Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 142	$ 172
Total increase (decrease) in unrealized gains included in cost of products sold	537	253
Purchases	57	38
Sales	(89)	(25)
Settlements	(476)	(397)
Transfers into Level 3	150	128
Transfers out of Level 3	(58)	(27)
Balance at end of period	263	142
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 gains included in cost of products sold	526	257
Purchases	0	0
Sales	0	0
Settlements	(476)	(397)
Transfers into Level 3	150	128
Transfers out of Level 3	(58)	(27)
Balance at end of period	245	103
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 gains included in cost of products sold	11	(4)
Purchases	57	38
Sales	(89)	(25)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at end of period	$ 18	$ 39