Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 39	$ 79
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	172	129
Total increase (decrease) in unrealized losses included in cost of products sold	53	92
Purchases	2	1
Sales	(18)	(7)
Settlements	(68)	(72)
Transfers into Level 3	23	15
Transfers out of Level 3	(13)	(24)
Balance at end of period	151	134
Significant Unobservable Inputs (Level 3) [Member] | Inventory Related Payables [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	30	16
Total increase (decrease) in unrealized losses included in cost of products sold	14	13
Purchases	2	1
Sales	(18)	(7)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance at end of period	28	23
Significant Unobservable Inputs (Level 3) [Member] | Commodity Derivative Contracts Losses [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	142	113
Total increase (decrease) in unrealized losses included in cost of products sold	39	79
Purchases	0	0
Sales	0	0
Settlements	(68)	(72)
Transfers into Level 3	23	15
Transfers out of Level 3	(13)	(24)
Balance at end of period	$ 123	$ 111