Acquisitions Narrative (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 04, 2014	May 31, 2015	Sep. 30, 2016	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired					$ 0	$ 75,000
Infostrada, SportsDirect, Covers, Enswers
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired		$ 69,849
Transaction costs							$ 3,000
Intangible assets, useful life (years)		12 years
Infostrada, SportsDirect, Covers, Enswers | Customer Relationships
Business Acquisition [Line Items]
Intangible assets, useful life (years)		11 years
Infostrada, SportsDirect, Covers, Enswers | Content Databases
Business Acquisition [Line Items]
Intangible assets, useful life (years)		14 years
Infostrada, SportsDirect, Covers, Enswers | Technologies
Business Acquisition [Line Items]
Intangible assets, useful life (years)		8 years
Infostrada, SportsDirect, Covers, Enswers | Trade Name and Trademarks
Business Acquisition [Line Items]
Intangible assets, useful life (years)		15 years
Infostrada, SportsDirect, Covers, Enswers | Non-competition Agreements
Business Acquisition [Line Items]
Intangible assets, useful life (years)		5 years
What's On
Business Acquisition [Line Items]
Payments to acquire businesses, net of cash acquired	$ 21,000
Business Combination, Consideration Transferred	27,000
Business Combination, Consideration Transferred, Liabilities Incurred	6,000
Consideration transferred, potential additional payment	$ 8,000
Consideration transferred, additional payment made			$ 4,000	$ 4,000