Acquisitions - Total Purchase Price for Acquisitions (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	May. 31, 2015	Sep. 30, 2015	Sep. 28, 2014	Dec. 28, 2014
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired		$ 75,000	$ 261,584
Goodwill		$ 3,945,265		$ 3,918,136
Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Cash consideration	$ 71,810
Cash acquired	(1,919)
Payments to acquire businesses, net of cash acquired	69,891
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	30,548
Total net assets acquired	$ 69,891
Intangible assets, useful life (years)	12 years
Customer Relationships | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 17,000
Intangible assets, useful life (years)	11 years
Content Databases | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 13,900
Intangible assets, useful life (years)	14 years
Technologies | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 6,900
Intangible assets, useful life (years)	8 years
Trade Name and Trademarks | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 5,200
Intangible assets, useful life (years)	15 years
Non-competition Agreements | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets subject to amortization	$ 1,100
Intangible assets, useful life (years)	5 years
Minimum | Customer Relationships | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets, useful life (years)	6 years
Minimum | Content Databases | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets, useful life (years)	10 years
Minimum | Technologies | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets, useful life (years)	4 years
Maximum | Customer Relationships | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets, useful life (years)	16 years
Maximum | Content Databases | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets, useful life (years)	16 years
Maximum | Technologies | Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Intangible assets, useful life (years)	10 years