Financial Instruments (Fair Value Of Short-Term Investments) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021
Financial Instruments
Fair Value	$ 881	$ 1,106	[1]
Short-term investments
Financial Instruments
Cost or Amortized Cost	880	1,105
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	0
Fair Value	881	1,106
Short-term investments | Corporate bonds
Financial Instruments
Cost or Amortized Cost	335	372
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	335	372
Short-term investments | U.S. Treasury securities
Financial Instruments
Cost or Amortized Cost	199	374
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	0
Fair Value	200	375
Short-term investments | U.S. agency securities
Financial Instruments
Cost or Amortized Cost	3	3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	3	3
Short-term investments | Commercial paper
Financial Instruments
Cost or Amortized Cost	126	136
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	126	136
Short-term investments | Debt Security, Government, Non-US [Member]
Financial Instruments
Cost or Amortized Cost	63	67
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	63	67
Short-term investments | Asset-backed Securities [Member]
Financial Instruments
Cost or Amortized Cost	117	112
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	117	112
Short-term investments | Certificates of Deposit [Member]
Financial Instruments
Cost or Amortized Cost	37	41
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 37	$ 41

[1] Derived from audited Consolidated Financial Statements.