Income Taxes (Tax or Benefit credited to AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Tax expense/ (benefit)	$ 6.3	$ (9.1)	$ 15.4
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Tax expense/ (benefit)	$ 7.5	$ (6.0)	$ 7.0