Segment Information - Summary of Selected Information Related to Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue	$ 34,610	$ 30,592
Net loss attributable to Actua Corporation	(14,331)	(14,765)
Segment Reporting Information, Profit (Loss) [Abstract]
General and administrative	(14,496)	(15,436)
Impairment related and other	(231)	(346)
Other (loss) income, net	(156)	1,537
Interest income	48	19
Net loss attributable to the noncontrolling interest	1,052	1,160
Net loss attributable to Actua Corporation	(14,331)	(14,765)
Assets	436,657		$ 450,144
Operating Segments
Segment Reporting Information [Line Items]
Revenue	34,610	30,592
Net loss attributable to Actua Corporation	(8,521)	(7,947)
Segment Reporting Information, Profit (Loss) [Abstract]
Net loss attributable to Actua Corporation	(8,521)	(7,947)
Assets	397,406		393,182
Operating Segments | Vertical Cloud
Segment Reporting Information [Line Items]
Revenue	34,610	30,592
Net loss attributable to Actua Corporation	(8,521)	(7,947)
Segment Reporting Information, Profit (Loss) [Abstract]
Net loss attributable to Actua Corporation	(8,521)	(7,947)
Assets	380,289		376,565
Operating Segments | Vertical Cloud (Venture)
Segment Reporting Information [Line Items]
Revenue	0	0
Net loss attributable to Actua Corporation	0	0
Segment Reporting Information, Profit (Loss) [Abstract]
Net loss attributable to Actua Corporation	0	0
Assets	17,117		16,617
Other
Segment Reporting Information [Line Items]
Revenue	0	0
Net loss attributable to Actua Corporation	(5,810)	(6,818)
Segment Reporting Information, Profit (Loss) [Abstract]
General and administrative	(6,945)	(9,291)
Impairment related and other	0	(95)
Other (loss) income, net	46	1,390
Interest income	37	18
Net loss attributable to the noncontrolling interest	1,052	1,160
Net loss attributable to Actua Corporation	(5,810)	$ (6,818)
Assets	$ 39,251		$ 56,962