Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 1,694	$ 2,091
Total increase (decrease) in unrealized gains included in cost of products sold	(55)	559
Purchases	10,459	16,114
Sales	(10,534)	(16,384)
Settlements	(378)	(948)
Transfers into Level 3	341	439
Transfers out of Level 3	(280)	(177)
Balance at end of period	1,247	1,694
Inventories Carried At Market [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,491	1,812
Total increase (decrease) in unrealized gains included in cost of products sold	(320)	15
Purchases	10,459	16,114
Sales	(10,534)	(16,384)
Transfers into Level 3	146	44
Transfers out of Level 3	(238)	(110)
Balance at end of period	1,004	1,491
Commodity Derivative Contracts Gains [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	203	279
Total increase (decrease) in unrealized gains included in cost of products sold	265	544
Settlements	(378)	(948)
Transfers into Level 3	195	395
Transfers out of Level 3	(42)	(67)
Balance at end of period	$ 243	$ 203