Restructuring and Related Reorganization Charges - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring and Related Activities [Abstract]
Restructuring and related reorganization charges	[1]	$ 16,738	$ 55,907	$ 104,871

[1] (1) Includes stock-based compensation as follows: Cost of revenue$10,173 $11,388 $5,307Selling and marketing39,855 46,654 33,164Technology and content54,633 63,536 26,766General and administrative44,689 108,149 80,082Restructuring and related reorganization charges— 12,690 32,749