Debt Obligations (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended										12 Months Ended			12 Months Ended			1 Months Ended	3 Months Ended	12 Months Ended			1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended		9 Months Ended	12 Months Ended			8 Months Ended	12 Months Ended			12 Months Ended		12 Months Ended		12 Months Ended
	Feb. 23, 2011	Oct. 03, 2011	Dec. 31, 2012	Dec. 31, 2011	Nov. 27, 2011	Dec. 04, 2008	Nov. 21, 2006	Dec. 31, 2012 DP&L [Member]	Dec. 31, 2011 DP&L [Member]	Dec. 04, 2008 DP&L [Member]	Nov. 21, 2006 DP&L [Member]	Dec. 31, 2012 U.S. Government note maturing in February 2061 - 4.20% [Member]	Dec. 31, 2011 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]	Dec. 31, 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]	Mar. 01, 2011 U.S. Government note maturing in February 2061 - 4.20% [Member] DP&L [Member]	Aug. 31, 2011 Revolving Credit Agreement with Bank Group [Member]	Apr. 20, 2010 Revolving Credit Agreement with Bank Group [Member]	Dec. 31, 2012 Revolving Credit Agreement with Bank Group [Member]	Oct. 31, 2012 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]	Oct. 03, 2011 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]	Dec. 31, 2011 Five Year Senior Unsecured Notes at 6.50% maturing on October 15, 2016 [Member]	Oct. 03, 2011 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]	Dec. 31, 2011 Ten Year Senior Unsecured Notes at 7.25% maturing at October 15, 2021 [Member]	Aug. 24, 2011 Unsecured Term Loan Agreement [Member]	Sep. 01, 2011 Senior Notes Maturing in September 2011 - 6.875% [Member]	Dec. 31, 2012 Note to DPL Capital Trust II Maturing in September 2031 - 8.125% [Member]	Dec. 31, 2011 Note to DPL Capital Trust II Maturing in September 2031 - 8.125% [Member]	Feb. 23, 2011 Note to DPL Capital Trust II Maturing in September 2031 - 8.125% [Member]	Dec. 31, 2012 Pollution control series maturing in November 2040 - variable rates: 0.04% - 0.26% and 0.06% - 0.32% [Member]	Dec. 31, 2011 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] DP&L [Member]	Dec. 31, 2011 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 Bank Term Loan - variable rates: 2.22% - 2.30% and 1.48% - 4.25% [Member]	Dec. 31, 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 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							220.0				220.0							125.0	200.0		75.0	200.0	200.0	200.0							425.0
Increase additional facility																		50.0	50.0				50.0	50.0
Letter of credit sublimit																		50.0	50.0	75.0			50.0	50.0
Collateralized debt						100.0				100.0
Long-term Debt, Gross			2,025.0	2,628.9				332.7	903.0			18.3	18.5	18.7	18.3	18.5	18.7									450.0	450.0		800.0	800.0			19.6	19.5			100.0		100.0	425.0	425.0
Purchase of principal amount	122.0
Interest expenses	12.2
Premium percentage	10.00%
Debt issuance costs and unamortized debt discount	3.1
Repayments of debt																																$ 297.4
Debt instrument interest percentage					6.875%							4.20%		4.20%	4.20%		4.20%								6.50%	6.50%		7.25%	7.25%			6.875%	8.125%		8.125%