Condensed Consolidated Statements of Comprehensive Income/(Loss) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	$ 0.1	$ 0.2	$ 0.1	$ 0.2
Income tax (expense) benefit on reclassification to earnings	0.0	(0.1)	0.0	(0.2)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(4.4)	(1.0)	(5.4)	12.4
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	1.1	(1.5)	1.6	(7.4)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	0.0	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	0.1	0.2	0.1	0.2
Income tax (expense) benefit on reclassification to earnings	0.0	(0.1)	0.0	(0.2)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(4.4)	(0.7)	(5.4)	9.9
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	1.2	(1.9)	1.9	(6.7)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	$ (0.6)	$ (0.3)	$ (1.6)	$ (1.0)