Consolidated Statements of Comprehensive Income/(Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	$ 0.1	$ 0.2	$ 0.6
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax	0.0	(0.2)	(0.7)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(10.3)	10.3	(10.6)
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	5.4	(9.5)	(2.3)
Income tax (expense)/benefit on prior service cost related to pension and postretirement activity	0.0	1.3	0.0
Income tax (expense)/benefit on net loss related to pension and postretirement activity	(1.2)	7.1	(2.7)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	(0.2)	0.0	0.3
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	0.9
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax	0.0	(0.2)	(0.7)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(10.3)	10.5	(0.6)
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	5.6	(11.5)	(2.5)
Income tax (expense)/benefit on prior service cost related to pension and postretirement activity	0.0	1.3	(0.2)
Income tax (expense)/benefit on net loss related to pension and postretirement activity	(1.0)	7.2	(1.9)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	$ (1.9)	$ (1.5)	$ (1.9)