Benefit Plans (Other Changes in Plan Assets and Benefit Obligation Recognized in Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Prior service cost for the period, net of income tax benefit/(expense)	$ 0.1	$ 0.0	$ 0.0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost for the period, net of income tax benefit/(expense)	0.1	0.0	0.0
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Reversal of amortization item, Net actuarial (gain) / loss	(5.5)	(9.0)	(1.0)
Reversal of amortization item, Prior service cost / (credit)	(1.1)	(0.9)	(6.1)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	(15.7)	(29.3)	18.7
Total recognized in net periodic benefit cost and Accumulated other comprehensive income, Regulatory assets and Regulatory liabilities	(10.4)	(21.7)	22.7
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	(9.1)	(21.7)	25.8
Prior service cost for the period, net of income tax benefit/(expense)	0.0	2.3	0.0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	0.0	2.3
Pension [Member] | THE DAYTON POWER AND LIGHT COMPANY [Member]
Defined Benefit Plan Disclosure [Line Items]
Reversal of amortization item, Net actuarial (gain) / loss	(7.7)	(11.4)	(8.7)
Reversal of amortization item, Prior service cost / (credit)	(1.2)	(1.1)	(1.3)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax	(18.0)	(31.9)	15.8
Total recognized in net periodic benefit cost and Accumulated other comprehensive income, Regulatory assets and Regulatory liabilities	(10.4)	(21.7)	22.7
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	(9.1)	(21.7)	25.8
Prior service cost for the period, net of income tax benefit/(expense)	0.0	2.3	$ 0.0
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment	$ 0.0	$ 2.3