Valuation And Qualifying Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 39	$ 36	$ 38
Expensed	(41)	(34)	(29)
Other Adjustments	0	2	(3)
Deductions	(28)	(29)	(34)
Balance at End of Period	52	39	36
Tax Valuation Allowance
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	311	331	357
Expensed	(95)	(3)	0
Other Adjustments	2	(17)	(13)
Deductions	0	0	(39)
Balance at End of Period	$ 214	$ 311	$ 331