Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Federal - Current	$ (7.6)	$ (5.5)	$ (45.1)
State and Local - Current	0.0	0.0	(0.1)
Total Current	(7.6)	(5.5)	(45.2)
Federal - Deferred	(2.1)	4.4	38.7
State and Local - Deferred	0.1	0.4	1.1
Total Deferred	(2.0)	4.8	39.8
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	(9.6)	(0.7)	(5.4)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income Taxes [Line Items]
Federal - Current	(0.8)	1.1	3.5
State and Local - Current	0.0	0.1	0.1
Total Current	(0.8)	1.2	3.6
Federal - Deferred	(2.4)	4.1	2.4
State and Local - Deferred	0.1	0.4	1.0
Total Deferred	(2.3)	4.5	3.4
Income Tax Expense (Benefit), Continuing Operations, Discontinued Operations	$ (3.1)	$ 5.7	$ 7.0