Consolidated Statements of Comprehensive Income/(Loss) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	$ (0.1)	$ 1.0	$ 0.1	$ 0.9
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax		(0.5)	(0.1)	(0.6)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	6.3	(6.0)	13.3	(6.7)
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	(2.7)	(1.0)	(5.8)	(1.4)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity				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)	1.0	0.1	0.9
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax		(0.5)	(0.1)	(0.6)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	3.7	(1.7)	10.6	(0.2)
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	(1.6)	(1.0)	(4.8)	(1.3)
Income tax (expense)/benefit on prior service cost related to pension and postretirement activity		(0.5)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	$ (0.3)		$ (0.7)