Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 422	$ 280	$ 804	$ 491
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	2,329	1,723	1,678	1,670
Total increase (decrease) in unrealized gains included in cost of products sold	508	321	842	444
Purchases	3,012	2,657	6,419	5,346
Sales	(3,625)	(2,958)	(7,135)	(5,782)
Settlements	(190)	(137)	(235)	(240)
Transfers into Level 3	329	242	350	265
Transfers out of Level 3	(522)	(301)	(78)	(156)
Balance at end of period	1,841	1,547	1,841	1,547
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	1,938	1,511	1,477	1,515
Total increase (decrease) in unrealized gains included in cost of products sold	279	237	396	216
Purchases	3,012	2,657	6,419	5,346
Sales	(3,625)	(2,958)	(7,135)	(5,782)
Settlements	0	0	0	0
Transfers into Level 3	306	232	306	232
Transfers out of Level 3	(511)	(291)	(64)	(139)
Balance at end of period	1,399	1,388	1,399	1,388
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	391	212	201	155
Total increase (decrease) in unrealized gains included in cost of products sold	229	84	446	228
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(190)	(137)	(235)	(240)
Transfers into Level 3	23	10	44	33
Transfers out of Level 3	(11)	(10)	(14)	(17)
Balance at end of period	$ 442	$ 159	$ 442	$ 159