Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ (253)	$ (157)	$ (463)	$ (177)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	329	159	226	263
Total increase (decrease) in unrealized losses included in cost of products sold	248	155	456	173
Purchases	2	11	8	15
Sales	(9)	(6)	(25)	(12)
Settlements	(211)	(88)	(333)	(187)
Transfers into Level 3	19	17	55	24
Transfers out of Level 3	(1)	(10)	(10)	(38)
Balance at end of period	377	238	377	238
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	20	16	27	18
Total increase (decrease) in unrealized losses included in cost of products sold	1	1	4	1
Purchases	2	11	8	15
Sales	(9)	(6)	(25)	(12)
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance at end of period	14	22	14	22
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	309	143	199	245
Total increase (decrease) in unrealized losses included in cost of products sold	247	154	452	172
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(211)	(88)	(333)	(187)
Transfers into Level 3	19	17	55	24
Transfers out of Level 3	(1)	(10)	(10)	(38)
Balance at end of period	$ 363	$ 216	$ 363	$ 216