Ownership of Coal-fired Facilities (Ownership Interests) (Details) (USD $) In Millions, unless otherwise specified			6 Months Ended																				6 Months Ended								6 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended		3 Months Ended			3 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 DP&L [Member]	Jun. 30, 2012 DP&L Share [Member] MW	Jun. 30, 2012 DP&L Share [Member] Beckjord Unit 6 [Member] MW	Jun. 30, 2012 DP&L Share [Member] Conesville Unit 4 [Member] MW	Jun. 30, 2012 DP&L Share [Member] East Bend Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] Killen Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] Miami Fort Units 7 and 8 [Member] MW	Jun. 30, 2012 DP&L Share [Member] Stuart Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] Zimmer Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] Transmission (At Varying Percentages) [Member] MW	Jun. 30, 2012 DP&L Share [Member] Hutchings Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] Beckjord Unit 6 [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] Conesville Unit 4 [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] East Bend Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] Killen Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] Miami Fort Units 7 and 8 [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] Stuart Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] Zimmer Station [Member] MW	Jun. 30, 2012 DP&L Share [Member] DP&L [Member] Hutchings Station [Member] MW	Jun. 30, 2012 DP&L Investment [Member]	Jun. 30, 2012 DP&L Investment [Member] Beckjord Unit 6 [Member]	Jun. 30, 2012 DP&L Investment [Member] Conesville Unit 4 [Member]	Jun. 30, 2012 DP&L Investment [Member] East Bend Station [Member]	Jun. 30, 2012 DP&L Investment [Member] Killen Station [Member]	Jun. 30, 2012 DP&L Investment [Member] Miami Fort Units 7 and 8 [Member]	Jun. 30, 2012 DP&L Investment [Member] Stuart Station [Member]	Jun. 30, 2012 DP&L Investment [Member] Zimmer Station [Member]	Jun. 30, 2012 DP&L Investment [Member] Transmission (At Varying Percentages) [Member]	Jun. 30, 2012 DP&L Investment [Member] Hutchings Station [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member]	Mar. 31, 2012 DP&L Investment [Member] DP&L [Member] Beckjord Unit 6 [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] Beckjord Unit 6 [Member]	Mar. 31, 2012 DP&L Investment [Member] DP&L [Member] Conesville Unit 4 [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] Conesville Unit 4 [Member]	Mar. 31, 2012 DP&L Investment [Member] DP&L [Member] East Bend Station [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] East Bend Station [Member]	Mar. 31, 2012 DP&L Investment [Member] DP&L [Member] Killen Station [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] Killen Station [Member]	Mar. 31, 2012 DP&L Investment [Member] DP&L [Member] Miami Fort Units 7 and 8 [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] Miami Fort Units 7 and 8 [Member]	Mar. 31, 2012 DP&L Investment [Member] DP&L [Member] Stuart Station [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] Stuart Station [Member]	Mar. 31, 2012 DP&L Investment [Member] DP&L [Member] Zimmer Station [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] Zimmer Station [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] Transmission (At Varying Percentages) [Member]	Mar. 31, 2012 DP&L Investment [Member] DP&L [Member] Hutchings Station [Member]	Jun. 30, 2012 DP&L Investment [Member] DP&L [Member] Hutchings Station [Member]
Ownership (%)				50.00%	16.50%	31.00%	67.00%	36.00%	35.00%	28.10%		100.00%		50.00%	16.50%	31.00%	67.00%	36.00%	35.00%	28.10%	100.00%
Production Capacity (MW)			2,465	207	129	186	402	368	808	365		365	2,465	207	129	186	402	368	808	365	365
Gross Plant In Service																						$ 918	$ 1	$ 1	$ 5	$ 313	$ 219	$ 203	$ 141	$ 35	$ 1	$ 3,276		$ 75		$ 121		$ 202		$ 624		$ 366		$ 737		$ 1,059	$ 92		$ 123
Accumulated Depreciation																						54	1	1	4	10	7	10	19	2		1,656		61		34		134		305		144		286		634	58		115
Construction Work in Process	$ 71.0	$ 71.0																				$ 71.0		$ 7.0	$ 7.0	$ 6.0	$ 2.0	$ 11.0	$ 38.0		$ 1.0	$ 71.0				$ 7.0		$ 7.0		$ 6.0		$ 2.0		$ 11.0		$ 38.0			$ 1.0
SCR and FGD Equipment Installed and In Service																							No	Yes	Yes	Yes	Yes	Yes	Yes		No		No		Yes		Yes		Yes		Yes		Yes		Yes			No