Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Segment information for our reportable segments
Operating revenues from external customers	$ 33,474	$ 35,167
Intersegment revenues	2,260	2,269
Operating income (loss)	1,061	(244)
Total assets by reportable segment
Reportable segment assets	45,501		44,477
Refining [Member]
Segment information for our reportable segments
Operating revenues from external customers	29,553	31,150
Intersegment revenues	2,205	2,255
Operating income (loss)	1,212	(119)
Total assets by reportable segment
Reportable segment assets	40,185		39,490
Retail [Member]
Segment information for our reportable segments
Operating revenues from external customers	2,917	2,935
Intersegment revenues	0	0
Operating income (loss)	42	40
Total assets by reportable segment
Reportable segment assets	2,125		2,043
Ethanol [Member]
Segment information for our reportable segments
Operating revenues from external customers	1,004	1,082
Intersegment revenues	55	14
Operating income (loss)	14	9
Total assets by reportable segment
Reportable segment assets	924		929
Corporate [Member]
Segment information for our reportable segments
Operating revenues from external customers	0	0
Intersegment revenues	0	0
Operating income (loss)	(207)	(174)
Total assets by reportable segment
Reportable segment assets	$ 2,267		$ 2,015