Valuation And Qualifying Accounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 36	$ 38	$ 34
Expensed	34	29	27
Other Adjustments	(2)	3	(2)
Deductions	(29)	(34)	(21)
Balance at End of Period	39	36	38
Tax Valuation Allowance
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	331	357	351
Expensed	(3)	0	17
Other Adjustments	(17)	13	3
Deductions	0	(39)	(14)
Balance at End of Period	$ 311	$ 331	$ 357