Consolidated Statements of Shareholders' Equity (USD $) In Millions	THE DAYTON POWER AND LIGHT COMPANY [Member]	Successor [Member]	Predecessor [Member]
Balance at Dec. 31, 2011	$ 1,357.9	$ 2,230.7
Net income	58.3	(1,777.3)
Change in fair value of available-for-sale securities, net of tax	0.5	0.5
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	(4.0)	(5.5)
Total comprehensive income / (Loss)	54.7	(1,783.2)
Balance at Sep. 30, 2012	1,266.3	376.2
Balance at Jun. 30, 2012
Net income	(11.2)	(1,810.9)
Change in fair value of available-for-sale securities, net of tax	0.2	0.2
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)	0.3
Total comprehensive income / (Loss)	(13.2)	(1,810.4)
Balance at Sep. 30, 2012	$ 1,266.3	$ 376.2