Acquisitions and Dispositions - Dispositions (Details) $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Jul. 31, 2017 USD ($)	Feb. 28, 2015 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)	Apr. 30, 2016 USD ($)
Dispositions
Gain on sale of business					$ 40,230	$ 3,156
Cash received from disposal of businesses and online properties, net of cash disposed				$ 4,285	36,815	5,071
Cracked | Sold
Dispositions
Total consideration received							$ 39,000
Restricted cash, current, in escrow					3,900		$ 3,900
Amount of escrow released	$ 3,900
Revenue					1,800	10,900
Pre-tax (loss) income					1,900	3,100
Gain on sale of business					38,100
Net assets sold					600
Transaction costs incurred during sale					300
Certain non-core online properties | Sold
Dispositions
Total consideration received					$ 2,100	1,200
Number of properties sold | item					2
Cash received from disposal of businesses and online properties, net of cash disposed			$ 400
Pluck Social Media | Sold
Dispositions
Total consideration received		$ 3,800
Gain on sale of business		$ 2,100
Other income, net | Certain non-core online properties | Sold
Dispositions
Gain on sale of business					$ 2,100	$ 1,000