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- Definition

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

+ References

No definition available.

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(1)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan.

+ References

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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- Definition

Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS - Assumptions Used to Calculate Net Periodic Cost and Benefit Obligations (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2018
Spire Missouri East \| Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.75%	3.50%	4.40%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.30%	3.75%
Spire Missouri East \| Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.60%	3.15%	4.00%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.30%	3.60%
Spire Missouri East \| Postretirement Plans \| Minimum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	5.75%	6.00%	6.25%
Spire Missouri East \| Postretirement Plans \| Maximum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	7.75%	7.75%	7.75%
Spire Missouri West \| Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.70%	3.50%	4.50%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.35%	3.70%
Spire Missouri West \| Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.60%	3.45%	4.30%
Expected long-term rate of return on plan assets	5.75%	5.50%	4.75%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.30%	3.60%
Spire Alabama \| Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%	3.00%
Expected long-term rate of return on plan assets	7.25%	7.25%	7.50%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.35%
Weighted average rate of future compensation increase	4.20%	3.65%
Spire Alabama \| Pension Plans \| Minimum
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.65%	3.45%	4.25%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate		3.65%
Spire Alabama \| Pension Plans \| Maximum
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.70%	3.50%	4.30%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate		3.70%
Spire Alabama \| Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average discount rate	3.80%	3.60%	4.50%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average discount rate	4.30%	3.80%
Spire Alabama \| Postretirement Plans \| Minimum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	3.75%	4.00%	4.50%
Spire Alabama \| Postretirement Plans \| Maximum
Assumptions used to calculate net periodic cost [Abstract]
Expected long-term rate of return on plan assets	6.00%	6.25%	7.25%
Spire Missouri \| Pension Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%	3.00%
Expected long-term rate of return on plan assets	7.75%	7.75%	7.75%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average rate of future compensation increase		3.70%		4.20%
Spire Missouri \| Postretirement Plans
Assumptions used to calculate net periodic cost [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%	3.00%
Assumptions used to calculate benefit obligations [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%
Laclede Gas, Alabama Gas Company, And Missouri Gas Energy \| Pension Plans
Assumptions used to calculate benefit obligations [Abstract]
Weighted average rate of future compensation increase	3.00%	3.00%