Goodwill And Acquisition-Related Intangibles, Net (Schedule Of Acquisition-Related Intangibles) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Mar. 31, 2012
Finite-Lived Intangible Assets
Gross Carrying Amount	$ 829	$ 829
Accumulated Amortization	(525)	(460)
Acquisition-Related Intangibles, Net	304	369	[1]
Developed And Core Technology
Finite-Lived Intangible Assets
Gross Carrying Amount	524	518
Accumulated Amortization	(274)	(229)
Acquisition-Related Intangibles, Net	250	289
Trade Names And Trademarks
Finite-Lived Intangible Assets
Gross Carrying Amount	130	131
Accumulated Amortization	(94)	(84)
Acquisition-Related Intangibles, Net	36	47
Registered User Base And Other Intangibles
Finite-Lived Intangible Assets
Gross Carrying Amount	90	90
Accumulated Amortization	(85)	(80)
Acquisition-Related Intangibles, Net	5	10
Carrier Contracts And Related
Finite-Lived Intangible Assets
Gross Carrying Amount	85	85
Accumulated Amortization	(72)	(67)
Acquisition-Related Intangibles, Net	13	18
In-Process Research And Development
Finite-Lived Intangible Assets
Gross Carrying Amount	0	5
Accumulated Amortization	0	0
Acquisition-Related Intangibles, Net	$ 0	$ 5

[1] Derived from audited consolidated financial statements.