Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 35.9	$ 36.6
Deferred tax assets related to state and local tax net operating loss carryforwards, net of related valuation allowances	35.7	36.6
Unrecognized Tax Benefits	0.4	0.4	$ 0.4	$ 1.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	0.0	0.0	(1.0)
Unrecognized tax benefits anticipated to result in a decrease of unrecognized tax benefits with 12 months of the balance sheet date, minimum	0.0
Cash Contribution from Parent Company	260.0		150.0
Payment against tax receivable balance from Parent	21.0		17.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits	0.4	0.4	0.4	$ 1.4
Decrease in Unrecognized Tax Benefits Due To Uncertainty In Timing of Deductibility	$ 0.0	$ 0.0	$ (1.0)