XML 112 R92.htm IDEA: XBRL DOCUMENT
v3.25.3

Pension Plans and Other Postretirement Benefits - Targeted and Actual Plan Assets by Category (Details) | Sep. 30, 2025 | Sep. 30, 2024
--- | --- | ---
Pension Plan [Member] | Spire Missouri [Member] |  |
Return seeking assets, target | 100.00% | 100.00%
Return seeking assets, actual | 100.00% | 100.00%
Pension Plan [Member] | Spire Missouri [Member] | Return Seeking Assets [Member] |  |
Return seeking assets, target | 70.00% | 70.00%
Return seeking assets, actual | 56.60% | 71.30%
Pension Plan [Member] | Spire Missouri [Member] | Liability Hedging Assets [Member] |  |
Return seeking assets, target | 30.00% | 30.00%
Return seeking assets, actual | 40.40% | 24.30%
Pension Plan [Member] | Spire Missouri [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] |  |
Return seeking assets, target | 0.00% | 0.00%
Return seeking assets, actual | 3.00% | 4.40%
Pension Plan [Member] | Spire Alabama Inc [Member] |  |
Return seeking assets, target | 100.00% | 100.00%
Return seeking assets, actual | 100.00% | 100.00%
Pension Plan [Member] | Spire Alabama Inc [Member] | Return Seeking Assets [Member] |  |
Return seeking assets, target | 75.00% | 75.00%
Return seeking assets, actual | 72.00% | 74.90%
Pension Plan [Member] | Spire Alabama Inc [Member] | Liability Hedging Assets [Member] |  |
Return seeking assets, target | 25.00% | 25.00%
Return seeking assets, actual | 16.80% | 22.60%
Pension Plan [Member] | Spire Alabama Inc [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] |  |
Return seeking assets, target | 0.00% | 0.00%
Return seeking assets, actual | 11.20% | 2.50%
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member] |  |
Return seeking assets, target | 100.00% |
Return seeking assets, actual | 100.00% | 100.00%
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member] | Defined Benefit Plan, Equity Securities [Member] |  |
Return seeking assets, target | 60.00% |
Return seeking assets, actual | 58.60% | 60.80%
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member] | Debt Securities [Member] |  |
Return seeking assets, target | 40.00% |
Return seeking assets, actual | 36.00% | 38.20%
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] |  |
Return seeking assets, target | 0.00% |
Return seeking assets, actual | 5.40% | 1.00%
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member] |  |
Return seeking assets, target | 100.00% |
Return seeking assets, actual | 100.00% | 100.00%
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member] | Defined Benefit Plan, Equity Securities [Member] |  |
Return seeking assets, target | 60.50% |
Return seeking assets, actual | 60.90% | 60.70%
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member] | Debt Securities [Member] |  |
Return seeking assets, target | 39.50% |
Return seeking assets, actual | 39.10% | 39.30%

X
- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=sr_ReturnSeekingAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=sr_LiabilityHedgingAssetsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanCashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |