Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023		Dec. 31, 2022
Operating Activities:
Net Income	$ 85.1		$ 91.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	67.0		62.1
Deferred income taxes and investment tax credits	21.0		21.6
Changes in assets and liabilities:
Accounts receivable	(255.5)		(156.9)
Inventories	2.9		49.7
Regulatory assets and liabilities	91.7		(90.1)
Accounts payable	54.0		(96.7)
Delayed/advance customer billings, net	4.0		(7.2)
Taxes accrued	(42.3)		(32.1)
Other assets and liabilities	40.9		(15.6)
Other	1.2		3.4
Net cash provided by (used in) operating activities	70.0		(170.8)
Delayed/advance customer billings	4.0		(7.2)
Investing Activities:
Capital expenditures	(226.5)		(154.8)
Other	1.3		3.1
Net cash used in investing activities	(225.2)		(151.7)
Financing Activities:
Issuance of long-term debt	0.0		205.0
Repayment of long-term debt	(6.6)		(31.2)
Issuance of short-term debt, net	92.0		189.5
Issuance of common stock	113.2		0.4
Dividends paid on common stock	(38.8)		(36.3)
Dividends paid on preferred stock	(3.7)		(3.7)
Other financing activities	(1.4)		(2.7)
Net cash provided by financing activities	154.7		321.0
Net Decrease in Cash, Cash Equivalents, and Restricted Cash	(0.5)		(1.5)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	25.8		20.5
Cash, Cash Equivalents, and Restricted Cash at End of Period	25.3		19.0
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(44.3)		(36.9)
Income taxes	(0.3)		(0.3)
Spire Missouri [Member]
Operating Activities:
Net Income	57.0	[1]	47.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	42.1		38.6
Deferred income taxes and investment tax credits	9.6		8.1
Changes in assets and liabilities:
Accounts receivable	(190.9)		(208.5)
Inventories	(9.4)		24.4
Regulatory assets and liabilities	81.6		(61.5)
Accounts payable	34.6		66.4
Delayed/advance customer billings, net	4.4		(7.1)
Taxes accrued	(33.9)		(26.2)
Other assets and liabilities	54.1		13.2
Other	0.5		0.4
Net cash provided by (used in) operating activities	49.7		(104.9)
Delayed/advance customer billings	4.4		(7.1)
Investing Activities:
Capital expenditures	(144.7)		(102.0)
Other	1.5		1.0
Net cash used in investing activities	(143.2)		(101.0)
Financing Activities:
Net cash provided by financing activities	92.7		205.9
Net Decrease in Cash, Cash Equivalents, and Restricted Cash	(0.8)		0.0
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	0.8		0.0
Cash, Cash Equivalents, and Restricted Cash at End of Period	0.0		0.0
Borrowings from Spire, net	92.7		205.9
Borrowings from (Repayments to) Spire, net	92.7		205.9
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(25.7)		(21.0)
Income taxes	0.0		0.0
Spire Alabama Inc [Member]
Operating Activities:
Net Income	11.1		9.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17.9		17.0
Deferred income taxes and investment tax credits	3.9		3.2
Changes in assets and liabilities:
Accounts receivable	(29.4)		(29.5)
Inventories	12.0		5.6
Regulatory assets and liabilities	8.5		(29.7)
Accounts payable	7.4		10.9
Delayed/advance customer billings, net	(0.3)		(0.1)
Taxes accrued	(2.0)		(2.5)
Other assets and liabilities	2.1		15.1
Other	0.1		0.1
Net cash provided by (used in) operating activities	31.3		(0.7)
Delayed/advance customer billings	(0.3)		(0.1)
Investing Activities:
Capital expenditures	(22.3)		(38.2)
Other	0.3		0.1
Net cash used in investing activities	(22.0)		(38.1)
Financing Activities:
Issuance of long-term debt	0.0		175.0
Dividends paid on common stock	(14.0)		(11.0)
Other financing activities	0.0		(1.0)
Net cash provided by financing activities	(10.5)		36.4
Net Decrease in Cash, Cash Equivalents, and Restricted Cash	(1.2)		(2.4)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	1.2		2.4
Cash, Cash Equivalents, and Restricted Cash at End of Period	0.0		0.0
Borrowings from Spire, net	4.5		(115.1)
Borrowings from (Repayments to) Spire, net	4.5		(115.1)
Return of capital to Spire	(1.0)		(11.5)
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(10.9)		(5.8)
Income taxes	$ 0.0		$ 0.0

[1] Accumulated other comprehensive income (loss)