Business Description and Basis of Presentation - Additional Information (Details)	6 Months Ended
	Jun. 30, 2018 Market Language Brand Segment
Description Of Business And Basis Of Presentation [Line Items]
Number of markets with localized versions of website | Market	48
Number of languages worldwide | Language	28
Number of reportable segment | Segment	2
Minimum
Description Of Business And Basis Of Presentation [Line Items]
Number of other media brands with websites | Brand	20