Derivative Instruments and Hedging Activities (Outstanding Derivative Instruments) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013 MWh	Dec. 31, 2012 MWh
Commodity Contract - FTR [Member]
Purchase of Units Derivative Instruments Financial Transmission Rights	7,100
Derivative, Nonmonetary Notional Amount MWh	7,100
Commodity Contract - Heating Oil [Member]
Purchase of Volume Units Derivative Instruments Heating Oil Futures	1,428,000
Derivative, Nonmonetary Notional Amount, Volume	1,428,000
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Purchase of Derivative Instruments Interest Rate Swaps		$ 160,000,000
Notional Amount of Derivatives		$ 160,000,000
Designated as Hedging Instrument [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	140,400	1,021,000
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(4,705,700)	(2,197,900)
Derivative, Nonmonetary Notional Amount MWh	(4,565,300)	(1,176,900)
Designated as Hedging Instrument [Member] | DP&L [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	140,400	1,021,000
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(4,705,700)	(2,197,900)
Derivative, Nonmonetary Notional Amount MWh	(4,565,300)	(1,176,900)
Not Designated as Hedging Instrument [Member] | Commodity Contract - FTR [Member]
Purchase of Units Derivative Instruments Financial Transmission Rights		6,900
Derivative, Nonmonetary Notional Amount MWh		6,900
Not Designated as Hedging Instrument [Member] | Commodity Contract - Heating Oil [Member]
Purchase of Volume Units Derivative Instruments Heating Oil Futures		1,764,000
Derivative, Nonmonetary Notional Amount, Volume		1,764,000
Not Designated as Hedging Instrument [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	3,177,800	2,510,700
Sales of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	(2,883,100)	(4,760,400)
Derivative, Nonmonetary Notional Amount MWh	294,700	(2,249,700)
Not Designated as Hedging Instrument [Member] | DP&L [Member] | Commodity Contract - FTR [Member]
Purchase of Units Derivative Instruments Financial Transmission Rights	7,100	6,900
Derivative, Nonmonetary Notional Amount MWh	7,100	6,900
Not Designated as Hedging Instrument [Member] | DP&L [Member] | Commodity Contract - Heating Oil [Member]
Purchase of Volume Units Derivative Instruments Heating Oil Futures	1,428,000	1,764,000
Derivative, Nonmonetary Notional Amount, Volume	1,428,000	1,764,000
Not Designated as Hedging Instrument [Member] | DP&L [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	3,172,400	2,296,600
Sales of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	(2,888,500)	(4,760,400)
Derivative, Nonmonetary Notional Amount MWh	283,900	(2,463,800)