Debt instrument interest rate reviving period.

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- Definition

Debt instrument maturity year.

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No definition available.

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- Definition

Debt instrument minimum resetting interest rate.

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No definition available.

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- Definition

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

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No definition available.

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- Definition

Maximum consolidated capitalization ratio percentage.

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- Definition

Percentage of change of control of principal and accrued interest.

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No definition available.

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- Definition

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

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No definition available.

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- Definition

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

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No definition available.

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- Definition

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

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

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Description of the payment terms of the debt instrument (for example, whether periodic payments include principal and frequency of payments) and discussion about any contingencies associated with the payment.

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Description of debt redemption features under terms of the debt agreement.

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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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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Date the credit facility terminates, in YYYY-MM-DD format.

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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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- Definition

The percentage rate used to calculate dividend payments on preferred stock.

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- Definition

Value of the difference between preference in liquidation and the par or stated values of the preferred shares.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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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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No definition available.

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Financing - Additional Information (Details) - USD ($)					3 Months Ended
Financing - Additional Information (Details) - USD ($)	Jan. 12, 2026	Dec. 17, 2025	Nov. 24, 2025	Oct. 23, 2025	Dec. 31, 2025	Sep. 30, 2025	Dec. 31, 2024
Short-Term Debt [Line Items]
Borrowings outstanding					$ 412,000,000	$ 1,317,000,000	$ 1,158,000,000
Subsequent Event [Member] \| Depositary Shares [Member]
Short-Term Debt [Line Items]
Preferred Stock, Shares Outstanding, Ending Balance	10,000,000
Subsequent Event [Member] \| Series A Preferred Stock [Member]
Short-Term Debt [Line Items]
Preferred stock percentage	5.90%
Aggregate liquidation preference	$ 250,000,000
6.375% Junior Subordinated Notes due 2086 [Member] \| Subsequent Event [Member]
Short-Term Debt [Line Items]
Debt Instrument face amount	$ 200,000,000
Debt instrument interest rate stated percentage	6.375%
Parent Company [Member] \| First Mortgage Bond [Member]
Short-Term Debt [Line Items]
Debt Instrument face amount				$ 200,000,000
Debt Instrument, Payment Terms				semi-annually on March 15 and September 15 of each year
Parent Company [Member] \| First Mortgage Bond [Member] \| Share-Based Payment Arrangement, Tranche One [Member]
Short-Term Debt [Line Items]
Debt Instrument face amount				$ 150,000,000
Debt instrument interest rate stated percentage				4.60%
Debt instrument maturity date				Sep. 15, 2030
Parent Company [Member] \| First Mortgage Bond [Member] \| Share-Based Payment Arrangement, Tranche Two [Member]
Short-Term Debt [Line Items]
Debt Instrument face amount				$ 50,000,000
Debt instrument interest rate stated percentage				4.65%
Debt instrument maturity date				Jan. 15, 2031
Commercial Paper [Member] \| Parent Company [Member]
Short-Term Debt [Line Items]
Borrowings outstanding					412,000,000	$ 1,317,000,000	$ 1,158,000,000
Short term borrowings used to support lending to utilities					224,100,000
Maximum [Member] \| Commercial Paper [Member]
Short-Term Debt [Line Items]
Borrowings outstanding					1,500,000,000
Spire [Member]
Short-Term Debt [Line Items]
Debt instrument redemption description			(i) at any time during the 90‑day period prior to the first reset date and (ii) on any interest payment date after the first reset date; they may also be redeemed at par within 120 days following a Tax Event or at 102% within 120 days following a Rating Agency Event, in each case plus accrued interest to (but excluding) the redemption date.
Maximum consolidated capitalization ratio percentage		70.00%
Percentage of change of control of principal and accrued interest		100.00%
Spire [Member] \| Junior Subordinated Notes [Member]
Short-Term Debt [Line Items]
Debt Instrument face amount			$ 900,000,000
Debt Instrument, Payment Terms			Interest is payable semiannually on June 1 and December 1, beginning June 1, 2026.
Debt instrument redemption price percentage			100.00%
Spire [Member] \| 2025 Series A Junior Subordinated Notes [Member]
Short-Term Debt [Line Items]
Debt Instrument face amount			$ 450,000,000
Debt instrument maturity year			2056
Debt instrument interest rate reviving period			5 years
Debt instrument basis spread on variable rate			2.556%
Debt instrument minimum resetting interest rate			6.25%
Debt instrument interest rate stated percentage			6.25%
Debt instrument maturity date			Jun. 01, 2031
Spire [Member] \| 2025 Series B Junior Subordinated Notes [Member]
Short-Term Debt [Line Items]
Debt Instrument face amount			$ 450,000,000
Debt instrument maturity year			2056
Debt instrument interest rate reviving period			5 years
Debt instrument basis spread on variable rate			2.327%
Debt instrument minimum resetting interest rate			6.45%
Debt instrument interest rate stated percentage			6.45%
Debt instrument maturity date			Jun. 01, 2036
Spire [Member] \| Series 2026 Senior Notes [Member] \| Master Note Purchase Agreement [Member]
Short-Term Debt [Line Items]
Debt Instrument face amount		$ 825,000,000
Spire [Member] \| Minimum [Member] \| Series 2026 Senior Notes [Member] \| Master Note Purchase Agreement [Member]
Short-Term Debt [Line Items]
Debt instrument interest rate stated percentage		4.59%
Debt instrument maturity date		Apr. 01, 2029
Spire [Member] \| Maximum [Member] \| Series 2026 Senior Notes [Member] \| Master Note Purchase Agreement [Member]
Short-Term Debt [Line Items]
Debt instrument interest rate stated percentage		5.44%
Debt instrument maturity date		Apr. 01, 2038
Revolving Credit Facility [Member]
Short-Term Debt [Line Items]
Line of credit facility maximum borrowing capacity					$ 1,500,000,000
Line of credit facility maturity date					Oct. 11, 2030
Line of credit facility covenant percentage of total capitalization					65.00%
Long-term line of credit					$ 0
Revolving Credit Facility [Member] \| Maximum [Member]
Short-Term Debt [Line Items]
Line of credit facility covenant percentage of total capitalization					70.00%
Revolving Credit Facility [Member] \| Spire [Member]
Short-Term Debt [Line Items]
Line of credit facility maximum borrowing capacity					$ 525,000,000
Revolving Credit Facility [Member] \| Spire Missouri [Member]
Short-Term Debt [Line Items]
Line of credit facility maximum borrowing capacity					700,000,000
Revolving Credit Facility [Member] \| Spire Alabama Inc [Member]
Short-Term Debt [Line Items]
Line of credit facility maximum borrowing capacity					$ 275,000,000