Property, Plant and Equipment with Corresponding Depreciation Rates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service	$ 1,990.4	$ 1,839.3
Total property, plant and equipment in service, Composite Rate	3.70%	3.80%	4.00%
Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	$ 306.9	$ 273.0
Distribution	1,547.0	1,453.7
General	34.1	17.7
Non-depreciable	71.2	65.1
Total property, plant and equipment in service	$ 1,959.2	$ 1,809.5
Transmission, Composite Rate	3.10%	3.20%
Distribution, Composite Rate	4.00%	4.00%
General, Composite Rate	3.20%	7.60%
Unregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Non-depreciable	$ 4.7	$ 5.0
Total property, plant and equipment in service	31.2	29.8
Other	$ 26.5	$ 24.8
Other, Composite Rate	4.20%	4.50%
THE DAYTON POWER AND LIGHT COMPANY [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service	$ 2,571.3	$ 2,437.3
Total property, plant and equipment in service, Composite Rate	2.80%	2.80%	2.90%
THE DAYTON POWER AND LIGHT COMPANY [Member] | Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	$ 456.5	$ 425.5
Distribution	1,996.6	1,917.0
General	48.0	29.7
Non-depreciable	$ 70.2	$ 65.1
Transmission, Composite Rate	2.10%	2.10%
Distribution, Composite Rate	3.10%	3.10%
General, Composite Rate	2.30%	3.60%