Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 1,247	$ 1,694
Total increase (decrease) in unrealized gains included in cost of products sold	236	(55)
Purchases	9,900	10,459
Sales	(9,567)	(10,534)
Settlements	(420)	(378)
Transfers into Level 3	238	341
Transfers out of Level 3	(172)	(280)
Balance at end of period	1,462	1,247
Inventories Carried At Market [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,004	1,491
Total increase (decrease) in unrealized gains included in cost of products sold	44	(320)
Purchases	9,900	10,459
Sales	(9,567)	(10,534)
Transfers into Level 3	70	146
Transfers out of Level 3	(129)	(238)
Balance at end of period	1,322	1,004
Commodity Derivative Contracts Gains [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	243	203
Total increase (decrease) in unrealized gains included in cost of products sold	192	265
Settlements	(420)	(378)
Transfers into Level 3	168	195
Transfers out of Level 3	(43)	(42)
Balance at end of period	$ 140	$ 243