Contractual Obligations, Commercial Commitments and Contingencies (Schedule Of Contractual Obligations And Commercial Commitments) (Details) $ in Millions	Dec. 31, 2020 USD ($)
Electricity Purchase Commitments [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Electricity Purchase Commitments	$ 120.8
Electricity Purchase Agreements Less Than 1 Year	86.0
Electricity Purchase Agreements in Years 2 and 3	34.8
Electricity Purchase Agreements in Years 4 and 5	0.0
Electricity Purchase Agreements, After Year 5	0.0
Electricity Purchase Commitments [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Electricity Purchase Commitments	120.8
Electricity Purchase Agreements Less Than 1 Year	86.0
Electricity Purchase Agreements in Years 2 and 3	34.8
Electricity Purchase Agreements in Years 4 and 5	0.0
Electricity Purchase Agreements, After Year 5	0.0
Other Intangible Assets [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Total Purchase orders and other contractual obligations	92.5
Purchase orders and other contractual obligations, Less than 1 year	87.8
Purchase orders and other contractual obligations, 2 - 3 years	4.7
Purchase orders and other contractual obligations, 4 - 5 years	0.0
Purchase orders and other contractual obligations, More than 5 years	0.0
Other Intangible Assets [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Total Purchase orders and other contractual obligations	90.3
Purchase orders and other contractual obligations, Less than 1 year	85.6
Purchase orders and other contractual obligations, 2 - 3 years	4.7
Purchase orders and other contractual obligations, 4 - 5 years	0.0
Purchase orders and other contractual obligations, More than 5 years	$ 0.0