Pension and Postretirement Benefits (Estimated Future Benefit Payments and Medicare Part D Reimbursements) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014
Pension [Member]
2014	$ 6.3
2015	23.9
2016	23.9
2017	24.3
2018	24.6
2019 - 2022	126.5
Postretirement [Member]
2014	0.5
2015	2.1
2016	2.0
2017	1.8
2018	1.6
2019 - 2022	6.7
DP&L [Member] | Pension [Member]
2014	6.3
2015	23.9
2016	23.9
2017	24.3
2018	24.6
2019 - 2022	126.5
DP&L [Member] | Postretirement [Member]
2014	0.5
2015	2.1
2016	2.0
2017	1.8
2018	1.6
2019 - 2022	$ 6.7