Property, Plant and Equipment (Ownership Interests) (Details) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2014 MW	Dec. 31, 2016 USD ($) MW
THE DAYTON POWER AND LIGHT COMPANY [Member] \| East Bend Station [Member]
Production Capacity (MW) \| MW	186
DP&L Share [Member] \| Conesville [Member]
Ownership (%)		16.50%
DP&L Share [Member] \| Killen Station [Member]
Ownership (%)		67.00%
DP&L Share [Member] \| Miami Fort Units 7 and 8 [Member]
Ownership (%)		36.00%
DP&L Share [Member] \| Stuart Station [Member]
Ownership (%)		35.00%
DP&L Share [Member] \| Zimmer Station [Member]
Ownership (%)		28.10%
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 [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 [Member]
Gross Plant In Service		$ 0.0
Accumulated Depreciation		0.0
Construction Work in Process		0.0
DP&L Investment [Member] \| Killen Station [Member]
Gross Plant In Service		34.0
Accumulated Depreciation		0.0
Construction Work in Process		2.0
DP&L Investment [Member] \| Miami Fort Units 7 and 8 [Member]
Gross Plant In Service		27.0
Accumulated Depreciation		0.0
Construction Work in Process		7.0
DP&L Investment [Member] \| Stuart Station [Member]
Gross Plant In Service		24.0
Accumulated Depreciation		0.0
Construction Work in Process		23.0
DP&L Investment [Member] \| Zimmer Station [Member]
Gross Plant In Service		7.0
Accumulated Depreciation		0.0
Construction Work in Process		9.0
DP&L Investment [Member] \| Transmission (At Varying Percentages) [Member]
Gross Plant In Service		43.0
Accumulated Depreciation		10.0
DP&L Investment [Member] \| Total Jointly-owned Stations [Member]
Gross Plant In Service		135.0
Accumulated Depreciation		10.0
Construction Work in Process		41.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Conesville [Member]
Gross Plant In Service		0.0
Accumulated Depreciation		0.0
Construction Work in Process		0.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Killen Station [Member]
Gross Plant In Service		34.0
Accumulated Depreciation		0.0
Construction Work in Process		2.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Miami Fort Units 7 and 8 [Member]
Gross Plant In Service		27.0
Accumulated Depreciation		0.0
Construction Work in Process		7.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Stuart Station [Member]
Gross Plant In Service		24.0
Accumulated Depreciation		0.0
Construction Work in Process		23.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Zimmer Station [Member]
Gross Plant In Service		7.0
Accumulated Depreciation		0.0
Construction Work in Process		9.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Transmission (At Varying Percentages) [Member]
Gross Plant In Service		99.0
Accumulated Depreciation		66.0
DP&L Investment [Member] \| THE DAYTON POWER AND LIGHT COMPANY [Member] \| Total Jointly-owned Stations [Member]
Gross Plant In Service		191.0
Accumulated Depreciation		66.0
Construction Work in Process		$ 41.0

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- Definition

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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- Definition

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

+ References

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- Definition

The period end amount of accumulated depreciation in a jointly owned electricity generation plant.

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- Definition

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

+ References

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