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Debt (Long-term Debt) (Details) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Debt Instrument [Line Items]    
Unamortized Deferred Financing Costs $ (1.7) $ (2.9)
Debt Instrument, Unamortized Discount (2.9)  
Debt Instrument, Unamortized Discount (Premium), Net (0.4) (0.6)
Total long-term debt at subsidiary 1,384.8 1,012.9
Less: current portion (0.2) 414.4
Long-term debt, net of current portion 1,798.1 1,425.6
Long-Term Debt, Maturity, Year Two 140.2  
Long-Term Debt, Maturity, Year Three 92.7  
Long-Term Debt, Maturity, Year Four 400.2  
Long-Term Debt, Maturity, Year Five 375.2  
Long-Term Debt, Maturity, after Year Five 803.5  
Total Maturities Before Unamortized Adjustments 1,812.0  
Unamortized Deferred Financing Costs, Consolidated (10.8)  
Long Term Debt Maturities Repayments Of Principal, Total 1,798.3  
Current portion - long-term debt 0.2  
4.35% Senior Notes due 2029 [Member]    
Debt Instrument [Line Items]    
Long-term Debt, Gross 400.0 400.0
U.S. Government note maturing in 2061 - 4.20% [Member]    
Debt Instrument [Line Items]    
Long-term Debt, Gross $ 16.4 16.6
Ten Year Senior Unsecured Bonds At 435 Maturing At April 15 2029 [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 4.35%  
Ten Year Senior Unsecured Notes At725 Maturing At October152025    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 4.125%  
Note to DPL Capital Trust II Maturing in 2031 - 8.125% [Member]    
Debt Instrument [Line Items]    
Long-term Debt, Gross $ 15.6 15.6
Debt Instrument, Interest Rate, Stated Percentage 8.125%  
THE DAYTON POWER AND LIGHT COMPANY [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Unamortized Discount (Premium), Net $ (2.5) (2.1)
THE DAYTON POWER AND LIGHT COMPANY [Member] | 3.20% First Mortgage Bonds due 2040 [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31) 3.20%  
THE DAYTON POWER AND LIGHT COMPANY [Member] | 4.25% Tax-exempt First Mortgage Bonds due 2027    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31) 4.25%  
Long-term Debt, Gross $ 100.0 100.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | 4.00% Tax-exempt First Mortgage Bonds due 2027    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31) 4.00%  
Long-term Debt, Gross $ 40.0 40.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | 3.2% Senior Notes due 2049    
Debt Instrument [Line Items]    
Long-term Debt, Gross $ 140.0 140.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | U.S. Government note maturing in 2061 - 4.20% [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 4.20%  
THE DAYTON POWER AND LIGHT COMPANY [Member] | 3.95% Senior Notes due 2049 [Member]    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31) 3.95%  
Long-term Debt, Gross $ 425.0 425.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.49% Tax-exempt First Mortgage Bonds due 2028    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31) 5.49%  
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.70% Tax-exempt First Mortgage Bonds due 2033    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31) 5.70%  
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.19% Tax-exempt First Mortgage Bonds due 2033    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31) 5.19%  
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.70% Senior Notes due 2033    
Debt Instrument [Line Items]    
Long-term Debt, Gross $ 107.5 107.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.19% Senior Notes due 2033    
Debt Instrument [Line Items]    
Long-term Debt, Gross 100.0 100.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.49% Senior Notes due 2028    
Debt Instrument [Line Items]    
Long-term Debt, Gross $ 92.5 $ 92.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | 4.55% First Mortgage Bond Due 2030    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Minimum (Deprecated 2016-01-31) 4.55%  
Long-term Debt, Gross $ 375.0