Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment information for our reportable segments
Operating revenues	$ 21,330	$ 33,663
Operating income (loss)	1,495	1,351
Total assets by reportable segment
Reportable segment assets	45,741		45,550
Refining [Member]
Total assets by reportable segment
Reportable segment assets	38,857		40,103
Ethanol [Member]
Total assets by reportable segment
Reportable segment assets	986		954
Corporate and Other [Member]
Total assets by reportable segment
Reportable segment assets	5,898		4,493
Operating Segments [Member] | Refining [Member]
Segment information for our reportable segments
Operating revenues	20,529	32,452
Operating income (loss)	1,641	1,280
Operating Segments [Member] | Ethanol [Member]
Segment information for our reportable segments
Operating revenues	801	1,211
Operating income (loss)	12	243
Corporate, Non-Segment [Member] | Corporate and Other [Member]
Segment information for our reportable segments
Operating income (loss)	(158)	(172)
Intersegment Eliminations [Member]
Segment information for our reportable segments
Operating revenues	28	25
Intersegment Eliminations [Member] | Refining [Member]
Segment information for our reportable segments
Operating revenues	0	0
Intersegment Eliminations [Member] | Ethanol [Member]
Segment information for our reportable segments
Operating revenues	$ 28	$ 25