Commitments And Contingencies (Tax Legislation, Guarantees, Indemnifications, And Performance Contracts) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Apr. 30, 2012	Mar. 31, 2012
Value of guarantees on both completed projects and projects under construction		$ 441
Value of performance contracts issued		15
Guarantee on obligations under construction contracts		$ 143
Dividend declared on common stock, per share	$ 0.27
Performance Contracts Associated With Savings Guarantees [Member] | Pepco Energy Services [Member]
Contract life, maximum remaining term		15 years
Performance Guarantee Contracts Associated With Production At Heat And Power Facilities [Member] | Pepco Energy Services [Member]
Contract life, maximum remaining term		20 years