Increase in negotiated rate amount per day.

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- Definition

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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No definition available.

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Public utilities length of pipeline.

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- Definition

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 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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Revenue related to investments.

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Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of public utility's approved rate increase (decrease) by regulatory agency.

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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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Regulatory Matters - Additional Information (Details) $ in Millions							6 Months Ended	7 Months Ended	9 Months Ended
	Jul. 15, 2019 USD ($)	May 03, 2019 USD ($)	Jan. 14, 2019 USD ($)	Nov. 30, 2018 USD ($)	Sep. 28, 2018 USD ($)	Apr. 25, 2018 USD ($)	Dec. 31, 2018 USD ($)	Jan. 31, 2019 USD ($)	Jun. 30, 2019 USD ($) mi $ / MMBTU	Jul. 09, 2019 USD ($)
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
Length of dual 20-inch diameter pipeline \| mi									10.1
Spire Missouri
Public Utilities, General Disclosures [Line Items]
Increase in negotiated rate per day \| $ / MMBTU									2
Spire Alabama
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount									$ 0.0
Public utilities, requested rate increase (decrease), amount				$ 8.7
Subsequent Event \| Spire Alabama
Public Utilities, General Disclosures [Line Items]
Regulatory preferred stock and debt securities issuance, amount authorized										$ 100.0
Infrastructure System Replacement Surcharge \| Spire Missouri East
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount		$ 6.4			$ 2.6
Applications requests for the approval of revenue related to commission amount								$ 7.4
Infrastructure System Replacement Surcharge \| Spire Missouri West
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount		$ 6.8			$ 5.4
Applications requests for the approval of revenue related to commission amount								$ 7.4
Infrastructure System Replacement Surcharge \| Spire Missouri
Public Utilities, General Disclosures [Line Items]
Applications requests for the approval of revenue related to commission amount							$ 3.0
Public utilities, requested rate increase (decrease), amount			$ 3.2
Infrastructure System Replacement Surcharge \| Subsequent Event \| Spire Missouri
Public Utilities, General Disclosures [Line Items]
Applications requests for the approval of revenue related to commission amount	$ 14.4
Estimate of possible loss in the event does not get a favorable outcome in appeal	$ 11.0
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
Pension Cost \| Infrastructure System Replacement Surcharge \| MoPSC
Public Utilities, General Disclosures [Line Items]
Regulatory assets recovery						$ 28.8