Inventories (Details) (USD $) In Millions	Jun. 30, 2011	Sep. 30, 2010	Jun. 30, 2010
Inventories
Total inventories	$ 271.6	$ 314.0	$ 249.2
Non-utility LPG and natural gas [Member]
Inventories
Total inventories	170.5	157.9	145.6
Gas Utility natural gas [Member]
Inventories
Total inventories	50.1	111.5	60.3
Materials, supplies and other [Member]
Inventories
Total inventories	$ 51.0	$ 44.6	$ 43.3

Carrying amount (lower of cost or market) as of the balance sheet date of inventories less all valuation and other allowances. Excludes noncurrent inventory balances (expected to remain on hand past one year or one operating cycle, if longer).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.6(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 35
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6386567&loc=d3e3927-108312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6361293&loc=d3e6676-107765

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant