Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ (210)	$ (20)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	226	263
Total increase (decrease) in unrealized losses included in cost of products sold	208	18
Purchases	6	4
Sales	(16)	(6)
Settlements	(122)	(99)
Transfers into Level 3	36	7
Transfers out of Level 3	(9)	(28)
Balance at end of period	329	159
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	27	18
Total increase (decrease) in unrealized losses included in cost of products sold	3	0
Purchases	6	4
Sales	(16)	(6)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at end of period	20	16
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	199	245
Total increase (decrease) in unrealized losses included in cost of products sold	205	18
Purchases	0	0
Sales	0	0
Settlements	(122)	(99)
Transfers into Level 3	36	7
Transfers out of Level 3	(9)	(28)
Balance at end of period	$ 309	$ 143