Goodwill And Acquisition-Related Intangibles, Net (Schedule Of Acquisition-Related Intangibles) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Mar. 31, 2012
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 835	$ 829
Accumulated Amortization	(501)	(460)
Acquisition-Related Intangibles, Net	334	369	[1]
Developed And Core Technology
Finite-Lived Intangible Assets
Gross Carrying Amount	525	518
Accumulated Amortization	(257)	(229)
Acquisition-Related Intangibles, Net	268	289
Trade Names And Trademarks
Finite-Lived Intangible Assets
Gross Carrying Amount	131	131
Accumulated Amortization	(91)	(84)
Acquisition-Related Intangibles, Net	40	47
Registered User Base And Other Intangibles
Finite-Lived Intangible Assets
Gross Carrying Amount	90	90
Accumulated Amortization	(83)	(80)
Acquisition-Related Intangibles, Net	7	10
Carrier Contracts And Related
Finite-Lived Intangible Assets
Gross Carrying Amount	85	85
Accumulated Amortization	(70)	(67)
Acquisition-Related Intangibles, Net	15	18
In-Process Research And Development
Finite-Lived Intangible Assets
Gross Carrying Amount	4	5
Accumulated Amortization	0	0
Acquisition-Related Intangibles, Net	$ 4	$ 5

[1] Derived from audited consolidated financial statements.