Contractual Obligations, Commercial Commitments and Contingencies (Narative) (Details) - THE DAYTON POWER AND LIGHT COMPANY [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Debt Obligation on 4.9% Equity Ownership [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Equity ownership interest	4.90%	4.90%
Equity Ownership Interest - Guaranteed Portion of Long-term Debt Obligation	$ 67.2
Equity ownership interest aggregate cost		$ 68.1
Electric Generation Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Debt obligation	$ 1,371.3	$ 1,389.6
Other OVEC Member [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Equity ownership interest	4.85%	4.85%

Equity ownership interest guaranteed portion of Long-term Debt Obligation

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- Definition

The noncontrolling equity interest in an electric generation company, accounted for under the cost method of accounting.

+ References

No definition available.

+ Details

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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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.

+ References

No definition available.

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