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Revenue - Additional Information (Details) $ in Millions | Feb. 28, 2021 USD ($)
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Spire Missouri |
Disaggregation Of Revenue [Line Items] |
Regulatory liability with a reduction in revenue | $ 25.0

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- Definition Regulatory liability with reduction in revenue. + References No definition available. + Details
Name: | sr_RegulatoryLiabilityWithReductionInRevenue
Namespace Prefix: | sr_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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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
Name: | us-gaap_DisaggregationOfRevenueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | dei_LegalEntityAxis=sr_SpireMissouriMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |