Derivative Instruments and Hedging Activities (Classification within the Condensed Consolidated Statements of Results of Operations or Balance Sheets of the Gains and Losses) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended							1 Months Ended	11 Months Ended	12 Months Ended				1 Months Ended	11 Months Ended	12 Months Ended		1 Months Ended	11 Months Ended	12 Months Ended				1 Months Ended	11 Months Ended	12 Months Ended				11 Months Ended	12 Months Ended		11 Months Ended	12 Months Ended			11 Months Ended	12 Months Ended				1 Months Ended	11 Months Ended	12 Months Ended					1 Months Ended	11 Months Ended	12 Months Ended					11 Months Ended	12 Months Ended				11 Months Ended	12 Months Ended					1 Months Ended	11 Months Ended	12 Months Ended					1 Months Ended	11 Months Ended	12 Months Ended					11 Months Ended	12 Months Ended			11 Months Ended	12 Months Ended				1 Months Ended	11 Months Ended	12 Months Ended					1 Months Ended	11 Months Ended	12 Months Ended					1 Months Ended	11 Months Ended	12 Months Ended					1 Months Ended	11 Months Ended	12 Months Ended			1 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 Wholesale Revenue [Member]	Dec. 31, 2012 Purchased Power [Member]	Dec. 31, 2012 Fuel [Member]	Dec. 31, 2012 O&M [Member]	Dec. 31, 2012 Partners Share of Gain Loss [Member]	Dec. 31, 2012 Regulatory Asset Liability [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member]	Nov. 27, 2011 Not Designated as Hedging Instrument [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] DP&L [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Wholesale Revenue [Member]	Nov. 27, 2011 Not Designated as Hedging Instrument [Member] Wholesale Revenue [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Wholesale Revenue [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Wholesale Revenue [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Purchased Power [Member]	Nov. 27, 2011 Not Designated as Hedging Instrument [Member] Purchased Power [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member] Purchased Power [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Purchased Power [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Purchased Power [Member] DP&L [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member] Purchased Power [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Fuel [Member]	Nov. 27, 2011 Not Designated as Hedging Instrument [Member] Fuel [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member] Fuel [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Fuel [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Fuel [Member] DP&L [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member] Fuel [Member] DP&L [Member]	Nov. 27, 2011 Not Designated as Hedging Instrument [Member] O&M [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] O&M [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] O&M [Member] DP&L [Member]	Nov. 27, 2011 Not Designated as Hedging Instrument [Member] Partners Share of Gain Loss [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member] Partners Share of Gain Loss [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Partners Share of Gain Loss [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Partners Share of Gain Loss [Member] DP&L [Member]	Nov. 27, 2011 Not Designated as Hedging Instrument [Member] Regulatory Asset Liability [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member] Regulatory Asset Liability [Member]	Dec. 31, 