Debt Obligations (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended					3 Months Ended			3 Months Ended			1 Months Ended		3 Months Ended			1 Months Ended	3 Months Ended			3 Months Ended		3 Months Ended				3 Months Ended		3 Months Ended
	Oct. 31, 2012	Mar. 31, 2013	Mar. 01, 2011	Dec. 04, 2008	Mar. 31, 2013 DP&L [Member]	Dec. 04, 2008 DP&L [Member]	Mar. 31, 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]	Mar. 01, 2011 U.S. Government note maturing in February 2061 - 4.20% [Member]	Mar. 31, 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]	Oct. 31, 2012 Revolving Credit Agreement with Bank Group [Member]	Aug. 31, 2011 Revolving Credit Agreement with Bank Group [Member]	Apr. 20, 2010 Revolving Credit Agreement with Bank Group [Member]	Mar. 31, 2013 Revolving Credit Agreement with Bank Group [Member]	Aug. 24, 2011 Revolving Credit Agreement with Bank Group [Member]	Aug. 24, 2011 Revolving Credit Agreement with Bank Group [Member] DP&L [Member]	Apr. 20, 2010 Revolving Credit Agreement with Bank Group [Member] DP&L [Member]	Mar. 31, 2013 Revolving Credit Agreement with Bank Group [Member] DP&L [Member]	Mar. 31, 2013 Revolving Credit Agreement with Bank Group [Member] DPL [Member]	Mar. 31, 2013 Five Year Senior Unsecured Notes at 6.50% maturing on October 15, 2016 [Member]	Dec. 31, 2012 Five Year Senior Unsecured Notes at 6.50% maturing on October 15, 2016 [Member]	Mar. 31, 2013 Ten Year Senior Unsecured Notes at 7.25% maturing at October 15, 2021 [Member]	Dec. 31, 2012 Ten Year Senior Unsecured Notes at 7.25% maturing at October 15, 2021 [Member]	Mar. 31, 2013 First Mortgage Bonds Maturing October 2013 [Member]	Mar. 31, 2013 First Mortgage Bonds Maturing October 2013 [Member] DP&L [Member]	Mar. 31, 2013 Note to DPL Capital Trust II Maturing in September 2031 - 8.125% [Member]	Dec. 31, 2012 Note to DPL Capital Trust II Maturing in September 2031 - 8.125% [Member]	Mar. 31, 2013 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member]	Mar. 31, 2013 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member] DP&L [Member]	Mar. 31, 2013 Bank Term Loan - variable rates: 2.22% - 2.30% and 1.48% - 4.25% [Member]	Dec. 31, 2012 Bank Term Loan - variable rates: 2.22% - 2.30% and 1.48% - 4.25% [Member]	Aug. 24, 2011 Bank Term Loan - variable rates: 2.22% - 2.30% and 1.48% - 4.25% [Member]
Additional principal amount of senior notes to be raised		$ 1,250.0																				$ 450.0		$ 800.0
Debt instrument maturity date																						Oct. 15, 2016		Oct. 15, 2021
Debt Instrument, Maturity Date Range, End							Feb. 01, 2061			Feb. 01, 2061												Oct. 01, 2016		Oct. 01, 2021				Sep. 01, 2031		Nov. 01, 2040	Nov. 01, 2040	Aug. 01, 2014
Unsecured revolving credit agreement														125.0	200.0	125.0	200.0	200.0	200.0
Future Line Of Credit Facility Minimum Borrowing Capacity					275.0															275.0	75.0
Future line of credit facility maximum borrowing capacity					350.0															350.0	150.0
Increase additional facility														50.0	50.0			50.0	50.0
Decrease additional facility	75.0												75.0
Letter of credit sublimit													75.0	50.0	50.0			50.0	50.0
Collateralized debt				100.0		100.0
Long-term Debt, Gross							$ 18.3	$ 18.3	$ 18.7	$ 18.3	$ 18.3	$ 18.7										$ 450.0	$ 450.0	$ 800.0	$ 800.0	$ 470.0	$ 470.0	$ 19.6	$ 19.6			$ 425.0	$ 425.0	$ 425.0
Debt instrument interest percentage			4.20%				4.20%			4.20%		4.20%										6.50%		7.25%				8.125%