Acquisitions - 2015 Acquisitions (Details) - USD ($) $ in Thousands		1 Months Ended	12 Months Ended
	Dec. 27, 2013	May 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 28, 2014
Business Acquisition [Line Items]
Cash	$ 2,816,000
Net cash			$ 0	$ 74,959	$ 279,833
Goodwill			$ 3,227,930	$ 3,228,224	$ 3,601,300
Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Cash		$ 71,768
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 income 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
Definite-lived intangible assets useful life, years		12 years
Customer relationships | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization		$ 17,000
Definite-lived intangible assets useful life, years		11 years
Content database | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization		$ 13,900
Definite-lived intangible assets useful life, years		14 years
Technologies | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization		$ 6,900
Definite-lived intangible assets useful life, years		8 years
Trade names and trademarks | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization		$ 5,200
Definite-lived intangible assets useful life, years		15 years
Noncompete Agreements | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization		$ 1,100
Definite-lived intangible assets useful life, years		5 years
Minimum | Customer relationships | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Definite-lived intangible assets useful life, years		6 years
Minimum | Content database | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Definite-lived intangible assets useful life, years		10 years
Minimum | Technologies | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Definite-lived intangible assets useful life, years		4 years
Maximum | Customer relationships | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Definite-lived intangible assets useful life, years		16 years
Maximum | Content database | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Definite-lived intangible assets useful life, years		16 years
Maximum | Technologies | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Definite-lived intangible assets useful life, years		10 years