Stock-Based Compensation, Dividend Restrictions, And Calculations Of Earnings Per Share Of Common Stock (Common Stock Reserved And Unissued) (Detail)	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	19,906,382	[1]
DRP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	1,786,871	[1]
Conectiv Incentive Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	1,093,701	[1],[2]
Potomac Electric Power Company Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	298,543	[1],[2]
Pepco Holdings Long-Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	7,665,981	[1],[2]
Two Thousand Twelve Long Term Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	8,000,000	[1]
Pepco Holdings Non-Management Directors Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	457,211	[1]
Pepco Holdings Retirement Savings Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares	604,075	[1]

[1] Excludes up to 31 million shares authorized by the Board of Directors on February 23, 2012 for potential issuance pursuant to the terms of the equity forward transaction.

[2] No further awards will be made under this plan.