Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 62		$ 145		$ 267		$ 516
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,180		1,378		1,694		2,091
Total increase (decrease) in net realized/unrealized gains included in cost of products sold	(32)	[1]	252	[2]	(240)	[3]	299	[4]
Purchases	2,652		2,526		8,319		10,474
Sales	(2,695)		(2,352)		(8,388)		(10,711)
Settlements	(45)		(166)		(306)		(529)
Transfers into Level 3	212		473		325		594
Transfers out of Level 3	(140)		(37)		(272)		(144)
Balance at end of period	1,132		2,074		1,132		2,074
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	1,026		1,139		1,491		1,812
Total increase (decrease) in net realized/unrealized gains included in cost of products sold	(106)	[1]	(33)	[2]	(423)	[3]	(208)	[4]
Purchases	2,652		2,526		8,319		10,474
Sales	(2,695)		(2,352)		(8,388)		(10,711)
Settlements	0		0		0		0
Transfers into Level 3	169		266		169		266
Transfers out of Level 3	(116)		(24)		(238)		(111)
Balance at end of period	930		1,522		930		1,522
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	154		239		203		279
Total increase (decrease) in net realized/unrealized gains included in cost of products sold	74	[1]	285	[2]	183	[3]	507	[4]
Purchases	0		0		0		0
Sales	0		0		0		0
Settlements	(45)		(166)		(306)		(529)
Transfers into Level 3	43		207		156		328
Transfers out of Level 3	(24)		(13)		(34)		(33)
Balance at end of period	$ 202		$ 552		$ 202		$ 552

[1] Includes increase in unrealized gains of $62 million relating to Level 3 assets still held at September 30, 2015.

[2] * Includes increase in unrealized gains of $145 million relating to Level 3 assets still held at September 30, 2014.

[3] * Includes increase in unrealized gains of $267 million relating to Level 3 assets still held at September 30, 2015.

[4] * Includes increase in unrealized gains of $516 million relating to Level 3 assets still held at September 30, 2014.