Segment and Related Information (Details 1) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Financial data for Products and Services
Electric Utilities Revenues	$ 4,503	$ 4,187	$ 8,497	$ 8,323
Retail [Member]
Financial data for Products and Services
Electric Utilities Revenues	3,842	3,571	7,238	7,030
Wholesale [Member]
Financial data for Products and Services
Electric Utilities Revenues	507	473	956	1,015
Other Electric Revenue [Member]
Financial data for Products and Services
Electric Utilities Revenues	$ 154	$ 143	$ 303	$ 278

Amount of revenue from external customers for the reportable segment. Such disclosure is presented if the amount is: (a) included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 131
-Paragraph 27
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_RevenuesFromExternalCustomers
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration