Cash and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

Cash And Marketable Securities [Abstract]

Schedule Of Amortized Cost, Fair Value And Gross Unrealized Gains And Losses Of The Company's Short- And Long-Term Investments In Debt And Equity Securities

			Gross Realized		Gross Realized
	Amortized		and Unrealized		and Unrealized		Fair
(In millions)	Cost		Gains		Losses		Value
Available-for-sale securities, December 31, 2019:
Debt securities	$	4	$	—	$	—	$	4
Equity securities		9		—		—		9
Total securities	$	13	$	—	$	—	$	13
Available-for-sale securities, December 31, 2018:
Debt securities	$	4	$	—	$	—	$	4
Equity securities		15		1		—		16
Total securities	$	19	$	1	$	—	$	21