CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Revenue	$ 27,937	$ 24,917	$ 79,977	$ 72,957
Operating expenses
Cost of revenue	7,441	6,663	21,451	20,533
Sales and marketing	10,281	9,551	30,861	26,911
General and administrative	11,228	12,542	34,926	40,889
Research and development	5,411	4,973	16,106	14,377
Amortization of intangible assets	3,524	3,266	10,732	10,146
Impairment related and other	45	285	393	982
Total operating expenses	37,930	37,280	114,469	113,838
Operating loss	(9,993)	(12,363)	(34,492)	(40,881)
Other income, net	2,831	96	2,726	1,537
Interest income	31	30	118	83
Interest expense	(27)	(36)	(93)	(104)
Loss before income taxes and noncontrolling interest	(7,158)	(12,273)	(31,741)	(39,365)
Income tax expense	(93)	(29)	(291)	(204)
Loss from continuing operations	(7,251)	(12,302)	(32,032)	(39,569)
Loss from discontinued operations, net of tax	(3,842)	(2,331)	(8,002)	(7,032)
Net loss	(11,093)	(14,633)	(40,034)	(46,601)
Less: Net loss attributable to the noncontrolling interest	(1,019)	(751)	(2,888)	(2,672)
Net loss attributable to Actua Corporation	(10,074)	(13,882)	(37,146)	(43,929)
Amounts attributable to Actua Corporation:
Net loss from continuing operations	(6,467)	(11,732)	(29,590)	(37,390)
Net loss from discontinued operations	(3,607)	(2,150)	(7,556)	(6,539)
Net loss attributable to Actua Corporation	$ (10,074)	$ (13,882)	$ (37,146)	$ (43,929)
Basic and diluted loss per share attributable to Actua Corporation:
Loss from continuing operations (in dollars per share)	$ (0.17)	$ (0.31)	$ (0.80)	$ (1.01)
Loss from discontinued operations (in dollars per share)	(0.10)	(0.06)	(0.21)	(0.18)
Net loss (in dollars per share)	$ (0.27)	$ (0.37)	$ (1.01)	$ (1.19)
Shares used in computation of basic and diluted loss per share (in shares)	36,776	37,146	36,943	37,038
Net loss	$ (11,093)	$ (14,633)	$ (40,034)	$ (46,601)
Other comprehensive loss:
Foreign currency translation adjustment	(71)	0	41	0
Comprehensive loss	(11,164)	(14,633)	(39,993)	(46,601)
Less: Comprehensive loss attributable to the noncontrolling interest	(1,019)	(751)	(2,888)	(2,672)
Comprehensive loss attributable to Actua Corporation	$ (10,145)	$ (13,882)	$ (37,105)	$ (43,929)