Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Operating Activities:
Net Income	$ 250.9	$ 217.5	$ 220.8
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	278.4	254.8	237.3
Deferred income taxes and investment tax credits	57.0	36.9	57.9
Changes in assets and liabilities:
Accounts receivable	12.7	334.2	(26.5)
Inventories	15.8	142.8	(117.2)
Regulatory assets and liabilities	341.4	(68.7)	(409.0)
Accounts payable	(25.1)	(389.2)	190.7
Delayed/advance customer billings, net	37.5	1.5	(25.5)
Taxes accrued	1.1	15.0	11.2
Other assets and liabilities	(65.6)	(117.6)	(93.5)
Other	8.3	13.0	8.8
Net cash provided by operating activities	912.4	440.2	55.0
Delayed/advance customer billings	37.5	1.5	(25.5)
Investing Activities:
Capital expenditures	(861.3)	(662.5)	(552.2)
Business acquisition, net of cash acquired	(175.9)	(37.0)	0.0
Other	10.0	4.0	5.5
Net cash used in investing activities	(1,027.2)	(695.5)	(546.7)
Financing Activities:
Issuance of long-term debt	495.0	755.0	300.0
Repayment of long-term debt	(456.6)	(281.2)	(55.8)
(Repayment) Issuance of short-term debt, net	(8.5)	(82.0)	365.5
Issuance of common stock	287.0	41.9	51.9
Dividends paid on common stock	(167.1)	(150.7)	(141.9)
Dividends paid on preferred stock	(14.8)	(14.8)	(14.8)
Other financing activities	(11.1)	(7.6)	(4.0)
Net cash provided by financing activities	123.9	260.6	500.9
Net Increase in Cash, Cash Equivalents, and Restricted Cash	9.1	5.3	9.2
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	25.8	20.5	11.3
Cash, Cash Equivalents, and Restricted Cash at End of Year	34.9	25.8	20.5
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(205.6)	(177.5)	(119.9)
Income taxes	(0.9)	(2.0)	(1.8)
Spire Missouri [Member]
Operating Activities:
Net Income	118.4	117.5	114.9	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	174.0	158.7	145.3
Deferred income taxes and investment tax credits	14.8	11.6	21.3
Changes in assets and liabilities:
Accounts receivable	(14.2)	16.0	163.8
Inventories	3.0	80.2	(45.4)
Regulatory assets and liabilities	310.8	(22.4)	(314.3)
Accounts payable	(5.3)	(45.7)	25.3
Delayed/advance customer billings, net	36.7	2.2	(26.4)
Taxes accrued	0.1	9.7	9.3
Other assets and liabilities	(65.2)	(108.4)	(48.0)
Other	1.4	1.7	1.4
Net cash provided by operating activities	574.5	221.1	47.2
Delayed/advance customer billings	36.7	2.2	(26.4)
Investing Activities:
Capital expenditures	(553.0)	(447.5)	(354.1)
Other	6.7	4.1	3.6
Net cash used in investing activities	(546.3)	(443.4)	(350.5)
Financing Activities:
Issuance of long-term debt	320.0	400.0	300.0
Repayment of long-term debt	(300.0)	(250.0)	0.0
(Repayment) Issuance of short-term debt, net	0.0	0.0	(250.0)
Issuance of common stock	0.0	38.7	51.1
Dividends paid on common stock	0.0	(57.0)	0.0
Other financing activities	(3.7)	(3.9)	(2.2)
Net cash provided by financing activities	(29.0)	223.1	303.3
Net Increase in Cash, Cash Equivalents, and Restricted Cash	(0.8)	0.8	0.0
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	0.8	0.0	0.0
Cash, Cash Equivalents, and Restricted Cash at End of Year	0.0	0.8	0.0
(Repayments to) borrowings from Spire, net	(45.3)	95.3	204.4
(Repayments to) borrowings from Spire, net	(45.3)	95.3	204.4
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(111.6)	(93.8)	(58.9)
Income taxes	(0.4)	(0.2)	0.0
Spire Alabama Inc [Member]
Operating Activities:
Net Income	80.1	66.0	68.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	72.8	69.3	66.8
Deferred income taxes and investment tax credits	26.9	20.3	23.2
Changes in assets and liabilities:
Accounts receivable	8.0	27.1	(21.2)
Inventories	15.6	17.2	(42.5)
Regulatory assets and liabilities	49.3	(49.5)	(101.7)
Accounts payable	2.4	(42.3)	26.3
Delayed/advance customer billings, net	0.7	(0.6)	0.5
Taxes accrued	0.3	3.3	0.8
Other assets and liabilities	(8.6)	18.7	(3.7)
Other	0.4	0.4	0.2
Net cash provided by operating activities	247.9	129.9	17.2
Delayed/advance customer billings	0.7	(0.6)	0.5
Investing Activities:
Capital expenditures	(112.8)	(117.6)	(141.5)
Other	0.8	1.3	0.8
Net cash used in investing activities	(112.0)	(116.3)	(140.7)
Financing Activities:
Issuance of long-term debt	0.0	175.0	0.0
Repayment of long-term debt	0.0	0.0	(50.0)
Dividends paid on common stock	(53.4)	(21.0)	(24.0)
Other financing activities	0.0	(1.0)	0.0
Net cash provided by financing activities	(135.6)	(14.8)	125.9
Net Increase in Cash, Cash Equivalents, and Restricted Cash	0.3	(1.2)	2.4
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	1.2	2.4	0.0
Cash, Cash Equivalents, and Restricted Cash at End of Year	1.5	1.2	2.4
(Repayments to) borrowings from Spire, net	(75.7)	(136.8)	211.9
(Repayments to) borrowings from Spire, net	(75.7)	(136.8)	211.9
Return of capital to Spire	(6.5)	(31.0)	(12.0)
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(32.9)	(30.1)	(21.0)
Income taxes	$ 0.0	$ 0.0	$ 0.0

[1] Accumulated other comprehensive income (loss)