Debt (Long-term Debt Maturities) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
2016	$ 575.1
2017	25.1
2018	25.1
2019	225.2
2020	250.2
Thereafter	913.0
Total Maturities	2,013.7
Unamortized discounts and premiums, net	(4.3)
Total long-term debt	2,009.4
THE DAYTON POWER AND LIGHT COMPANY [Member]
Debt Instrument [Line Items]
2016	445.1
2017	0.1
2018	0.1
2019	0.2
2020	200.2
Thereafter	117.4
Total Maturities	763.1
Unamortized discounts and premiums, net	(0.2)
Total long-term debt	$ 762.9