Related Party Transactions - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018 USD ($) Director	Dec. 31, 2017 USD ($)
Related Party Transaction [Line Items]
Advertising expenses	$ 25,700,000	$ 30,500,000
Board of Directors Chairman
Related Party Transaction [Line Items]
Number of board of directors | Director	2
Galore Media, Inc.
Related Party Transaction [Line Items]
Advertising expenses	$ 0
Galore Media, Inc. | Maximum
Related Party Transaction [Line Items]
Advertising expenses		$ 100,000