Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Estimated annual effective income tax rate	35.00%
Tax Refund		$ 19.9
Decrease in income tax expense		1.2
Effective income tax rates	(31.80%)	(11.20%)	(2.80%)
Unrecognized Tax Benefits Due To Uncertainity In Timing Of Deductibility	0.9
Deferred tax assets related to state and local tax net operating loss carryforwards, net of related valuation allowances	27.1	20.7
Deferred Tax Assets Operating Loss Carryforwards State And Local Valuation Allowances	21.9	16.6
Tax expense (benefit) interest and penalties recorded in the statements of results of operations	0.4	0	1.2
DP&L [Member]
Estimated annual effective income tax rate	35.00%
Tax Refund	19.9
Decrease in income tax expense	1.2
Additional tax increase / decrease	0.7	1.1	7.6
Unrecognized Tax Benefits Due To Uncertainity In Timing Of Deductibility	$ 0.9