Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Operating Activities:
Net Income	$ 95.0	$ 81.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	81.4	72.3
Deferred income taxes and investment tax credits	21.9	19.4
Changes in assets and liabilities:
Accounts receivable	(280.5)	(239.8)
Inventories	23.0	21.2
Regulatory assets and liabilities	17.9	36.7
Accounts payable	92.0	96.9
Delayed/advance customer billings, net	(14.1)	4.3
Taxes accrued	(45.3)	(43.8)
Other assets and liabilities	86.7	30.5
Other	3.0	2.1
Net cash provided by operating activities	81.0	81.1
Investing Activities:
Capital expenditures	(202.8)	(260.6)
Other	1.5	0.5
Net cash used in investing activities	(201.3)	(260.1)
Financing Activities:
Issuance of long-term debt, net	1,100.0	0.0
Repayment of long-term debt	7.5	7.0
(Repayment) issuance of short-term debt	(905.0)	211.0
Issuance of common stock	0.3	32.8
Dividends paid on common stock	(47.2)	(44.6)
Dividends paid on preferred stock	(3.7)	(3.7)
Debt issuance costs	(12.7)	0.0
Other	(5.2)	(2.5)
Net cash provided by financing activities	119.0	186.0
Net (Decrease) Increase in Cash, Cash Equivalents, and Restricted Cash	(1.3)	7.0
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	41.2	34.9
Cash, Cash Equivalents, and Restricted Cash at End of Period	39.9	41.9
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(34.3)	(34.1)
Income taxes	(1.3)	(0.2)
Spire Missouri [Member]
Operating Activities:
Net Income	77.2	53.4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	52.8	45.7
Deferred income taxes and investment tax credits	15.3	8.0
Changes in assets and liabilities:
Accounts receivable	(176.9)	(142.2)
Inventories	13.7	9.6
Regulatory assets and liabilities	22.0	46.5
Accounts payable	39.2	44.3
Delayed/advance customer billings, net	(13.9)	3.5
Taxes accrued	(38.2)	(34.9)
Other assets and liabilities	62.6	25.4
Other	0.5	0.3
Net cash provided by operating activities	54.3	59.6
Investing Activities:
Capital expenditures	(148.0)	(178.3)
Other	0.5	0.9
Net cash used in investing activities	(147.5)	(177.4)
Financing Activities:
Issuance of long-term debt, net	200.0	0.0
(Repayments to) Borrowings from Spire, net	(100.6)	85.6
Issuance of common stock	0.0	32.2
Dividends paid	5.0	0.0
Other	(1.2)	0.0
Net cash provided by financing activities	93.2	117.8
Net (Decrease) Increase in Cash, Cash Equivalents, and Restricted Cash	(0.0)	0.0
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	0.0	0.0
Cash, Cash Equivalents, and Restricted Cash at End of Period	0.0	0.0
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(18.9)	(20.2)
Income taxes	(0.1)	0.0
Spire Alabama Inc [Member]
Operating Activities:
Net Income	19.6	15.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17.4	17.8
Deferred income taxes and investment tax credits	6.5	5.2
Changes in assets and liabilities:
Accounts receivable	(41.6)	(29.0)
Inventories	7.0	5.3
Regulatory assets and liabilities	(4.3)	(7.0)
Accounts payable	16.7	12.8
Delayed/advance customer billings, net	(0.1)	0.7
Taxes accrued	(2.4)	(3.6)
Other assets and liabilities	2.0	3.9
Other	0.1	0.1
Net cash provided by operating activities	20.9	21.9
Investing Activities:
Capital expenditures	(41.3)	(34.5)
Net cash used in investing activities	(41.3)	(34.5)
Financing Activities:
(Repayments to) Borrowings from Spire, net	34.5	18.6
Dividends paid on common stock	(16.0)	(7.5)
Net cash provided by financing activities	18.5	11.1
Net (Decrease) Increase in Cash, Cash Equivalents, and Restricted Cash	(1.9)	(1.5)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	1.9	1.5
Cash, Cash Equivalents, and Restricted Cash at End of Period	0.0	0.0
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(9.4)	(9.6)
Income taxes	$ 0.0	$ 0.0