Debt Obligations (Current portion - Long-term Debt) (Details) (USD $) In Millions, unless otherwise specified						6 Months Ended	9 Months Ended	12 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended			9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Mar. 01, 2011	Sep. 30, 2013 DP&L [Member]	Dec. 31, 2012 DP&L [Member]	Jun. 30, 2013 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member]	Sep. 30, 2013 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member]	Dec. 31, 2012 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member]	Jun. 30, 2013 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member] DP&L [Member]	Sep. 30, 2013 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member] DP&L [Member]	Dec. 31, 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, 2013 First Mortgage Bonds Maturing in October 2013 - 5.125% [Member]	Dec. 31, 2012 First Mortgage Bonds Maturing in October 2013 - 5.125% [Member]	Sep. 30, 2013 First Mortgage Bonds Maturing in October 2013 - 5.125% [Member] DP&L [Member]	Dec. 31, 2012 First Mortgage Bonds Maturing in October 2013 - 5.125% [Member] DP&L [Member]	Sep. 30, 2013 U.S. Government note maturing in February 2061 - 4.20% [Member]	Dec. 31, 2012 U.S. Government note maturing in February 2061 - 4.20% [Member]	Sep. 30, 2013 U.S. Government note maturing in February 2061 - 4.20% [Member] DP&L [Member]	Dec. 31, 2012 U.S. Government note maturing in February 2061 - 4.20% [Member] DP&L [Member]	Mar. 01, 2011 U.S. Government note maturing in February 2061 - 4.20% [Member] DP&L [Member]	Sep. 30, 2013 Bank Term Loan maturing in May 2018 [Member]
Obligation for capital lease	$ 0.1	$ 0.3		$ 0.2	$ 0.3
Current portion - long-term debt	480.4	584.9		470.3	570.4			100.0			100.0	470.2	484.5	470.0	470.0						10.0
Debt instrument maturity year							Nov. 01, 2040			Nov. 01, 2040		Oct. 01, 2013		Oct. 01, 2013		Feb. 01, 2061		Feb. 01, 2061			May 01, 2018
Debt instrument interest percentage			4.20%									5.125%		5.125%		4.20%		4.20%		4.20%
Debt instrument interest percentage minimum							0.06%	0.04%		0.06%	0.04%										2.44%
Debt instrument interest percentage maximum						0.24%	0.24%	0.26%	0.24%		0.26%										2.45%
U.S. Government note maturing in February 2061 - 4.20%, current																$ 0.1	$ 0.1	$ 0.1	$ 0.1