Regulatory Assets and Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Deferred Storm Costs [Member]
Disallowance of regulatory asset	$ 24.0
Fuel and purchased power recovery costs [Member]
Disallowance of regulatory asset	5.3
DP&L [Member] \| Deferred Storm Costs [Member]
Disallowance of regulatory asset	24.0
DP&L [Member] \| Fuel and purchased power recovery costs [Member]
Disallowance of regulatory asset	$ 5.3

Discloses the amount of any reduction to the carrying amounts of regulated assets that result from impairment (for example, rate actions of a regulator).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 35

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6066304&loc=d3e44026-110379

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_AmountOfImpairmentToCarryingAmountOfRegulatoryAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant