Stock-Based Compensation (Tables)

6 Months Ended

Sep. 30, 2016

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

Schedule of assumptions used in the Black-Scholes valuation model

	ESPP Purchase Rights
	Three Months Ended September 30,
	2016		2015
Risk-free interest rate	0.5 - 0.6%		0.3 - 0.4%
Expected volatility	29 - 32%		32	%
Weighted-average volatility	31	%	32	%
Expected term	6 - 12 months		6 - 11.5 months
Expected dividends	None		None

Schedule Of Stock-Based Compensation Expense By Statement Of Operations

	Three Months Ended September 30,				Six Months Ended September 30,
	2016		2015		2016		2015
Cost of revenue	$	1	$	1	$	2	$	1
Research and development	27		$	25	54		51
Marketing and sales	8		7		15		12
General and administrative	12		11		25		25
Stock-based compensation expense	$	48	$	44	$	96	$	89

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

	Options (in thousands)		Weighted- Average Exercise Prices		Weighted- Average Remaining Contractual Term  (in years)	Aggregate Intrinsic Value (in millions)
Outstanding as of March 31, 2016	3,278		$	35.09
Granted	3		69.77
Exercised	(318	)	30.06
Forfeited, cancelled or expired	(31	)	35.84
Outstanding as of September 30, 2016	2,932		$	35.66	5.04	$	146
Vested and expected to vest	2,874		$	35.75	4.99	$	143
Exercisable as of September 30, 2016	2,337		$	36.83	4.44	$	114

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

	Restricted Stock Rights (in thousands)		Weighted- Average Grant Date Fair Values
Outstanding as of March 31, 2016	7,157		$	44.04
Granted	2,330		75.31
Vested	(3,384	)	35.43
Forfeited or cancelled	(364	)	55.26
Outstanding as of September 30, 2016	5,739		$	61.10

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, 2016	636		$	64.49
Granted	353		98.04
Vested	(558	)	50.08
Vested above target	238		44.99
Forfeited or cancelled	(15	)	86.39
Outstanding as of September 30, 2016	654		$	87.29

Repurchase Program, Total [Member]

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

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

	May 2014 Program			May 2015 Program			Total
(in millions)	Shares	Amount		Shares	Amount		Shares	Amount
Three months ended September 30, 2016	—	$	—	1.6	$	127	1.6	$	127
Six months ended September 30, 2016	—	$	—	3.5	$	256	3.5	$	256
Three months ended September 30, 2015	—	$	—	1.8	$	126	1.8	$	126
Six months ended September 30, 2015	1.0	$	57	3.0	$	201	4.0	$	258