Note 6 - Financing (Details Textual) - USD ($) $ in Thousands	Jan. 03, 2024	Dec. 31, 2023
Commercial Paper [Member] \| Parent Company [Member]
Short Term Borrowings Used to Support Lending to Utilities		$ 810,800
Spire Missouri [Member] \| Unsecured Term Loan [Member] \| London Interbank Offered Rate LIBOR 1 [Member]
Line of Credit Facility, Covenant, Percentage of Total Capitalization		65.00%
Spire Missouri [Member] \| Loans Payable [Member] \| Subsequent Event [Member]
Debt Instrument, Face Amount	$ 200,000
Debt Instrument, Interest Rate, Basis for Effective Rate	0.10%
Spire Missouri [Member] \| Loans Payable [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] \| Subsequent Event [Member]
Debt Instrument, Basis Spread on Variable Rate	0.90%
Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,300,000
Long-Term Line of Credit		$ 0
Revolving Credit Facility [Member] \| Maximum [Member]
Line of Credit Facility, Covenant, Percentage of Total Capitalization		70.00%
Revolving Credit Facility [Member] \| Spire [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 450,000
Revolving Credit Facility [Member] \| Spire Missouri [Member]
Line of Credit Facility, Maximum Borrowing Capacity		575,000
Revolving Credit Facility [Member] \| Spire Alabama Inc [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 275,000

Percentage of total capitalization in the covenant of line of credit facility.

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- Definition

Amount of short-term borrowing used to support lending to utilities.

+ References

No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Description of any adjustments made to the stated rate to determine the effective rate.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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