Related Party Transactions (Schedule of related Party Transactions) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Revenue—Non-Regulated	$ 8,272us-gaap_ElectricalGenerationRevenue	$ 7,835us-gaap_ElectricalGenerationRevenue	$ 8,187us-gaap_ElectricalGenerationRevenue
Cost of Sales—Non-Regulated	6,528us-gaap_ElectricProductionExpense	5,807us-gaap_ElectricProductionExpense	5,987us-gaap_ElectricProductionExpense
Interest expense	1,471us-gaap_InterestExpense	1,482us-gaap_InterestExpense	1,544us-gaap_InterestExpense
Affiliated Entity
Related Party Transaction [Line Items]
Revenue—Non-Regulated	830	825	820
Cost of Sales—Non-Regulated	218	161	120
Interest expense	$ 8	$ 5	$ 10

Revenue from generation of electricity, a process of producing electric energy by transforming other forms of energy such as nuclear, fossil fuel, solar, geothermal, hydro, and wind.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(b))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

Name:	us-gaap_ElectricalGenerationRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Cost incurred directly related to electricity produced and sold during the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2(b))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

Name:	us-gaap_ElectricProductionExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.9)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 9

-Article 9

+ Details

Name:	us-gaap_InterestExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionLineItems
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Data Type:	xbrli:stringItemType
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Period Type:	duration

- Details

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