Pension and Postretirement Benefits (Estimated Amounts that will be Amortized from Accumulated Other Comprehensive Income, Regulatory Assets And Regulatory Liabilities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) / loss	$ 5.8
Prior service cost	2.0
Pension [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) / loss	9.8
Prior service cost	3.3
Postretirement [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) / loss	(0.5)
Postretirement [Member] | DP&L [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) / loss	(0.7)
Prior service cost	$ 0.1