The amount of annual revenue increase from new rates.

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- Definition

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

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No definition available.

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Public utilities average base rate increase decrease percentage.

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- Definition

Public utilities average return on equity percentage

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Percentage of prior year revenues for maximum return on equity under public utilities.

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No definition available.

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- Definition

Public utility after-tax total rate of return, infrastructure system replacement surcharge.

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- Definition

Public utility rate base amount.

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- Definition

Under recovered bill.

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- Definition

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

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No definition available.

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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.

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No definition available.

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

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No definition available.

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

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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.

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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

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-Topic 980
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-Section 55
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478098/980-340-55-2

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Regulatory Matters - Additional Information (Details) - USD ($) $ in Millions								1 Months Ended	6 Months Ended
	Jun. 01, 2026	Feb. 19, 2026	Jan. 01, 2026	Dec. 01, 2025	Nov. 21, 2025	Jan. 01, 2025	Oct. 24, 2024	Feb. 28, 2025	Mar. 31, 2026	Oct. 24, 2025
Spire Alabama Inc [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, return on average common equity										9.94%
Spire Alabama Inc [Member] \| Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate, increase (decrease) annualized revenue	$ 2.9
Spire Alabama Inc [Member] \| Alabama Public Service Commission [Member]
Public Utilities, General Disclosures [Line Items]
Annual revenue increase from rates, amount				$ 12.9
Public Utilities Maximum Return on Equity Percentage of Prior Year Revenues									4.00%
Spire Gulf [Member]
Public Utilities, General Disclosures [Line Items]
Annual revenue increase from rates, amount				$ 2.9
Spire Mississippi [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate, increase (decrease) annualized revenue			$ 0.6			$ 0.6
Spire Missouri [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, request rate increase (decrease), amount							$ 210.0	$ 137.4
Public utilities, under recovered bill									$ 11.9
Public utility rate base amount									$ 4,379.6
Public utilities, requested rate increase (decrease), amount		$ 16.5			$ 30.3
Public utility after-tax total rate of return, infrastructure system replacement surcharge									7.05%
Spire Missouri [Member] \| Infrastructure System Replacement Surcharge [Member]
Public Utilities, General Disclosures [Line Items]
Public utilities, approved rate increase (decrease), amount								$ 72.6
Spire Tennessee [Member]
Public Utilities, General Disclosures [Line Items]
Average annual base rate increase									4.00%
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