Debt Obligations (Current portion - Long-term Debt) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended			9 Months Ended			3 Months Ended
Sep. 30, 2011	Mar. 01, 2011	Dec. 31, 2010	Sep. 30, 2011 DP&L [Member] U.S. Government note maturing in February 2061 - 4.20% [Member]	Sep. 30, 2011 Senior Notes Maturing in September 2011 - 6.875% [Member]	Dec. 31, 2010 Senior Notes Maturing in September 2011 - 6.875% [Member]	Sep. 30, 2011 DP&L [Member]	Dec. 31, 2010 DP&L [Member]
Obligation for capital lease							$ 0.3	$ 0.1
Total current portion - long-term debt	0.4		297.5	18.5			0.4	0.1
Senior notes maturing in September 2011					$ 297.4	$ 297.4
Debt instrument maturity year	2061			February 2061			2026
Debt instrument interest percentage		4.20%		4.20%	6.875%

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal, through the balance sheet date and due to be paid within one year (or one operating cycle, if longer) of the balance sheet date.

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Interest rate stated in the contractual debt agreement.

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When presenting a range of maturity dates, the latest date when the outstanding debt instruments are required to be repaid. May be presented in a variety of ways (for example: year only, month and year, day, month and year, and number of years).

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Total of the portions of the carrying amounts as of the balance sheet date of long-term debt, which may include notes payable, bonds payable, debentures, mortgage loans, and commercial paper, which are scheduled to be repaid within one year or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Carrying value as of the balance sheet date of the portion of long-term notes having the highest claim on the assets of the issuer in case of bankruptcy or liquidation, due within one year or the normal operating cycle, if longer. Senior note holders are paid off in full before any payments are made to debt holders having a lesser priority of repayment.

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