Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 1,099	$ 377	$ 963	$ 226
Total increase (decrease) in unrealized losses included in cost of products sold	306	630	1,358	1,086
Purchases	1	20	30	28
Sales	(27)	(7)	(29)	(32)
Settlements	(654)	(188)	(1,667)	(521)
Transfers into Level 3	60	24	284	79
Transfers out of Level 3	(50)	(21)	(204)	(31)
Balance at end of period	735	835	735	835
Long-term Debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	24	0	34	0
Total increase (decrease) in unrealized losses included in cost of products sold	(7)	15	(17)	15
Purchases	0	17	0	17
Balance at end of period	17	32	17	32
Inventory Related Payables [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	38	14	11	27
Total increase (decrease) in unrealized losses included in cost of products sold	3	(3)	3	1
Purchases	1	3	30	11
Sales	(27)	(7)	(29)	(32)
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	15	7	15	7
Commodity Derivative Contracts Losses [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,037	363	918	199
Total increase (decrease) in unrealized losses included in cost of products sold	310	618	1,372	1,070
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(654)	(188)	(1,667)	(521)
Transfers into Level 3	60	24	284	79
Transfers out of Level 3	(50)	(21)	(204)	(31)
Balance at end of period	$ 703	$ 796	$ 703	$ 796