2012 Not Designated as Hedging Instrument [Member] Regulatory Asset Liability [Member] DP&L [Member]	Dec. 31, 2011 Not Designated as Hedging Instrument [Member] Regulatory Asset Liability [Member] DP&L [Member]	Dec. 31, 2010 Not Designated as Hedging Instrument [Member] Regulatory Asset Liability [Member] DP&L [Member]	Dec. 31, 2011 NYMEX Coal [Member]	Nov. 27, 2011 NYMEX Coal [Member]	Dec. 31, 2012 NYMEX Coal [Member]	Dec. 31, 2010 NYMEX Coal [Member]	Dec. 31, 2012 NYMEX Coal [Member] DP&L [Member]	Dec. 31, 2011 NYMEX Coal [Member] DP&L [Member]	Dec. 31, 2010 NYMEX Coal [Member] DP&L [Member]	Dec. 31, 2011 NYMEX Coal [Member] Fuel [Member]	Nov. 27, 2011 NYMEX Coal [Member] Fuel [Member]	Dec. 31, 2012 NYMEX Coal [Member] Fuel [Member]	Dec. 31, 2010 NYMEX Coal [Member] Fuel [Member]	Dec. 31, 2012 NYMEX Coal [Member] Fuel [Member] DP&L [Member]	Dec. 31, 2011 NYMEX Coal [Member] Fuel [Member] DP&L [Member]	Dec. 31, 2010 NYMEX Coal [Member] Fuel [Member] DP&L [Member]	Nov. 27, 2011 NYMEX Coal [Member] Partners Share of Gain Loss [Member]	Dec. 31, 2012 NYMEX Coal [Member] Partners Share of Gain Loss [Member]	Dec. 31, 2010 NYMEX Coal [Member] Partners Share of Gain Loss [Member]	Dec. 31, 2012 NYMEX Coal [Member] Partners Share of Gain Loss [Member] DP&L [Member]	Dec. 31, 2011 NYMEX Coal [Member] Partners Share of Gain Loss [Member] DP&L [Member]	Nov. 27, 2011 NYMEX Coal [Member] Regulatory Asset Liability [Member]	Dec. 31, 2012 NYMEX Coal [Member] Regulatory Asset Liability [Member]	Dec. 31, 2010 NYMEX Coal [Member] Regulatory Asset Liability [Member]	Dec. 31, 2012 NYMEX Coal [Member] Regulatory Asset Liability [Member] DP&L [Member]	Dec. 31, 2011 NYMEX Coal [Member] Regulatory Asset Liability [Member] DP&L [Member]	Dec. 31, 2010 NYMEX Coal [Member] Regulatory Asset Liability [Member] DP&L [Member]	Dec. 31, 2011 Heating Oil [Member]	Nov. 27, 2011 Heating Oil [Member]	Dec. 31, 2012 Heating Oil [Member]	Dec. 31, 2010 Heating Oil [Member]	Dec. 31, 2012 Heating Oil [Member] DP&L [Member]	Dec. 31, 2011 Heating Oil [Member] DP&L [Member]	Dec. 31, 2010 Heating Oil [Member] DP&L [Member]	Dec. 31, 2011 Heating Oil [Member] Fuel [Member]	Nov. 27, 2011 Heating Oil [Member] Fuel [Member]	Dec. 31, 2012 Heating Oil [Member] Fuel [Member]	Dec. 31, 2010 Heating Oil [Member] Fuel [Member]	Dec. 31, 2012 Heating Oil [Member] Fuel [Member] DP&L [Member]	Dec. 31, 2011 Heating Oil [Member] Fuel [Member] DP&L [Member]	Dec. 31, 2010 Heating Oil [Member] Fuel [Member] DP&L [Member]	Nov. 27, 2011 Heating Oil [Member] O&M [Member]	Dec. 31, 2012 Heating Oil [Member] O&M [Member]	Dec. 31, 2012 Heating Oil [Member] O&M [Member] DP&L [Member]	Dec. 31, 2011 Heating Oil [Member] O&M [Member] DP&L [Member]	Nov. 27, 2011 Heating Oil [Member] Regulatory Asset Liability [Member]	Dec. 31, 2012 Heating Oil [Member] Regulatory Asset Liability [Member]	Dec. 31, 2010 Heating Oil [Member] Regulatory Asset Liability [Member]	Dec. 31, 2012 Heating Oil [Member] Regulatory Asset Liability [Member] DP&L [Member]	Dec. 31, 2010 Heating Oil [Member] Regulatory Asset Liability [Member] DP&L [Member]	Dec. 31, 2011 FTR's [Member]	Nov. 27, 2011 FTR's [Member]	Dec. 31, 2012 FTR's [Member]	Dec. 31, 2010 FTR's [Member]	Dec. 31, 2012 FTR's [Member] DP&L [Member]	Dec. 31, 2011 FTR's [Member] DP&L [Member]	Dec. 31, 2010 FTR's [Member] DP&L [Member]	Dec. 31, 2011 FTR's [Member] Purchased Power [Member]	Nov. 27, 2011 FTR's [Member] Purchased Power [Member]	Dec. 31, 2012 FTR's [Member] Purchased