Stock-Based Compensation and Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2020

Compensation Related Costs [Abstract]

Weighted-Average Valuation Assumptions

We used the following weighted-average assumptions in applying the Black-Scholes valuation model for determination of options:

	Three Months Ended March 31,
	2020	2019
Risk-free interest rate	—%	2.60% - 2.64%
Expected term (years)	0	6.3 - 6.6
Expected dividend yield	—	—
Expected volatility	—%	50.2%

Employee and Non-Employee Stock-Based Compensation Expense

The following table summarizes the components of stock-based compensation expense in the consolidated statements of operations (in thousands):

	Three Months Ended March 31,
	2020		2019
			As Restated
Cost of revenue	$	5,507	$	18,312
Research and development	6,096		14,230
Sales and marketing	3,890		11,512
General and administrative	7,526		23,768
	$	23,019	$	67,822

Stock Option and RSU Activity

The following table presents the stock activity and the total number of RSUs available for grant under our stock plans as of March 31, 2020:

	Plan Shares Available for Grant
Balances at December 31, 2019	17,233,144
Added to plan	6,263,315
Granted	(78,338	)
Cancelled	385,766
Expired	(284,039	)
Balances at March 31, 2020	23,519,848

The following table summarizes the stock option activity under our stock plans during the reporting period (in thousands), except per share amounts:

	Outstanding Options
	Number of Shares		Weighted Average Exercise Price		Remaining Contractual Life (Years)	Aggregate Intrinsic Value
						(in thousands)
December 31, 2019	17,837,316		$	20.76	6.94	$	14,964
Exercised	(110,949	)	6.14
Cancelled	(219,729	)	25.79
Balances at March 31, 2020	17,506,638		20.79		6.66	6,814
Vested and expected to vest at Current period end	16,856,937		21.20		6.57	6,071
Exercisable at Current period end	9,499,310		28.59		4.76	9

RSU Activity and Related Information

A summary of our RSUs activity and related information is as follows:

	Number of Awards Outstanding		Weighted Average Grant Date Fair Value
Unvested Balance at December 31, 2019	10,112,266		$	17.29
Granted	78,338		10.88
Vested	(3,010,606	)	19.80
Forfeited	(167,564	)	15.77
Balances at March 31, 2020	7,012,434		16.18

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions

We use the Black-Scholes option pricing model to determine the fair value of shares purchased under the 2018 ESPP with the following weighted average assumptions on the date of grant:

	Three Months Ended March 31,
	2020	2019
Risk-free interest rate	1.51%	2.60% - 2.64%
Expected term (years)	0.5 - 2.0	0.5 - 2.0
Expected dividend yield	—	—
Expected volatility	61.0%	50.2%