Goodwill And Acquisition-Related Intangibles, Net (Schedule Of Acquisition-Related Intangibles) (Details) (USD $) In Millions	Sep. 30, 2011	Mar. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Acquisition-Related Intangibles, Gross Carrying Amount	$ 829	$ 520
Acquisition-Related Intangibles, Accumulated Amortization	(413)	(376)
Acquisition-Related Intangibles, Net	416	144	[1]
Developed And Core Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-Related Intangibles, Gross Carrying Amount	510	259
Acquisition-Related Intangibles, Accumulated Amortization	(197)	(180)
Acquisition-Related Intangibles, Net	313	79
Trade Names And Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-Related Intangibles, Gross Carrying Amount	130	90
Acquisition-Related Intangibles, Accumulated Amortization	(77)	(70)
Acquisition-Related Intangibles, Net	53	20
Carrier Contracts And Related [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-Related Intangibles, Gross Carrying Amount	85	85
Acquisition-Related Intangibles, Accumulated Amortization	(64)	(62)
Acquisition-Related Intangibles, Net	21	23
Registered User Base And Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-Related Intangibles, Gross Carrying Amount	89	86
Acquisition-Related Intangibles, Accumulated Amortization	(75)	(64)
Acquisition-Related Intangibles, Net	14	22
In-Process Research And Development [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisition-Related Intangibles, Gross Carrying Amount	15
Acquisition-Related Intangibles, Net	$ 15

[1] Derived from audited consolidated financial statements.