Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 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)	$ 79	$ 1	$ 204	$ 499
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	186	512	172	129
Total increase (decrease) in unrealized losses included in cost of products sold	73	2	197	499
Purchases	2	3	19	5
Sales	(5)	(3)	(25)	(11)
Settlements	(123)	(247)	(289)	(392)
Transfers into Level 3	35	33	108	115
Transfers out of Level 3	(3)	(167)	(17)	(212)
Balance at end of period	165	133	165	133
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	32	12	30	16
Total increase (decrease) in unrealized losses included in cost of products sold	(9)	3	(4)	5
Purchases	2	3	19	5
Sales	(5)	(3)	(25)	(11)
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance at end of period	20	15	20	15
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	154	500	142	113
Total increase (decrease) in unrealized losses included in cost of products sold	82	(1)	201	494
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(123)	(247)	(289)	(392)
Transfers into Level 3	35	33	108	115
Transfers out of Level 3	(3)	(167)	(17)	(212)
Balance at end of period	$ 145	$ 118	$ 145	$ 118