Equity Award Plans - Summary of Activity for Restricted Common Stock, RSAs and RSUs and Summary of Information Related to Unvested Restricted Common Stock, RSAs and RSUs and those Expected to Vest (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Beginning balance, unvested (shares)	20,054
Granted (shares)	6,496
Vested (shares)	(1,475)
Cancelled (shares)	(1,179)
Ending balance, unvested (shares)	23,896	20,054
Expected to vest (shares)	7,030
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning balance, unvested, weighted average grant date fair value (per share)	$ 33.68
Weighted average grant date fair value, granted (per share)	12.56
Weighted average grant date fair value, vested (per share)	40.45
Weighted average grant date fair value, cancelled (per share)	34.29
Ending balance, unvested, weighted average grant date fair value (per share)	26.82	$ 33.68
Weighted average grant date fair value, expected to vest (per share)	$ 21.49
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Beginning balance, weighted-average remaining contractual term	1 year 7 months 6 days	1 year 7 months 6 days
Ending balance, weighted-average remaining contractual term	1 year 7 months 6 days	1 year 7 months 6 days
Expected to vest, weighted-average remaining contractual term	1 year 7 months 6 days
Beginning balance, aggregate intrinsic value	$ 415,912
Ending balance, aggregate intrinsic value	429,886	$ 415,912
Expected to vest, aggregate intrinsic value	$ 126,465