Consolidated Statements of Comprehensive Income/(Loss) (Parenthetical) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended		11 Months Ended	12 Months Ended
	Dec. 31, 2011 Successor [Member]	Dec. 31, 2013 Successor [Member]	Dec. 31, 2012 Successor [Member]	Nov. 27, 2011 Predecessor [Member]	Dec. 31, 2013 THE DAYTON POWER AND LIGHT COMPANY [Member]	Dec. 31, 2012 THE DAYTON POWER AND LIGHT COMPANY [Member]	Dec. 31, 2011 THE DAYTON POWER AND LIGHT COMPANY [Member]
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities		$ 0.6	$ (0.2)		$ 0.9	$ (0.2)	$ 4.3
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax		(0.7)			(0.7)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	0.3	(10.6)	1.4	31.2	(0.6)	1.6	0.5
Income tax (expense)/benefit on reclassification of earnings related to derivative activity		(2.3)	0.4	(0.3)	(2.5)	0.5	0.1
Income tax (expense)/benefit on prior service cost related to pension and postretirement activity	0.2				(0.2)	(0.5)	(0.4)
Income tax (expense)/benefit on net loss related to pension and postretirement activity	(0.2)	(2.7)	1.0	(0.7)	(1.9)	0.8	5.4
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity		$ 0.3		$ 1.5	$ (1.9)	$ (1.5)	$ (1.5)