Derivatives And Risk Management (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015
Derivative [Line Items]
Accumulated other comprehensive income, net gain related to hedging activities	$ 90
Deferred income tax liability, accumulated other comprehensive income	56
Cash flow hedge after-tax net gain to be transferred from accumulated other comprehensive income to earnings during the next twelve months	90
Interest Rate Swaps [Member]
Derivative [Line Items]
Notional amount	$ 170
Year 2015 [Member] \| Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	181,000,000,000
Designated as Hedging Instrument [Member] \| Year 2015 [Member] \| Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	91,000,000,000
Not Designated as Hedging Instrument [Member] \| Year 2015 [Member] \| Basis Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	11,000,000,000
Not Designated as Hedging Instrument [Member] \| Year 2015 [Member] \| Fixed Price Call Options [Member]
Derivative [Line Items]
Volume of natural gas production	151,000,000,000
Not Designated as Hedging Instrument [Member] \| Year 2015 [Member] \| Fixed Price Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	90,000,000,000
Not Designated as Hedging Instrument [Member] \| Year 2016 [Member] \| Basis Swaps [Member]
Derivative [Line Items]
Volume of natural gas production	4,000,000,000
Not Designated as Hedging Instrument [Member] \| Year 2016 [Member] \| Fixed Price Call Options [Member]
Derivative [Line Items]
Volume of natural gas production	120,000,000,000

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

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- Definition

Deferred income tax liability related to the accumulated change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges.

+ References

No definition available.

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- Definition

Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14A

-URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669686-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e681-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669646-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=7668309&loc=d3e80784-113994

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- Definition

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7668309&loc=d3e80748-113994

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- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

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