Goodwill And Acquisition-Related Intangibles, Net (Schedule Of Acquisition-Related Intangibles) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Mar. 31, 2015
Finite-Lived Intangible Assets
Gross carrying amount	$ 833	$ 833
Accumulated amortization	(762)	(722)
Acquisition-related intangibles, net	71	111	[1]
Developed And Core Technology
Finite-Lived Intangible Assets
Gross carrying amount	531	531
Accumulated amortization	(474)	(439)
Acquisition-related intangibles, net	57	92
Trade Names And Trademarks
Finite-Lived Intangible Assets
Gross carrying amount	130	130
Accumulated amortization	(116)	(111)
Acquisition-related intangibles, net	14	19
Registered User Base And Other Intangibles
Finite-Lived Intangible Assets
Gross carrying amount	87	87
Accumulated amortization	(87)	(87)
Acquisition-related intangibles, net	0	0
Carrier Contracts And Related
Finite-Lived Intangible Assets
Gross carrying amount	85	85
Accumulated amortization	(85)	(85)
Acquisition-related intangibles, net	$ 0	$ 0

[1] Derived from audited Consolidated Financial Statements.