Debt Obligations (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended		9 Months Ended				9 Months Ended			9 Months Ended			1 Months Ended		3 Months Ended				3 Months Ended		9 Months Ended		9 Months Ended				9 Months Ended			9 Months Ended		9 Months Ended
	Oct. 31, 2012	Feb. 23, 2011	Sep. 30, 2012	Mar. 01, 2011	Dec. 04, 2008	Dec. 04, 2008 DP&L [Member]	Sep. 30, 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]	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]	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]	Oct. 19, 2012 Revolving Credit Agreement with Bank Group [Member]	Sep. 30, 2012 Revolving Credit Agreement with Bank Group [Member]	Aug. 24, 2011 Revolving Credit Agreement with Bank Group [Member]	Apr. 20, 2010 Revolving Credit Agreement with Bank Group [Member] DP&L [Member]	Apr. 20, 2008 Revolving Credit Agreement with Bank Group [Member] DP&L [Member]	Sep. 30, 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]	Sep. 30, 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]	Dec. 31, 2011 Senior Notes Maturing in September 2011 - 6.875% [Member]	Sep. 30, 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]	Sep. 30, 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]	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]	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]	Sep. 30, 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																					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
Unsecured revolving credit agreement														125.0	200.0		125.0	200.0	200.0	200.0					425.0
Increase additional facility	125.0													50.0	50.0				50.0
Decrease additional facility	75.0												75.0
Letter of credit sublimit															50.0	75.0		50.0	50.0
Collateralized debt					100	100
Long-term Debt, Gross							18.4	18.5	18.7	18.4	18.5	18.7									450.0	450.0	800.0	800.0			19.6	19.5		100.0	100.0	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
Debt instrument interest percentage				4.20%			4.20%			4.20%											6.50%		7.25%			6.875%	8.125%		8.125%