FAIR VALUE MEASUREMENTS (Details) (Fair Value, Measurements, Recurring, USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Sep. 30, 2014
ASSETS
Total	$ 23.8us-gaap_AssetsFairValueDisclosure	$ 22.7us-gaap_AssetsFairValueDisclosure
LIABILITIES
Total	17.7us-gaap_LiabilitiesFairValueDisclosure	4.5us-gaap_LiabilitiesFairValueDisclosure
Quoted Prices in Active Markets (Level 1)
ASSETS
Total	20.4	19.1
LIABILITIES
Total	17.0	6.5
Significant Observable Inputs (Level 2)
ASSETS
Total	8.3	7.9
LIABILITIES
Total	21.7	5.5
Significant Unobservable Inputs (Level 3)
ASSETS
Total	0.5	0.2
LIABILITIES
Total	0	0
Effects of Netting and Cash Margin Receivables /Payables
ASSETS
Total	(5.4)	(4.5)
LIABILITIES
Total	(21.0)	(7.5)
Gas Utility
ASSETS
U. S. Stock/Bond Mutual Funds	20.3	19.6
NYMEX natural gas contracts	0	0
OTCBB natural gas contracts		0
Total	20.3	19.6
LIABILITIES
NYMEX/ICE natural gas contracts	0	0
OTCBB natural gas contracts	14.5	4.0
NYMEX gasoline and heating oil contracts	0	0
Interest rate swaps	2.9
Total	17.4	4.0
Gas Utility \| Quoted Prices in Active Markets (Level 1)
ASSETS
U. S. Stock/Bond Mutual Funds	16.4	15.7
NYMEX natural gas contracts	0.6	2.4
OTCBB natural gas contracts		0
Total	17.0	18.1
LIABILITIES
NYMEX/ICE natural gas contracts	14.1	5.2
OTCBB natural gas contracts	0	0
NYMEX gasoline and heating oil contracts	1.0	0.2
Interest rate swaps	0
Total	15.1	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	0
OTCBB natural gas contracts		0.1
Total	3.9	4.0
LIABILITIES
NYMEX/ICE natural gas contracts	0	0
OTCBB natural gas contracts	14.5	4.1
NYMEX gasoline and heating oil contracts	0	0
Interest rate swaps	2.9
Total	17.4	4.1
Gas Utility \| Significant Unobservable Inputs (Level 3)
ASSETS
U. S. Stock/Bond Mutual Funds	0	0
NYMEX natural gas contracts	0	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
Interest rate swaps	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	(0.6)	(2.4)
OTCBB natural gas contracts		(0.1)
Total	(0.6)	(2.5)
LIABILITIES
NYMEX/ICE natural gas contracts	(14.1)	(5.2)
OTCBB natural gas contracts	0	(0.1)
NYMEX gasoline and heating oil contracts	(1.0)	(0.2)
Interest rate swaps	0
Total	(15.1)	(5.5)
Gas Marketing
ASSETS
NYMEX natural gas contracts	0.8	0.4
Natural gas commodity contracts	2.7	2.7
LIABILITIES
NYMEX natural gas contracts	0	0
Natural gas commodity contracts	0.3	0.5
Gas Marketing \| Quoted Prices in Active Markets (Level 1)
ASSETS
NYMEX natural gas contracts	3.4	1.0
Natural gas commodity contracts	0	0
LIABILITIES
NYMEX natural gas contracts	1.9	1.1
Natural gas commodity contracts	0	0
Gas Marketing \| Significant Observable Inputs (Level 2)
ASSETS
NYMEX natural gas contracts	1.7	1.2
Natural gas commodity contracts	2.7	2.7
LIABILITIES
NYMEX natural gas contracts	3.5	0.7
Natural gas commodity contracts	0.8	0.7
Gas Marketing \| Significant Unobservable Inputs (Level 3)
ASSETS
NYMEX natural gas contracts	0	0
Natural gas commodity contracts	0.5	0.2
LIABILITIES
NYMEX natural gas contracts	0	0
Natural gas commodity contracts	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	(0.5)	(0.2)
LIABILITIES
NYMEX natural gas contracts	(5.4)	(1.8)
Natural gas commodity contracts	(0.5)	(0.2)
Laclede Gas
ASSETS
U. S. Stock/Bond Mutual Funds	20.3	19.6
NYMEX natural gas contracts	0	0
OTCBB natural gas contracts		0
Total	20.3	19.6
LIABILITIES
NYMEX/ICE natural gas contracts		0
OTCBB natural gas contracts	14.5	4.0
NYMEX gasoline and heating oil contracts	0	0
NYMEX natural gas contracts	0
Total	14.5	4.0
Laclede Gas \| Quoted Prices in Active Markets (Level 1)
ASSETS
U. S. Stock/Bond Mutual Funds	16.4	15.7
NYMEX natural gas contracts	0.6	2.4
OTCBB natural gas contracts		0
Total	17.0	18.1
LIABILITIES
NYMEX/ICE natural gas contracts		5.2
OTCBB natural gas contracts	0	0
NYMEX gasoline and heating oil contracts	1.0	0.2
NYMEX natural gas contracts	14.1
Total	15.1	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	0
OTCBB natural gas contracts		0.1
Total	3.9	4.0
LIABILITIES
NYMEX/ICE natural gas contracts		0
OTCBB natural gas contracts	14.5	4.1
NYMEX gasoline and heating oil contracts	0	0
NYMEX natural gas contracts	0
Total	14.5	4.1
Laclede Gas \| Significant Unobservable Inputs (Level 3)
ASSETS
U. S. Stock/Bond Mutual Funds	0	0
NYMEX natural gas contracts	0	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	(0.6)	(2.4)
OTCBB natural gas contracts		(0.1)
Total	(0.6)	(2.5)
LIABILITIES
NYMEX/ICE natural gas contracts		(5.2)
OTCBB natural gas contracts	0	(0.1)
NYMEX gasoline and heating oil contracts	(1.0)	(0.2)
NYMEX natural gas contracts	(14.1)
Total	(15.1)	(5.5)
Alagasco
LIABILITIES
Interest rate swaps	2.9	0
Total	2.9	0
Alagasco \| Quoted Prices in Active Markets (Level 1)
LIABILITIES
Interest rate swaps	0	0
Total	0	0
Alagasco \| Significant Observable Inputs (Level 2)
LIABILITIES
Interest rate swaps	2.9	0
Total	2.9	0
Alagasco \| Significant Unobservable Inputs (Level 3)
LIABILITIES
Interest rate swaps	0	0
Total	0	0
Alagasco \| Effects of Netting and Cash Margin Receivables /Payables
LIABILITIES
Interest rate swaps	0	0
Total	$ 0	$ 0

Derivative Assets, OTCBB Natural Gas Contracts, Fair Value

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