FAIR VALUE MEASUREMENTS (Details) (Fair Value, Measurements, Recurring, USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014
ASSETS
Total	$ 26.3us-gaap_AssetsFairValueDisclosure
Quoted Prices in Active Markets (Level 1)
ASSETS
Total	21.7
Significant Observable Inputs (Level 2)
ASSETS
Total	9.0
Significant Unobservable Inputs (Level 3)
ASSETS
Total	0.2
Effects of Netting and Cash Margin Receivables /Payables
ASSETS
Total	(4.6)
Gas Utility
ASSETS
U. S. Stock/Bond Mutual Funds	20.2	19.6
NYMEX natural gas contracts		0
OTCBB natural gas contracts		0
Total	20.2	19.6
LIABILITIES
NYMEX/ICE natural gas contracts	0	0
OTCBB natural gas contracts	19.5	4.0
NYMEX gasoline and heating oil contracts	0	0
Total	19.5	4.0
Gas Utility \| Quoted Prices in Active Markets (Level 1)
ASSETS
U. S. Stock/Bond Mutual Funds	16.3	15.7
NYMEX natural gas contracts		2.4
OTCBB natural gas contracts		0
Total	16.3	18.1
LIABILITIES
NYMEX/ICE natural gas contracts	19.4	5.2
OTCBB natural gas contracts	0	0
NYMEX gasoline and heating oil contracts	1.3	0.2
Total	20.7	5.4
Gas Utility \| Significant Observable Inputs (Level 2)
ASSETS
U. S. Stock/Bond Mutual Funds	3.9	3.9
NYMEX natural gas contracts		0
OTCBB natural gas contracts		0.1
Total	3.9	4.0
LIABILITIES
NYMEX/ICE natural gas contracts	0	0
OTCBB natural gas contracts	19.5	4.1
NYMEX gasoline and heating oil contracts	0	0
Total	19.5	4.1
Gas Utility \| Significant Unobservable Inputs (Level 3)
ASSETS
U. S. Stock/Bond Mutual Funds	0	0
NYMEX natural gas contracts		0
Total	0	0
LIABILITIES
NYMEX/ICE natural gas contracts	0	0
OTCBB natural gas contracts	0	0
NYMEX gasoline and heating oil contracts	0	0
Total	0	0
Gas Utility \| Effects of Netting and Cash Margin Receivables /Payables
ASSETS
U. S. Stock/Bond Mutual Funds	0	0
NYMEX natural gas contracts		(2.4)
OTCBB natural gas contracts		(0.1)
Total	0	(2.5)
LIABILITIES
NYMEX/ICE natural gas contracts	(19.4)	(5.2)
OTCBB natural gas contracts	0	(0.1)
NYMEX gasoline and heating oil contracts	(1.3)	(0.2)
Total	(20.7)	(5.5)
Gas Marketing
ASSETS
NYMEX natural gas contracts	2.1	0.4
Natural gas commodity contracts	4.0	2.7
Total		22.7
LIABILITIES
NYMEX natural gas contracts	0	0
Natural gas commodity contracts	0.8	0.5
Total	20.3	4.5
Gas Marketing \| Quoted Prices in Active Markets (Level 1)
ASSETS
NYMEX natural gas contracts	5.4	1.0
Natural gas commodity contracts	0
Total		19.1
LIABILITIES
NYMEX natural gas contracts	3.4	1.1
Natural gas commodity contracts	0	0
Total	24.1	6.5
Gas Marketing \| Significant Observable Inputs (Level 2)
ASSETS
NYMEX natural gas contracts	1.0	1.2
Natural gas commodity contracts	4.1	2.7
Total		7.9
LIABILITIES
NYMEX natural gas contracts	4.5	0.7
Natural gas commodity contracts	1.1	0.7
Total	25.1	5.5
Gas Marketing \| Significant Unobservable Inputs (Level 3)
ASSETS
NYMEX natural gas contracts	0	0
Natural gas commodity contracts	0.2	0.2
Total		0.2
LIABILITIES
NYMEX natural gas contracts	0	0
Natural gas commodity contracts	0	0
Total	0	0
Gas Marketing \| Effects of Netting and Cash Margin Receivables /Payables
ASSETS
NYMEX natural gas contracts	(4.3)	(1.8)
Natural gas commodity contracts	(0.3)	(0.2)
Total		(4.5)
LIABILITIES
NYMEX natural gas contracts	(7.9)	(1.8)
Natural gas commodity contracts	(0.3)	(0.2)
Total	(28.9)	(7.5)
Laclede Gas
ASSETS
U. S. Stock/Bond Mutual Funds	20.2	19.6
NYMEX natural gas contracts		0
OTCBB natural gas contracts		0
Total	20.2	19.6
LIABILITIES
NYMEX/ICE natural gas contracts		0
