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Benefit Plans (Fair Value Measurements for Pension Plan Assets) (Details) - Pension [Member] - USD ($)
$ in Millions
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets $ 274.4 $ 363.5 $ 365.1
Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 1.9 1.9  
Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 272.5 361.6  
Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 0.0 0.0  
Defined Benefit Plan, Common Collective Trust      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 272.5 361.6  
Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 0.0 0.0  
Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 272.5 361.6  
Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 0.0 0.0  
THE DAYTON POWER AND LIGHT COMPANY [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 274.4 363.5 $ 365.1
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 1.9 1.9  
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 272.5 361.6  
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 0.0 0.0  
THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 272.5 361.6  
THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 0.0 0.0  
THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 272.5 361.6  
THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Pension Plan Assets 0.0 0.0  
Debt Securities [Member] | Defined Benefit Plan, Common Collective Trust      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 125.7 144.0  
Debt Securities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
Debt Securities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 125.7 144.0  
Debt Securities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
Debt Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 125.7 144.0  
Debt Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
Debt Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 125.7 144.0  
Debt Securities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
U.S. Equities [Member] | Defined Benefit Plan, Common Collective Trust      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 88.5 151.8  
U.S. Equities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
U.S. Equities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 88.5 151.8  
U.S. Equities [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
U.S. Equities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 88.5 151.8  
U.S. Equities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
U.S. Equities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 88.5 151.8  
U.S. Equities [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
Cash and Cash Equivalents [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 1.9 1.9  
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 1.9 1.9  
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
Cash and Cash Equivalents [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 1.9 1.9  
Cash and Cash Equivalents [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 1.9 1.9  
Cash and Cash Equivalents [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
Cash and Cash Equivalents [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
US Government Debt Securities | Defined Benefit Plan, Common Collective Trust      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 58.3 65.8  
US Government Debt Securities | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
US Government Debt Securities | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 58.3 65.8  
US Government Debt Securities | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
US Government Debt Securities | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 58.3 65.8  
US Government Debt Securities | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 1 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 0.0 0.0  
US Government Debt Securities | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 2 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities 58.3 65.8  
US Government Debt Securities | THE DAYTON POWER AND LIGHT COMPANY [Member] | Defined Benefit Plan, Common Collective Trust | Fair Value, Inputs, Level 3 [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Total Equity Securities $ 0.0 $ 0.0