Fair Value Measurements (Reconciliation Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016		Mar. 31, 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)	$ 18		$ 25
Significant Unobservable Inputs (Level 3) [Member]
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	(51)	[1]	(262)	[2]
Purchases	2,356		2,817
Sales	(2,237)		(2,803)
Settlements	(97)		(144)
Transfers into Level 3	120		158
Transfers out of Level 3	(151)		(243)
Balance at end of period	1,187		1,217
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	1,004		1,491
Total increase (decrease) in unrealized gains included in cost of products sold	(114)	[1]	(331)	[2]
Purchases	2,356		2,817
Sales	(2,237)		(2,803)
Settlements	0		0
Transfers into Level 3	88		103
Transfers out of Level 3	(128)		(238)
Balance at end of period	969		1,039
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	243		203
Total increase (decrease) in unrealized gains included in cost of products sold	63	[1]	69	[2]
Purchases	0		0
Sales	0		0
Settlements	(97)		(144)
Transfers into Level 3	32		55
Transfers out of Level 3	(23)		(5)
Balance at end of period	$ 218		$ 178

[1] Includes increase in unrealized gains of $18 million relating to Level 3 assets still held at March 31, 2016.

[2] * Includes increase in unrealized gains of $25 million relating to Level 3 assets still held at March 31, 2015.