Summary of Significant Accounting Policies (Financial Statement Presentation) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill		$ 452.8	$ 759.1	$ 2,576.3
Goodwill, Impairment Loss	1,850.0	306.3	1,817.2
DP&L [Member]
Goodwill		317.0	623.3	2,440.5
Goodwill, Impairment Loss		$ (306.3)	$ (1,817.2)

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

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-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13854-109267

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 350

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-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

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