Earnings Per Share - Basic (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic earnings per share
Net income available for common stockholders	$ (13,518)	$ 7,026	$ (8,037)	$ 25,752
Less: Dividends and undistributed earnings allocated to participating securities	(314)	(191)	(997)	(612)
Net income available for common stockholders, net of dividends and undistributed earnings allocated to participating securities	$ (13,832)	$ 6,835	$ (9,034)	$ 25,140
Weighted average shares of common stock outstanding
Outstanding	79,199,142	38,351,465	53,520,346	38,264,139
Basic Earnings per share	$ (0.17)	$ 0.18	$ (0.17)	$ 0.66
Class A
Weighted average shares of common stock outstanding
Outstanding	79,199,142	38,351,465	53,520,346	38,264,139
Basic Earnings per share	$ (0.17)	$ 0.18	$ (0.17)	$ 0.66
Virtu Financial
Weighted average shares of common stock outstanding
Ownership interest (as a percent)	48.00%		48.00%