Fair Value Measurements (Reconciliation Of Liabilities 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
Inventory Related Payables [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 33	$ 196
Total increase (decrease) in unrealized losses included in cost of products sold	10
Purchases	176	(1)
Sales	(4)	82
Transfers into Level 3	1
Transfers out of Level 3		(140)
Balance at end of period	216	137
Commodity Derivative Contracts Losses [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	138	192
Total increase (decrease) in unrealized losses included in cost of products sold	118	159
Settlements	(102)	(141)
Transfers into Level 3	23	12
Transfers out of Level 3	(6)	(38)
Balance at end of period	171	184
Total Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	171	388
Total increase (decrease) in unrealized losses included in cost of products sold	128	159
Purchases	176	(1)
Sales	(4)	82
Settlements	(102)	(141)
Transfers into Level 3	24	12
Transfers out of Level 3	(6)	(178)
Balance at end of period	387	321
Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized losses on derivative liabilities	$ (117)