Consolidated Statements of Comprehensive Income/(Loss) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2011 Successor [Member]	Dec. 31, 2012 Successor [Member]	Nov. 27, 2011 Predecessor [Member]	Dec. 31, 2010 Predecessor [Member]	Dec. 31, 2012 THE DAYTON POWER AND LIGHT COMPANY [Member]	Dec. 31, 2011 THE DAYTON POWER AND LIGHT COMPANY [Member]	Dec. 31, 2010 THE DAYTON POWER AND LIGHT COMPANY [Member]
Net income	$ (6.2)	$ (1,729.8)	$ 150.5	$ 290.3	$ 91.2	$ 193.2	$ 277.7
Available-for-sale securities activity:
Change in fair value of available-for-sale securities		0.5		0.4	0.5	(7.8)	(1.0)
Reclassification to earnings		(0.1)			(0.1)
Total change in fair value of available-for-sale securities		0.4		0.4	0.4	(7.8)	(1.0)
Derivative activity:
Change in derivative fair value	(0.5)	(1.5)	(58.2)	12.3	(3.0)	(1.2)	3.1
Reclassification of earnings		(0.5)	(0.3)	(5.9)	(3.4)	(0.2)	(5.9)
Total change in fair value of derivatives	(0.5)	(2.0)	(58.5)	6.4	(6.4)	(1.4)	(2.8)
Pension and postretirement activity:
Prior service cost for the period	(0.2)		0.1	7.0	0.8	0.5	1.2
Net loss for the period	0.3	(1.9)	0.3	(6.1)	(1.5)	(8.0)	0.4
Reclassification to earnings			2.8	2.4	2.7	2.3	1.7
Total change in unfunded pension obligation	0.1	(1.9)	3.2	3.3	2.0	(5.2)	3.3
Other comprehensive income / (loss)	(0.4)	(3.5)	(55.3)	10.1	(4.0)	(14.4)	(0.5)
Net comprehensive income / (loss)	$ (6.6)	$ (1,733.3)	$ 95.2	$ 300.4	$ 87.2	$ 178.8	$ 277.2