Dispositions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	$ (11.9)	$ 31.5	$ 38.9
Payments for Removal Costs	8.9	51.0	14.5
Beckjord [Member]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest			(11.7)
Payments for Removal Costs			14.5
Hutchings
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	4.7
Payments for Removal Costs	7.0
Payments for Removal Costs, Additional Payments	2.3
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	58.1	124.3	104.4
Payments for Removal Costs	$ 7.0	$ 0.0	14.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | Beckjord [Member]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest			(12.4)
Payments for Removal Costs			$ 14.5