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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ (81)	$ (118)	$ (258)	$ (364)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	238	222	263	142
Total increase (decrease) in unrealized losses included in cost of products sold	79	118	252	372
Purchases	26	30	41	54
Sales	(4)	(12)	(16)	(61)
Settlements	(167)	(130)	(354)	(348)
Transfers into Level 3	13	30	37	136
Transfers out of Level 3	(4)	(11)	(42)	(48)
Balance at end of period	181	247	181	247
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	22	22	18	39
Total increase (decrease) in unrealized losses included in cost of products sold	(3)	4	(2)	12
Purchases	26	30	41	54
Sales	(4)	(12)	(16)	(61)
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	41	44	41	44
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	216	200	245	103
Total increase (decrease) in unrealized losses included in cost of products sold	82	114	254	360
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(167)	(130)	(354)	(348)
Transfers into Level 3	13	30	37	136
Transfers out of Level 3	(4)	(11)	(42)	(48)
Balance at end of period	$ 140	$ 203	$ 140	$ 203