Equity-Based Compensation - Total aggregate fair value of restricted stock and shares surrendered by Actua's employees (Detail) - Restricted Stock - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock vested in period, fair value	$ 776	$ 5,243	$ 875	$ 10,839	$ 6,019	$ 11,714
Shares paid for tax withholding for share based payments (in shares)	736	191,898	26,032	207,649	192,634	233,681