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
	Mar. 31, 2013	Mar. 31, 2012
Inventories Carried At Market [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 1,745	$ 1,624
Total increase (decrease) in unrealized gains included in cost of products sold	(697)	41
Purchases	4,684	1,286
Sales	(3,700)	(285)
Transfers into Level 3	40	72
Transfers out of Level 3	(50)	(1,013)
Balance at end of period	2,022	1,725
Commodity Derivative Contracts Gains [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	143	198
Total increase (decrease) in unrealized gains included in cost of products sold	136	165
Settlements	(96)	(100)
Transfers into Level 3	48	19
Transfers out of Level 3	(8)	(50)
Balance at end of period	223	232
Total Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,888	1,822
Total increase (decrease) in unrealized gains included in cost of products sold	(561)	206
Purchases	4,684	1,286
Sales	(3,700)	(285)
Settlements	(96)	(100)
Transfers into Level 3	88	91
Transfers out of Level 3	(58)	(1,063)
Balance at end of period	2,245	1,957
Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains on derivative assets	$ 130