PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Expected Future Benefit Payments (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014
Pension Plans \| Pensions from Qualified Trust
Expected benefit payments [Abstract]
2015	$ 22.3
2016	25.2
2017	27.0
2018	30.6
2019	32.9
2020 - 2024	224.4
Pension Plans \| Pensions from Laclede Gas Funds
Expected benefit payments [Abstract]
2015	0.5
2016	0.5
2017	0.6
2018	0.6
2019	0.7
2020 - 2024	4.4
Pension Plans \| Benefits Paid from Alagasco Funds
Expected benefit payments [Abstract]
2015	9.9
2016	10.2
2017	10.6
2018	10.6
2019	11.2
2020 - 2024	58.7
Postretirement Plans \| Pensions from Qualified Trust
Expected benefit payments [Abstract]
2015	9.7
2016	10.6
2017	11.5
2018	12.5
2019	13.9
2020 - 2024	87.0
Postretirement Plans \| Pensions from Laclede Gas Funds
Expected benefit payments [Abstract]
2015	0.3
2016	0.3
2017	0.3
2018	0.4
2019	0.4
2020 - 2024	2.1
Postretirement Plans \| Benefits Paid from Alagasco Funds
Expected benefit payments [Abstract]
2015	3.8
2016	3.8
2017	3.8
2018	3.8
2019	3.8
2020 - 2024	18.6
Laclede Gas \| Pension Plans \| Pensions from Qualified Trust
Expected benefit payments [Abstract]
2015	22.3
2016	25.2
2017	27.0
2018	30.6
2019	32.9
2020 - 2024	224.4
Laclede Gas \| Pension Plans \| Pensions from Laclede Gas Funds
Expected benefit payments [Abstract]
2015	0.5
2016	0.5
2017	0.6
2018	0.6
2019	0.7
2020 - 2024	$ 4.4

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Amount of benefits expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

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- Definition

Amount of benefits expected to be paid in the next fiscal year following the latest fiscal year from a defined benefit plan.

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- Definition

Amount of benefits expected to be paid in the fifth fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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Amount of benefits expected to be paid in the fourth fiscal year following the latest fiscal year from a defined benefit plan.

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Amount of benefits expected to be paid in the third fiscal year following the latest fiscal year from a defined benefit plan.

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Amount of benefits expected to be paid in the second fiscal year following the latest fiscal year from a defined benefit plan.

+ References

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