Stock-Based Compensation And Employee Benefit Plans (Tables)

12 Months Ended

Mar. 31, 2018

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule Of Assumptions Used In The Black-Scholes Valuation Model

	ESPP Purchase Rights
	Year Ended March 31,
	2018		2017		2016
Risk-free interest rate	1.1 - 2.0%		0.5 - 0.8%		0.3 - 0.6%
Expected volatility	28 - 30%		25 - 32%		32 - 36%
Weighted-average volatility	29	%	27	%	33	%
Expected term	6 - 12 months		6 - 12 months		6 - 12 months
Expected dividends	None		None		None

Schedule Of Assumptions Used In Monte-Carlo Simulation Model

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

	Year Ended March 31,
	2018		2017		2016
Risk-free interest rate	1.5 - 1.6%		0.8	%	1.0	%
Expected volatility	17 - 46%		16 - 57%		14 - 53%
Weighted-average volatility	28	%	29	%	26	%
Expected dividends	None		None		None

Schedule Of Stock-Based Compensation Expense By Statement Of Operations

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 Consolidated Statements of Operations (in millions):

	Year Ended March 31,
	2018		2017		2016
Cost of revenue	$	3	$	3	$	2
Research and development	146		109		103
Marketing and sales	32		31		24
General and administrative	61		53		49
Stock-based compensation expense	$	242	$	196	$	178

Summary Of Outstanding And Exercisable Stock Options

The following table summarizes outstanding and exercisable stock options as of March 31, 2018:

	Options Outstanding						Options Exercisable
Range of Exercise Prices	Number of Shares (in thousands)	Weighted- Average Remaining Contractual Term  (in years)	Weighted- Average Exercise Prices		Potential Dilution		Number of Shares (in thousands)	Weighted- Average Exercise Prices		Potential Dilution
$11.53 - $22.42	119	1.41	$	19.80	—	%	119	$	19.80	0.1	%
26.25 - 26.25	750	5.59	26.25		0.3	%	750	26.25		0.2	%
33.60 - 47.06	746	5.94	36.01		0.2	%	746	36.01		0.2	%
$11.53 - $47.06	1,615	5.44	$	30.28	0.5	%	1,615	$	30.28	0.5	%

Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity [Table Text Block]

The following table summarizes our ESPP activity for fiscal years ended March 31, 2018, 2017 and 2016:

	Shares Issued (in millions)	Exercise Prices for Purchase Rights	Weighted-Average Fair Values of Purchase Rights
Fiscal Year 2016	0.9	$32.16 - $54.78	$	12.97
Fiscal Year 2017	0.7	$54.60 - $67.56	$	17.93
Fiscal Year 2018	0.6	$67.56 - $99.82	$	21.57

Shares Repurchased and Retired

The following table summarizes total shares repurchased during fiscal years 2018, 2017, and 2016:

	May 2014 Program			May 2015 Program			February 2016 Program			May 2017 Program			Total
(In millions)	Shares	Amount		Shares	Amount		Shares	Amount		Shares	Amount		Shares	Amount
Fiscal Year 2016	1.0	$	57	6.9	$	461	7.8	$	500	—	$	—	15.7	$	1,018
Fiscal Year 2017	—	$	—	6.5	$	508	—	$	—	—	$	—	6.5	$	508
Fiscal Year 2018	—	$	—	0.3	$	31	—	$	—	5.0	$	570	5.3	$	601

Employee Stock Option [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Disclosure Of Stock-Based Compensation Arrangements By Stock-Based Payment Award

The following table summarizes our stock option activity for the fiscal year ended March 31, 2018:

	Options (in thousands)		Weighted- Average Exercise Prices		Weighted- Average Remaining Contractual Term  (in years)	Aggregate Intrinsic Value (in millions)
Outstanding as of March 31, 2017	2,377		$	33.35
Granted	5		113.39
Exercised	(764	)	40.30
Forfeited, cancelled or expired	(3	)	41.71
Outstanding as of March 31, 2018	1,615		$	30.28	5.44	$	147
Vested and expected to vest	1,615		$	30.28	5.44	$	147
Exercisable as of March 31, 2018	1,615		$	30.28	5.44	$	147

Restricted Stock Rights [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Disclosure Of Stock-Based Compensation Arrangements By Stock-Based Payment Award

Each restricted stock unit granted reduces the number of shares available for grant by 1.43 shares under our Equity Plan. The following table summarizes our restricted stock units activity, excluding market-based restricted stock unit activity which is discussed below, for the fiscal year ended March 31, 2018:

	Restricted Stock Units (in thousands)		Weighted- Average Grant Date Fair Values
Outstanding as of March 31, 2017	5,153		$	65.03
Granted	3,841		110.05
Vested	(2,581	)	59.49
Forfeited or cancelled	(465	)	80.97
Outstanding as of March 31, 2018	5,948		$	94.57

Performance Based Restricted Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Disclosure Of Stock-Based Compensation Arrangements By Stock-Based Payment Award

	Performance- Based Restricted Stock Units (in thousands)	Weighted- Average Grant Date Fair Value
Outstanding as of March 31, 2017	—	$	—
Granted	796	110.51
Forfeited or cancelled	—	—
Outstanding as of March 31, 2018	796	$	110.51

Market Based Restricted Stock Units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Disclosure Of Stock-Based Compensation Arrangements By Stock-Based Payment Award

:

	Market-Based Restricted  Stock Units (in thousands)		Weighted- Average  Grant Date Fair Value
Outstanding as of March 31, 2017	1,282		$	87.37
Granted	706		140.93
Vested	(430	)	76.27
Forfeited or cancelled	(216	)	91.88
Outstanding as of March 31, 2018	1,342		$	118.35