Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Operating Activities:
Net Income	$ 81.3	$ 85.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	72.3	67.0
Deferred income taxes and investment tax credits	19.4	21.0
Changes in assets and liabilities:
Accounts receivable	(239.8)	(255.5)
Inventories	21.2	2.9
Regulatory assets and liabilities	36.7	91.7
Accounts payable	96.9	54.0
Delayed/advance customer billings, net	4.3	4.0
Taxes accrued	(43.8)	(42.3)
Other assets and liabilities	30.5	40.9
Other	2.1	1.2
Net cash provided by operating activities	81.1	70.0
Investing Activities:
Capital expenditures	(260.6)	(226.5)
Other	0.5	1.3
Net cash used in investing activities	(260.1)	(225.2)
Financing Activities:
Repayment of long-term debt	(7.0)	(6.6)
Issuance of short-term debt, net	211.0	92.0
Issuance of common stock	32.8	113.2
Dividends paid on common stock	(44.6)	(38.8)
Dividends paid on preferred stock	(3.7)	(3.7)
Other	(2.5)	(1.4)
Net cash provided by financing activities	186.0	154.7
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash	7.0	(0.5)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	34.9	25.8
Cash, Cash Equivalents, and Restricted Cash at End of Period	41.9	25.3
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(34.1)	(44.3)
Income taxes	(0.2)	(0.3)
Spire Missouri [Member]
Operating Activities:
Net Income	53.4	57.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	45.7	42.1
Deferred income taxes and investment tax credits	8.0	9.6
Changes in assets and liabilities:
Accounts receivable	(142.2)	(190.9)
Inventories	9.6	(9.4)
Regulatory assets and liabilities	46.5	81.6
Accounts payable	44.3	34.6
Delayed/advance customer billings, net	3.5	4.4
Taxes accrued	(34.9)	(33.9)
Other assets and liabilities	25.4	54.1
Other	0.3	0.5
Net cash provided by operating activities	59.6	49.7
Investing Activities:
Capital expenditures	(178.3)	(144.7)
Other	0.9	1.5
Net cash used in investing activities	(177.4)	(143.2)
Financing Activities:
Issuance of long-term debt	32.2	0.0
Borrowings from Spire, net	85.6	92.7
Net cash provided by financing activities	117.8	92.7
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash	0.0	(0.8)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	0.0	0.8
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	(20.2)	(25.7)
Income taxes	0.0	0.0
Spire Alabama Inc [Member]
Operating Activities:
Net Income	15.7	11.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17.8	17.9
Deferred income taxes and investment tax credits	5.2	3.9
Changes in assets and liabilities:
Accounts receivable	(29.0)	(29.4)
Inventories	5.3	12.0
Regulatory assets and liabilities	(7.0)	8.5
Accounts payable	12.8	7.4
Delayed/advance customer billings, net	0.7	(0.3)
Taxes accrued	(3.6)	(2.0)
Other assets and liabilities	3.9	2.1
Other	0.1	0.1
Net cash provided by operating activities	21.9	31.3
Investing Activities:
Capital expenditures	(34.5)	(22.3)
Other	0.0	0.3
Net cash used in investing activities	(34.5)	(22.0)
Financing Activities:
Borrowings from Spire, net	18.6	4.5
Return of capital to Spire	0.0	(1.0)
Dividends paid on common stock	(7.5)	(14.0)
Net cash provided by financing activities	11.1	(10.5)
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash	(1.5)	(1.2)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	1.5	1.2
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	(9.6)	(10.9)
Income taxes	$ 0.0	$ 0.0