Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
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
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	0.4	$ 0.4	$ 1.4
Balance at end of year	0.4	0.4	0.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	0.0	0.0	(1.0)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	0.4	0.4	1.4
Balance at end of year	0.4	0.4	0.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	$ 0.0	$ 0.0	$ (1.0)