Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2016

Equity [Abstract]

Weighted-Average Grant Date Fair Value of Stock Options and Related Assumptions

The following table presents the weighted-average grant date fair value of stock options and the related assumptions used to estimate the fair value in our consolidated financial statements:

	Year Ended December 31,
	2016			2015			2014
Expected term, in years		6			6			5
Risk-free interest rates		1.53	%		1.65	%		1.31	%
Expected volatility		50	%		53	%		56	%
Dividend yield		—			—			—
Weighted-average estimated fair value of options granted    during the year	$	1.30		$	1.51		$	3.44

Stock-Based Expense Related to Grants of Employee and Consultant Stock Options, Restricted Stock and ZSUs

We recorded stock-based expense related to grants of employee and consultant stock options, restricted stock and ZSUs in our consolidated statements of operations as follows (in thousands):

	Year Ended December 31,
	2016		2015		2014
Cost of revenue	$	3,720	$	4,547	$	4,623
Research and development		84,236		94,548		83,673
Sales and marketing		7,254		7,501		5,927
General and administrative		12,251		24,979		35,010
Total stock-based expense	$	107,461	$	131,575	$	129,233

Schedule of Share Based Compensation Stock Option Activity

The following table shows stock option activity for 2016 (in thousands, except weighted-average exercise price and remaining contractual term):

	Outstanding Options
				Weighted-		Aggregate		Weighted-
				Average		Intrinsic Value of		Average
				Exercise		Stock Options		Contractual Term
	Stock Options			Price		Outstanding		(in years)
Balance as of December 31, 2015		23,215		$	1.93	$	35,949		5.36
Granted		21,300			2.63
Forfeited and cancelled		(3,635	)		6.33
Exercised		(4,022	)		0.34
Balance as of December 31, 2016		36,858		$	2.08	$	26,411		6.81
As of December 31, 2016
Exercisable options		15,768		$	1.30	$	24,892		3.28
Vested and expected to vest		27,521		$	1.88	$	25,815		5.89

Schedule of Share Based Compensation Restricted Stock Units Award Activity

The following table shows a summary of ZSU activity for  2016 (in thousands, except weighted-average fair value and remaining term):

	Outstanding ZSUs
				Weighted- Average Grant Date		Aggregate Intrinsic Value of
				Fair		Unvested
	Shares			Value		ZSUs
Unvested as of December 31, 2015		62,436		$	3.06	$	167,328
Granted		42,260			2.41
Vested		(32,357	)		2.74
Forfeited and cancelled		(12,887	)		3.59
Unvested as of December 31, 2016		59,452		$	2.66	$	152,792

Common Stock Reserved for Future Issuance

As of December 31, 2016, we had reserved shares of common stock for future issuance as follows (in thousands):

	December 31, 2016
Stock options outstanding		36,858
ZSUs outstanding		59,452
2011 Equity Incentive Plan		99,447
2011 Employee Stock Purchase Plan		78,013
		273,770

Schedule of Accumulated Other Comprehensive Income Loss

The components of accumulated other comprehensive income, net of taxes, were as follows (in thousands):

	Foreign Currency Translation			Unrealized Gains (Losses) on Available- for-Sale Securities			Total
Balance as of December 31, 2014	$	(28,781	)	$	(394	)	$	(29,175	)
Other comprehensive income (loss) before reclassifications		(23,480	)		307			(23,173	)
Amounts reclassified from accumulated other comprehensive    income (loss)		—			(40	)		(40	)
Net current-period other comprehensive income (loss)		(23,480	)		267			(23,213	)
Balance as of December 31, 2015	$	(52,261	)	$	(127	)	$	(52,388	)
Other comprehensive income (loss) before reclassifications		(76,410	)		105			(76,305	)
Amounts reclassified from accumulated other comprehensive    income (loss)		—			(1	)		(1	)
Net current-period other comprehensive income (loss)		(76,410	)		104			(76,306	)
Balance as of December 31, 2016	$	(128,671	)	$	(23	)	$	(128,694	)