Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment information for our reportable segments
Operating revenues	$ 34,034	$ 34,662	$ 67,508	$ 69,829
Operating income (loss)	808	1,361	1,869	1,117
Total assets by reportable segment
Reportable segment assets	44,177		44,177		44,477
Refining [Member]
Total assets by reportable segment
Reportable segment assets	40,527		40,527		39,490
Retail [Member]
Total assets by reportable segment
Reportable segment assets	0		0		2,043
Ethanol [Member]
Total assets by reportable segment
Reportable segment assets	867		867		929
Corporate and Other [Member]
Total assets by reportable segment
Reportable segment assets	2,783		2,783		2,015
Operating Segments [Member] | Refining [Member]
Segment information for our reportable segments
Operating revenues	31,564	30,488	61,117	61,638
Operating income (loss)	921	1,364	2,133	1,245
Operating Segments [Member] | Retail [Member]
Segment information for our reportable segments
Operating revenues	979	3,062	3,896	5,997
Operating income (loss)	39	172	81	212
Operating Segments [Member] | Ethanol [Member]
Segment information for our reportable segments
Operating revenues	1,491	1,112	2,495	2,194
Operating income (loss)	95	5	109	14
Corporate, Non-Segment [Member] | Corporate and Other [Member]
Segment information for our reportable segments
Operating revenues	0	0	0	0
Operating income (loss)	(247)	(180)	(454)	(354)
Intersegment Eliminations [Member]
Segment information for our reportable segments
Operating revenues	686	2,249	2,946	4,518
Intersegment Eliminations [Member] | Refining [Member]
Segment information for our reportable segments
Operating revenues	671	2,203	2,876	4,458
Intersegment Eliminations [Member] | Retail [Member]
Segment information for our reportable segments
Operating revenues	0	0	0	0
Intersegment Eliminations [Member] | Ethanol [Member]
Segment information for our reportable segments
Operating revenues	$ 15	$ 46	$ 70	$ 60