Stock-Based Compensation (Tables)

9 Months Ended

Dec. 31, 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
	Nine Months Ended December 31,
	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 December 31,				Nine Months Ended December 31,
	2016		2015		2016		2015
Cost of revenue	$	—	$	—	$	2	$	1
Research and development	27		26		81		77
Marketing and sales	8		5		23		17
General and administrative	13		11		38		36
Stock-based compensation expense	$	48	$	42	$	144	$	131

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	4		72.43
Exercised	(370	)	30.13
Forfeited, cancelled or expired	(31	)	35.78
Outstanding as of December 31, 2016	2,881		$	35.78	4.78	$	124
Vested and expected to vest	2,843		$	35.84	4.74	$	122
Exercisable as of December 31, 2016	2,326		$	36.81	4.20	$	98

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	2,529		75.68
Vested	(3,658	)	36.39
Forfeited or cancelled	(487	)	56.76
Outstanding as of December 31, 2016	5,541		$	62.41

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	(28	)	84.94
Outstanding as of December 31, 2016	641		$	87.37

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 December 31, 2016	—	$	—	1.5	$	127	1.5	$	127
Nine months ended December 31, 2016	—	$	—	5.0	$	383	5.0	$	383
Three months ended December 31, 2015	—	$	—	1.8	$	126	1.8	$	126
Nine months ended December 31, 2015	1.0	$	57	4.8	$	327	5.8	$	384