Fair Value Measurements (Fair Value and Cost of Non-Derivative Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Carrying Value [Member] \| Debt [Member]
Long-term Debt	$ 1,837.6	$ 1,535.9
Carrying Value [Member] \| Debt [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Long-term Debt	1,012.5	712.7
Fair Value [Member] \| Money Market Funds [Member]
Total Master Trust Assets, Fair Value	0.6	0.5
Fair Value [Member] \| Money Market Funds [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member]
Total Master Trust Assets, Fair Value	$ 0.6	$ 0.5

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant