Derivatives And Risk Management (Summary Of Before Tax Effect Of Cash Flow Hedges On Consolidated Financial Statements) (Details) - Fixed Price Swaps [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain Recognized in Other Comprehensive Income (Effective Portion)	$ 45	$ 122
Gas Sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) Reclassified from Accumulated Other Comprehensive Income into Earnings (Effective Portion)	$ 209	$ (26)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

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- Definition

The effective portion of gain reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

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