Goodwill And Other Intangible Assets (Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Gross Balance, Subject to Amortization	$ 152.1		$ 149.6
Amortization of intangibles	(108.1)		(13.3)
Net Balance, Subject to Amortization	44.0		136.3
Intangible Assets, Gross Balance	158.2		155.7
Intangible Assets, Net (Excluding Goodwill)	50.1		142.4
Electric Security Plan [Member]
Gross Balance, Subject to Amortization	87.0	[1]	87.0	[1]
Amortization of intangibles	(87.0)	[1]	(8.6)	[1]
Net Balance, Subject to Amortization			78.4	[1]
Customer Contracts [Member]
Gross Balance, Subject to Amortization	28.0	[2]	28.0	[2]
Amortization of intangibles	(19.7)	[2]	(3.0)	[2]
Net Balance, Subject to Amortization	8.3	[2]	25.0	[2]
Customer Relationships [Member]
Gross Balance, Subject to Amortization	31.8	[3]	31.8	[3]
Amortization of intangibles	(1.1)	[3]	(0.5)	[3]
Net Balance, Subject to Amortization	30.7	[3]	31.3	[3]
Other Intangible Assets [Member]
Gross Balance, Subject to Amortization	5.3	[4]	2.8	[4]
Amortization of intangibles	(0.3)	[4]	(1.2)	[4]
Net Balance, Subject to Amortization	5.0	[4]	1.6	[4]
Trademarks [Member]
Gross Balance, Not Subject to Amortization	6.1	[5]	6.1	[5]
Net Balance, Not Subject to Amortization	$ 6.1	[5]	$ 6.1	[5]

[1] (a) Represents the value of DP&L’s Electric Security Plan which is a rate plan for the supply and pricing of electric generation services. It provides a level of price stability to consumers of electricity compared to market-based electricity prices.

[2] (b) Represents above market contracts that DPLER has with third party customers existing as of the Merger date.

[3] (c) Represents relationships DPLER has with third party customers as of the Merger date, where DPLER has regular contact with the customer, and the customer has the ability to make direct contact with DPLER.

[4] (d) Consists of various intangible assets including renewable energy credits, emission allowances, and other intangibles, none of which are individually significant.

[5] (e) Trademark/Trade name represents the value assigned to the trade names of DPLER and MC Squared.