Derivative Instruments (Schedule Of Derivative Assets And Liabilities Statement) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivative Asset, Fair Value, Gross Asset	$ 13	$ 5
Derivative Liability, Fair Value, Gross Liability	48	31
Designated as Hedging Instrument [Member] | Commodity Derivatives
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	5
Current | Designated as Hedging Instrument [Member] | Commodity Derivatives
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	5
Current | Derivatives Not Designated as Cash Flow Hedges | Commodity Derivatives
Derivative Asset, Fair Value, Gross Asset	10	4
Derivative Liability, Fair Value, Gross Liability	1	1
Long Term | Derivatives Not Designated as Cash Flow Hedges | Commodity Derivatives
Derivative Asset, Fair Value, Gross Asset	3	1
Derivative Liability, Fair Value, Gross Liability	0	0
Long Term | Derivatives Not Designated as Cash Flow Hedges | Embedded Derivatives
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	$ 47	$ 25