Goodwill And Other Intangible Assets (Change In Goodwill) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2012 DPL [Member]	Dec. 31, 2011 DPL [Member]	Dec. 31, 2012 DP&L [Member]	Dec. 31, 2011 DP&L [Member]	Dec. 31, 2011 DPLER [Member]	Dec. 31, 2012 DPLER [Member]
Goodwill, Beginning Balance	$ 2,576.3	$ 2,576.3	$ 2,576.3		$ 2,440.5			$ 135.8
Goodwill, Acquired During Period				2,576.3		2,440.5	135.8
Goodwill, Gross			2,576.3	2,576.3	2,440.5	2,440.5	135.8	135.8
Goodwill, Impairment Loss	1,850.0	1,817.2	(1,817.2)		(1,817.2)
Goodwill, Impaired, Accumulated Impairment Loss			(1,817.2)		(1,817.2)
Goodwill, Ending Balance		$ 759.1	$ 759.1	$ 2,576.3	$ 623.3	$ 2,440.5	$ 135.8	$ 135.8

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details

- Definition

The aggregate amount of goodwill acquired in the period and allocated to the reportable segment. The value is stated at fair value based on the purchase price allocation.

+ References+ Details

- Definition

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

+ References

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+ Details