Fair Value Disclosures (Fair Value Of Assets And Liabilities Measured On Recurring Basis) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Derivative instruments, assets	$ 198		$ 114
Derivative instruments, liabilities	137		216
Quoted Prices In Active Markets For Identical Instruments (Level 1) [Member]
Derivative instruments, assets	131	[1]	26	[1]
Derivative instruments, liabilities	46	[1]	75	[1]
Quoted Prices In Active Markets For Identical Instruments (Level 1) [Member] | Treasury Fund [Member]
Cash equivalents	113	[1]	17	[1]
Quoted Prices In Active Markets For Identical Instruments (Level 1) [Member] | Money Market Funds [Member]
Executive deferred compensation plan assets	18	[1]	9	[1]
Quoted Prices In Active Markets For Identical Instruments (Level 1) [Member] | Natural Gas [Member]
Derivative instruments, liabilities	46	[1],[2],[3]	75	[1],[2],[3]
Significant Other Observable Inputs (Level 2) [Member]
Derivative instruments, assets	48	[1]	69	[1]
Derivative instruments, liabilities	72	[1]	118	[1]
Significant Other Observable Inputs (Level 2) [Member] | Electricity [Member]
Derivative instruments, assets	5	[1],[3],[4]	22	[1],[3],[4]
Derivative instruments, liabilities	41	[1],[3],[4]	88	[1],[3],[4]
Significant Other Observable Inputs (Level 2) [Member] | Natural Gas [Member]
Derivative instruments, liabilities	1	[1],[2],[3]
Significant Other Observable Inputs (Level 2) [Member] | Capacity [Member]
Derivative instruments, liabilities	1	[1]
Significant Other Observable Inputs (Level 2) [Member] | Life Insurance Contracts [Member]
Executive deferred compensation plan assets	43	[1]	47	[1]
Executive deferred compensation plan liabilities	29	[1]	30	[1]
Significant Unobservable Inputs (Level 3) [Member]
Derivative instruments, assets	19		19
Derivative instruments, liabilities	19		23
Significant Unobservable Inputs (Level 3) [Member] | Natural Gas [Member]
Derivative instruments, assets	2	[2],[3]
Derivative instruments, liabilities	19	[2],[3]	23	[2],[3]
Significant Unobservable Inputs (Level 3) [Member] | Life Insurance Contracts [Member]
Executive deferred compensation plan assets	17		19
Electricity [Member]
Derivative instruments, assets	5	[3],[4]	22	[3],[4]
Derivative instruments, liabilities	41	[3],[4]	88	[3],[4]
Treasury Fund [Member]
Cash equivalents	113		17
Money Market Funds [Member]
Executive deferred compensation plan assets	18		9
Natural Gas [Member]
Derivative instruments, assets	2	[2],[3]
Derivative instruments, liabilities	66	[2],[3]	98	[2],[3]
Capacity [Member]
Derivative instruments, liabilities	1
Life Insurance Contracts [Member]
Executive deferred compensation plan assets	60		66
Executive deferred compensation plan liabilities	$ 29		$ 30

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

[2] 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 primarily represent natural gas options purchased by DPL as part of a natural gas hedging program approved by the DPSC.

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

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