Debt (Long-term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Unamortized Deferred Financing Costs	$ (4.9)	$ (6.7)
Debt Instrument, Unamortized Discount	(2.8)
Debt Instrument, Unamortized Discount (Premium), Net	(0.6)	(0.7)
Total long-term debt at subsidiary	1,012.5	712.7
Less: current portion	(0.2)	(0.2)
Long-term debt, net of current portion	1,837.4	1,535.7
Long-Term Debt, Maturity, Year Two	415.2
Long-Term Debt, Maturity, Year Three	0.2
Long-Term Debt, Maturity, Year Four	140.2
Long-Term Debt, Maturity, Year Five	92.7
Long-Term Debt, Maturity, after Year Five	1,203.9
Total Maturities Before Unamortized Adjustments	1,852.4
Unamortized Deferred Financing Costs, Consolidated	(12.0)
Long Term Debt Maturities Repayments Of Principal, Total	1,837.6
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	$ 16.8	17.0
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		(6.9)
Debt Instrument, Unamortized Discount	$ (7.1)	(2.4)
Debt Instrument, Unamortized Discount (Premium), Net	(2.2)	(2.4)
Less: current portion	(0.2)	(0.2)
Long-term debt, net of current portion	1,012.3	712.5
Long-Term Debt, Maturity, Year Two	0.2
Long-Term Debt, Maturity, Year Three	0.2
Long-Term Debt, Maturity, Year Four	140.2
Long-Term Debt, Maturity, Year Five	92.7
Long-Term Debt, Maturity, after Year Five	788.3
Total Maturities Before Unamortized Adjustments	1,021.8
Unamortized Deferred Financing Costs, Consolidated	(2.2)
Long Term Debt Maturities Repayments Of Principal, Total	1,012.5
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	$ 16.8	17.0
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
THE DAYTON POWER AND LIGHT COMPANY [Member] | 5.19% Senior Notes due 2033
Debt Instrument [Line Items]
Long-term Debt, Gross	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