Segment and Related Information - Financial Data for Products and Services (Details) (USD $)	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Revenue from External Customer [Line Items]
Electric Revenue	$ 4,627,000,000	$ 3,885,000,000
Financial data for Products and Services
Electric Utilities' Revenues	4,644,000,000	3,897,000,000
Retail [Member]
Revenue from External Customer [Line Items]
Electric Revenue	3,858,000,000	3,298,000,000
Wholesale [Member]
Revenue from External Customer [Line Items]
Electric Revenue	604,000,000	432,000,000
Other [Member]
Revenue from External Customer [Line Items]
Electric Revenue	$ 165,000,000	$ 155,000,000

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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)

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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