Schedule II - Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Valuation and qualifying accounts
Balance at Beginning of Period	$ 496	$ 573	$ 558
Charged to Costs and Expenses	80	63	113
Charged to Other Accounts	183	4
Deductions	(87)	(144)	(98)
Balance at End of Period	672	496	573
Valuation and qualifying accounts, classified as current	287	101	98
Allowance for doubtful accounts
Valuation and qualifying accounts
Balance at Beginning of Period	17	16		16
Charged to Costs and Expenses	4	1
Charged to Other Accounts	(2)
Balance at End of Period	19	17		16
Environmental
Valuation and qualifying accounts
Balance at Beginning of Period	330	344	360
Charged to Costs and Expenses	79	60	56
Charged to Other Accounts	(7)
Deductions	(68)	(74)	(72)
Balance at End of Period	334	330	344
Litigation, tax and other reserves
Valuation and qualifying accounts
Balance at Beginning of Period	166	229	198
Charged to Costs and Expenses	1	3	57
Charged to Other Accounts	190	4
Deductions	(19)	(70)	(26)
Balance at End of Period	$ 338	$ 166	$ 229