(Fair Value Of Short-Term Investments By Stated Maturity Date Schedule) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Financial Instruments [Line Items]
Short-term investments, Fair Value	$ 583	$ 388
Short-Term Investments [Member]
Financial Instruments [Line Items]
Due in 1 year or less, Amortized Cost	318	160
Due in 1-2 years, Amortized Cost	156	126
Due in 2-3 years, Amortized Cost	104	101
Due in 3-4 years, Amortized Cost	5	0
Short-term investments, Amortized Cost	583	387
Due in 1 year or less, Fair Value	318	160
Due in 1-2 years, Fair Value	156	127
Due in 2-3 years, Fair Value	104	101
Due in 3-4 years, Fair Value	5	0
Short-term investments, Fair Value	$ 583	$ 388