Power [Member]	Dec. 31, 2010 FTR's [Member] Purchased Power [Member]	Dec. 31, 2012 FTR's [Member] Purchased Power [Member] DP&L [Member]	Dec. 31, 2011 FTR's [Member] Purchased Power [Member] DP&L [Member]	Dec. 31, 2010 FTR's [Member] Purchased Power [Member] DP&L [Member]	Dec. 31, 2011 Forward Power Contracts [Member]	Nov. 27, 2011 Forward Power Contracts [Member]	Dec. 31, 2012 Forward Power Contracts [Member]	Dec. 31, 2010 Forward Power Contracts [Member]	Dec. 31, 2012 Forward Power Contracts [Member] DP&L [Member]	Dec. 31, 2011 Forward Power Contracts [Member] DP&L [Member]	Dec. 31, 2010 Forward Power Contracts [Member] DP&L [Member]	Dec. 31, 2011 Forward Power Contracts [Member] Wholesale Revenue [Member]	Nov. 27, 2011 Forward Power Contracts [Member] Wholesale Revenue [Member]	Dec. 31, 2012 Forward Power Contracts [Member] Wholesale Revenue [Member]	Dec. 31, 2012 Forward Power Contracts [Member] Wholesale Revenue [Member] DP&L [Member]	Dec. 31, 2011 Forward Power Contracts [Member] Wholesale Revenue [Member] DP&L [Member]	Dec. 31, 2011 Forward Power Contracts [Member] Purchased Power [Member]	Nov. 27, 2011 Forward Power Contracts [Member] Purchased Power [Member]	Dec. 31, 2012 Forward Power Contracts [Member] Purchased Power [Member]	Dec. 31, 2012 Forward Power Contracts [Member] Purchased Power [Member] DP&L [Member]	Dec. 31, 2011 Forward Power Contracts [Member] Purchased Power [Member] DP&L [Member]
Change in unrealized gain / (loss)	$ 17.0							$ (2.7)	$ (49.5)	$ 35.8	$ 15.7	$ (51.8)	$ 35.8																													$ (1.4)	$ (50.7)	$ 14.5	$ 33.5	$ 14.5	$ (52.1)	$ 33.5																			$ (0.5)	$ 0.6	$ (1.6)	$ 2.8	$ (1.6)	$ 0.1	$ 2.8																		$ (0.2)	$ (0.2)	$ (0.6)	$ (0.2)	$ (0.1)	$ (0.6)								$ (0.8)	$ 0.8	$ 4.3	$ 0.1	$ 3.0	$ 0.3	$ 0.1
Derivative, Gain (Loss) on Derivative, Net	(32.1)							(1.9)	7.6		(22.2)	7.8																														(1.2)	8.7	(29.5)	3.2	(29.5)	7.5	3.2																			0.1	2.2	1.9	(1.6)	1.9	2.3	(1.6)																	0.1	(0.6)	0.5	(1.5)	0.5	(0.6)	(1.5)								(0.9)	(2.7)	(5.0)	(0.1)	4.9	(1.4)	(0.1)
Gain (Loss) on Derivative Instruments, Net, Pretax	(15.1)							(4.6)	(41.9)	35.8	(6.5)	(44.0)	35.8																													(2.6)	(42.0)	(15.0)	36.7	(15.0)	(44.6)	36.7																			(0.4)	2.8	0.3	1.2	0.3	2.4	1.2																	0.1	(0.8)	0.3	(2.1)	0.3	(0.7)	(2.1)								(1.7)	(1.9)	(0.7)		7.9	(1.1)
Partner's share of gain (loss)						4.2		(0.3)					20.1																				(25.9)	20.1	4.2	(26.1)						(0.3)						20.1								(25.9)	4.2	20.1	4.2	(26.1)
Regulatory (asset)/liability							0.4	(0.2)																													(6.9)	5.7	0.4	(7.1)	5.7	(0.1)																			(7.0)	1.0	4.6	1.0	(7.1)	4.6	(0.1)																		0.1	(0.6)	1.1	(0.6)	1.1
Derivative Instruments, Gain (Loss) Recognized in Income, Net	$ (15.1)	$ (5.1)	$ 4.7	$ (19.5)	$ 0.2			$ (4.6)	$ (41.9)	$ 35.8	$ (6.5)	$ (44.0)	$ 35.8	$ 0.6	$ (3.8)	$ 2.7	$ 2.5	$ (2.2)	$ 1.1	$ (2.1)	$ 5.5	$ (4.3)	$ (2.1)	$ (2.5)	$ (6.6)	$ 12.1	$ (19.5)	$ (9.2)	$ 12.1	$ 0.2	$ 0.2	$ 0.2										$ (2.6)	$ (42.0)	$ (15.0)	$ 36.7	$ (15.0)	$ (44.6)	$ 36.7	$ (2.2)	$ (9.1)	$ (20.2)	$ 12.0	$ (20.2)	$ (11.4)	$ 12.0												$ (0.4)	$ 2.8	$ 0.3	$ 1.2	$ 0.3	$ 2.4	$ 1.2	$ (0.3)	$ 2.5	$ 0.7	$ 0.1	$ 0.7	$ 2.2	$ 0.1	$ 0.2	$ 0.2	$ 0.2	$ 0.2						$ 0.1	$ (0.8)	$ 0.3	$ (2.1)	$ 0.3	$ (0.7)	$ (2.1)	$ 0.1	$ (0.8)	$ 0.3	$ (2.1)	$ 0.3	$ (0.7)	$ (2.1)	$ (1.7)	$ (1.9)	$ (0.7)		$ 7.9	$ (1.1)		$ 0.6	$ (3.8)	$ (5.1)	$ 2.7	$ 2.5	$ (2.3)	$ 1.9	$ 4.4	$ 5.2	$ (3.6)