Ownership of Coal-fired Facilities (Ownership Interests) (Details) $ in Millions	9 Months Ended
Sep. 30, 2015 USD ($) MW
THE DAYTON POWER AND LIGHT COMPANY [Member] \| Total Jointly-owned Stations [Member]
Construction Work in Process	$ 25.0
DP&L Share [Member] \| Conesville Unit 4 [Member]
Ownership (%)	16.50%
Production Capacity (MW) \| MW	129
DP&L Share [Member] \| Killen Station [Member]
Ownership (%)	67.00%
Production Capacity (MW) \| MW	402
DP&L Share [Member] \| Miami Fort Units 7 and 8 [Member]
Ownership (%)	36.00%
Production Capacity (MW) \| MW	368
DP&L Share [Member] \| Stuart Station [Member]
Ownership (%)	35.00%
Production Capacity (MW) \| MW	808
DP&L Share [Member] \| Zimmer Station [Member]
Ownership (%)	28.10%
Production Capacity (MW) \| MW	371
DP&L Share [Member] \| Total Jointly-owned Stations [Member]
Production Capacity (MW) \| MW	2,078
DP&L Share [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Conesville Unit 4 [Member]
Ownership (%)	16.50%
Production Capacity (MW) \| MW	129
DP&L Share [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Killen Station [Member]
Ownership (%)	67.00%
Production Capacity (MW) \| MW	402
DP&L Share [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Miami Fort Units 7 and 8 [Member]
Ownership (%)	36.00%
Production Capacity (MW) \| MW	368
DP&L Share [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Stuart Station [Member]
Ownership (%)	35.00%
Production Capacity (MW) \| MW	808
DP&L Share [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Zimmer Station [Member]
Ownership (%)	28.10%
Production Capacity (MW) \| MW	371
DP&L Share [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Total Jointly-owned Stations [Member]
Production Capacity (MW) \| MW	2,078
DP&L Investment [Member] \| Conesville Unit 4 [Member]
Gross Plant In Service	$ 25.0
Accumulated Depreciation	4.0
Construction Work in Process	$ 1.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| Killen Station [Member]
Gross Plant In Service	$ 340.0
Accumulated Depreciation	30.0
Construction Work in Process	$ 1.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| Miami Fort Units 7 and 8 [Member]
Gross Plant In Service	$ 218.0
Accumulated Depreciation	31.0
Construction Work in Process	$ 4.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| Stuart Station [Member]
Gross Plant In Service	$ 234.0
Accumulated Depreciation	21.0
Construction Work in Process	$ 14.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| Zimmer Station [Member]
Gross Plant In Service	$ 186.0
Accumulated Depreciation	44.0
Construction Work in Process	$ 5.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| Transmission (At Varying Percentages) [Member]
Gross Plant In Service	$ 42.0
Accumulated Depreciation	7.0
Construction Work in Process	0.0
DP&L Investment [Member] \| Total Jointly-owned Stations [Member]
Gross Plant In Service	1,045.0
Accumulated Depreciation	137.0
Construction Work in Process	25.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Conesville Unit 4 [Member]
Gross Plant In Service	25.0
Accumulated Depreciation	8.0
Construction Work in Process	$ 1.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Killen Station [Member]
Gross Plant In Service	$ 655.0
Accumulated Depreciation	324.0
Construction Work in Process	$ 1.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Miami Fort Units 7 and 8 [Member]
Gross Plant In Service	$ 365.0
Accumulated Depreciation	169.0
Construction Work in Process	$ 4.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Stuart Station [Member]
Gross Plant In Service	$ 771.0
Accumulated Depreciation	335.0
Construction Work in Process	$ 14.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Zimmer Station [Member]
Gross Plant In Service	$ 1,104.0
Accumulated Depreciation	688.0
Construction Work in Process	$ 5.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Transmission (At Varying Percentages) [Member]
Gross Plant In Service	$ 98.0
Accumulated Depreciation	63.0
Construction Work in Process	0.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Total Jointly-owned Stations [Member]
Gross Plant In Service	3,018.0
Accumulated Depreciation	$ 1,587.0

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SCR and FGD Equipment Installed and In Service

+ References

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The period end amount owned by the reporting utility of a jointly owned utility plant in service.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 360

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 10.C)

-URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 10

-Section C

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The period end amount of construction work in progress at a jointly owned electricity generation plant.

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The proportionate share of interest (percent) in a jointly owned utility plant.

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