Discontinued Operations - Loss from Discontinued Operations, net of tax (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Major classes of line items constituting pretax loss of discontinued operations
Total discontinued operations, net of income taxes	$ 0	$ (2,081)
Discontinued operations attributable to Actua Corporation	$ 0	(1,971)
GovDelivery | Held-for-sale
Major classes of line items constituting pretax loss of discontinued operations
Revenue		9,424
Cost of revenue		(3,470)
Selling, general, administrative and other operating expenses		(7,935)
Other non-major income and expense items		(79)
Total discontinued operations before income taxes		(2,060)
Income tax benefit (expense)		(21)
Total discontinued operations, net of income taxes		(2,081)
Less: discontinued operations attributable to noncontrolling interests		(110)
Discontinued operations attributable to Actua Corporation		$ (1,971)