Supplemental Financial Information (Accumulated Other Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended			9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended				9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 DP&L [Member]	Sep. 30, 2013 DP&L [Member]	Sep. 30, 2014 DP&L [Member]	Sep. 30, 2013 DP&L [Member]	Dec. 31, 2013 DP&L [Member]	Sep. 30, 2014 Available-for-sale Securities [Member]	Dec. 31, 2013 Available-for-sale Securities [Member]	Sep. 30, 2014 Available-for-sale Securities [Member] DP&L [Member]	Dec. 31, 2013 Available-for-sale Securities [Member] DP&L [Member]	Sep. 30, 2014 Derivative [Member]	Dec. 31, 2013 Derivative [Member]	Sep. 30, 2014 Derivative [Member] DP&L [Member]	Dec. 31, 2012 Derivative [Member] DP&L [Member]	Sep. 30, 2014 Other Pension Plan, Defined Benefit [Member]	Dec. 31, 2013 Other Pension Plan, Defined Benefit [Member]	Sep. 30, 2014 Other Pension Plan, Defined Benefit [Member] DP&L [Member]	Dec. 31, 2013 Other Pension Plan, Defined Benefit [Member] DP&L [Member]
Total Reclassifications out of AOCI	$ 3.6	$ 1.7	$ 14.6	$ 4.7		$ 4.1	$ 2.3	$ 17.8	$ 6.4		$ 0.4		$ 0.4		$ 14.2		$ 15.3				$ 2.1
Total Adjustments to AOCI			(24.4)					(26.9)			(0.6)		(0.6)		(23.8)		(26.3)
Other Comprehensive Income (Loss), Net of Tax	4.4	8.1	(9.8)	22.1				(9.1)			(0.2)		(0.2)		(9.6)		(11.0)				2.1
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 14.8		$ 14.8		$ 24.6	$ (35.8)		$ (35.8)		$ (26.7)	$ 0.4	$ 0.6	$ 0.6	$ 0.8	$ 11.0	$ 20.6	$ (4.8)	$ 6.2	$ 3.4	$ 3.4	$ (31.6)	$ (33.7)