Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Unamortized Deferred Financing Costs	$ (2.9)	$ (4.9)
Debt Instrument, Unamortized Discount	(2.7)
Debt Instrument, Unamortized Discount (Premium), Net	(0.6)	(0.6)
Total long-term debt at subsidiary	1,012.9	1,012.5
Less: current portion	(414.4)	(0.2)
Long-term debt, net of current portion	1,425.6	1,837.4
Long-Term Debt, Maturity, Year Two	0.2
Long-Term Debt, Maturity, Year Three	140.2
Long-Term Debt, Maturity, Year Four	92.7
Long-Term Debt, Maturity, Year Five	400.2
Long-Term Debt, Maturity, after Year Five	803.7
Total Maturities Before Unamortized Adjustments	1,852.2
Unamortized Deferred Financing Costs, Consolidated	(9.5)
Long Term Debt Maturities Repayments Of Principal, Total	1,840.0
Current portion - long-term debt	415.2
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	$ 16.6	16.8
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]
Unamortized Deferred Financing Costs		(7.1)
Debt Instrument, Unamortized Discount	$ (6.6)
Debt Instrument, Unamortized Discount (Premium), Net	(2.1)	(2.2)
Less: current portion	(0.2)	(0.2)
Long-term debt, net of current portion	1,012.7	1,012.3
Long-Term Debt, Maturity, Year Two	0.2
Long-Term Debt, Maturity, Year Three	140.2
Long-Term Debt, Maturity, Year Four	92.7
Long-Term Debt, Maturity, Year Five	0.2
Long-Term Debt, Maturity, after Year Five	788.1
Total Maturities Before Unamortized Adjustments	1,021.6
Unamortized Deferred Financing Costs, Consolidated	(2.1)	(2.2)
Long Term Debt Maturities Repayments Of Principal, Total	1,012.9
Current portion - long-term debt	$ 0.2
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]
Long-term Debt, Gross	$ 16.6	16.8
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
Debt Instrument, Interest Rate, Stated Percentage	3.95%
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