Customer refund.

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- Definition

Gas supply adjustment decrease on annual basis.

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- Definition

Public utilities annual authorized revenue.

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Public utilities approved rate authorized future annualized revenue.

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Public utilities approved rate increase decrease costs from buildings sold excluded from rate base.

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Public utilities approved rate increase decrease in regulatory assets excluded from rate base.

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Public Utilities, Approved Rate Increase (Decrease), Rate Case Expenses Excluded From Rate Base

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Amount authorized by State regulatory for the issuance of debt securities, preferred stock, capital leases, and to issue common stock and receive paid-in capital which remains available to issue at period end.

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Remaining balance of customer refund impacts revenue and earnings.

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Remaining Recovery Period of Certain Regulatory Assets for which No Return on Investment During Recovery Period is Provided

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No definition available.

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- Definition

Amount charged against operating income increasing loss contingency liability, after adjustments to reduce previously estimated charges.

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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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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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Amount of expense (reversal of expense) which increases (decreases) the restructuring reserve from an adjustment to a previously accrued restructuring liability.

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Regulatory Matters - Additional Information (Details) - USD ($) $ in Millions					1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Aug. 04, 2020	Nov. 16, 2019	May 25, 2019	Apr. 25, 2018	Dec. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019	Mar. 24, 2020
Public Utilities, General Disclosures [Line Items]
Remaining recovery period for certain regulatory assets for which no return on investment during recovery period is provided (in years)									20 years
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided (in years)									15 years
Customer refund applied to provision accrued						$ (4.8)	$ 0.0		$ 0.0	$ 0.0
APSC \| Spire Alabama
Public Utilities, General Disclosures [Line Items]
Requested rate increase					$ 5.9
Gas supply adjustment decrease on annual basis									13.9
Regulatory preferred stock and debt securities issuance, amount authorized												$ 150.0
GPSC \| Spire Gulf
Public Utilities, General Disclosures [Line Items]
Requested rate increase					$ 1.6
Infrastructure System Replacement Surcharge \| MoPSC
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), costs from buildings sold in 2014 excluded from rate base				$ (1.8)
Rate case expenses				(0.9)
Infrastructure System Replacement Surcharge \| MoPSC \| Spire Missouri
Public Utilities, General Disclosures [Line Items]
Approved rate authorized future annualized revenue									$ 40.3
Payment of customer refund						15.0
Customer refund applied to provision accrued								$ 4.8			$ 12.2
Remaining balance impacts revenue and earnings						2.8
Accrued provision reversal amount						$ 2.0
Annual authorized revenue		$ 8.8	$ 12.4
Infrastructure System Replacement Surcharge \| MoPSC \| Spire Missouri \| Subsequent Event
Public Utilities, General Disclosures [Line Items]
Approved rate authorized future annualized revenue	$ 8.7
Pension Cost \| Infrastructure System Replacement Surcharge \| MoPSC
Public Utilities, General Disclosures [Line Items]
Regulatory assets recovery				$ (28.8)