Commitments And Contingencies (Tax Legislation, Guarantees, And Dividends) (Details) (USD $) In Millions, except Per Share data	0 Months Ended	9 Months Ended
Oct. 27, 2011	Sep. 30, 2011 Pepco Energy Services [Member]
Liability for guarantee contracts, current value		$ 422
Longest remaining term of guarantees, in years		15
Dividend declared on common stock, per share	$ 0.27

Describe the approximate term of the guarantee or each group of similar guarantees.

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 13

-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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsTerm
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration