Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer, Excluding Assessed Tax	$ 865.1	$ 861.6	$ 861.4
REVENUE	876.5	861.0	869.0
RTO Revenue	120.5	88.5	63.7
RTO Capacity Revenue	0.9	3.5	4.3
Contract with Customer, Asset, before Allowance for Credit Loss	103.9	90.4
Utility [Member]
REVENUE	867.6	852.0	860.1
RTO Revenue	120.4	88.4	63.6
RTO Capacity Revenue	0.9	3.5	4.3
Corporate and Other
REVENUE	14.7	14.1	13.3
RTO Revenue	0.1	0.1	0.1
RTO Capacity Revenue	0.0	0.0	0.0
Adjustments and Eliminations
REVENUE	(5.8)	(5.1)	(4.4)
RTO Revenue	0.0	0.0	0.0
RTO Capacity Revenue	0.0	0.0	0.0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	856.2	852.6	852.5
REVENUE	867.6	852.0	860.1
RTO Revenue	120.4
RTO Capacity Revenue	0.9
Contract with Customer, Asset, before Allowance for Credit Loss	103.1	89.4
Wholesale Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	16.6	15.1	40.2
Wholesale Revenue [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	17.5	15.8	41.0
Wholesale Revenue [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Wholesale Revenue [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax	(0.9)	(0.7)	(0.8)
Wholesale Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	17.5
Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	9.7	9.6	9.6
Other non-606 revenue	11.4	(0.6)	7.6
Other Revenues [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Other non-606 revenue	11.4	(0.6)	7.6
Other Revenues [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	9.7	9.6	9.6
Other non-606 revenue	4.9	4.4	3.6
Other Revenues [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Other non-606 revenue	(4.9)	(4.4)	(3.6)
Other Revenues [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Other non-606 revenue	11.4
Retail Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	717.4	744.9	743.6
Retail Revenue [Member] | Residential Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	451.4	478.9	467.3
Retail Revenue [Member] | Commercial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	161.2	162.1	166.0
Retail Revenue [Member] | Industrial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	67.0	66.6	74.3
Retail Revenue [Member] | Governmental Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	26.5	24.3	24.1
Retail Revenue [Member] | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	11.3	13.0	11.9
Retail Revenue [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	717.4	744.9	743.6
Retail Revenue [Member] | Utility [Member] | Residential Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	451.4	478.9	467.3
Retail Revenue [Member] | Utility [Member] | Commercial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	161.2	162.1	166.0
Retail Revenue [Member] | Utility [Member] | Industrial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	67.0	66.6	74.3
Retail Revenue [Member] | Utility [Member] | Governmental Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	26.5	24.3	24.1
Retail Revenue [Member] | Utility [Member] | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	11.3	13.0	11.9
Retail Revenue [Member] | Corporate and Other
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Residential Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Commercial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Industrial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Governmental Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Corporate and Other | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Residential Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Commercial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Industrial Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Governmental Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | Adjustments and Eliminations | Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	0.0	0.0	0.0
Retail Revenue [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 717.4	$ 744.9	$ 743.6