Equity (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Equity Contribution from Parent	$ (239.0)	$ 0.0	$ (132.5)
Retained earnings / (deficit)	$ (2,686.9)	$ (2,722.6)
Common stock, shares authorized	1,500	1,500
Common stock, shares outstanding	1	1
Non-cash capital contribution			132.5
Cash Contribution from Parent Company	$ 260.0		150.0
Payment against tax receivable balance from Parent	21.0		17.5
THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Equity Contribution from Parent	(260.0)	$ 0.0	(150.0)
Retained earnings / (deficit)	$ 29.3	$ (5.4)
Common stock, shares authorized	50,000,000
Common stock, shares outstanding	41,172,173	41,172,173
Dividends, Common Stock, Cash	$ 83.0	$ (64.0)	42.0
Payments of Ordinary Dividends, Common Stock	83.0		52.0
Other Paid-In Capital [Member]
Class of Stock [Line Items]
Equity Contribution from Parent	(239.0)		(132.5)
Other Paid-In Capital [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Class of Stock [Line Items]
Equity Contribution from Parent	260.0		150.0
Dividends, Common Stock, Cash	56.3	49.0	42.0
Payments of Ordinary Dividends, Common Stock	$ 83.0	64.0	52.0
Dividends, Common Stock		$ 64.0	$ 42.0