The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624177-113959

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1),(2)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

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DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Gains (Losses) on Derivative Instruments (Details) - USD ($) $ in Millions		12 Months Ended
	Jun. 03, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Designated as Hedging Instrument \| Cash Flow Hedging
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income		$ (1.1)	$ (4.4)	$ 2.5
Ineffective portion of gain (loss) on derivatives recognized in income		0.3	(0.4)	(0.2)
Designated as Hedging Instrument \| Cash Flow Hedging \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives		(4.0)	(5.5)	(4.5)
Designated as Hedging Instrument \| Cash Flow Hedging \| Natural gas contracts
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income		(0.6)	(3.5)	2.7
Ineffective portion of gain (loss) on derivatives recognized in income		0.2	(0.5)	0.0
Designated as Hedging Instrument \| Cash Flow Hedging \| Natural gas contracts \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives		(0.6)	(4.3)	(4.6)
Designated as Hedging Instrument \| Cash Flow Hedging \| Natural gas contracts \| Gas Marketing Operating Revenues
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income		4.3	1.7	4.2
Ineffective portion of gain (loss) on derivatives recognized in income		0.1	0.0	(0.1)
Designated as Hedging Instrument \| Cash Flow Hedging \| Natural gas contracts \| Gas Marketing Operating Expenses
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income		(4.9)	(5.2)	(1.5)
Ineffective portion of gain (loss) on derivatives recognized in income		0.1	(0.5)	0.1
Designated as Hedging Instrument \| Cash Flow Hedging \| Gasoline and heating oil contracts \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives		0.0	(1.2)	0.1
Designated as Hedging Instrument \| Cash Flow Hedging \| Gasoline and heating oil contracts \| Gas Utility Other Operating Expenses
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income		(0.5)	(0.9)	(0.2)
Ineffective portion of gain (loss) on derivatives recognized in income		0.1	0.1	(0.2)
Designated as Hedging Instrument \| Cash Flow Hedging \| Interest rate swaps
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives	$ (0.4)
Designated as Hedging Instrument \| Cash Flow Hedging \| Interest rate swaps \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives		(3.4)	0.0	0.0
Not Designated as Hedging Instrument
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives		10.6	(11.1)	(5.7)
Not Designated as Hedging Instrument \| Gasoline and heating oil contracts \| Other Income and (Income Deductions) - Net
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives		0.0	(0.2)	0.0
Not Designated as Hedging Instrument \| Natural gas commodity contracts \| Gas Marketing Operating Revenues
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives		12.3	(1.3)	(8.7)
Not Designated as Hedging Instrument \| NYMEX / ICE natural gas contracts \| Gas Marketing Operating Revenues
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives		(1.7)	(9.6)	3.0
Laclede Gas \| Designated as Hedging Instrument \| Cash Flow Hedging \| Gasoline and heating oil contracts \| Other Comprehensive Income (Loss)
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) recognized in OCI on derivatives		0.0	(1.2)	0.1
Laclede Gas \| Designated as Hedging Instrument \| Cash Flow Hedging \| Gasoline and heating oil contracts \| Gas Utility Other Operating Expenses
Derivatives in Cash Flow Hedging Relationships [Abstract]
Effective portion of gain (loss) reclassified from AOCI to income		(0.5)	(0.9)	(0.2)
Ineffective portion of gain (loss) on derivatives recognized in income		0.1	0.1	(0.2)
Laclede Gas \| Not Designated as Hedging Instrument \| Gasoline and heating oil contracts \| Other Income and (Income Deductions) - Net
Derivatives Not Designated as Hedging Instruments [Abstract]
Gain (loss) recognized in income on derivatives		$ 0.0	$ (0.2)	$ 0.0