CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities:
Net Income	$ 276.3	$ 200.6
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	102.3	96.7
Deferred income taxes and investment tax credits	68.5	42.8
Changes in assets and liabilities:
Accounts receivable	(342.3)	(64.4)
Inventories	14.0	69.5
Regulatory assets and liabilities	(6.7)	74.7
Accounts payable	141.3	(50.5)
Delayed/advance customer billings, net	(44.6)	(33.6)
Taxes accrued	(11.1)	(14.1)
Other assets and liabilities	(44.3)	0.1
Other	5.8	(0.1)
Net cash provided by operating activities	159.2	321.7
Investing Activities:
Capital expenditures	(303.5)	(346.1)
Other	(0.8)	1.5
Net cash used in investing activities	(304.3)	(344.6)
Financing Activities:
Issuance of long-term debt	325.0	510.0
Repayment of long-term debt	(5.4)	(140.0)
Issuance (repayment) of short-term debt, net	5.5	(182.6)
Issuance of common stock	0.7	15.2
Dividends paid on common stock	(65.9)	(63.8)
Dividends paid on preferred stock	(7.4)	(7.4)
Other	(7.5)	(5.9)
Net cash provided by financing activities	245.0	125.5
Net Increase in Cash, Cash Equivalents, and Restricted Cash	99.9	102.6
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	4.1	5.8
Cash and Cash Equivalents at End of Period	104.0	108.4
Supplemental disclosure of cash (paid) received for:
Interest, net of amounts capitalized	(48.5)	(46.7)
Income taxes	(1.1)	(1.7)
Spire Missouri
Operating Activities:
Net Income	149.7	122.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	61.4	58.3
Deferred income taxes and investment tax credits	26.7	16.4
Changes in assets and liabilities:
Accounts receivable	(251.1)	(67.6)
Inventories	(18.7)	39.3
Regulatory assets and liabilities	(28.7)	59.8
Accounts payable	32.3	6.8
Delayed/advance customer billings, net	(46.5)	(27.9)
Taxes accrued	(9.7)	(9.8)
Other assets and liabilities	(50.3)	(1.9)
Other	0.3	0.3
Net cash provided by operating activities	(134.6)	196.2
Investing Activities:
Capital expenditures	(184.1)	(183.2)
Other	0.5	0.3
Net cash used in investing activities	(183.6)	(182.9)
Financing Activities:
Issuance of long-term debt	0.0	275.0
Repayment of long-term debt	0.0	(100.0)
Issuance of short-term debt, net	250.0	185.1
Repayments to Spire, net	68.2	(346.8)
Dividends paid on common stock	0.0	(22.6)
Other	0.0	(1.5)
Net cash provided by financing activities	318.2	(10.8)
Net Increase in Cash, Cash Equivalents, and Restricted Cash	0.0	2.5
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	0.0	2.6
Cash and Cash Equivalents at End of Period	0.0	5.1
Supplemental disclosure of cash (paid) received for:
Interest, net of amounts capitalized	(22.9)	(21.6)
Income taxes	0.0	0.0
Spire Alabama
Operating Activities:
Net Income	77.0	71.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	30.2	28.9
Deferred income taxes and investment tax credits	26.1	23.9
Changes in assets and liabilities:
Accounts receivable	(33.7)	(27.9)
Inventories	6.2	18.3
Regulatory assets and liabilities	14.6	13.7
Accounts payable	9.9	(10.8)
Delayed/advance customer billings, net	(0.9)	(5.3)
Taxes accrued	(2.9)	(4.4)
Other assets and liabilities	(4.6)	(7.8)
Other	0.1	(2.5)
Net cash provided by operating activities	122.0	97.1
Investing Activities:
Capital expenditures	(78.9)	(75.8)
Lending to Spire, net of repayments	(20.0)	0.0
Other	0.3	(3.0)
Net cash used in investing activities	(98.6)	(78.8)
Financing Activities:
Issuance of long-term debt	150.0	100.0
Repayment of long-term debt	0.0	(40.0)
Issuance (repayment) of short-term debt, net	0.0	50.0
Return of capital to Spire	(22.0)	(20.0)
Repayments to Spire, net	(121.3)	(95.7)
Dividends paid on common stock	(11.0)	(12.0)
Other	(0.9)	(0.5)
Net cash provided by financing activities	(5.2)	(18.2)
Net Increase in Cash, Cash Equivalents, and Restricted Cash	18.2	0.1
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	0.0	0.0
Cash and Cash Equivalents at End of Period	18.2	0.1
Supplemental disclosure of cash (paid) received for:
Interest, net of amounts capitalized	(8.4)	(9.5)
Income taxes	$ 0.0	$ 0.0