Derivative Instruments and Hedging Activities (Fair Value and Balance Sheet Location (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014 DP&L [Member]	Jun. 30, 2014 Total Assets [Member]	Dec. 31, 2013 Total Assets [Member]	Jun. 30, 2014 Total Assets [Member] DP&L [Member]	Dec. 31, 2013 Total Assets [Member] DP&L [Member]	Jun. 30, 2014 Total Liabilities [Member]	Dec. 31, 2013 Total Liabilities [Member]	Jun. 30, 2014 Total Liabilities [Member] DP&L [Member]	Dec. 31, 2013 Total Liabilities [Member] DP&L [Member]	Dec. 31, 2013 Commodity Contract - FTR [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member]	Dec. 31, 2013 Commodity Contract - FTR [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member] DP&L [Member]	Jun. 30, 2014 Commodity Contract - FTR [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member]	Mar. 31, 2014 Commodity Contract - FTR [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member] DP&L [Member]	Jun. 30, 2014 Commodity Contract - Heating Oil [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member]	Dec. 31, 2013 Commodity Contract - Heating Oil [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member] DP&L [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member] DP&L [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member] DP&L [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member] DP&L [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Deferred Credit [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Credit [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Credit [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Credit [Member] DP&L [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Credit [Member] DP&L [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Asset [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Asset [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Asset [Member] DP&L [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Asset [Member] DP&L [Member]	Jun. 30, 2014 Not Designated as Hedging Instrument [Member] Commodity Contract - Heating Oil [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member] DP&L [Member]	Dec. 31, 2013 Not Designated as Hedging Instrument [Member] Commodity Contract - Heating Oil [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member] DP&L [Member]	Jun. 30, 2014 Cash Flow Hedging [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member]	Dec. 31, 2013 Cash Flow Hedging [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member]	Jun. 30, 2014 Cash Flow Hedging [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member] DP&L [Member]	Dec. 31, 2013 Cash Flow Hedging [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Prepayments and Current Assets [Member] DP&L [Member]	Jun. 30, 2014 Cash Flow Hedging [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member]	Dec. 31, 2013 Cash Flow Hedging [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member]	Jun. 30, 2014 Cash Flow Hedging [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member] DP&L [Member]	Dec. 31, 2013 Cash Flow Hedging [Member] Forward Contract Power [Member] Short-term Derivative Positions [Member] Other Current Liabilities [Member] DP&L [Member]	Jun. 30, 2014 Cash Flow Hedging [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Credit [Member]	Jun. 30, 2014 Cash Flow Hedging [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Credit [Member] DP&L [Member]	Jun. 30, 2014 Cash Flow Hedging [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Asset [Member]	Dec. 31, 2013 Cash Flow Hedging [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Asset [Member]	Jun. 30, 2014 Cash Flow Hedging [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Asset [Member] DP&L [Member]	Dec. 31, 2013 Cash Flow Hedging [Member] Forward Contract Power [Member] Long-term Derivative Positions [Member] Other Deferred Asset [Member] DP&L [Member]
Derivative Asset, Fair Value			$ 16.0	$ 13.8	$ 16.6	$ 13.8					$ 0.2	$ 0.2			$ 0.1	$ 0.2	$ 12.9	$ 4.9	$ 13.1	$ 4.9									$ 1.9	$ 5.0	$ 2.3	$ 5.0	$ 0.1	$ 0.2	$ 0.8	$ 0.5	$ 0.8	$ 0.5							$ 0.3	$ 3.0	$ 0.3	$ 3.0
Derivative, Fair Value, Net			4.0	5.9	4.7	5.9	4.8	0.3	4.9	0.3	0.2	0.2	1.3	1.3			3.8	0.7	4.1	0.7	0.3	0.3	0.1	0.1	0.1		0.2		0.1	4.7	0.5	4.7			0.1	0.3	0.1	0.3	3.1	0.2	3.1	0.2
Derivative, Collateral, net			(0.1)	(3.2)	(0.1)	(3.2)	(18.8)	(5.6)	(18.8)	(5.6)					(0.1)	(0.2)					(5.0)	(5.0)	(2.3)	(2.3)	(0.1)	(1.0)	(0.1)	(1.0)					(0.1)	(0.2)					(11.2)	(2.3)	(11.2)	(2.3)	(2.5)	(2.5)		(3.0)		(3.0)
Derivative, Fair Value, Offset, Net			(11.9)	(4.7)	(11.8)	(4.7)	(11.9)	(4.7)	(11.9)	(4.7)							(9.1)	(4.2)	(9.0)	(4.2)	(9.1)	(9.1)	(4.2)	(4.2)	(1.8)	(0.3)	(1.8)	(0.3)	(1.8)	(0.3)	(1.8)	(0.3)			(0.7)	(0.2)	(0.7)	(0.2)	(0.7)	(0.2)	(0.7)	(0.2)	(0.3)	(0.3)	(0.3)		(0.3)
Derivative Liability, Fair Value	$ 35.5	$ 35.6					$ 35.5	$ 10.6	$ 35.6	$ 10.6			$ 1.3	$ 1.3							$ 14.4	$ 14.4	$ 6.6	$ 6.6	$ 2.0	$ 1.3	$ 2.1	$ 1.3											$ 15.0	$ 2.7	$ 15.0	$ 2.7	$ 2.8	$ 2.8