(Fair Value Of Short-Term Investments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Financial Instruments [Line Items]
Fair Value	$ 583	$ 388
Short-Term Investments [Member]
Financial Instruments [Line Items]
Cost or Amortized Cost	583	387
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Fair Value	583	388
Short-Term Investments [Member] | Corporate Bonds [Member]
Financial Instruments [Line Items]
Cost or Amortized Cost	279	177
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Fair Value	279	178
Short-Term Investments [Member] | U.S. Treasury Securities [Member]
Financial Instruments [Line Items]
Cost or Amortized Cost	114	85
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	114	85
Short-Term Investments [Member] | U.S. Agency Securities [Member]
Financial Instruments [Line Items]
Cost or Amortized Cost	80	76
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	80	76
Short-Term Investments [Member] | Commercial Paper [Member]
Financial Instruments [Line Items]
Cost or Amortized Cost	110	49
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 110	$ 49