Fair Value Measurements (Reconciliation Of Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 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)	$ 85	$ 419	$ 124	$ 498
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	151	134	172	129
Total increase (decrease) in unrealized losses included in cost of products sold	72	406	124	498
Purchases	16	1	17	2
Sales	(3)	(1)	(20)	(8)
Settlements	(98)	(73)	(166)	(146)
Transfers into Level 3	49	67	73	83
Transfers out of Level 3	(1)	(22)	(14)	(46)
Balance at end of period	186	512	186	512
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	28	23	30	16
Total increase (decrease) in unrealized losses included in cost of products sold	(9)	(11)	5	2
Purchases	16	1	17	2
Sales	(3)	(1)	(20)	(8)
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	32	12	32	12
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	123	111	142	113
Total increase (decrease) in unrealized losses included in cost of products sold	81	417	119	496
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(98)	(73)	(166)	(146)
Transfers into Level 3	49	67	73	83
Transfers out of Level 3	(1)	(22)	(14)	(46)
Balance at end of period	$ 154	$ 500	$ 154	$ 500