Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Taxes [Line Items]
Federal - Current	$ (17.7)	$ (20.0)	$ (7.6)
State and Local - Current	(0.1)	0.4	0.0
Total Current	(17.8)	(19.6)	(7.6)
Federal - Deferred	10.2	24.5	(2.1)
State and Local - Deferred	4.6	1.7	0.1
Total Deferred	14.8	26.2	(2.0)
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	(3.0)	6.6	(9.6)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Federal - Current	0.0	4.1	(0.8)
State and Local - Current	(0.1)	0.4	0.0
Total Current	(0.1)	4.5	(0.8)
Federal - Deferred	(1.3)	7.3	(2.4)
State and Local - Deferred	4.6	1.7	0.1
Total Deferred	3.3	9.0	(2.3)
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	$ 3.2	$ 13.5	$ (3.1)