Property, Plant and Equipment with Corresponding Depreciation Rates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service	$ 2,977.6	$ 2,521.9
Total property, plant and equipment in service, Composite Rate	2.90%	3.20%	3.30%
Property Plant And Equipment, Net of Depreciation	$ 2,405.9	$ 1,986.8
Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	571.7	535.1
Construction in Progress, Gross	165.5	234.2
Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	759.9	505.3
Distribution	2,044.7	1,860.9
General	20.0	19.3
Non-depreciable	112.0	99.5
Total property, plant and equipment in service	$ 2,936.6	$ 2,485.0
Transmission, Composite Rate	2.00%	2.50%
Distribution, Composite Rate	3.30%	3.50%
General, Composite Rate	5.60%	5.90%
Unregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Non-depreciable	$ 5.4	$ 5.6
Other	35.6	31.3
Total property, plant and equipment in service	$ 41.0	$ 36.9
Other, Composite Rate	3.50%	4.10%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service	$ 3,497.3	$ 3,063.2
Total property, plant and equipment in service, Composite Rate	2.40%	2.60%	2.80%
Property Plant And Equipment, Net of Depreciation	$ 2,381.8	$ 1,965.1
Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	1,115.5	1,098.1
Construction in Progress, Gross	164.4	230.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	899.1	648.0
Distribution	2,453.9	2,283.4
General	32.3	32.2
Non-depreciable	$ 112.0	$ 99.6
Transmission, Composite Rate	1.70%	2.00%
Distribution, Composite Rate	2.80%	2.90%
General, Composite Rate	3.40%	3.50%