Valuation and Qualifying Accounts (Details) - 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	$ 31	$ 25	$ 27
Charges to Earnings	27	19	12
Charges to Other Accounts	(8)	1	(3)
Deductions	(16)	(14)	(11)
Balance of End of Period	34	31	25
Other reserves
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	22	24	30
Balance of End of Period	$ 19	$ 22	$ 24