Fair Value Measurements, Level 3 Reconciliation (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Investments of Certain Benefit Plans [Member]
Reconciliation of the beginning and ending balances for fair value measurements developed using significant unobservable inputs
Balance as of beginning of period	$ 11	$ 11	$ 11	$ 10
Purchases	0	0	0	0
Transfers in and/or out of Level 3	0	0	0	0
Balance as of end of period	11	11	11	11
The amount of total gains (losses) included in income attributable to the change in unrealized gains (losses) relating to assets still held at end of period	0	0	0	1
Investments of Certain Benefit Plans [Member] | Operating Expense [Member] | Refining [Member]
Reconciliation of the beginning and ending balances for fair value measurements developed using significant unobservable inputs
Total gains (losses) included in refining operating expenses	0	0	0	1
Other Investments [Member]
Reconciliation of the beginning and ending balances for fair value measurements developed using significant unobservable inputs
Balance as of beginning of period	0	0	0	0
Purchases	0	5	0	21
Transfers in and/or out of Level 3	0	0	0	0
Balance as of end of period	0	0	0	0
The amount of total gains (losses) included in income attributable to the change in unrealized gains (losses) relating to assets still held at end of period	0	(5)	0	(21)
Other Investments [Member] | Operating Expense [Member] | Refining [Member]
Reconciliation of the beginning and ending balances for fair value measurements developed using significant unobservable inputs
Total gains (losses) included in refining operating expenses	$ 0	$ (5)	$ 0	$ (21)