Significant Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) subsidiary	Sep. 30, 2014 customer	Sep. 30, 2015 USD ($) revenue_source customer	Sep. 30, 2014 customer	Dec. 31, 2014 USD ($)
Significant Accounting Policies [Line Items]
Redeemable noncontrolling interests	$ 9,200		$ 9,200		$ 10,346
Additional paid-in capital	3,567,437		3,567,437		3,553,430
Noncontrolling interests	14,674		14,674		18,288
Accounts receivables, net of allowance	(27,617)		$ (27,617)		(23,134)
Actua's Consolidated Revenue
Significant Accounting Policies [Line Items]
Number of customers represented for more than 10% of consolidated revenue | customer		0	0	0
Channel Intelligence
Significant Accounting Policies [Line Items]
Proceeds from escrow releases	4,000		$ 4,000
MSDSonline One
Significant Accounting Policies [Line Items]
Number of sources of revenues | revenue_source			2
FolioDynamix
Significant Accounting Policies [Line Items]
Initial subscription arrangement, minimum			3 years
Initial subscription arrangement, maximum			5 years
Correction of Error, Recognition of Permanent Equity | Restatement Adjustment
Significant Accounting Policies [Line Items]
Redeemable noncontrolling interests					4,100
Additional paid-in capital					(1,400)
Noncontrolling interests					$ (2,700)
Shareholder Notes Receivable, Balance Sheet Reclassification | Restatement Adjustment
Significant Accounting Policies [Line Items]
Noncontrolling interests	1,800		$ 1,800
Accounts receivables, net of allowance	$ 1,800		$ 1,800
Number of subsidiaries | subsidiary	2