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

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://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

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- Definition

Amount of (increase) decrease to benefit obligation of defined benefit plan from remeasurement due to settlement. Excludes decrease to benefit obligation for settlement payment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 715
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-Section 50
-Paragraph 1
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-Publisher FASB
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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

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-Topic 715
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- Definition

Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Details

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- Details

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Pension Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Sep. 30, 2023
Pension Plan [Member]
Loss on lump-sum settlements	$ 0	$ 1,000,000	$ 0	$ 1,000,000
Spire Missouri [Member]
Weighted average discount rate	5.70%		5.70%		6.25%
Lump-sum payments settlement			$ 2,600,000
Loss on lump-sum settlements			1,000,000
Spire Missouri [Member] \| Pension Plan [Member]
Loss on lump-sum settlements	$ 0	$ 1,000,000	0	$ 1,000,000
Spire Missouri [Member] \| Pension Plan [Member] \| Qualified Plan [Member]
Defined benefit plan, plan assets, contributions by employer			31,100,000
Anticipated contributions to pension plans qualified trusts			4,400,000
Spire Missouri [Member] \| Pension Plan [Member] \| Nonqualified Plan [Member]
Defined benefit plan, plan assets, contributions by employer			0
Spire Missouri [Member] \| Other Postretirement Benefits Plan [Member]
Defined benefit plan, plan assets, contributions by employer	2,500,000		2,500,000
Anticipated contributions to pension plans qualified trusts			0
Spire Alabama Inc [Member] \| Pension Plan [Member]
Defined benefit plan, plan assets, contributions by employer			21,000,000
Anticipated contributions to pension plans qualified trusts			2,800,000
Spire Alabama Inc [Member] \| Other Postretirement Benefits Plan [Member]
Defined benefit plan, plan assets, contributions by employer	$ 0		0
Anticipated contributions to pension plans qualified trusts			$ 0