Schedule II Valuation And Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Provision for Uncollectible Accounts [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 0.3	$ 2.8	$ 0.4
Additions	2.5	(0.4)	3.0
Deductions	2.3	2.1	0.6
Balance at End of Period	0.5	0.3	2.8
Provision for Uncollectible Accounts [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	0.3	2.8	0.4
Additions	2.5	(0.4)	3.0
Deductions	2.3	2.1	0.6
Balance at End of Period	0.5	0.3	2.8
Valuation Allowance For Deferred Tax Assets [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	37.1	39.0	29.0
Additions	0.0	1.5	11.0
Deductions	0.5	3.4	1.0
Balance at End of Period	$ 36.6	$ 37.1	$ 39.0