Ownership of Coal-fired Facilities (Ownership Interests) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012 MW
Construction Work in Process	$ 31.0
DP&L [Member]
Construction Work in Process	31.0
DP&L [Member] | Beckjord Unit 6 [Member]
Ownership (%)	50.00%
Production Capacity (MW)	207
Gross Plant In Service	76
Accumulated Depreciation	62
SCR and FGD Equipment Installed and In Service	No
DP&L [Member] | Conesville Unit 4 [Member]
Ownership (%)	16.50%
Production Capacity (MW)	129
Gross Plant In Service	25
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] | East Bend Station [Member]
Ownership (%)	31.00%
Production Capacity (MW)	186
Gross Plant In Service	208
Accumulated Depreciation	135
Construction Work in Process	1.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] | Killen Station [Member]
Ownership (%)	67.00%
Production Capacity (MW)	402
Gross Plant In Service	628
Accumulated Depreciation	308
Construction Work in Process	4.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] | Miami Fort Units 7 and 8 [Member]
Ownership (%)	36.00%
Production Capacity (MW)	368
Gross Plant In Service	364
Accumulated Depreciation	146
Construction Work in Process	3.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] | Stuart Station [Member]
Ownership (%)	35.00%
Production Capacity (MW)	808
Gross Plant In Service	740
Accumulated Depreciation	290
Construction Work in Process	12.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] | Zimmer Station [Member]
Ownership (%)	28.10%
Production Capacity (MW)	365
Gross Plant In Service	1,097
Accumulated Depreciation	639
Construction Work in Process	3.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L [Member] | Total Jointly-owned Stations [Member]
Production Capacity (MW)	2,465
Gross Plant In Service	3,230
Accumulated Depreciation	1,639
Construction Work in Process	23.0
DP&L [Member] | Transmission (At Varying Percentages) [Member]
Gross Plant In Service	92
Accumulated Depreciation	59
DP&L [Member] | Hutchings Station [Member]
Ownership (%)	100.00%
Production Capacity (MW)	365
SCR and FGD Equipment Installed and In Service	No
DP&L Share [Member] | Beckjord Unit 6 [Member]
Ownership (%)	50.00%
Production Capacity (MW)	207
DP&L Share [Member] | Conesville Unit 4 [Member]
Ownership (%)	16.50%
Production Capacity (MW)	129
DP&L Share [Member] | East Bend Station [Member]
Ownership (%)	31.00%
Production Capacity (MW)	186
DP&L Share [Member] | Killen Station [Member]
Ownership (%)	67.00%
Production Capacity (MW)	402
DP&L Share [Member] | Miami Fort Units 7 and 8 [Member]
Ownership (%)	36.00%
Production Capacity (MW)	368
DP&L Share [Member] | Stuart Station [Member]
Ownership (%)	35.00%
Production Capacity (MW)	808
DP&L Share [Member] | Zimmer Station [Member]
Ownership (%)	28.10%
Production Capacity (MW)	365
DP&L Share [Member] | Total Jointly-owned Stations [Member]
Production Capacity (MW)	2,465
DP&L Share [Member] | Hutchings Station [Member]
Ownership (%)	100.00%
Production Capacity (MW)	365
DP&L Investment [Member] | Beckjord Unit 6 [Member]
Gross Plant In Service	1
Accumulated Depreciation	1
SCR and FGD Equipment Installed and In Service	No
DP&L Investment [Member] | Conesville Unit 4 [Member]
Gross Plant In Service	42
Accumulated Depreciation	4
Construction Work in Process	8.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] | East Bend Station [Member]
Gross Plant In Service	11
Accumulated Depreciation	6
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	316
Accumulated Depreciation	15
Construction Work in Process	4.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] | Miami Fort Units 7 and 8 [Member]
Gross Plant In Service	217
Accumulated Depreciation	9
Construction Work in Process	3.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] | Stuart Station [Member]
Gross Plant In Service	206
Accumulated Depreciation	16
Construction Work in Process	12.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] | Zimmer Station [Member]
Gross Plant In Service	182
Accumulated Depreciation	27
Construction Work in Process	3.0
SCR and FGD Equipment Installed and In Service	Yes
DP&L Investment [Member] | Total Jointly-owned Stations [Member]
Gross Plant In Service	1,010
Accumulated Depreciation	80
Construction Work in Process	31.0
DP&L Investment [Member] | Transmission (At Varying Percentages) [Member]
Gross Plant In Service	35
Accumulated Depreciation	$ 2
DP&L Investment [Member] | Hutchings Station [Member]
SCR and FGD Equipment Installed and In Service	No