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, 2016		Jun. 30, 2015		Jun. 30, 2016		Jun. 30, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 3		$ 180		$ 14		$ 205
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	1,187		1,217		1,247		1,694
Total increase (decrease) in unrealized gains included in cost of products sold	(73)	[1]	57	[2]	(61)	[3]	(166)	[4]
Purchases	2,686		2,851		5,042		5,668
Sales	(2,506)		(2,890)		(4,743)		(5,693)
Settlements	(120)		(117)		(217)		(261)
Transfers into Level 3	113		132		145		186
Transfers out of Level 3	(35)		(70)		(161)		(248)
Balance at end of period	1,252		1,180		1,252		1,180
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	969		1,039		1,004		1,491
Total increase (decrease) in unrealized gains included in cost of products sold	(105)	[1]	17	[2]	(155)	[3]	(275)	[4]
Purchases	2,686		2,851		5,042		5,668
Sales	(2,506)		(2,890)		(4,743)		(5,693)
Settlements	0		0		0		0
Transfers into Level 3	79		74		79		73
Transfers out of Level 3	(24)		(65)		(128)		(238)
Balance at end of period	1,099		1,026		1,099		1,026
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	218		178		243		203
Total increase (decrease) in unrealized gains included in cost of products sold	32	[1]	40	[2]	94	[3]	109	[4]
Purchases	0		0		0		0
Sales	0		0		0		0
Settlements	(120)		(117)		(217)		(261)
Transfers into Level 3	34		58		66		113
Transfers out of Level 3	(11)		(5)		(33)		(10)
Balance at end of period	$ 153		$ 154		$ 153		$ 154

[1] Includes decrease in unrealized gains of $3 million relating to Level 3 assets still held at June 30, 2016.

[2] * Includes increase in unrealized gains of $180 million relating to Level 3 assets still held at June 30, 2015.

[3] * Includes increase in unrealized gains of $14 million relating to Level 3 assets still held at June 30, 2016.

[4] * Includes increase in unrealized gains of $205 million relating to Level 3 assets still held at June 30, 2015