Stockholders' Equity - Stock-Based Expense Related to Grants of Employee and Consultant Stock Options, Restricted Stock and Restricted Stock Units (ZSUs) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	$ 30,436	$ 36,295	$ 99,803	$ 93,468
Cost of revenue [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	991	1,110	2,835	3,391
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	22,308	24,281	70,485	60,293
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	2,045	1,187	5,181	4,505
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based expense	$ 5,092	$ 9,717	$ 21,302	$ 25,279