Ownership of Coal-fired Facilities (Narrative) (Details)	9 Months Ended
Sep. 30, 2015 generating_facility
THE DAYTON POWER AND LIGHT COMPANY [Member]
Jointly Owned Utility Plant Interests [Line Items]
Number of generating facilities	5

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Balance Type:	na
Period Type:	duration