Fair Value Disclosures - Fair Value of Financial Liabilities Measured on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	$ 4,850	$ 5,004
Transition Bonds, Fair Value	284	341
Long-term Project Funding, Fair Value	12	13
Total Liabilities, Fair Value	5,146	5,358
Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value
Transition Bonds, Fair Value
Long-term Project Funding, Fair Value
Total Liabilities, Fair Value
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	4,289	4,517
Transition Bonds, Fair Value	284	341
Long-term Project Funding, Fair Value
Total Liabilities, Fair Value	4,573	4,858
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	561	487
Transition Bonds, Fair Value
Long-term Project Funding, Fair Value	12	13
Total Liabilities, Fair Value	573	500
Potomac Electric Power Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	2,127	2,160
Total Liabilities, Fair Value	2,127	2,160
Potomac Electric Power Co [Member] | Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value
Total Liabilities, Fair Value
Potomac Electric Power Co [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	2,127	2,160
Total Liabilities, Fair Value	2,127	2,160
Potomac Electric Power Co [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value
Total Liabilities, Fair Value
Delmarva Power & Light Co/De [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	960	990
Total Liabilities, Fair Value	960	990
Delmarva Power & Light Co/De [Member] | Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value
Total Liabilities, Fair Value
Delmarva Power & Light Co/De [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	850	877
Total Liabilities, Fair Value	850	877
Delmarva Power & Light Co/De [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	110	113
Total Liabilities, Fair Value	110	113
Atlantic City Electric Co [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	959	1,016
Transition Bonds, Fair Value	285	341
Total Liabilities, Fair Value	1,244	1,357
Atlantic City Electric Co [Member] | Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value
Transition Bonds, Fair Value
Total Liabilities, Fair Value
Atlantic City Electric Co [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	744	884
Transition Bonds, Fair Value	285	341
Total Liabilities, Fair Value	1,029	1,225
Atlantic City Electric Co [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, Fair Value	215	132
Transition Bonds, Fair Value
Total Liabilities, Fair Value	$ 215	$ 132