Condensed Consolidated Statements of Comprehensive Income/(Loss) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	$ 0.3	$ (0.1)	$ 0.0	$ 0.1
Income tax (expense) benefit on reclassification to earnings	(0.2)	0.0	0.0	(0.1)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(1.0)	6.3	(1.0)	13.3
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	0.9	(2.7)	0.5	(5.8)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	(0.5)	0.0	(0.4)	0.0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	0.2	(0.1)	0.0	0.1
Income tax (expense) benefit on reclassification to earnings	(0.2)	0.0	0.0	(0.1)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(1.0)	3.7	(1.0)	10.6
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	1.0	(1.6)	0.7	(4.8)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	$ (0.5)	$ (0.3)	$ (1.0)	$ (0.7)