Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 1,670	$ 1,597
Total increase (decrease) in unrealized gains included in cost of products sold	744	1,026
Purchases	10,833	11,153
Sales	(11,167)	(11,728)
Settlements	(421)	(468)
Transfers into Level 3	182	237
Transfers out of Level 3	(163)	(147)
Balance at end of period	$ 1,678	1,670
Document Period End Date	Dec. 31, 2019
Inventories Carried At Market [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 1,515	1,486
Total increase (decrease) in unrealized gains included in cost of products sold	327	631
Purchases	10,833	11,153
Sales	(11,167)	(11,728)
Transfers into Level 3	108	80
Transfers out of Level 3	(139)	(107)
Balance at end of period	1,477	1,515
Commodity Derivative Contracts Gains [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	155	111
Total increase (decrease) in unrealized gains included in cost of products sold	417	395
Settlements	(421)	(468)
Transfers into Level 3	74	157
Transfers out of Level 3	(24)	(40)
Balance at end of period	$ 201	$ 155