Fair Value Measurements (Schedule Of Carrying Value And Fair Value Measurement Information For Financial Assets And Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets	$ 56	$ 45
Derivatives, liabilities	(149)	(48)
Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,121	1,871
Debt	(12,545)	(13,032)
Capital lease obligations	(13)	(17)
Total Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,121	1,871
Debt	(11,217)	(11,927)
Capital lease obligations	(13)	(16)
Level 1 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,026	1,471
Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	95	400
Debt	(11,217)	(11,927)
Capital lease obligations	(13)	(16)
Commodity Derivatives [Member] | Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets	54	35
Derivatives, liabilities	(28)	(18)
Commodity Derivatives [Member] | Total Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets	54	35
Derivatives, liabilities	(28)	(18)
Commodity Derivatives [Member] | Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets	54	35
Derivatives, liabilities	(28)	(18)
Interest Rate Derivatives [Member] | Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets	2	2
Derivatives, liabilities	(95)	(22)
Interest Rate Derivatives [Member] | Total Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets	2	2
Derivatives, liabilities	(95)	(22)
Interest Rate Derivatives [Member] | Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets	2	2
Derivatives, liabilities	(95)	(22)
Foreign Currency Derivatives [Member] | Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets		8
Derivatives, liabilities	(26)	(8)
Foreign Currency Derivatives [Member] | Total Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets		8
Derivatives, liabilities	(26)	(8)
Foreign Currency Derivatives [Member] | Level 2 Inputs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives, assets		8
Derivatives, liabilities	$ (26)	$ (8)