Condensed Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	$ (0.1)	$ (0.3)
Income tax (expense) benefit on reclassification to earnings	0.0	0.2
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(11.6)	(0.1)
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	4.8	(0.3)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	(0.1)	0.0
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	(0.1)	(0.2)
Income tax (expense) benefit on reclassification to earnings	0.0	0.2
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(11.6)	(0.1)
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	4.6	(0.3)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	$ (0.8)	$ (0.5)

Amount of tax expense (benefit), after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e640-108580

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss) for actuarial gain (loss) related to pension and other postretirement benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e689-108580

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Amount of tax expense (benefit), before reclassification adjustments, related to increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e640-108580

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