Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - THE DAYTON POWER AND LIGHT COMPANY [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 4.8	$ 4.9
Tax positions taken during prior periods	0.0	0.0
Lapse of applicable statute of limitations	0.0	(0.1)
Balance at end of year	$ 4.8	$ 4.8

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
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-SubTopic 10
-Section 50
-Paragraph 15A
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- Definition

Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 15A
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- Definition

Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

+ References

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-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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