Ownership of Coal-fired Facilities (Ownership Interests) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2011 mW
Construction Work in Process	49.0
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	3,236
Accumulated Depreciation	1,596
Construction Work in Process	49.0
DP&L [Member] | DP&L Investment [Member] | Beckjord Unit 6 [Member]
Gross Plant In Service	75
Accumulated Depreciation	55
Construction Work in Process	1.0
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	30
Construction Work in Process	4.0
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	294
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	354
Accumulated Depreciation	134
Construction Work in Process	10.0
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	274
Construction Work in Process	17.0
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	620
Construction Work in Process	15.0
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	113
Construction Work in Process	1.0
SCR and FGD Equipment Installed and In Service	No