Consolidated Statements of Shareholders' Equity (USD $) In Millions	THE DAYTON POWER AND LIGHT COMPANY [Member]	Successor [Member]	Predecessor [Member]	Total
Balance at Dec. 31, 2011	$ 1,357.9	$ 2,230.7
Net income	69.4	26.6
Change in fair value of available-for-sale securities, net of tax	0.3	0.3		0.3
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	(1.6)	(5.8)
Total comprehensive income	67.8	20.2
Balance at Jun. 30, 2012	1,355.3	2,180.3
Balance at Mar. 31, 2012
Net income	31.3	4.9
Change in fair value of available-for-sale securities, net of tax	(0.1)	(0.1)
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)	(13.4)
Total comprehensive income	31.4	(8.6)
Balance at Jun. 30, 2012	$ 1,355.3	$ 2,180.3