Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (20)	$ (198)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	263	142
Total increase (decrease) in unrealized losses included in cost of products sold	18	215
Purchases	4	21
Sales	(6)	(2)
Settlements	(99)	(57)
Transfers into Level 3	7	65
Transfers out of Level 3	(28)	(18)
Balance at end of period	159	366
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	18	39
Total increase (decrease) in unrealized losses included in cost of products sold	0	17
Purchases	4	21
Sales	(6)	(2)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at end of period	16	75
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	245	103
Total increase (decrease) in unrealized losses included in cost of products sold	18	198
Purchases	0	0
Sales	0	0
Settlements	(99)	(57)
Transfers into Level 3	7	65
Transfers out of Level 3	(28)	(18)
Balance at end of period	$ 143	$ 291