Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Other Investments	$ 0.2	$ 0.2
Deferred Compensation Arrangement with Individual, Compensation Expense	0.0	0.4	$ 0.4
Sales to related party	3.6	4.9	4.2
Charges for Services Provided	33.8	41.0	46.5
Net payable to the Service Company	(11.0)	(4.8)
Due to Affiliate	2.0	(0.5)
THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Deferred Compensation Arrangement with Individual, Compensation Expense	(0.3)	0.3	0.4
Sales to related party	3.5	4.9	4.2
Charges for Services Provided	31.2	25.7	39.0
Net payable to the Service Company	(11.0)	(4.8)
Premiums paid for Insurance Services provided by MVIC	3.1	2.7	3.1
Due to Affiliate	3.5	0.5
Note to DPL Capital Trust II Maturing in 2031 - 8.125% [Member]
Related Party Transaction [Line Items]
Note payable to trust	15.6	15.6
Prepaid Expenses and Other Current Assets [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	35.7	19.6
Other Current Liabilities [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties
Other Current Liabilities [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties
AES Ohio Generation [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Charges for Services Provided	0.0	0.0	5.4
Receivable from sale of software to AES [Member]
Related Party Transaction [Line Items]
Due to Affiliate	5.1
Income Taxes Paid, Net [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	22.5	14.6	28.1
Charges for health, welfare and benefit plans [Member] \| Subsidiary of Common Parent [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	11.2	7.9	15.4
Charges for health, welfare and benefit plans [Member] \| Subsidiary of Common Parent [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	10.4	8.7	14.3
Consulting Services [Member] \| Subsidiary of Common Parent [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	0.7	2.0	0.0
Consulting Services [Member] \| Subsidiary of Common Parent [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	0.7	2.0	0.0
Charges for affiliates for non-power goods or services [Member] \| Subsidiary of Common Parent [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Amounts of Transaction	$ 4.1	$ 7.1	$ 3.7

Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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