Public Utilities, Approved Rate Increase (Decrease), Annualized Revenue

No definition available.

Name:	sr_PublicUtilitiesApprovedRateIncreaseDecreaseAnnualizedRevenue
Namespace Prefix:	sr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Public utility rate base amount.

+ References

No definition available.

+ Details

Name:	sr_PublicUtilityRateBaseAmount
Namespace Prefix:	sr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Public utility, rate base, percentage change.

+ References

No definition available.

+ Details

Name:	sr_PublicUtilityRateBasePercentageChange
Namespace Prefix:	sr_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Regulatory asset percentage change of tariff

+ References

No definition available.

+ Details

Name:	sr_RegulatoryAssetPercentageChangeOfTariff
Namespace Prefix:	sr_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of public utility's requested equity to capital, including debt and equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedEquityCapitalStructurePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of public utility's amended requested rate increase (decrease) with regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmendedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of public utility's requested rate increase (decrease) with regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's requested return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 340
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478742/980-340-50-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 55
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478098/980-340-55-2

+ Details

Name:	us-gaap_RemainingRecoveryPeriodOfRegulatoryAssetsForWhichNoReturnOnInvestmentDuringRecoveryPeriodIsProvided1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	dei_LegalEntityAxis=sr_SpireAlabamaIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=sr_AlabamaPublicServiceCommissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=sr_SpireGulfMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=sr_SpireMississippiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=sr_MissouriPublicServiceCommissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=sr_InfrastructureSystemReplacementSurchargeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAssetAxis=sr_FutureIncomeTaxesDueFromCustomersAndPensionAndOtherPostretirementBenefitCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAssetAxis=sr_PgaAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAssetAxis=sr_PgaAssetsNotEarningAReturnMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Regulatory Matters - Additional Information (Details) - USD ($) $ in Millions									1 Months Ended	3 Months Ended	26 Months Ended
	Jan. 17, 2025	Jan. 01, 2025	Dec. 04, 2024	Dec. 01, 2024	Nov. 25, 2024	Jan. 01, 2024	Dec. 13, 2023	Dec. 01, 2023	Aug. 31, 2024	Dec. 31, 2024	Nov. 25, 2024	Nov. 15, 2024
Spire Alabama Inc [Member] \| Alabama Public Service Commission [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate, increase (decrease) annualized revenue				$ (4.0)		$ 14.3				$ (4.1)
Spire Gulf [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate, increase (decrease) annualized revenue			$ 1.3				$ 2.7	$ (2.0)
Spire Mississippi [Member] \| Missouri Public Service Commission [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate, increase (decrease) annualized revenue						$ 1.0
Spire Mississippi [Member] \| Missouri Public Service Commission [Member] \| Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate, increase (decrease) annualized revenue		$ 0.6
Spire Missouri [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory asset, percentage change of tariff												30.00%
Public utilities, request rate increase (decrease), amount									$ 235.9
Public utility rate base amount					$ 4,386.0
Public utility, rate base, percentage change											32.00%
Public utilities, requested equity, percentage					55.00%
Public utilities, requested return on equity, percentage					10.50%
Public utilities, requested rate increase (decrease), amount					$ 289.5
Spire Missouri [Member] \| Infrastructure System Replacement Surcharge [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount									$ 53.6
Spire Missouri [Member] \| Infrastructure System Replacement Surcharge [Member] \| Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, requested rate increase (decrease), amount	$ 19.0
Future Income Taxes Due From Customers and Pension and Other Postretirement Benefit Costs [Member]
Public Utilities, General Disclosures [Line Items]
Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided (Year)										20 years
PGA Assets [Member]
Public Utilities, General Disclosures [Line Items]
Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided (Year)										1 year
PGA Assets Not Earning a Return [Member]
Public Utilities, General Disclosures [Line Items]
Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided (Year)										15 years