Goodwill And Acquisition-Related Intangibles, Net (Schedule Of Acquisition-Related Intangibles) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Acquisition-related intangibles, Gross Carrying Amount	$ 833	$ 829
Acquisition-related intangibles, Accumulated Amortization	(580)	(460)
Acquisition-related intangibles, net	253	369
Developed And Core Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-related intangibles, Gross Carrying Amount	527	518
Acquisition-related intangibles, Accumulated Amortization	(324)	(229)
Acquisition-related intangibles, net	203	289
Trade Names And Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-related intangibles, Gross Carrying Amount	130	131
Acquisition-related intangibles, Accumulated Amortization	(99)	(84)
Acquisition-related intangibles, net	31	47
Registered User Base And Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-related intangibles, Gross Carrying Amount	87	90
Acquisition-related intangibles, Accumulated Amortization	(84)	(80)
Acquisition-related intangibles, net	3	10
Carrier Contracts And Related [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-related intangibles, Gross Carrying Amount	85	85
Acquisition-related intangibles, Accumulated Amortization	(73)	(67)
Acquisition-related intangibles, net	12	18
In-Process Research And Development [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-related intangibles, Gross Carrying Amount	4	5
Acquisition-related intangibles, Accumulated Amortization	0	0
Acquisition-related intangibles, net	$ 4	$ 5