Debt Obligations (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended				6 Months Ended						9 Months Ended			9 Months Ended			1 Months Ended	3 Months Ended	4 Months Ended			3 Months Ended	8 Months Ended	1 Months Ended			4 Months Ended		4 Months Ended	3 Months Ended	9 Months Ended			3 Months Ended	9 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	Dec. 04, 2008	Jun. 30, 2013 Cash on hand [Member]	Jun. 30, 2013 Credit Facility [Member]	Jun. 30, 2013 Other Debt [Member]	Sep. 30, 2013 DP&L [Member]	Dec. 31, 2012 DP&L [Member]	Dec. 04, 2008 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]	Mar. 01, 2011 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]	Aug. 31, 2011 Revolving Credit Agreement with Bank Group [Member]	Apr. 20, 2010 Revolving Credit Agreement with Bank Group [Member]	May 10, 2013 Revolving Credit Agreement with Bank Group [Member]	Oct. 19, 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]	Aug. 24, 2011 Revolving Credit Agreement with Bank Group [Member] DP&L [Member]	Aug. 24, 2011 Revolving Credit Agreement with Bank Group expiring 2014 [Member]	Sep. 30, 2013 Revolving Credit Agreeement with Bank Group Expiring 2018 [Member]	May 10, 2013 Revolving Credit Agreeement with Bank Group Expiring 2018 [Member]	May 10, 2013 Revolving Credit Agreeement with Bank Group Expiring 2018 [Member] DP&L [Member]	Sep. 30, 2013 Revolving Credit Agreeement with Bank Group Expiring 2018 [Member] DP&L [Member]	May 10, 2013 Revolving 100M Credit Facility [Member]	Sep. 30, 2013 Five Year Senior Unsecured Notes at 6.50% maturing on October 15, 2016 [Member]	Sep. 30, 2013 Five Year Senior Unsecured Notes at 6.50% maturing on October 15, 2016 [Member]	Jun. 30, 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]	Sep. 30, 2013 Ten Year Senior Unsecured Notes at 7.25% maturing at October 15, 2021 [Member]	Sep. 30, 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]	Sep. 30, 2013 First Mortgage Bonds Maturing October 2013 [Member]	Sep. 30, 2013 First Mortgage Bonds Maturing October 2013 [Member] DP&L [Member]	Sep. 30, 2013 First Mortgage Bonds Maturing in September 2016 - 1.9%	Sep. 30, 2013 First Mortgage Bonds Maturing in September 2016 - 1.9% DP&L [Member]		Sep. 30, 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]	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]	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 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]	Sep. 30, 2013 Bank Term Loan maturing in May 2018 [Member]	May 10, 2013 Bank Term Loan maturing in May 2018 [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			May 01, 2018
Unsecured revolving credit agreement																		200.0		75.0	200.0	200.0	200.0	125.0		300.0	300.0		100.0
Increase additional facility																	50.0	50.0	100.0			50.0	50.0				100.0		50.0
Decrease additional facility																								75.0
Letter of credit sublimit																	50.0	50.0	100.0			50.0	50.0	75.0			100.0		100.0
Letters of credit outstanding																									0.4			0.4
Collateralized debt				100.0						100.0
Loans Payable, Noncurrent																																450.0
Line of Credit Facility, Remaining Borrowing Capacity																									299.6			299.6
Long-term Debt, Gross											18.3	18.3	18.7	18.3	18.3	18.7														450.0	450.0		450.0	800.0	800.0	800.0	470.0	470.0	445.0	445.0	[1]	19.6	19.6	100.0		100.0			425.0	425.0	190.0	200.0
Current portion - long-term debt	480.4	584.9						470.3	570.4																																				100.0		100.0				10.0
Term Loan Amortization Year 1																																																				5.00%
Repayments of debt					$ 175.0	$ 50.0	$ 200.0
Debt instrument interest percentage			4.20%								4.20%			4.20%		4.20%														6.50%	6.50%			7.25%	7.25%							8.125%

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