CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating Activities:
Net Income	$ 229.3	$ 276.3
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	115.8	102.3
Deferred income taxes and investment tax credits	59.1	68.5
Changes in assets and liabilities:
Accounts receivable	(3.4)	(342.3)
Inventories	136.9	14.0
Regulatory assets and liabilities	(230.5)	(6.7)
Accounts payable	(21.1)	141.3
Delayed/advance customer billings, net	(71.4)	(44.6)
Taxes accrued	(11.2)	(11.1)
Other assets and liabilities	(51.4)	(44.3)
Other	3.0	5.8
Accounts receivable	3.4	342.3
Inventories	(136.9)	(14.0)
Regulatory assets and liabilities	230.5	6.7
Delayed/advance customer billings, net	71.4	44.6
Other assets and liabilities	51.4	44.3
Net cash provided by operating activities	155.1	159.2
Investing Activities:
Capital expenditures	(275.9)	(303.5)
Other	2.7	(0.8)
Net cash used in investing activities	(273.2)	(304.3)
Capital expenditures	275.9	303.5
Other	(2.7)	0.8
Financing Activities:
Issuance of long-term debt	300.0	325.0
Repayment of long-term debt	(55.8)	(5.4)
(Repayment) issuance of short-term debt, net	(64.9)	5.5
Issuance of common stock	24.0	0.7
Dividends paid on common stock	(70.1)	(65.9)
Dividends paid on preferred stock	(7.4)	(7.4)
Other	(3.8)	(7.5)
Net cash provided by financing activities	122.0	245.0
Net Increase in Cash, Cash Equivalents, and Restricted Cash	3.9	99.9
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	11.3	4.1
Cash, Cash Equivalents, and Restricted Cash at End of Period	15.2	104.0
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(56.5)	(48.5)
Income taxes	(0.2)	(1.1)
Spire Missouri
Operating Activities:
Net Income	143.5	149.7
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	70.1	61.4
Deferred income taxes and investment tax credits	26.9	26.7
Changes in assets and liabilities:
Accounts receivable	18.2	(251.1)
Inventories	92.4	(18.7)
Regulatory assets and liabilities	(181.3)	(28.7)
Accounts payable	12.9	32.3
Delayed/advance customer billings, net	(70.8)	(46.5)
Taxes accrued	(3.8)	(9.7)
Other assets and liabilities	(41.7)	(50.3)
Other	0.7	0.3
Accounts receivable	(18.2)	251.1
Inventories	(92.4)	18.7
Regulatory assets and liabilities	181.3	28.7
Delayed/advance customer billings, net	70.8	46.5
Other assets and liabilities	41.7	50.3
Net cash provided by operating activities	67.1	(134.6)
Investing Activities:
Capital expenditures	(176.0)	(184.1)
Other	1.4	0.5
Net cash used in investing activities	(174.6)	(183.6)
Capital expenditures	176.0	184.1
Other	(1.4)	(0.5)
Financing Activities:
Issuance of long-term debt	300.0	0.0
(Repayment) issuance of short-term debt, net	(250.0)	250.0
Issuance of common stock	23.3	0.0
Borrowings from (repayments to) Spire, net	36.2	68.2
Other	(2.0)	0.0
Net cash provided by financing activities	107.5	318.2
Net 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	(28.3)	(22.9)
Income taxes	0.0	0.0
Spire Alabama
Operating Activities:
Net Income	74.6	77.0
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	33.2	30.2
Deferred income taxes and investment tax credits	25.1	26.1
Changes in assets and liabilities:
Accounts receivable	(34.9)	(33.7)
Inventories	1.3	6.2
Regulatory assets and liabilities	(50.7)	14.6
Accounts payable	7.4	9.9
Delayed/advance customer billings, net	(0.6)	(0.9)
Taxes accrued	(6.1)	(2.9)
Other assets and liabilities	(14.2)	(4.6)
Other	(0.1)	0.1
Accounts receivable	34.9	33.7
Inventories	(1.3)	(6.2)
Regulatory assets and liabilities	50.7	(14.6)
Delayed/advance customer billings, net	0.6	0.9
Other assets and liabilities	14.2	4.6
Net cash provided by operating activities	35.0	122.0
Investing Activities:
Capital expenditures	(71.0)	(78.9)
Lending to Spire, net of repayments	0.0	20.0
Other	0.6	0.3
Net cash used in investing activities	(70.4)	(98.6)
Capital expenditures	71.0	78.9
Other	(0.6)	(0.3)
Lending to Spire, net of repayments	0.0	(20.0)
Financing Activities:
Issuance of long-term debt	0.0	150.0
Repayment of long-term debt	(50.0)	0.0
Return of capital to Spire	(6.0)	(22.0)
Borrowings from (repayments to) Spire, net	107.6	(121.3)
Dividends paid on common stock	(16.0)	(11.0)
Other	0.0	(0.9)
Net cash provided by financing activities	35.6	(5.2)
Net Increase in Cash, Cash Equivalents, and Restricted Cash	0.2	18.2
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	0.0	0.0
Cash, Cash Equivalents, and Restricted Cash at End of Period	0.2	18.2
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(10.1)	(8.4)
Income taxes	$ 0.0	$ 0.0