Financial Instruments (Fair Value Of Short-Term Investments) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Sep. 30, 2021	Mar. 31, 2021
Financial Instruments
Fair Value		$ 342	$ 1,106	[1]
Short-term investments
Financial Instruments
Cost or Amortized Cost		342	1,105
Gross Unrealized Gains	$ 1	0
Gross Unrealized Losses	0	0
Fair Value		342	1,106
Short-term investments | Corporate bonds
Financial Instruments
Cost or Amortized Cost		152	372
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value		152	372
Short-term investments | U.S. Treasury securities
Financial Instruments
Cost or Amortized Cost		65	374
Gross Unrealized Gains	1	0
Gross Unrealized Losses	0	0
Fair Value		65	375
Short-term investments | U.S. agency securities
Financial Instruments
Cost or Amortized Cost		0	3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value		0	3
Short-term investments | Commercial paper
Financial Instruments
Cost or Amortized Cost		35	136
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value		35	136
Short-term investments | Debt Security, Government, Non-US [Member]
Financial Instruments
Cost or Amortized Cost		32	67
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value		32	67
Short-term investments | Asset-backed Securities [Member]
Financial Instruments
Cost or Amortized Cost		40	112
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value		40	112
Short-term investments | Certificates of Deposit [Member]
Financial Instruments
Cost or Amortized Cost		18	41
Gross Unrealized Gains	0	0
Gross Unrealized Losses	$ 0	0
Fair Value		$ 18	$ 41

[1] Derived from audited Consolidated Financial Statements.