Consolidated Businesses - Additional Information (Detail) - USD ($)					12 Months Ended
	Oct. 31, 2016	Sep. 16, 2016	Jan. 22, 2016	Nov. 25, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2016	Mar. 31, 2015
Business Acquisition [Line Items]
Impact of subsidiary equity transactions					$ 5,719,000	$ (4,803,000)	$ 1,658,000
Payments to acquire additional interest in subsidiaries					5,400,000	4,000,000
Actua's share of consolidated business equity transactions					(500,000)
Additional paid-in capital
Business Acquisition [Line Items]
Impact of subsidiary equity transactions					$ 4,924,000	$ (4,441,000)	$ 2,551,000
GovDelivery
Business Acquisition [Line Items]
Ownership percentage					94.00%	93.00%		92.00%	91.00%
Payments to acquire additional interest in subsidiaries					$ 2,500,000	$ 1,900,000
VelocityEHS
Business Acquisition [Line Items]
Ownership percentage					99.00%	98.00%		98.00%	96.00%
Payments to acquire additional interest in subsidiaries					$ 2,400,000	$ 1,400,000
FolioDynamix
Business Acquisition [Line Items]
Payments to acquire additional interest in subsidiaries					500,000
WellNet | VelocityEHS
Business Acquisition [Line Items]
Business acquisition, consideration transferred				$ 700,000
Intangible assets recorded in connection with acquisition				$ 2,900,000
Cash paid for acquisition					2,200,000
ErgoAdvocate | VelocityEHS
Business Acquisition [Line Items]
Business acquisition, consideration transferred			$ 1,250,000
Cash paid for acquisition			1,000,000
Liabilities incurred to be paid in one year			$ 250,000
E3 Solutions | VelocityEHS
Business Acquisition [Line Items]
Business acquisition, consideration transferred		$ 3,000,000
Cash paid for acquisition		2,700,000
Liabilities incurred to be paid in equal halves on one year and 18 month anniversaries of the closing		$ 300,000
SAS
Business Acquisition [Line Items]
Contingent consideration liability	$ 8,400,000				$ 8,800,000
SAS | FolioDynamix
Business Acquisition [Line Items]
Business acquisition, consideration transferred	3,900,000
Consideration transferred, net of working capital adjustment	2,900,000
Liabilities incurred to be paid over 15 month period	1,000,000
Maximum consideration payable	$ 25,000,000.0