Consolidated Statements of Comprehensive Income/(Loss) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
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
Successor [Member]
Net income	4.9		26.6
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	(0.1)		0.3
Total change in fair value of available-for-sale securities	(0.1)		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	(13.4)		(5.8)
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	0.1		(0.8)
Total change in fair value of derivatives	(13.3)		(6.6)
Pension and postretirement activity:
Reclassification to earnings, net of income tax benefit/(expense) of $(0.0) and $0.4, respectively, for the three months and $0.0 and $(0.8), respectively, for the six months	(0.1)		(0.1)
Total change in unfunded pension obligation	(0.1)		(0.1)
Other comprehensive income / (loss)	(13.5)		(6.4)
Net comprehensive income / (loss)	(8.6)		20.2
Predecessor [Member]
Net income		31.7		75.2
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		0
Total change in fair value of available-for-sale securities		0		0
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		(11.3)		(10.1)
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		1.3		1.3
Total change in fair value of derivatives		(10.0)		(8.8)
Pension and postretirement activity:
Reclassification to earnings, net of income tax benefit/(expense) of $(0.0) and $0.4, respectively, for the three months and $0.0 and $(0.8), respectively, for the six months		0.4		1.6
Total change in unfunded pension obligation		0.4		1.6
Other comprehensive income / (loss)		(9.6)		(7.2)
Net comprehensive income / (loss)		22.1		68.0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Net income	31.3	30.8	69.4	83.5
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	(0.1)	1.8	0.3	2.7
Total change in fair value of available-for-sale securities	(0.1)	1.8	0.3	2.7
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	(0.1)	(0.7)	(1.6)	(0.9)
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	(0.5)	0	(2.3)	0
Total change in fair value of derivatives	(0.6)	(0.7)	(3.9)	(0.9)
Pension and postretirement activity:
Reclassification to earnings, net of income tax benefit/(expense) of $(0.0) and $0.4, respectively, for the three months and $0.0 and $(0.8), respectively, for the six months	0.8	0.4	2.0	1.4
Total change in unfunded pension obligation	0.8	0.4	2.0	1.4
Other comprehensive income / (loss)	0.1	1.5	(1.6)	3.2
Net comprehensive income / (loss)	$ 31.4	$ 32.3	$ 67.8	$ 86.7