Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation and qualifying accounts
Balance at Beginning of Period	$ 672	$ 496	$ 573
Charged to Costs and Expenses	119	80	63
Charged to Other Accounts	2	183	4
Deductions	(314)	(87)	(144)
Balance at End of Period	479	672	496
Valuation and qualifying accounts, classified as current	98	287	101
Allowance for doubtful accounts
Valuation and qualifying accounts
Balance at Beginning of Period	19	17	16
Charged to Costs and Expenses	9	4	1
Charged to Other Accounts	(3)	(2)
Deductions	(5)
Balance at End of Period	20	19	17
Environmental
Valuation and qualifying accounts
Balance at Beginning of Period	334	330	344
Charged to Costs and Expenses	117	79	60
Charged to Other Accounts		(7)
Deductions	(65)	(68)	(74)
Balance at End of Period	386	334	330
Litigation, tax and other reserves
Valuation and qualifying accounts
Balance at Beginning of Period	338	166	229
Charged to Costs and Expenses	2	1	3
Charged to Other Accounts	2	190	4
Deductions	(249)	(19)	(70)
Balance at End of Period	$ 93	$ 338	$ 166