Consolidated Statements of Comprehensive Income/(Loss) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Successor [Member]
Net income	$ (1,810.9)		$ (1,777.3)
Available-for-sale securities activity:
Change in fair value of available-for-sale securities, net of income tax benefit/(expense) of $0.1 and $0.0, respectively for the three months and $(0.2) and $0.0, respectively for the six months	0.2		0.5
Total change in fair value of available-for-sale securities	0.2		0.5
Derivative activity:
Change in derivative fair value, net of income tax expense of $7.4 and $6.0, respectively for the three months and $3.3 and $5.4, respectively, for the six months	0.3		(5.5)
Reclassification of earnings, net of income tax (expense)/benefit of $0.0 and $(1.0), respectively, for the three months and $0.7 and $(1.3), respectively, for the six months			(0.8)
Total change in fair value of derivatives	0.3		(6.3)
Pension and postretirement activity:
Reclassification to earnings, net of income tax benefit/(expense) of $(0.0) and $(0.3), respectively, for the three months and $0.0 and $(0.8), respectively, for the six months			(0.1)
Total change in unfunded pension obligation			(0.1)
Other comprehensive income / (loss)	0.5		(5.9)
Net comprehensive income / (loss)	(1,810.4)		(1,783.2)
Predecessor [Member]
Net income		67.1		142.3
Available-for-sale securities activity:
Change in fair value of available-for-sale securities, net of income tax benefit/(expense) of $0.1 and $0.0, respectively for the three months and $(0.2) and $0.0, respectively for the six months		(0.3)		(0.3)
Total change in fair value of available-for-sale securities		(0.3)		(0.3)
Derivative activity:
Change in derivative fair value, net of income tax expense of $7.4 and $6.0, respectively for the three months and $3.3 and $5.4, respectively, for the six months		(48.1)		(59.5)
Reclassification of earnings, net of income tax (expense)/benefit of $0.0 and $(1.0), respectively, for the three months and $0.7 and $(1.3), respectively, for the six months		1.5		4.1
Total change in fair value of derivatives		(46.6)		(55.4)
Pension and postretirement activity:
Reclassification to earnings, net of income tax benefit/(expense) of $(0.0) and $(0.3), respectively, for the three months and $0.0 and $(0.8), respectively, for the six months		0.9		2.5
Total change in unfunded pension obligation		0.9		2.5
Other comprehensive income / (loss)		(46.0)		(53.2)
Net comprehensive income / (loss)		21.1		89.1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Net income	(11.2)	63.9	58.3	147.4
Available-for-sale securities activity:
Change in fair value of available-for-sale securities, net of income tax benefit/(expense) of $0.1 and $0.0, respectively for the three months and $(0.2) and $0.0, respectively for the six months	0.2	(0.4)	0.5	2.3
Total change in fair value of available-for-sale securities	0.2	(0.4)	0.5	2.3
Derivative activity:
Change in derivative fair value, net of income tax expense of $7.4 and $6.0, respectively for the three months and $3.3 and $5.4, respectively, for the six months	(2.5)	1.8	(4.0)	0.7
Reclassification of earnings, net of income tax (expense)/benefit of $0.0 and $(1.0), respectively, for the three months and $0.7 and $(1.3), respectively, for the six months	(0.7)	(0.5)	(3.1)	(0.5)
Total change in fair value of derivatives	(3.2)	1.3	(7.1)	0.2
Pension and postretirement activity:
Reclassification to earnings, net of income tax benefit/(expense) of $(0.0) and $(0.3), respectively, for the three months and $0.0 and $(0.8), respectively, for the six months	1.0	1.0	3.0	2.6
Total change in unfunded pension obligation	1.0	1.0	3.0	2.6
Other comprehensive income / (loss)	(2.0)	1.9	(3.6)	5.1
Net comprehensive income / (loss)	$ (13.2)	$ 65.8	$ 54.7	$ 152.5