XML 115 R96.htm IDEA: XBRL DOCUMENT
v3.20.2

Pension Plans and Other Postretirement Benefits - Schedule of Targeted and Actual Plan Assets by Category (Details) | Sep. 30, 2020 | Sep. 30, 2019
--- | --- | ---
Spire Missouri | Pension Plans |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 100.00% | 100.00%
Actual allocation of plan assets | 100.00% | 100.00%
Spire Missouri | Pension Plans | Return Seeking Assets |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 70.00% | 56.50%
Actual allocation of plan assets | 70.00% | 57.00%
Spire Missouri | Pension Plans | Liability Hedging Assets |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 30.00% | 43.50%
Actual allocation of plan assets | 27.00% | 39.80%
Spire Missouri | Pension Plans | Other |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 0.00% | 0.00%
Actual allocation of plan assets | 3.00% | 3.20%
Spire Missouri | Other Postretirement Plans |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 100.00% |
Actual allocation of plan assets | 100.00% | 100.00%
Spire Missouri | Other Postretirement Plans | Other |  |
Targeted and actual plan assets by category [Abstract] |  |
Actual allocation of plan assets | 4.80% | 2.80%
Spire Missouri | Other Postretirement Plans | Equity markets |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 60.00% |
Actual allocation of plan assets | 57.40% | 58.40%
Spire Missouri | Other Postretirement Plans | Debt securities |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 40.00% |
Actual allocation of plan assets | 37.80% | 38.80%
Spire Alabama | Pension Plans |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 100.00% | 100.00%
Actual allocation of plan assets | 100.00% | 100.00%
Spire Alabama | Pension Plans | Return Seeking Assets |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 70.00% | 60.00%
Actual allocation of plan assets | 71.00% | 58.50%
Spire Alabama | Pension Plans | Liability Hedging Assets |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 30.00% | 29.00%
Actual allocation of plan assets | 27.00% | 29.80%
Spire Alabama | Pension Plans | Other |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 0.00% | 11.00%
Actual allocation of plan assets | 2.00% | 11.70%
Spire Alabama | Other Postretirement Plans |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 100.00% |
Actual allocation of plan assets | 100.00% | 100.00%
Spire Alabama | Other Postretirement Plans | Equity markets |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 60.00% |
Actual allocation of plan assets | 61.80% | 60.30%
Spire Alabama | Other Postretirement Plans | Debt securities |  |
Targeted and actual plan assets by category [Abstract] |  |
Targeted allocation of plan assets | 40.00% |
Actual allocation of plan assets | 38.20% | 39.70%

X
- References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanAssetsTargetAllocationsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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 -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix: | us-gaap_
Data Type: | num: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 -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
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=sr_OtherSecuritiesMember
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_EquitySecuritiesMember
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: |

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