Financial Instruments (Fair Value Of Short-Term Investments) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2015	Mar. 31, 2015
Financial Instruments
Fair Value	$ 1,069	$ 953	[1]
Short-Term Investments
Financial Instruments
Cost or Amortized Cost	1,069	952
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Fair Value	1,069	953
Short-Term Investments | Corporate bonds
Financial Instruments
Cost or Amortized Cost	565	467
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	565	467
Short-Term Investments | U.S. Treasury securities
Financial Instruments
Cost or Amortized Cost	218	214
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	218	214
Short-Term Investments | U.S. agency securities
Financial Instruments
Cost or Amortized Cost	191	161
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Fair Value	191	162
Short-Term Investments | Commercial paper
Financial Instruments
Cost or Amortized Cost	95	110
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 95	$ 110

[1] Derived from audited consolidated financial statements.