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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 148	$ 3	$ 34	$ (14)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,302	1,187	1,462	1,247
Total increase (decrease) in unrealized gains included in cost of products sold	228	(73)	50	(61)
Purchases	2,329	2,686	5,577	5,042
Sales	(2,677)	(2,506)	(5,871)	(4,743)
Settlements	(140)	(120)	(209)	(217)
Transfers into Level 3	134	113	181	145
Transfers out of Level 3	(70)	(35)	(84)	(161)
Balance at end of period	1,106	1,252	1,106	1,252
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	1,129	969	1,322	1,004
Total increase (decrease) in unrealized gains included in cost of products sold	157	(105)	(90)	(155)
Purchases	2,329	2,686	5,577	5,042
Sales	(2,677)	(2,506)	(5,871)	(4,743)
Settlements	0	0	0	0
Transfers into Level 3	115	79	115	79
Transfers out of Level 3	(53)	(24)	(53)	(128)
Balance at end of period	1,000	1,099	1,000	1,099
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	173	218	140	243
Total increase (decrease) in unrealized gains included in cost of products sold	71	32	140	94
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(140)	(120)	(209)	(217)
Transfers into Level 3	19	34	66	66
Transfers out of Level 3	(17)	(11)	(31)	(33)
Balance at end of period	$ 106	$ 153	$ 106	$ 153