Anticipated contributions to the pension plans for fiscal year 2012 for non-qualified plans.

No definition available.

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- Definition

Anticipated contributions to the pension plans for the next fiscal year for qualified trusts.

+ References

No definition available.

+ Details

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- Definition

Anticipated contribution to the postretirement plans for the next fiscal year for qualified trusts.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

Current investment policy that target allocation of assets to equity securities.

+ References

No definition available.

+ Details

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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

Gains and losses not yet includible in pension/postretirement benefit cost are amortized only to the extent that such gain or loss exceeds 10% of the greater of the benefit obligation or the market-related value of plan assets

+ References

No definition available.

+ Details

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- Definition

Disclosure under Missouri Public Service Commission Order, the return on plan assets if based on the market-related value of plan assets implemented prospectively over a four-year period.

+ References

No definition available.

+ Details

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- Definition

Current investment policy that target allocation of assets to debt securities.

+ 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

-- None. No documentation exists for this element. --

+ 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 amount of annual recovery of postretirement benefit costs allowed in rates by the Missouri Public Service Commission. The differences between these amounts and those calculated pursuant to GAAP are deferred as regulatory assets or liabilities.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of annual recovery of net pension costs allowed in rates for qualified pension plans by the Missouri Public Service Commission. The differences between these amounts and those calculated pursuant to GAAP are deferred as regulatory assets or liabilities.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

+ Details

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- Details

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- Details

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- Details

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- Details

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PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013	Jan. 01, 2011	Feb. 20, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Extent of Lump-sum payments recognized, percentage	100.00%
Lump-sum payments recognized as settlements	$ 71.1	$ 22.1
Implementation period used to calculate return on plan assets	4 years
Gains or losses includible in cost amortized to extent exceeds benefit obligations or market-related value of plan assets, percentage	10.00%
Anticipated Contributions to pension plans for qualified trust	$ 26.0
Anticipated contributions to pension plans for non-qualified plans	$ 0.5
Medical insurance available until age is reached after early retirement	65 years
Amortization period for transition obligation excluded from postretirement benefit cost	20 years
Recovery in rates for postretirement benefit				$ 9.5
Laclede Gas
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments recognized as settlements	$ 58.2
Recovery in rates for the qualified pension plans base allowance				$ 15.5
Other Plans [Abstract]
401(K) plans, cost of defined contributions	8.0	6.7	$ 5.0
Alagasco
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments recognized as settlements	12.9
Other Plans [Abstract]
401(K) plans, cost of defined contributions	3.0	4.7	7.1
Missouri Gas Energy (MGE)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Recovery in rates for the qualified pension plans base allowance					$ 10.0
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments recognized as settlements	71.1	$ 22.1	$ 79.5
Pension Plans \| Laclede Gas
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments recognized as settlements	58.2
Pension Plans \| Alagasco
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Lump-sum payments recognized as settlements	$ 12.9
Postretirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current investment policy targets an asset allocation to equity securities	60.00%
Investment policy targets asset allocation to debt securities	40.00%
Anticipated contributions to the postretirement plans for qualified trusts	$ 14.3
Anticipated payment directly to participants in postretirement plan	$ 0.4