Changes in Stock Appreciation Rights (Detail) (SARs, USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
SARs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
SARs, Granted	500				500
SARs, Exercised	3,165	[1]	220,874	[1]	321,442	[1]	376,362	[1]
SARs, Forfeited	5,001				5,001		5,346
Weighted Average Base Price, Granted	$ 17.31				$ 17.31
Weighted Average Base Price, Exercised	$ 10.54	[1]	$ 7.59	[1]	$ 8.21	[1]	$ 12.43	[1]
Weighted Average Base Price, Forfeited	$ 10.16				$ 10.16		$ 9.95
Weighted Average Fair Value, Granted	$ 9.48				$ 9.48
Weighted Average Fair Value, Exercised	$ 5.67	[1]	$ 4.55	[1]	$ 4.73	[1]	$ 7.46	[1]
Weighted Average Fair Value, Forfeited	$ 5.44				$ 5.44		$ 5.39

[1] The exercise of SARs listed in the three-month period table resulted in the issuance of 897 shares and 55,619 shares of Actua’s Common Stock during the three months ended September 30, 2014 and 2013, respectively. The exercise of SARs listed in the nine-month period table resulted in the issuance of 129,990 shares and 99,851 shares of Actua’s Common Stock during the nine months ended September 30, 2014 and 2013, respectively.