Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 381	$ 210
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,678	1,670
Total increase (decrease) in unrealized gains included in cost of products sold	404	117
Purchases	3,407	2,689
Sales	(3,510)	(2,824)
Settlements	(45)	(103)
Transfers into Level 3	462	320
Transfers out of Level 3	(67)	(146)
Balance at end of period	2,329	1,723
Significant Unobservable Inputs (Level 3) [Member] | Inventories Carried At Market [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,477	1,515
Total increase (decrease) in unrealized gains included in cost of products sold	187	(27)
Purchases	3,407	2,689
Sales	(3,510)	(2,824)
Settlements	0	0
Transfers into Level 3	441	297
Transfers out of Level 3	(64)	(139)
Balance at end of period	1,938	1,511
Significant Unobservable Inputs (Level 3) [Member] | Commodity Derivative Contracts Gains [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	201	155
Total increase (decrease) in unrealized gains included in cost of products sold	217	144
Purchases	0	0
Sales	0	0
Settlements	(45)	(103)
Transfers into Level 3	21	23
Transfers out of Level 3	(3)	(7)
Balance at end of period	$ 391	$ 212