CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Operating Activities:
Net income	$ 271.7	$ 88.6	$ 184.6
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	213.1	197.3	181.7
Impairments	0.0	148.6	0.0
Deferred income taxes and investment tax credits	67.0	9.0	31.8
Changes in assets and liabilities:
Accounts receivable	(343.0)	36.2	2.7
Inventories	(111.0)	2.6	13.6
Regulatory assets and liabilities	76.6	0.6
Accounts payable	177.7	(43.1)	(6.4)
Delayed/advance customer billings, net	(12.4)	7.0	12.4
Taxes accrued	8.9	2.9	3.5
Other assets and liabilities	(116.1)	12.0	31.0
Other	17.3	8.2	(4.0)
Net cash provided by operating activities	249.8	469.9	450.9
Investing Activities:
Capital expenditures	(624.8)	(638.4)	(823.3)
Other business acquisitions			(7.9)
Other	2.8	6.8	(7.1)
Net cash used in investing activities	(622.0)	(631.6)	(838.3)
Financing Activities:
Issuance of preferred stock			242.0
Issuance of long-term debt	629.1	510.0	230.0
Repayment of long-term debt	(115.4)	(147.0)	(184.1)
Issuance (repayment) of short-term debt, net	24.0	(95.2)	189.6
Issuance of common stock	1.0	41.1	19.5
Dividends paid on common stock	(133.2)	(128.0)	(119.0)
Dividends paid on preferred stock	(14.8)	(14.8)	(3.4)
Other	(11.3)	(6.1)	(2.8)
Net cash provided by financing activities	379.4	160.0	371.8
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash	7.2	(1.7)	(15.6)
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	4.1	5.8	21.4
Cash, Cash Equivalents, and Restricted Cash at End of Year	11.3	4.1	5.8
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(98.7)	(100.0)	(102.4)
Income taxes	(1.5)	(2.9)	(2.7)
Spire Missouri
Operating Activities:
Net income	144.1	130.2	115.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	129.2	118.0	111.5
Deferred income taxes and investment tax credits	25.3	17.1	13.2
Changes in assets and liabilities:
Accounts receivable	(207.4)	(3.7)	(0.3)
Inventories	(79.0)	2.7	29.0
Regulatory assets and liabilities	35.9	27.3	32.7
Accounts payable	23.1	2.3	(8.4)
Delayed/advance customer billings, net	(13.0)	13.7	13.9
Taxes accrued	2.1	2.7	4.4
Other assets and liabilities	(115.0)	(6.1)	(2.6)
Other	0.7	0.6	5.2
Net cash provided by operating activities	(54.0)	304.8	313.6
Investing Activities:
Capital expenditures	(382.6)	(356.0)	(356.9)
Other	1.3	1.3	1.3
Net cash used in investing activities	(381.3)	(354.7)	(355.6)
Financing Activities:
Issuance of long-term debt	304.1	275.0	100.0
Repayment of long-term debt	(55.0)	(107.0)	(50.0)
Issuance (repayment) of short-term debt, net	250.0
(Repayments of) borrowings from Spire	(60.3)	(85.2)	41.1
Dividends paid on common stock		(33.9)	(48.5)
Other	(3.5)	(1.6)
Net cash provided by financing activities	435.3	47.3	42.6
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash		(2.6)	0.6
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year		2.6	2.0
Cash, Cash Equivalents, and Restricted Cash at End of Year			2.6
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(45.9)	(46.0)	(48.7)
Income taxes	0.0	0.0	0.0
Spire Alabama
Operating Activities:
Net income	73.8	65.7	60.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	62.1	59.3	56.2
Deferred income taxes and investment tax credits	25.0	22.0	20.5
Changes in assets and liabilities:
Accounts receivable	(17.8)	7.3	0.8
Inventories	(15.4)	11.9	(1.2)
Regulatory assets and liabilities	29.2	(23.5)	(28.2)
Accounts payable	14.0	(15.1)	4.5
Delayed/advance customer billings, net	0.5	(6.6)	(2.5)
Taxes accrued	2.5	0.6	(0.9)
Other assets and liabilities	(37.8)	18.9	34.8
Other	0.3	0.2	(3.2)
Net cash provided by operating activities	136.4	140.7	141.1
Investing Activities:
Capital expenditures	(169.8)	(150.4)	(174.5)
Other	0.7	1.6	(3.3)
Net cash used in investing activities	(169.1)	(148.8)	(177.8)
Financing Activities:
Issuance of long-term debt	150.0	100.0	90.0
Repayment of long-term debt	0.0	(40.0)	0.0
(Repayments of) borrowings from Spire	(72.4)	(7.4)	(13.8)
Return of capital to Spire	(22.0)	(20.0)	(20.0)
Dividends paid on common stock	(22.0)	(24.0)	(19.0)
Other	(0.9)	(0.5)	(0.5)
Net cash provided by financing activities	32.7	8.1	36.7
Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash	0.0	0.0	0.0
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	0.0	0.0	0.0
Cash, Cash Equivalents, and Restricted Cash at End of Year	0.0	0.0	0.0
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(17.9)	(19.0)	(19.2)
Income taxes	$ 0.0	$ 0.0	$ 0.0