CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Revenue	$ 20,762	$ 16,071	$ 58,213	$ 41,521
Operating expenses
Cost of Revenue	5,911	4,501	16,329	12,822
Sales and marketing	10,718	7,571	28,834	19,794
General and administrative	13,798	7,852	36,722	23,875
Research and development	3,960	2,149	10,760	6,726
Amortization of intangibles assets	2,369	2,176	6,963	6,211
Impairment related and other	256	470	1,092	767
Total operating expenses	37,012	24,719	100,700	70,195
Operating income (loss)	(16,250)	(8,648)	(42,487)	(28,674)
Other income (loss), net	83	(68)	1,020	(178)
Interest income	160	63	392	150
Interest expense	(9)	(370)	(1,600)	(1,076)
Income (loss) before income taxes, equity loss and noncontrolling interest	(16,016)	(9,023)	(42,675)	(29,778)
Income tax (expense) benefit	1,870	99	2,375	(30)
Equity loss	(144)	(295)	(776)	(1,919)
Income (loss) from continuing operations	(14,290)	(9,219)	(41,076)	(31,727)
Income (loss) from discontinued operations, including gain on sale, net of tax	2,426	4,980	3,789	35,654
Net income (loss)	(11,864)	(4,239)	(37,287)	3,927
Less: Net income (loss) attributable to the noncontrolling interest	(1,184)	(907)	(3,563)	(4,951)
Net income (loss) attributable to Actua Corporation	(10,680)	(3,332)	(33,724)	8,878
Amounts attributable to Actua Corporation:
Net income (loss) from continuing operations	(13,106)	(8,022)	(37,513)	(28,473)
Net income (loss) from discontinued operations	2,426	4,690	3,789	37,351
Net income (loss) attributable to Actua Corporation	(10,680)	(3,332)	(33,724)	8,878
Basic income (loss) per share attributable to Actua Corporation:
Income (loss) from continuing operations	$ (0.35)	$ (0.22)	$ (1.01)	$ (0.78)
Income (loss) from discontinued operations	$ 0.06	$ 0.13	$ 0.10	$ 1.02
Net income (loss)	$ (0.29)	$ (0.09)	$ (0.91)	$ 0.24
Shares used in computation of basic income (loss) per share	37,335	36,303	37,248	36,494
Diluted income (loss) per share attributable to Actua Corporation:
Income (loss) from continuing operations	$ (0.35)	$ (0.22)	$ (1.01)	$ (0.78)
Income (loss) from discontinued operations	$ 0.06	$ 0.13	$ 0.10	$ 1.02
Net income (loss)	$ (0.29)	$ (0.09)	$ (0.91)	$ 0.24
Shares used in computation of diluted income (loss) per share	37,335	36,303	37,248	36,494
Other comprehensive income
Unrealized holding gain (loss) in marketable securities				23
Reclassified adjustments/realized net (gains) loss on marketable securities				(23)
Other accumulated other comprehensive income (loss)		38		88
Comprehensive income (loss)	(11,864)	(4,201)	(37,287)	4,015
Less: Comprehensive income (loss) attributable to noncontrolling interests	(1,184)	(869)	(3,563)	(4,863)
Comprehensive income (loss) attributable to Actua Corporation	$ (10,680)	$ (3,332)	$ (33,724)	$ 8,878