Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ (635)	$ (81)	$ (1,100)	$ (258)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	377	238	226	263
Total increase (decrease) in unrealized losses included in cost of products sold	630	79	1,086	252
Purchases	20	26	28	41
Sales	(7)	(4)	(32)	(16)
Settlements	(188)	(167)	(521)	(354)
Transfers into Level 3	24	13	79	37
Transfers out of Level 3	(21)	(4)	(31)	(42)
Balance at end of period	835	181	835	181
Significant Unobservable Inputs (Level 3) [Member] | Long-term Debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	0		0
Total increase (decrease) in unrealized losses included in cost of products sold	15		15
Purchases	17		17
Balance at end of period	32		32
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	14	22	27	18
Total increase (decrease) in unrealized losses included in cost of products sold	(3)	(3)	1	(2)
Purchases	3	26	11	41
Sales	(7)	(4)	(32)	(16)
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	7	41	7	41
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	363	216	199	245
Total increase (decrease) in unrealized losses included in cost of products sold	618	82	1,070	254
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(188)	(167)	(521)	(354)
Transfers into Level 3	24	13	79	37
Transfers out of Level 3	(21)	(4)	(31)	(42)
Balance at end of period	$ 796	$ 140	$ 796	$ 140