OTCBB natural gas contracts	19.5	4.0
NYMEX gasoline and heating oil contracts	0	0
NYMEX natural gas contracts	0
Total	19.5	4.0
Laclede Gas \| Quoted Prices in Active Markets (Level 1)
ASSETS
U. S. Stock/Bond Mutual Funds	16.3	15.7
NYMEX natural gas contracts		2.4
OTCBB natural gas contracts		0
Total	16.3	18.1
LIABILITIES
NYMEX/ICE natural gas contracts		5.2
OTCBB natural gas contracts	0	0
NYMEX gasoline and heating oil contracts	1.3	0.2
NYMEX natural gas contracts	19.4
Total	20.7	5.4
Laclede Gas \| Significant Observable Inputs (Level 2)
ASSETS
U. S. Stock/Bond Mutual Funds	3.9	3.9
NYMEX natural gas contracts		0
OTCBB natural gas contracts		0.1
Total	3.9	4.0
LIABILITIES
NYMEX/ICE natural gas contracts		0
OTCBB natural gas contracts	19.5	4.1
NYMEX gasoline and heating oil contracts	0	0
NYMEX natural gas contracts	0
Total	19.5	4.1
Laclede Gas \| Significant Unobservable Inputs (Level 3)
ASSETS
U. S. Stock/Bond Mutual Funds	0	0
NYMEX natural gas contracts		0
Total	0	0
LIABILITIES
NYMEX/ICE natural gas contracts		0
OTCBB natural gas contracts	0	0
NYMEX gasoline and heating oil contracts	0	0
NYMEX natural gas contracts	0
Total	0	0
Laclede Gas \| Effects of Netting and Cash Margin Receivables /Payables
ASSETS
U. S. Stock/Bond Mutual Funds	0	0
NYMEX natural gas contracts		(2.4)
OTCBB natural gas contracts		(0.1)
Total	0	(2.5)
LIABILITIES
NYMEX/ICE natural gas contracts		(5.2)
OTCBB natural gas contracts	0	(0.1)
NYMEX gasoline and heating oil contracts	(1.3)	(0.2)
NYMEX natural gas contracts	(19.4)
Total	$ (20.7)	$ (5.5)

Derivative Assets, OTCBB Natural Gas Contracts, Fair Value

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Derivative Liabilities, OTCBB Natural Gas Contracts, Fair Value

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- Definition

This element represents a certain statement of financial position asset caption which represents a class of natural gas derivative contract assets, or which may include an individual asset, measured at fair value on a recurring basis.

+ References

No definition available.

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+ References

No definition available.

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- Definition

This element represents a certain statement of financial position liability caption which represents a class of gasoline and heating oil derivative contract liabilities, or which may include an individual liability, measured at fair value on a recurring basis.

+ References

No definition available.

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- Definition

This element represents a certain statement of financial position liability caption which represents a class of natural gas derivative commodity contract liabilities, or which may include an individual liability, measured at fair value on a recurring basis.

+ References

No definition available.

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- Definition

This element represents a certain statement of financial position liability caption which represents a class of natural gas derivative contract liabilities, or which may include an individual liability, measured at fair value on a recurring basis.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

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Fair value of financial and nonfinancial obligations.

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