Debt Obligations (Current portion - Long-term Debt) (Details) (USD $) In Millions, unless otherwise specified						9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Mar. 01, 2011	Sep. 30, 2012 DP&L [Member]	Dec. 31, 2011 DP&L [Member]	Sep. 30, 2012 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member]	Sep. 30, 2012 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member] DP&L [Member]	Sep. 30, 2012 U.S. Government note maturing in February 2061 - 4.20% [Member]	Sep. 30, 2012 U.S. Government note maturing in February 2061 - 4.20% [Member] DP&L [Member]	Dec. 31, 2011 U.S. Government note maturing in February 2061 - 4.20% [Member] DP&L [Member]	Dec. 31, 2011 Senior Notes Maturing in September 2011 - 6.875% [Member]
Obligation for capital lease	$ 0.3	$ 0.3		$ 0.3	$ 0.3
Total current portion - long-term debt	0.4	0.4		0.4	0.4
Senior notes maturing in September 2011											297.4
Debt instrument maturity year						Nov. 01, 2040	Nov. 01, 2040	Feb. 01, 2061	Feb. 01, 2061
Debt instrument interest percentage			4.20%					4.20%	4.20%		6.875%
U.S. Government note maturing in February 2061 - 4.20%, current	$ 0.1	$ 0.1							$ 0.1	$ 0.1