Note 12 - Income Taxes - Summary of Federal and State Loss and Contribution and Tax Credit Carryforwards (Details) $ in Millions	Sep. 30, 2022 USD ($)
Federal and state loss carryforwards	$ 1,047.7
Contribution carryforwards	10.4
Tax credit carryforwards	4.6
Spire Missouri [Member]
Federal and state loss carryforwards	462.3
Contribution carryforwards	7.0
Tax credit carryforwards	3.4
Spire Alabama Inc [Member]
Federal and state loss carryforwards	556.7
Contribution carryforwards	0.4
Tax credit carryforwards	$ 0.0

Amount of charitable contribution carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

No definition available.

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- Definition

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32559-109319

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- Definition

The amount of the tax credit carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

+ Details

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- Details

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- Details

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