Stock-Based Compensation (Tables)

6 Months Ended

Sep. 30, 2014

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

Schedule of assumptions used in the Black-Scholes valuation model

	Stock Option Grants				ESPP
	Three Months Ended September 30,		Six Months Ended September 30,		Three Months Ended September 30,
	2014		2014		2014		2013
Risk-free interest rate	1.2 - 1.9%		1.1 - 1.9%		0.04 - 0.1%		0.1	%
Expected volatility	36 - 38%		36 - 40%		34 - 35%		36 - 37%
Weighted-average volatility	37	%	38	%	35	%	37	%
Expected term	4.5		4.5		6 - 12 months		6 - 12 months
Expected dividends	None		None		None		None

Schedule Of Stock-Based Compensation Expense By Statement Of Operations

	Three Months Ended September 30,				Six Months Ended September 30,
	2014		2013		2014		2013
Cost of revenue	$	1	$	1	$	1	$	1
Research and development	23		23		39		43
Marketing and sales	6		6		10		13
General and administrative	10		8		19		14
Stock-based compensation expense	$	40	$	38	$	69	$	71

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, 2014	5,311		$	37.43
Granted	1,244		35.75
Exercised	(291	)	20.51
Forfeited, cancelled or expired	(210	)	49.83
Outstanding as of September 30, 2014	6,054		$	37.47	5.35	$	34
Vested and expected to vest	5,671		$	37.85	5.07	$	32
Exercisable as of September 30, 2014	3,744		$	41.43	2.85	$	22

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
Balance as of March 31, 2014	13,536		$	19.70
Granted	3,893		35.70
Vested	(4,705	)	19.63
Forfeited or cancelled	(930	)	22.53
Balance as of September 30, 2014	11,794		$	24.79

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 Values
Balance as of March 31, 2014	54		$	15.39
Vested	(49	)	15.39
Forfeited or cancelled	(5	)	15.39
Balance as of September 30, 2014	—		—

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
Balance as of March 31, 2014	978		$	24.83
Granted	193		46.96
Vested	(671	)	21.45
Vested above target	192		16.80
Forfeited or cancelled	(29	)	33.70
Balance as of September 30, 2014	663		$	31.97