Derivative Instruments and Hedging Activities (Outstanding Derivative Instruments) (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2014 MWh	Dec. 31, 2013 MWh
Designated as Hedging Instrument [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	40,700	140,400
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(3,543,000)	(4,705,700)
Derivative, Nonmonetary Notional Amount MWh	(3,502,300)	(4,565,300)
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	40,700	140,400
Sales of Units Derivative Instruments Forward Power Contracts Designated as Cash Flow Hedge	(3,543,000)	(4,705,700)
Derivative, Nonmonetary Notional Amount MWh	(3,502,300)	(4,565,300)
Not Designated as Hedging Instrument [Member] | Commodity Contract - FTR [Member]
Purchase of Units Derivative Instruments Financial Transmission Rights	17,400	7,100
Derivative, Nonmonetary Notional Amount MWh	17,400	7,100
Not Designated as Hedging Instrument [Member] | Commodity Contract - Heating Oil [Member]
Purchase of Volume Units Derivative Instruments Heating Oil Futures	672,000	1,428,000
Derivative, Nonmonetary Notional Amount, Volume	672,000	1,428,000
Not Designated as Hedging Instrument [Member] | Forward Contract Power [Member]
Purchase of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	2,320,000	3,177,800
Sales of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	(3,357,900)	(2,883,100)
Derivative, Nonmonetary Notional Amount MWh	(1,037,900)	294,700
Not Designated as Hedging Instrument [Member] | DP&L [Member] | Commodity Contract - FTR [Member]
Purchase of Units Derivative Instruments Financial Transmission Rights	17,400	7,100
Derivative, Nonmonetary Notional Amount MWh	17,400	7,100
Not Designated as Hedging Instrument [Member] | DP&L [Member] | Commodity Contract - Heating Oil [Member]
Purchase of Volume Units Derivative Instruments Heating Oil Futures	672,000	1,428,000
Derivative, Nonmonetary Notional Amount, Volume	672,000	1,428,000
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	2,320,000	3,172,400
Sales of Units Derivative Instruments Forward Power Contracts Not Designated as Hedged	(3,463,500)	(2,888,500)
Derivative, Nonmonetary Notional Amount MWh	(1,143,500)	283,900