Share-based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended			20 Months Ended
	Apr. 21, 2015	Apr. 15, 2015	Jul. 08, 2011	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Share-based Compensation.
Expense recognized				$ 6,400
Number of Class A-2 capital interests contributed by Class A-2 members to Virtu East MIP LLC			2,625,000
Non-voting common interest units outstanding				12,301,067	14,231,535		14,231,535
Number of non-voting common interest units forfeited or repurchased				1,930,468	1,162,891	57,106
Weighted Average Remaining Life, outstanding
Weighted Average Remaining Life						9 years 3 months 15 days
Weighted average remaining contractual life, granted						10 years
Class A
Share-based Compensation.
Expense recognized				$ 300	$ 10,600	$ 13,200
Accrued compensation expense				$ 11,000
Granted (in shares)				19,719	656,019	576,693
Class B interests | East MIP
Share-based Compensation.
Vesting period			4 years
Non-voting common interest units (formerly Class B interests)
Share-based Compensation.
Expense recognized				$ 700	$ 1,100	$ 44,900
Unrecognized share-based compensation expense				$ 100	$ 800		$ 800
Weighted average period for compensation expense expected to be recognized				1 month 6 days	1 year
Capitalized software development costs				$ 40	$ 90	9,200
Amortization expense related to share based compensation					700	8,500
Non-voting common interest units (formerly Class B interests) | East MIP
Share-based Compensation.
Amortization expense related to share based compensation				70
Non-voting common interest units (formerly Class A 2 profits interests)
Share-based Compensation.
Expense recognized				700	1,300	1,500
Unrecognized share-based compensation expense				$ 100	$ 800		800
Weighted average period for compensation expense expected to be recognized				1 month 6 days	9 months 18 days
Non-voting common interest units (formerly Class A 2 profits interests) | Maximum
Share-based Compensation.
Vesting period		4 years
Non-qualified stock options | 2015 Management Incentive Plan
Share-based Compensation.
Vesting period	4 years
Expiration period	10 years
Expense recognized				$ 5,200	$ 5,600	$ 4,700
Unrecognized share-based compensation expense				$ 7,500	$ 14,200		$ 14,200
Weighted average period for compensation expense expected to be recognized				1 year 3 months 18 days	2 years 3 months 18 days
Forfeited or repurchased (in shares)				496,000	760,000	234,000
Outstanding (in shares)				8,234,000	8,994,000
Granted (in shares)						9,228,000
Forfeited or expired (in shares)				(496,000)	(760,000)	(234,000)
Outstanding (in shares)				7,738,000	8,234,000	8,994,000	8,234,000
Weighted Average Exercise Price Per Share
Outstanding (in dollars per share)				$ 19.00	$ 19.00
Granted (in dollars per share)						$ 19.00
Outstanding (in dollars per share)				$ 19.00	$ 19.00	$ 19.00	$ 19.00
Weighted Average Remaining Life, outstanding
Weighted Average Remaining Life				7 years 3 months 15 days	8 years 3 months 15 days
Options Exercisable, Number of Options (in shares)				3,869,000	2,058,500		2,058,500
Options Exercisable, Weighted Average Exercise Price (in dollars per share)				$ 19.00	$ 19.00		$ 19.00
Restricted stock units
Share-based Compensation.
Unrecognized share-based compensation expense				$ 14,300	$ 28,500		$ 28,500
Weighted average period for compensation expense expected to be recognized				1 year 6 months	2 years 7 months 6 days
Restricted stock units | Class A
Share-based Compensation.
Expense recognized				$ 9,900	$ 6,300	$ 500
Restricted stock units | 2015 Management Incentive Plan
Activity
Outstanding (in shares)				1,573,441	984,466
Granted (in shares)				64,402	1,019,148	984,466
Forfeited (in shares)				(258,250)	(133,138)
Vested (in shares)				(526,546)	(297,035)
Outstanding (in shares)				853,047	1,573,441	984,466	1,573,441
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Outstanding (in dollars per share)				$ 18.28	$ 22.32
Granted (in dollars per share)				18.09	16.06	$ 22.32
Forfeited (in dollars per share)				18.40	22.51
Vested (in dollars per share)				18.75	16.48
Outstanding (in dollars per share)				$ 17.94	$ 18.28	$ 22.32	$ 18.28
Restricted stock units | 2015 Management Incentive Plan | Maximum
Share-based Compensation.
Vesting period							4 years