Pension and Postretirement Benefits (Net Periodic Benefit Cost (Income)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Pension [Member]
Service cost	$ 1.8		$ 1.5
Interest cost	4.3		4.4
Expected return on assets	(5.7)		(5.8)
Actuarial (gain) / loss	1.5		0.9
Prior service cost	0.5		0.4
Net periodic benefit cost / (income)	2.4		1.4
Postretirement [Member]
Service cost			0.1
Interest cost	0.2		0.2
Expected return on assets			(0.1)
Actuarial (gain) / loss	(0.1)		(0.1)
Net periodic benefit cost / (income)	0.1		0.1
DP&L [Member] | Pension [Member]
Service cost	1.8		1.5
Interest cost	4.3	[1]	4.4	[1]
Expected return on assets	(5.7)		(5.7)
Actuarial (gain) / loss	2.4		1.6
Prior service cost	0.8		0.7
Net periodic benefit cost / (income)	3.6		2.5
DP&L [Member] | Postretirement [Member]
Interest cost	0.2	[1]	0.2	[1]
Actuarial (gain) / loss	$ (0.2)		$ (0.2)

[1] 6. Pension and Postretirement Benefits DP&L sponsors a defined benefit pension plan for the vast majority of its employees. We generally fund pension plan benefits as accrued in accordance with the minimum funding requirements of ERISA and, in addition, make voluntary contributions from time to time. There were no contributions made during the three months ended March 31, 2015 or 2014. The amounts presented in the following tables for pension include the collective bargaining plan formula, the traditional management plan formula, the cash balance plan formula and the SERP, in the aggregate.  The amounts presented for postretirement include both health and life insurance.  The pension and postretirement costs below have not been adjusted for amounts billed to the Service Company for former DP&L employees who are now employed by the Service Company but are still participants in the DP&L plan.  See "Related Party Transactions" discussion in Note 1, "Overview and Summary of Significant Accounting Policies". The net periodic benefit cost / (income) of the pension and postretirement benefit plans for the three months ended March 31, 2015 and 2014 was: Net Periodic Benefit Cost / (Income)PensionPostretirementThree months ended Three months ended March 31,March 31,$ in millions2015201420152014Service cost$ 1.8$ 1.5$ -$ 0.1Interest cost 4.3 4.4 0.2 0.2Expected return on plan assets (5.7) (5.8) - (0.1)Amortization of unrecognized:Prior service cost 0.5 0.4 - -Actuarial loss / (gain) 1.5 0.9 (0.1) (0.1)Net periodic benefit cost$ 2.4$ 1.4$ 0.1$ 0.1Benefit payments and Medicare Part D reimbursements, which reflect future service, are estimated to be paid as follows:$ in millionsPensionPostretirement2015$ 18.6$ 1.42016 25.2 1.82017 25.7 1.72018 26.3 1.62019 26.7 1.52020 - 2024 137.0 6.1