Earnings Per Share - Basic (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 27, 2016
Basic earnings per share
Net income available for common stockholders	$ 2,939	$ 32,980	$ 20,887
Less: Dividends and undistributed earnings allocated to participating securities	(1,326)	(809)
Net income available for common stockholders, net of dividends and undistributed earnings allocated to participating securities	$ 1,613	$ 32,171	$ 20,887
Weighted average shares of common stock outstanding
Outstanding	62,579,147	38,539,091	34,964,312
Ownership interest (as a percent)				29.40%
Basic Earnings per share	$ 0.03	$ 0.83	$ 0.60
Class A
Weighted average shares of common stock outstanding
Outstanding	62,579,147	38,539,091	34,964,312
Basic Earnings per share	$ 0.03	$ 0.83	$ 0.60
Virtu Financial
Weighted average shares of common stock outstanding
Ownership interest (as a percent)	48.30%