Stockholders' Equity - Stock-Based Expense Related to Grants of Employee and Consultant Stock Options, Restricted Stock and ZSUs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	$ 107,461	$ 131,575	$ 129,233
Cost of Revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	3,720	4,547	4,623
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	84,236	94,548	83,673
Sales and Marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	7,254	7,501	5,927
General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	$ 12,251	$ 24,979	$ 35,010