PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Narrative (Details) (USD $)	3 Months Ended
Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Extent of lump-sum payments recognized, percentage	100.00%
Medical insurance available until age is reached after early retirement	65 years
Amortization period for transition obligation excluded from postretirement benefit cost (in years)	20 years
Pension Plans \| Laclede Gas
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions made by employer	5,400,000
Pension Plans \| Missouri Gas Energy (MGE)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments recognized as settlements	900,000
Anticipated contributions to pension plans for qualified trust	21,000,000
Pension Plans \| Alagasco
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments recognized as settlements	1,000,000
Contributions made by employer	0
Anticipated contributions to pension plans for qualified trust	0
Nonqualified Pension Plans \| Laclede Gas
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions made by employer	100,000
Nonqualified Pension Plans \| Missouri Gas Energy (MGE)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Anticipated contributions to pension plans for qualified trust	500,000
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions made by employer	0
Anticipated contributions to pension plans for qualified trust	18,100,000
Anticipated payment directly to participants in postretirement plan	300,000

Anticipated payment to the postretirement plans participants for the next fiscal year for non-qualified trusts.

No definition available.

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- Definition

Defined Benefit Plan, Lump-sum Payment Recognized as Settlement Gain (Loss), Minimum Threshold

+ References

No definition available.

+ Details

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- Definition

Reflects the upper limit on age eligibility, post early retirement, when medical insurance is available to retiree.

+ References

No definition available.

+ Details

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- Definition

Lump-sum payments recognized as settlements

+ References

No definition available.

+ Details

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- Definition

The amortization period for transition obligation not yet in postretirement benefit costs.

+ References

No definition available.

+ Details

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- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ 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 (b)(3)

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

+ Details

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- Definition

Amount of employer's best estimate of contributions expected to be paid to the plan in the current remaining fiscal period.

+ References

No definition available.

+ Details

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