Schedule II Valuation And Qualifying Accounts (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance For Doubtful Accounts, Accounts Receivable [Member]
Allowance for doubtful accounts
Balance at Beginning of Period		$ 20	$ 21	$ 19
Additions Charged to Costs and Expenses		28	24	31
Deductions	[1]	24	24	30
Balance at End of Period		24	20	21
Allowance For Doubtful Accounts, Notes Feceivable [Member]
Allowance for doubtful accounts
Balance at Beginning of Period		1	1	2
Additions Charged to Costs and Expenses			(1)
Balance at End of Period		1	1	1
Income Tax Valuation Allowance [Member]
Allowance for doubtful accounts
Balance at Beginning of Period		11	11	7
Additions Charged to Costs and Expenses		1		4
Balance at End of Period		$ 12	$ 11	$ 11

[1] Deductions in the allowance for doubtful accounts for accounts receivable reflect write-offs of uncollectible accounts.