Fair Value Measurements (Reconciliation Of Assets 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, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 392	$ 165	$ 1,200	$ 656
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,841	1,547	1,678	1,670
Total increase (decrease) in unrealized gains included in cost of products sold	544	118	1,358	467
Purchases	3,181	2,772	9,600	8,118
Sales	(2,703)	(2,643)	(9,838)	(8,425)
Settlements	(96)	(106)	(331)	(346)
Transfers into Level 3	303	234	347	267
Transfers out of Level 3	(398)	(331)	(142)	(160)
Balance at end of period	2,672	1,591	2,672	1,591
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	1,399	1,388	1,477	1,515
Total increase (decrease) in unrealized gains included in cost of products sold	258	27	626	148
Purchases	3,181	2,772	9,600	8,118
Sales	(2,703)	(2,643)	(9,838)	(8,425)
Settlements	0	0	0	0
Transfers into Level 3	290	213	290	213
Transfers out of Level 3	(333)	(327)	(63)	(139)
Balance at end of period	2,092	1,430	2,092	1,430
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	442	159	201	155
Total increase (decrease) in unrealized gains included in cost of products sold	286	91	732	319
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(96)	(106)	(331)	(346)
Transfers into Level 3	13	21	57	54
Transfers out of Level 3	(65)	(4)	(79)	(21)
Balance at end of period	$ 580	$ 161	$ 580	$ 161