Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 847	$ 381
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	3,042	1,678
Total increase (decrease) in unrealized gains included in cost of products sold	973	404
Purchases	6,385	3,407
Sales	(6,632)	(3,510)
Settlements	(428)	(45)
Transfers into Level 3	539	462
Transfers out of Level 3	(125)	(67)
Balance at end of period	3,754	2,329
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	2,183	1,477
Total increase (decrease) in unrealized gains included in cost of products sold	730	187
Purchases	6,385	3,407
Sales	(6,632)	(3,510)
Settlements	0	0
Transfers into Level 3	516	441
Transfers out of Level 3	(112)	(64)
Balance at end of period	3,070	1,938
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	859	201
Total increase (decrease) in unrealized gains included in cost of products sold	243	217
Purchases	0	0
Sales	0	0
Settlements	(428)	(45)
Transfers into Level 3	23	21
Transfers out of Level 3	(13)	(3)
Balance at end of period	$ 684	$ 391