Derivative Instruments and Hedging Activities (Narrative) (Details) $ in Millions	Jun. 30, 2015 USD ($)
Fair value of commodity derivative instruments	$ 18.7
Collateral Already Posted, Aggregate Fair Value	7.4
Liability position offset by the asset position of counterparties with master netting agreements	9.6
Collateral if debt were to fall below investment grade	1.7
THE DAYTON POWER AND LIGHT COMPANY [Member]
Fair value of commodity derivative instruments	18.9
Collateral Already Posted, Aggregate Fair Value	7.4
Liability position offset by the asset position of counterparties with master netting agreements	9.6
Collateral if debt were to fall below investment grade	$ 1.9

The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (e)

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Fair value, after effects of master netting arrangements, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset offset against the right to receive collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

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