Derivatives And Risk Management (Balance Sheet Classification Of Derivative Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative assets	$ 339	$ 79
Derivative liabilities	23	41
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	165	21
Derivative liabilities		4
Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	165	21
Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities		4
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	174	58
Derivative liabilities	23	37
Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	163	37
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	9	13
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Other Long-Term Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	4	1
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	2
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Other Long-Term Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1	8
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	3	2
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	2	3
Not Designated as Hedging Instrument [Member] | Fixed Price Call Options [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	2
Not Designated as Hedging Instrument [Member] | Fixed Price Call Options [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ 10	$ 31