Ownership of Coal-fired Facilities (Ownership Interests) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2011 mW
Construction Work in Process	42.0
DP&L [Member] \| DP&L Share [Member]
Production Capacity (MW)	2,465
DP&L [Member] \| DP&L Share [Member] \| Beckjord Unit 6 [Member]
Ownership (%)	50.00%
Production Capacity (MW)	207
DP&L [Member] \| DP&L Share [Member] \| Conesville Unit 4 [Member]
Ownership (%)	16.50%
Production Capacity (MW)	129
DP&L [Member] \| DP&L Share [Member] \| East Bend Station [Member]
Ownership (%)	31.00%
Production Capacity (MW)	186
DP&L [Member] \| DP&L Share [Member] \| Killen Station [Member]
Ownership (%)	67.00%
Production Capacity (MW)	402
DP&L [Member] \| DP&L Share [Member] \| Miami Fort Units 7 and 8 [Member]
Ownership (%)	36.00%
Production Capacity (MW)	368
DP&L [Member] \| DP&L Share [Member] \| Stuart Station [Member]
Ownership (%)	35.00%
Production Capacity (MW)	808
DP&L [Member] \| DP&L Share [Member] \| Zimmer Station [Member]
Ownership (%)	28.10%
Production Capacity (MW)	365
DP&L [Member] \| DP&L Share [Member] \| Transmission (At Varying Percentages) [Member]
Production Capacity (MW)
DP&L [Member] \| DP&L Share [Member] \| Hutchings Station [Member]
Ownership (%)	100.00%
Production Capacity (MW)	390
DP&L [Member] \| DP&L Investment [Member]
Gross Plant In Service	3,249
Accumulated Depreciation	1,611
Construction Work in Process	42.0
DP&L [Member] \| DP&L Investment [Member] \| Beckjord Unit 6 [Member]
Gross Plant In Service	76
Accumulated Depreciation	57
Construction Work in Process
SCR and FGD Equipment Installed and In Service	No
DP&L [Member] \| DP&L Investment [Member] \| Conesville Unit 4 [Member]
Gross Plant In Service	119
Accumulated Depreciation	31
Construction Work in Process	5.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] \| DP&L Investment [Member] \| East Bend Station [Member]
Gross Plant In Service	201
Accumulated Depreciation	132
Construction Work in Process
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] \| DP&L Investment [Member] \| Killen Station [Member]
Gross Plant In Service	617
Accumulated Depreciation	298
Construction Work in Process	2.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] \| DP&L Investment [Member] \| Miami Fort Units 7 and 8 [Member]
Gross Plant In Service	366
Accumulated Depreciation	137
Construction Work in Process	2.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] \| DP&L Investment [Member] \| Stuart Station [Member]
Gross Plant In Service	719
Accumulated Depreciation	275
Construction Work in Process	15.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] \| DP&L Investment [Member] \| Zimmer Station [Member]
Gross Plant In Service	1,060
Accumulated Depreciation	624
Construction Work in Process	18.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] \| DP&L Investment [Member] \| Transmission (At Varying Percentages) [Member]
Gross Plant In Service	91
Accumulated Depreciation	57
Construction Work in Process
DP&L [Member] \| DP&L Investment [Member] \| Hutchings Station [Member]
Gross Plant In Service	124
Accumulated Depreciation	114
Construction Work in Process	1.0
SCR and FGD Equipment Installed and In Service	No

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- Definition

SCR and FGD Equipment Installed and In Service

+ Details

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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 SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 10

-Section C

Reference 2: 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

+ Details

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- Definition

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

+ References

+ Details

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- Definition

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

+ References

+ Details

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- Definition

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

+ References

+ Details

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