Income Taxes (Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Depreciation / property basis	$ (199.4)	$ (185.5)
Income taxes recoverable	9.5	9.2
Deferred Tax Liabilities, Regulatory Assets and Liabilities	(39.3)	(22.8)
Investment tax credit	0.0	0.1
Compensation and employee benefits	(3.7)	(2.8)
Long-term debt	4.9	5.1
Other	0.7	(2.3)
Deferred Income Tax Liabilities, Net	(227.3)	(199.0)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Depreciation / property basis	(195.3)	(181.3)
Income taxes recoverable	9.5	9.2
Deferred Tax Liabilities, Regulatory Assets and Liabilities	(39.3)	(22.8)
Investment tax credit	0.0	0.1
Compensation and employee benefits	4.1	3.1
Other	2.1	0.6
Deferred Income Tax Liabilities, Net	(206.1)	(194.9)
Operating Loss Carryforwards	$ 21.0	$ 2.4