Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts
Valuation and qualifying accounts
Balance at Beginning of Period	$ 558	$ 20	$ 19
Charged to Costs and Expenses	37	543	9
Charged to Other Accounts	(2)	(3)	(3)
Deductions	1	(2)	(5)
Balance at End of Period	594	558	20
Valuation and qualifying accounts, classified as current	18	17	20
Environmental, litigation, tax and other reserves
Valuation and qualifying accounts
Balance at Beginning of Period	997	479	672
Charged to Costs and Expenses	45	61	119
Charged to Other Accounts	53	531	2
Deductions	(160)	(74)	(314)
Balance at End of Period	935	997	479
Valuation and qualifying accounts, classified as current	$ 163	$ 197	$ 98