Derivative Financial Instruments (Schedule Of Derivative Instruments) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative Assets, Current	$ 43	$ 76
Derivative Assets, Noncurrent	62	91
Derivative Liabilities, Current	41	12
Derivative Liabilities, Noncurrent	5	10
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Net	105	167
Derivative Liability, Fair Value, Net	46	22
Not Designated as Hedging Instrument [Member] | Commodity Price Derivatives [Member] | Derivatives - Current [Member]
Derivative [Line Items]
Total derivatives, Asset, Gross	46	73
Total derivatives, Liability. Gross	54	19
Derivative Assets Offset In Balance Sheet	(13)	(7)
Derivative Liabilities Offset In Balance Sheet	(13)	(7)
Derivative Assets, Current	33	66
Derivative Liabilities, Current	41	12
Not Designated as Hedging Instrument [Member] | Commodity Price Derivatives [Member] | Derivatives - Noncurrent [Member]
Derivative [Line Items]
Total derivatives, Asset, Gross	67	95
Total derivatives, Liability. Gross	6	4
Derivative Assets Offset In Balance Sheet	(5)	(4)
Derivative Liabilities Offset In Balance Sheet	(5)	(4)
Derivative Assets, Noncurrent	62	91
Derivative Liabilities, Noncurrent	1	0
Not Designated as Hedging Instrument [Member] | Interest Rate Derivatives [Member] | Derivatives - Current [Member]
Derivative [Line Items]
Total derivatives, Asset, Gross	10	10
Derivative Assets Offset In Balance Sheet	0	0
Derivative Assets, Current	10	10
Not Designated as Hedging Instrument [Member] | Interest Rate Derivatives [Member] | Derivatives - Noncurrent [Member]
Derivative [Line Items]
Total derivatives, Asset, Gross	12	15
Total derivatives, Liability. Gross	16	25
Derivative Assets Offset In Balance Sheet	(12)	(15)
Derivative Liabilities Offset In Balance Sheet	(12)	(15)
Derivative Assets, Noncurrent	0	0
Derivative Liabilities, Noncurrent	$ 4	$ 10