Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended									12 Months Ended			1 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013		Mar. 31, 2013	Dec. 31, 2014 segments	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014
Segment information for our three reportable segments
Operating revenues	$ 27,859	$ 34,408	$ 34,914	$ 33,663	$ 34,429	$ 36,137	$ 34,034	[1]	$ 33,474	$ 130,844	$ 138,074	$ 138,393
Depreciation and amortization expense										1,690	1,720	1,549
Operating income (loss)	1,796	1,670	1,085	1,351	1,562	532	805	[1]	1,058	5,902	3,957	5,044
Total expenditures for long-lived assets										2,822	2,757	3,413
Segment Information (Textual)
Number of reportable segments										2
Mount Vernon Ethanol Plant [Member]
Segment Information (Textual)
Payments to acquire idled corn ethanol plant													34
Refining [Member]
Segment information for our three reportable segments
Operating revenues										126,004	129,064	122,068
Ethanol [Member]
Segment information for our three reportable segments
Operating revenues										4,840	5,114	4,317
Retail [Member]
Segment information for our three reportable segments
Operating revenues										0	3,896	12,008
Corporate, Non-Segment [Member] | Corporate and Other [Member]
Segment information for our three reportable segments
Operating revenues										0	0	0
Depreciation and amortization expense										44	68	43
Operating income (loss)										(768)	(826)	(741)
Total expenditures for long-lived assets										30	65	66
Operating Segments [Member] | Refining [Member]
Segment information for our three reportable segments
Operating revenues										126,004	129,064	122,068
Depreciation and amortization expense										1,597	1,566	1,345
Operating income (loss)										5,884	4,211	5,484
Total expenditures for long-lived assets										2,750	2,597	3,147
Operating Segments [Member] | Ethanol [Member]
Segment information for our three reportable segments
Operating revenues										4,840	5,114	4,317
Depreciation and amortization expense										49	45	42
Operating income (loss)										786	491	(47)
Total expenditures for long-lived assets										42	33	36
Operating Segments [Member] | Retail [Member]
Segment information for our three reportable segments
Operating revenues										0	3,896	12,008
Depreciation and amortization expense										0	41	119
Operating income (loss)										0	81	348
Total expenditures for long-lived assets										0	62	164
Intersegment Eliminations [Member]
Segment information for our three reportable segments
Operating revenues										100	3,004	9,061
Intersegment Eliminations [Member] | Refining [Member]
Segment information for our three reportable segments
Operating revenues										0	2,876	8,946
Intersegment Eliminations [Member] | Ethanol [Member]
Segment information for our three reportable segments
Operating revenues										100	128	115
Intersegment Eliminations [Member] | Retail [Member]
Segment information for our three reportable segments
Operating revenues										$ 0	$ 0	$ 0

[1] The separation of our retail business was completed on May 1, 2013.