Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits Due To Uncertainity In Timing Of Deductibility	$ 1.4
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	3.5
Balance at end of year	1.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	2.1
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits Due To Uncertainity In Timing Of Deductibility	1.4
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	4.8
Balance at end of year	1.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	$ 3.4
Forecast [Member]
Income Tax Contingency [Line Items]
Unrecognized tax benefits anticipated to result in a decrease of unrecognized tax benefits with 12 months of the balance sheet date, minimum		$ 0.0