares)												6,075,837
Class A-1
Membership interests issued (in shares)	1,964,826							0	1,964,826
Aggregate capital balance | $	$ 19,648								$ 19,648
Membership interests outstanding (in shares)	1,964,826							0	1,964,826
Virtu Financial
Number of classes of members interests issued | item													3
Virtu Financial | Temasek
Maximum amount of payments to be made if value of interest acquired exceeds certain limit of transaction price | $													$ 3,900
Ratio of interest acquired over transaction price													1.7
Virtu Financial | Class A-1
Number of members that haves the right to call for redemption | item			3
Members interests granted (in shares)				0	0	0	0
Members interests forfeited (in shares)				0	0	0	0
Members interests distributed (in shares)				0	0	0	0
Members interests redeemed (in shares)				0	0	0	0
Amount of unrecovered capital for entitlement of distributions of capital proceeds | $	$ 0							$ 0	$ 0
Conversion ratio to convert from Class A-1 to Class A-2									1
Virtu Financial | Class A-1 | Minimum
Threshold of gross proceeds raised from an initial public offering for a qualified IPO | $								$ 100,000
Number of times the invested amount to determine the valuation of the entity								1.75
Virtu Financial | Class A-1 | Silver Lake Member
Redeemable interests issued (in shares)			25,000,000
Redeemable interests held (in shares)	7,381,224								7,381,224
Percentage of indirect ownership interest held in the entity	57.90%
Number of members can be appointed in Entity's board | item			1
Virtu Financial | Class A-1 | Affiliate of Vincent Viola
Membership interests issued (in shares)			1,964,826
Aggregate capital balance | $			$ 270,000
Virtu Financial | Class A-1 | Temasek Member
Redeemable interests transferred from one member to another member (in shares)	5,376,603
Number of members can be appointed in Entity's board | item			1
Number of members can be appointed in Entity's board by other members in consultation with Temasek member | item			1
Virtu Financial | Class A-1 | SLT Member
Redeemable interests transferred from one member to another member (in shares)	12,242,173
Percentage of indirect ownership interest held in the entity	42.10%
Virtu Financial | Class A-2 capital interests
Membership interests issued (in shares)	93,786,659							0	93,786,659
Membership interests outstanding (in shares)	93,786,659							0	93,786,659
Repurchase of capital interests (in shares)		1,452,667
Carrying value of repurchased capital interests | $		$ 1,400
Repurchase price of repurchased capital interests | $		6,000
Reduction in accumulated deficit due to excess of repurchase price over carrying value | $		4,600
Reduction in capital interests for carrying value of repurchased interests | $		$ 1,400
Amount of unrecovered capital for entitlement of distributions of capital proceeds | $	$ 0								$ 0
Virtu Financial | Class A-2 capital interests | East MIP
Contribution of capital interests to incentive plan (in shares)			2,625,000
Virtu Financial | Class A-2 capital interests | Temasek Member
Membership interests issued (in shares)	214,433								214,433
Member's interests transferred from one entity to another entity (in shares)	1,614,322
Virtu Financial | Class A-2 profits interests | Employee Holdco
Membership interests issued (in shares)	6,069,007							0	6,069,007
Membership interests outstanding (in shares)	6,069,007							0	6,069,007
Virtu Financial | Class B interests
Members interests issued during the period (in shares)								0	0	2.65
Membership interests outstanding (in shares)				0		0
Non-voting interests vesting period								4 years
Percentage of capital proceeds issued	12.915%								12.915%
Percentage of capital proceeds outstanding	12.915%								12.915%
Virtu Financial | Class B interests | East MIP
Non-voting interests vesting period											4 years
Virtu Financial
Ownership interest (as a percent)								27.50%