Contractual Obligations, Commercial Commitments and Contingenciesl (Schedule Of Contractual Obligations And Commercial Commitments) (Details) $ in Millions	Dec. 31, 2016 USD ($)
Coal Contracts [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Total Coal Contracts	$ 284.3
Coal Contracts, Less than 1 year	230.3
Coal Contracts, 2 - 3 years	54.0
Coal Contracts, 4 - 5 years	0.0
Coal Contracts, More than 5 years	0.0
Coal Contracts [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Total Coal Contracts	284.3
Coal Contracts, Less than 1 year	230.3
Coal Contracts, 2 - 3 years	54.0
Coal Contracts, 4 - 5 years	0.0
Coal Contracts, More than 5 years	0.0
Other Intangible Assets [Member]
Contractual Obligations, Commercial Commitments And Contingencies [Line Items]
Total Purchase orders and other contractual obligations	109.8
Purchase orders and other contractual obligations, Less than 1 year	43.1
Purchase orders and other contractual obligations, 2 - 3 years	33.6
Purchase orders and other contractual obligations, 4 - 5 years	33.1
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	109.8
Purchase orders and other contractual obligations, Less than 1 year	43.1
Purchase orders and other contractual obligations, 2 - 3 years	33.6
Purchase orders and other contractual obligations, 4 - 5 years	33.1
Purchase orders and other contractual obligations, More than 5 years	$ 0.0