Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 198	$ 39
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	142	172
Total increase (decrease) in unrealized losses included in cost of products sold	215	53
Purchases	21	2
Sales	(2)	(18)
Settlements	(57)	(68)
Transfers into Level 3	65	23
Transfers out of Level 3	(18)	(13)
Balance at end of period	366	151
Significant Unobservable Inputs (Level 3) [Member] | Inventory Related Payables [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	39	30
Total increase (decrease) in unrealized losses included in cost of products sold	17	14
Purchases	21	2
Sales	(2)	(18)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at end of period	75	28
Significant Unobservable Inputs (Level 3) [Member] | Commodity Derivative Contracts Losses [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	103	142
Total increase (decrease) in unrealized losses included in cost of products sold	198	39
Purchases	0	0
Sales	0	0
Settlements	(57)	(68)
Transfers into Level 3	65	23
Transfers out of Level 3	(18)	(13)
Balance at end of period	$ 291	$ 123