Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) (Significant Unobservable Inputs (Level 3) [Member], Fair Value, Measurements, Recurring [Member], USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains on derivative assets	$ 289			$ 553
Inventories Carried At Market [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,926		1,462	1,745		1,624
Total increase (decrease) in unrealized gains included in cost of products sold	162	[1]	164	(677)	[2]	240
Purchases	2,896		2,390	11,795		4,516
Sales	(3,264)		(2,225)	(11,576)		(3,616)
Settlements	0		0	0		0
Transfers into Level 3	35		157	35		317
Transfers out of Level 3	(483)		(193)	(50)		(1,326)
Balance at end of period	1,272		1,755	1,272		1,755
Commodity Derivative Contracts Gains [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	267		171	143		198
Total increase (decrease) in unrealized gains included in cost of products sold	143	[1]	109	372	[2]	366
Purchases	0		0	0		(2)
Sales	0		0	0		0
Settlements	(153)		(95)	(381)		(341)
Transfers into Level 3	69		128	209		152
Transfers out of Level 3	(64)		(31)	(81)		(91)
Balance at end of period	262		282	262		282
Total Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	2,193		1,633	1,888		1,822
Total increase (decrease) in unrealized gains included in cost of products sold	305	[1]	273	(305)	[2]	606
Purchases	2,896		2,390	11,795		4,514
Sales	(3,264)		(2,225)	(11,576)		(3,616)
Settlements	(153)		(95)	(381)		(341)
Transfers into Level 3	104		285	244		469
Transfers out of Level 3	(547)		(224)	(131)		(1,417)
Balance at end of period	$ 1,534		$ 2,037	$ 1,534		$ 2,037

[1] Includes gains of $289 million that are attributable to the change in unrealized gains relating to Level 3 assets still held at September 30, 2013.

[2] Includes gains of $553 million that are attributable to the change in unrealized gains relating to Level 3 assets still held at September 30, 2013.