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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ (157)	$ (48)	$ (177)	$ (246)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	159	366	263	142
Total increase (decrease) in unrealized losses included in cost of products sold	155	39	173	254
Purchases	11	3	15	24
Sales	(6)	(47)	(12)	(49)
Settlements	(88)	(161)	(187)	(218)
Transfers into Level 3	17	41	24	106
Transfers out of Level 3	(10)	(19)	(38)	(37)
Balance at end of period	238	222	238	222
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	16	75	18	39
Total increase (decrease) in unrealized losses included in cost of products sold	1	(9)	1	8
Purchases	11	3	15	24
Sales	(6)	(47)	(12)	(49)
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	22	22	22	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	143	291	245	103
Total increase (decrease) in unrealized losses included in cost of products sold	154	48	172	246
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(88)	(161)	(187)	(218)
Transfers into Level 3	17	41	24	106
Transfers out of Level 3	(10)	(19)	(38)	(37)
Balance at end of period	$ 216	$ 200	$ 216	$ 200