Schedule II Valuation And Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss, Current	$ 0.9	$ 0.5	$ 0.3
Accounts Receivable, Credit Loss Expense (Reversal)	5.4	2.5
Accounts Receivable, Allowance for Credit Loss, Writeoff	(6.0)	(4.1)
Accounts Receivable, Allowance for Credit Loss, Recovery	1.0	1.8
THE DAYTON POWER AND LIGHT COMPANY [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Accounts Receivable, Allowance for Credit Loss, Current	0.9	0.5	0.3
Accounts Receivable, Credit Loss Expense (Reversal)	5.4	2.5
Accounts Receivable, Allowance for Credit Loss, Writeoff	(6.0)	(4.1)
Accounts Receivable, Allowance for Credit Loss, Recovery	1.0	1.8
Provision for Uncollectible Accounts [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	0.5	0.3	2.8
Additions	5.4	5.0	(0.4)
Deductions	2.5	2.3	2.1
Balance at End of Period	0.9	0.5	0.3
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	0.5	0.3	2.8
Additions	5.4	2.5	(0.4)
Deductions	5.0	2.3	2.1
Balance at End of Period	0.9	0.5	0.3
Valuation Allowance For Deferred Tax Assets [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	36.6	37.1	39.0
Additions	0.7	0.0	1.5
Deductions	1.6	0.5	3.4
Balance at End of Period	$ 35.7	$ 36.6	$ 37.1