Consolidated Businesses - Additional Information (Detail) - USD ($)				3 Months Ended
	Oct. 31, 2016	Sep. 16, 2016	Jan. 22, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Payments to Acquire Business Two, Net of Cash Acquired				$ 250,000	$ 2,150,000
Impact of subsidiary equity transactions				499,000	620,000
Payments to acquired additional interest in subsidiaries					5,400,000
Actua's share of consolidated business equity transactions					4,900,000
Additional Paid-In Capital
Business Acquisition [Line Items]
Impact of subsidiary equity transactions				507,000	$ 492,000
ErgoAdvocate | VelocityEHS
Business Acquisition [Line Items]
Business acquisition, consideration transferred			$ 1,250,000
Cash paid for acquisition			$ 1,000,000
Payments to Acquire Business Two, Net of Cash Acquired				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	$ 7,900,000			$ 8,600,000		$ 8,600,000
SAS | FolioDynamix
Business Acquisition [Line Items]
Business acquisition, consideration transferred	3,900,000
Maximum consideration payable	25,000,000.0
Consideration transferred, net of working capital adjustment	2,900,000
Liabilities incurred to be paid over 15 month period	$ 1,000,000