Stock-Based Compensation (Tables)

The assumptions used in the Monte-Carlo simulation model to value our market-based restricted stock units were as follows:


	Three Months Ended June 30,
	2020		2019
Risk-free interest rate	0.2	%	1.8	%
Expected volatility	23 - 63%		15 - 61%
Weighted-average volatility	37	%	29	%
Expected dividends	None		None

The following table summarizes stock-based compensation expense resulting from stock options, restricted stock units, market-based restricted stock units, performance-based restricted stock units, and the ESPP purchase rights included in our Condensed Consolidated Statements of Operations (in millions):


	Three Months Ended June 30,
	2020		2019
Cost of revenue	$	1	$	1
Research and development	66		49
Marketing and sales	11		7
General and administrative	24		16
Stock-based compensation expense	$	102	$	73

The following table summarizes our stock option activity for the three months ended June 30, 2020:


	Options (in thousands)	Weighted- Average Exercise Prices		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in millions)
Outstanding as of March 31, 2020	1,074	$	30.85
Granted	1	113.27
Exercised	(81)	31.88
Forfeited, cancelled or expired	—	—
Outstanding as of June 30, 2020	994	$	30.85	3.64	$	102
Vested and expected to vest	994	$	30.85	3.64	$	102
Exercisable as of June 30, 2020	994	$	30.85	3.64	$	102

The following table summarizes our restricted stock unit activity for the three months ended June 30, 2020:


	Restricted Stock Rights (in thousands)	Weighted- Average Grant Date Fair Values
Outstanding as of March 31, 2020	6,217	$	100.42
Granted	2,556	125.26
Vested	(1,431)	103.79
Forfeited or cancelled	(84)	103.75
Outstanding as of June 30, 2020	7,258	$	108.47

The following table summarizes our performance-based restricted stock unit activity, presented with the maximum number of shares that could potentially vest, for the three months ended June 30, 2020:


	Performance- Based Restricted Stock Units (in thousands)	Weighted- Average Grant Date Fair Value
Outstanding as of March 31, 2020	579	$	110.51
Granted	—	—
Forfeited or cancelled	—	—
Outstanding as of June 30, 2020	579	$	110.51

The following table summarizes our market-based restricted stock unit activity, presented with the maximum number of shares that could potentially vest, for the three months ended June 30, 2020:


	Market-Based Restricted Stock Units (in thousands)	Weighted- Average Grant Date Fair Value
Outstanding as of March 31, 2020	1,898	$	128.41
Granted	874	145.78
Vested	(157)	113.72
Forfeited or cancelled	(378)	137.88
Outstanding as of June 30, 2020	2,237	$	134.62

The following table summarizes total shares repurchased during the three months ended June 30, 2020 and 2019:



(In millions)	Shares	Amount
Three months ended June 30, 2020	0.7	$	78

Three months ended June 30, 2019	3.2	$	305