Pension and Postretirement Benefits (Net Periodic Benefit Cost (Income)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013
Period in which the difference between market related value of assets is calculated in years, max			five
Period in which the difference between actual and estimated asset returns in MRVA is calculated			three
Market related value of assets			$ 351.0		$ 346.0
Pension [Member]
Service cost	1.5	1.8	4.5		5.4
Interest cost	4.3	3.8	13.1		11.6
Expected return on assets	(5.8)	(5.8)	(17.2)		(17.6)
Actuarial (gain) / loss	0.9	1.3	2.6		3.7
Prior service cost	0.4	0.3	1.1		1.1
Net periodic benefit cost / (income)	1.3	1.4	4.1		4.2
Postretirement [Member]
Service cost			0.1		0.1
Interest cost	0.2	0.2	0.6		0.6
Expected return on assets			(0.1)		(0.2)
Actuarial (gain) / loss	(0.1)	(0.1)	(0.4)		(0.3)
Net periodic benefit cost / (income)	0.1	0.1	0.2		0.2
DP&L [Member]
Market related value of assets			351.0		346.0
DP&L [Member] | Pension [Member]
Service cost	1.5	1.8	4.4		5.4
Interest cost	4.3	3.8	13.0	[1]	11.6	[1]
Expected return on assets	(5.7)	(5.8)	(17.0)		(17.6)
Actuarial (gain) / loss	1.6	2.3	4.8		6.9
Prior service cost	0.7	0.7	2.1		2.1
Net periodic benefit cost / (income)	2.4	2.8	7.3		8.4
DP&L [Member] | Postretirement [Member]
Service cost			0.1		0.1
Interest cost	0.2	0.2	0.6	[1]	0.6	[1]
Expected return on assets	(0.1)	(0.1)	(0.2)		(0.2)
Actuarial (gain) / loss	(0.2)	(0.2)	(0.5)		(0.5)
Prior service cost	0.1	0.1	0.1		0.1
Net periodic benefit cost / (income)			$ 0.1		$ 0.1

[1] 7. 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 and nine months ended September 30, 2014 or 2013, respectively. The amounts presented in the following tables for pension include both 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 net periodic benefit cost / (income) of the pension and postretirement benefit plans for the three and nine months ended September 30, 2014 and 2013 was: Net Periodic Benefit Cost / (Income)PensionPostretirementThree months ended Three months ended September 30,September 30,$ in millions2014201320142013Service cost$ 1.5$ 1.8$ -$ -Interest cost 4.3 3.8 0.2 0.2Expected return on plan assets (a) (5.8) (5.8) - -Amortization of unrecognized:Prior service cost 0.4 0.3 - -Actuarial loss / (gain) 0.9 1.3 (0.1) (0.1)Net periodic benefit cost$ 1.3$ 1.4$ 0.1$ 0.1Net Periodic Benefit Cost / (Income)PensionPostretirementNine months ended Nine months ended September 30,September 30,$ in millions2014201320142013Service cost$ 4.5$ 5.4$ 0.1$ 0.1Interest cost 13.1 11.6 0.6 0.6Expected return on plan assets (a) (17.2) (17.6) (0.1) (0.2)Amortization of unrecognized:Prior service cost 1.1 1.1 - -Actuarial loss / (gain) 2.6 3.7 (0.4) (0.3)Net periodic benefit cost$ 4.1$ 4.2$ 0.2$ 0.2For purposes of calculating the expected return on pension plan assets, under GAAP, the market-related value of assets (MRVA) is used. GAAP requires that the difference between actual plan asset returns and estimated plan asset returns be included in the MRVA equally over a period not to exceed five years. We use a methodology under which we include the difference between actual and estimated asset returns in the MRVA equally over a three year period. The MRVA used in the calculation of expected return on pension plan assets for the 2014 and 2013 net periodic benefit cost was approximately $351 million and $346 million, respectively. Benefit payments and Medicare Part D reimbursements, which reflect future service, are estimated to be paid as follows:$ in millionsPensionPostretirement2014$ 6.3$ 0.52015 23.9 2.12016 23.9 2.02017 24.3 1.82018 24.6 1.62019 - 2023 126.5 6.7