Commitments And Contingencies (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Jun. 30, 2013
Site Contingency [Line Items]
Estimated minimum liability for environmental remediation	$ 16.8
Rate recovery period	11 years
Former Manufactured Gas Plant Site [Member]
Site Contingency [Line Items]
Estimated minimum liability for environmental remediation	$ 13.9

Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 55

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6591318&loc=d3e44360-110383

Name:	us-gaap_RemainingRecoveryPeriodOfRegulatoryAssetsForWhichNoReturnOnInvestmentDuringRecoveryPeriodIsProvided1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration