Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Income and Expenses [Abstract]
Advertising expense	$ 262,701	$ 226,969	$ 206,351
Research and development expense	96,917	69,025	54,933
Stockholders’ (deficit) equity	(1,523,874)	(792,015)	(166,491)	$ 1,309,837
Foreign currency translation adjustment, net of tax	18,546	363	(100)
Foreign currency translation adjustment, tax	$ 11,286
Minimum
Deferred Revenue Arrangement [Line Items]
Length of prepaid subscriptions, term	3 months
Maximum
Deferred Revenue Arrangement [Line Items]
Length of prepaid subscriptions, term	12 months
Accumulated Other Comprehensive (Loss) Income
Other Income and Expenses [Abstract]
Stockholders’ (deficit) equity	$ 18,407	$ (139)	$ (502)	$ (402)