Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state and local operating loss carryforwards.

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A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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- Definition

This element represents the total of interest expense recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties in the period in which the entity claims or expects to claim a tax position, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2011	Nov. 27, 2011	Dec. 31, 2012	Dec. 31, 2010	Dec. 31, 2012 DP&L [Member]	Dec. 31, 2011 DP&L [Member]	Dec. 31, 2010 DP&L [Member]
Estimated annual effective income tax rate			35.00%		35.00%
Decrease in income tax expense					$ 7.6	$ 2.4	$ 0.3
Effective income tax rates			(2.80%)
Unrecognized Tax Benefits Due To Uncertainity In Timing Of Deductibility			19.4		19.4
Unrecognized tax liabilities that would affect the effective tax rate			1.1		1.1
Deferred tax assets related to state and local tax net operating loss carryforwards, net of related valuation allowances	15.4		20.4
Deferred Tax Assets Operating Loss Carryforwards State And Local Valuation Allowances	6.7		16.2
Tax expense (benefit) interest and penalties recorded in the statements of results of operations	$ 0	$ 2.3	$ 1.2	$ 0.3