Pension and Postretirement Benefits (Estimated Future Benefit Payments and Medicare Part D Reimbursements) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Pension [Member]
2012	$ 5.8
2013	22.7
2014	23.2
2015	23.8
2016	24.0
2017 - 2021	124.4
Postretirement [Member]
2012	0.6
2013	2.3
2014	2.2
2015	2.0
2016	1.9
2017 - 2021	7.5
DP&L [Member] \| Pension [Member]
2012	5.8
2013	22.7
2014	23.2
2015	23.8
2016	24.0
2017 - 2021	124.4
DP&L [Member] \| Postretirement [Member]
2012	0.6
2013	2.3
2014	2.2
2015	2.0
2016	1.9
2017 - 2021	$ 7.5

Amount of benefits expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year from a defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

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Amount of benefits expected to be paid in the next fiscal year following the latest fiscal year from a defined benefit plan.

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Amount of benefits expected to be paid in the fifth fiscal year following the latest fiscal year from a defined benefit plan.

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Amount of benefits expected to be paid in the fourth fiscal year following the latest fiscal year from a defined benefit plan.

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Amount of benefits expected to be paid in the third fiscal year following the latest fiscal year from a defined benefit plan.

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Amount of benefits expected to be paid in the second fiscal year following the latest fiscal year from a defined benefit plan.

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