Derivative Instruments and Hedging Activities (Gains or Losses Recognized in AOCI for the Cash Flow Hedges) (Details) (USD $) In Millions, unless otherwise specified	2 Months Ended	3 Months Ended			1 Months Ended	11 Months Ended	12 Months Ended		1 Months Ended	11 Months Ended	12 Months Ended		3 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
	Nov. 27, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2011 Forward Contract Power [Member]	Nov. 27, 2011 Forward Contract Power [Member]	Dec. 31, 2013 Forward Contract Power [Member]	Dec. 31, 2012 Forward Contract Power [Member]	Dec. 31, 2011 Interest Rate Contract [Member]	Nov. 27, 2011 Interest Rate Contract [Member]	Dec. 31, 2013 Interest Rate Contract [Member]	Dec. 31, 2012 Interest Rate Contract [Member]	Dec. 31, 2011 DP&L [Member]	Sep. 30, 2011 DP&L [Member]	Jun. 30, 2011 DP&L [Member]	Mar. 31, 2011 DP&L [Member]	Dec. 31, 2013 DP&L [Member] Forward Contract Power [Member]		Dec. 31, 2012 DP&L [Member] Forward Contract Power [Member]	Dec. 31, 2011 DP&L [Member] Forward Contract Power [Member]	Dec. 31, 2013 DP&L [Member] Interest Rate Contract [Member]	Dec. 31, 2011 DP&L [Member] Interest Rate Contract [Member]	Dec. 31, 2010 DP&L [Member] Interest Rate Contract [Member]	Dec. 31, 2011 Interest Expense [Member] Interest Rate Contract [Member]	Nov. 27, 2011 Interest Expense [Member] Interest Rate Contract [Member]	Dec. 31, 2012 Interest Expense [Member] Interest Rate Contract [Member]	Dec. 31, 2013 Interest Expense [Member] DP&L [Member] Interest Rate Contract [Member]	Dec. 31, 2012 Interest Expense [Member] DP&L [Member] Interest Rate Contract [Member]	Dec. 31, 2011 Interest Expense [Member] DP&L [Member] Interest Rate Contract [Member]	Dec. 31, 2011 Revenue [Member] Forward Contract Power [Member]	Nov. 27, 2011 Revenue [Member] Forward Contract Power [Member]	Dec. 31, 2013 Revenue [Member] Forward Contract Power [Member]	Dec. 31, 2012 Revenue [Member] Forward Contract Power [Member]	Dec. 31, 2013 Revenue [Member] DP&L [Member] Forward Contract Power [Member]	Dec. 31, 2012 Revenue [Member] DP&L [Member] Forward Contract Power [Member]	Dec. 31, 2011 Revenue [Member] DP&L [Member] Forward Contract Power [Member]	Dec. 31, 2011 Purchased Power [Member] Forward Contract Power [Member]	Nov. 27, 2011 Purchased Power [Member] Forward Contract Power [Member]	Dec. 31, 2013 Purchased Power [Member] Forward Contract Power [Member]	Dec. 31, 2013 Purchased Power [Member] DP&L [Member] Forward Contract Power [Member]	Dec. 31, 2012 Purchased Power [Member] DP&L [Member] Forward Contract Power [Member]	Dec. 31, 2011 Purchased Power [Member] DP&L [Member] Forward Contract Power [Member]
Beginning accumulated derivative gain / (loss) in AOCI					$ (1.0)	$ (1.8)	$ (3.0)	$ 0.3	$ (37.9)	$ 21.4	$ 0.5	$ (0.8)					$ (4.7)		$ (0.8)	$ (1.8)	$ 7.3	$ 9.8	$ 12.2
Net gains / (losses) associated with current period hedging transactions					0.1	(1.2)	1.0	(2.6)	(0.6)	(57.0)	18.7	1.1					1.0		(3.0)	(1.2)
Net income (loss)	8.2	67.1	31.7	43.5									45.8	63.9	30.8	52.7
Ending accumulated derivative gain / (loss) in AOCI					0.3	(1.0)	1.4	(3.0)	(0.8)	(37.9)	19.2	0.5					1.0		(4.7)	(0.8)	5.2	9.8	12.2
Net gains / (losses) associated with the ineffective portion of the hedging transaction									0.4	5.1	0.8	0.2
Portion expected to be reclassified to earnings in the next twelve months							(2.5)				(1.0)						(2.2)	[1]			(1.1)
Maximum length of time that we are hedging our exposure to variability in future cash flows related to forecasted transactions (in months)							36 months				0 months						36 months				0 months
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net																								$ (0.2)	$ (2.3)	$ 0.2	$ (2.1)	$ (2.5)	$ (2.4)	$ 0.1	$ 1.1	$ 2.1	$ (0.7)	$ 1.4	$ (1.1)	$ 1.2	$ 0.1	$ 0.9	$ 1.3	$ 3.3	$ 0.2	$ 1.0

[1] (b)The actual amounts that we reclassify from AOCI to earnings related to power can differ from the estimate above due to market price changes.