Fair Value Disclosures (Fair Value Of Financial Assets And Liabilities Measured On A Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, assets	$ 192		$ 114
Derivative instruments, liabilities	128		216
Executive deferred compensation plan liabilities			30
Electricity [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, assets			22	[1],[2]
Derivative instruments, liabilities	32	[1],[2]	88	[1],[2]
Treasury Fund [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	114		17
Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Executive deferred compensation plan assets	18		9
Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, liabilities	67	[1],[3]	98	[1],[3]
Capacity [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, liabilities	1	[1]
Life Insurance Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Executive deferred compensation plan assets	60		66
Executive deferred compensation plan liabilities	28
Quoted Prices In Active Markets For Identical Instruments (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, assets	132	[4]	26	[4]
Derivative instruments, liabilities	50	[4]	75	[4]
Quoted Prices In Active Markets For Identical Instruments (Level 1) [Member] | Treasury Fund [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	114	[4]	17	[4]
Quoted Prices In Active Markets For Identical Instruments (Level 1) [Member] | Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Executive deferred compensation plan assets	18	[4]	9	[4]
Quoted Prices In Active Markets For Identical Instruments (Level 1) [Member] | Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, liabilities	50	[1],[3],[4]	75	[1],[3],[4]
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, assets	43	[4]	69	[4]
Derivative instruments, liabilities	61	[4]	118	[4]
Executive deferred compensation plan liabilities			30	[4]
Significant Other Observable Inputs (Level 2) [Member] | Electricity [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, assets			22	[1],[2],[4]
Derivative instruments, liabilities	32	[1],[2],[4]	88	[1],[2],[4]
Significant Other Observable Inputs (Level 2) [Member] | Capacity [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, liabilities	1	[1],[4]
Significant Other Observable Inputs (Level 2) [Member] | Life Insurance Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Executive deferred compensation plan assets	43	[4]	47	[4]
Executive deferred compensation plan liabilities	28	[4]
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, assets	17		19
Derivative instruments, liabilities	17		23
Significant Unobservable Inputs (Level 3) [Member] | Natural Gas [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative instruments, liabilities	17	[1],[3]	23	[1],[3]
Significant Unobservable Inputs (Level 3) [Member] | Life Insurance Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Executive deferred compensation plan assets	$ 17		$ 19

[1] The fair value of derivative assets and liabilities reflect netting by counterparty before the impact of collateral.

[2] Represents wholesale electricity futures and swaps that are used mainly as part of Pepco Energy Services' retail energy supply business.

[3] Level 1 instruments represent wholesale gas futures and swaps that are used mainly as part of Pepco Energy Services' retail energy supply business and level 3 instruments represent natural gas options purchased by DPL as part of a natural gas hedging program approved by the DPSC.

[4] There were no significant transfers of instruments between level 1 and level 2 valuation categories.