Debt Obligations (Long-term Debt) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended				6 Months Ended				6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended			6 Months Ended					6 Months Ended	12 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Mar. 01, 2011	Jun. 30, 2013 DP&L [Member]	Dec. 31, 2012 DP&L [Member]	Jun. 30, 2013 First Mortgage Bonds Maturing in October 2013 - 5.125% [Member]	Jun. 30, 2013 First Mortgage Bonds Maturing in October 2013 - 5.125% [Member] DP&L [Member]	Jun. 30, 2013 Pollution Control Series Maturing in January 2028 - 4.70% [Member]	Dec. 31, 2012 Pollution Control Series Maturing in January 2028 - 4.70% [Member]	Jun. 30, 2013 Pollution Control Series Maturing in January 2028 - 4.70% [Member] DP&L [Member]	Dec. 31, 2012 Pollution Control Series Maturing in January 2028 - 4.70% [Member] DP&L [Member]	Jun. 30, 2013 Pollution Control Series Maturing in January 2034 - 4.80% [Member]	Dec. 31, 2012 Pollution Control Series Maturing in January 2034 - 4.80% [Member]	Jun. 30, 2013 Pollution Control Series Maturing in January 2034 - 4.80% [Member] DP&L [Member]	Dec. 31, 2012 Pollution Control Series Maturing in January 2034 - 4.80% [Member] DP&L [Member]	Jun. 30, 2013 Pollution Control Series Maturing in September 2036 - 4.80% [Member]	Dec. 31, 2012 Pollution Control Series Maturing in September 2036 - 4.80% [Member]	Jun. 30, 2013 Pollution Control Series Maturing in September 2036 - 4.80% [Member] DP&L [Member]	Dec. 31, 2012 Pollution Control Series Maturing in September 2036 - 4.80% [Member] 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]	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]	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]	Jun. 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]	Jun. 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]	Jun. 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]	Jun. 30, 2013 Bank Term Loan maturing in May 2018 [Member]	May 10, 2013 Bank Term Loan maturing in May 2018 [Member]	Jun. 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]	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]	Jun. 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]
Long-term debt, gross								$ 36.1	$ 36.1	$ 35.3	$ 35.3	$ 179.6	$ 179.6	$ 179.1	$ 179.1	$ 96.3	$ 96.3	$ 100.0	$ 100.0	$ 100.0		$ 100.0		$ 18.3	$ 18.3	$ 18.7	$ 18.3	[1]	$ 18.3	[1]	$ 18.7		$ 425.0	$ 425.0	$ 200.0	$ 200.0	$ 19.6	$ 19.6	$ 450.0	$ 450.0	$ 800.0	$ 800.0
Total long-term debt at subsidary	430.3	330.4
Obligation for capital lease		0.1			0.1
Total long-term debt	$ 1,899.9	$ 2,025.0		$ 432.7	$ 332.7
Debt instrument maturity year						Oct. 01, 2013	Oct. 01, 2013	Jan. 01, 2028		Jan. 01, 2028		Jan. 01, 2034		Jan. 01, 2034		Sep. 01, 2036		Sep. 01, 2036		Nov. 01, 2040		Nov. 01, 2040		Feb. 01, 2061			Feb. 01, 2061					Aug. 01, 2014			May 01, 2018		Sep. 01, 2031		Oct. 01, 2016		Oct. 01, 2021
Debt instrument interest percentage			4.20%			5.125%	5.125%	4.70%		4.70%		4.80%		4.80%		4.80%		4.80%						4.20%			4.20%				4.20%						8.125%		6.50%		7.25%
Debt instrument interest percentage minimum																				0.08%	0.04%	0.08%	0.04%									2.46%	2.22%		2.45%
Debt instrument interest percentage maximum																				0.24%	0.26%	0.24%	0.26%									2.46%	2.47%		2.45%

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