Derivative Instruments and Hedging Activities (Outstanding Derivative Instruments) (Details) (USD $)	6 Months Ended
	Jun. 30, 2011 MWH		Dec. 31, 2010 MWH
FTRs [Member] | MTM position [Member]
Purchase of Units Derivative Instruments Financial Transmission Rights	17,000	[1]	9,000	[1]
Sales of Units Derivative Instruments Financial Transmission Rights				[1]
Derivative, Nonmonetary Notional Amount	17,000	[1]	9,000	[1]
Heating Oil [Member] | MTM position [Member]
Purchase of Volume Units Derivative Instruments Heating Oil Futures	4,578,000	[1]	6,216,000	[1]
Sales of Volume Units Derivative Instruments Heating Oil Futures				[1]
Derivative, Nonmonetary Notional Amount	4,578,000	[1]	6,216,000	[1]
DPL [Member] | Forward Power Contracts [Member] | MTM position [Member]
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(1,338,700)	[2]
Purchase of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	1,311,300	[2]
Derivative, Nonmonetary Notional Amount	(27,400)	[2]
Forward Power Contracts [Member] | MTM position [Member]
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(423,200)	[1]
Purchase of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	446,900	[1]	195,600	[1]
Sales of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged			(108,500)	[1]
Derivative, Nonmonetary Notional Amount	23,700	[1]	87,100	[1]
Forward Power Contracts [Member] | Cash Flow Hedge [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	927,200	[1]
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(965,700)	[1]
Purchase of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged			580,800	[1]
Sales of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged			(572,900)	[1]
Derivative, Nonmonetary Notional Amount	(38,500)	[1]	7,900	[1]
NYMEX Coal [Member] | MTM position [Member]
Purchase of Volume Units Derivative Instruments Coal Contracts	3,588,300	[1],[3]	4,006,800	[1],[3]
Sales of Volume Units Derivative Instruments Coal Contracts				[1],[3]
Derivative, Nonmonetary Notional Amount	3,588,300	[1],[3]	4,006,800	[1],[3]
Interest Rate Swap [Member] | Cash Flow Hedge [Member]
Purchase of Derivative Instruments Interest Rate Swaps	460,000,000	[2]	360,000,000	[2]
Sales of Derivative Instruments Interest Rate Swaps				[2]
Notional Amount of Derivatives	460,000,000	[2]	360,000,000	[2]

[1] Reflected in both DPL's and DP&L's Condensed Consolidated Financial Statements.

[2] Reflected in only DPL's Condensed Consolidated Financial Statements.

[3] Includes our partners' share for the jointly-owned plants that DP&L operates.