Acquisitions - Total Purchase Price for Acquisitions (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	May 31, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Net cash		$ 0	$ 75,000
Goodwill		$ 3,563,522		$ 3,561,812
Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Cash	$ 71,768
Less: cash acquired	(1,919)
Net cash	69,849
Restricted cash and cash equivalents	404
Accounts receivable and other current assets	2,481
Property and equipment	805
Deferred tax assets	3,816
Other long term assets	157
Accounts payable and other current liabilities	(1,507)
Deferred revenue	(339)
Deferred tax liabilities	(10,097)
Other liabilities	(477)
Total identifiable net assets	39,343
Goodwill	30,506
Total net assets acquired	$ 69,849
Intangible assets, useful life (years)	12 years
Infostrada, SportsDirect, Covers, Enswers | Customer Relationships
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 17,000
Intangible assets, useful life (years)	11 years
Infostrada, SportsDirect, Covers, Enswers | Content Databases
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 13,900
Intangible assets, useful life (years)	14 years
Infostrada, SportsDirect, Covers, Enswers | Technologies
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 6,900
Intangible assets, useful life (years)	8 years
Infostrada, SportsDirect, Covers, Enswers | Trade Name and Trademarks
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 5,200
Intangible assets, useful life (years)	15 years
Infostrada, SportsDirect, Covers, Enswers | Non-competition Agreements
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 1,100
Intangible assets, useful life (years)	5 years
Infostrada, SportsDirect, Covers, Enswers | Minimum | Customer Relationships
Business Acquisition [Line Items]
Intangible assets, useful life (years)	6 years
Infostrada, SportsDirect, Covers, Enswers | Minimum | Content Databases
Business Acquisition [Line Items]
Intangible assets, useful life (years)	10 years
Infostrada, SportsDirect, Covers, Enswers | Minimum | Technologies
Business Acquisition [Line Items]
Intangible assets, useful life (years)	4 years
Infostrada, SportsDirect, Covers, Enswers | Maximum | Customer Relationships
Business Acquisition [Line Items]
Intangible assets, useful life (years)	16 years
Infostrada, SportsDirect, Covers, Enswers | Maximum | Content Databases
Business Acquisition [Line Items]
Intangible assets, useful life (years)	16 years
Infostrada, SportsDirect, Covers, Enswers | Maximum | Technologies
Business Acquisition [Line Items]
Intangible assets, useful life (years)	10 years