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			6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012
Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains on derivative assets	$ 134			$ 264
Inventories Carried At Market [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	2,022		1,725	1,745		1,624
Total increase (decrease) in unrealized gains included in cost of products sold	172	[1]	35	(516)	[2]	76
Purchases	4,215		840	8,899		2,126
Sales	(4,611)		(1,106)	(8,312)		(1,391)
Settlements	0		0	0		0
Transfers into Level 3	160		88	160		160
Transfers out of Level 3	(32)		(120)	(50)		(1,133)
Balance at end of period	1,926		1,462	1,926		1,462
Commodity Derivative Contracts Gains [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	223		232	143		198
Total increase (decrease) in unrealized gains included in cost of products sold	93	[1]	92	229	[2]	257
Purchases	0		(2)	0		(2)
Sales	0		0	0		0
Settlements	(132)		(146)	(228)		(246)
Transfers into Level 3	92		5	140		24
Transfers out of Level 3	(9)		(10)	(17)		(60)
Balance at end of period	267		171	267		171
Total Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	2,245		1,957	1,888		1,822
Total increase (decrease) in unrealized gains included in cost of products sold	265	[1]	127	(287)	[2]	333
Purchases	4,215		838	8,899		2,124
Sales	(4,611)		(1,106)	(8,312)		(1,391)
Settlements	(132)		(146)	(228)		(246)
Transfers into Level 3	252		93	300		184
Transfers out of Level 3	(41)		(130)	(67)		(1,193)
Balance at end of period	$ 2,193		$ 1,633	$ 2,193		$ 1,633

[1] Includes gains of $134 million that are attributable to the change in unrealized gains relating to Level 3 assets still held at June 30, 2013.

[2] Includes gains of $264 million that are attributable to the change in unrealized gains relating to Level 3 assets still held at June 30, 2013.