Fair Value Measurements (Assets and Liabilities Measured on a Recurring and Nonrecurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	$ 8.0	$ 7.8
Debt Instrument, Fair Value Disclosure	1,709.0	1,723.0
Money Market Funds [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.4	0.6
Mutual Fund | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	7.6	7.2
Debt [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	1,840.0	1,837.6
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	8.0	7.8
Debt Instrument, Fair Value Disclosure	0.0	0.0
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.4	0.6
Fair Value, Inputs, Level 1 [Member] | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	7.6	7.2
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	0.0	0.0
Debt Instrument, Fair Value Disclosure	1,692.4	1,706.2
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.0	0.0
Fair Value, Inputs, Level 2 [Member] | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.0	0.0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	0.0	0.0
Debt Instrument, Fair Value Disclosure	16.6	16.8
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.0	0.0
Fair Value, Inputs, Level 3 [Member] | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.0	0.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	8.0	7.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Money Market Funds [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.4	0.6
THE DAYTON POWER AND LIGHT COMPANY [Member] | Mutual Fund | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	7.6	7.2
THE DAYTON POWER AND LIGHT COMPANY [Member] | Debt [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Fair Value Disclosure	911.4	926.7
THE DAYTON POWER AND LIGHT COMPANY [Member] | Debt [Member] | Carrying Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term Debt	1,012.9	1,012.5
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	8.0	7.8
Debt Instrument, Fair Value Disclosure	0.0	0.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.4	0.6
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 1 [Member] | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	7.6	7.2
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	0.0	0.0
Debt Instrument, Fair Value Disclosure	894.8	909.9
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.0	0.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 2 [Member] | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.0	0.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	0.0	0.0
Debt Instrument, Fair Value Disclosure	16.6	16.8
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	0.0	0.0
THE DAYTON POWER AND LIGHT COMPANY [Member] | Fair Value, Inputs, Level 3 [Member] | Mutual Fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Master Trust Assets, Fair Value	$ 0.0	$ 0.0