Changes in Stock Appreciation Rights (Detail) (SARs, USD $)	3 Months Ended				15 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2015
SARs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
SARs, Granted	1,500				500
Number of Shares, Vested	7,897	[1]	293,925	[1]
Weighted Average Base Price, Granted	$ 16.69
Weighted Average Base Price, Exercised	$ 10.61	[1]	$ 8.07	[1]
Weighted Average Fair Value, Granted	$ 8.99
Weighted Average Fair Value, Exercised	$ 5.72	[1]	$ 4.70	[1]

[1] The exercise of SARs listed in the three-month period table resulted in the issuance of 1,869 shares and 120,459 shares of Actua’s Common Stock during the three months ended March 31, 2015 and 2014, respectively.