Spire (SR) 10-K 16 Nov 23 2023 Q2 Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2023	Nov. 10, 2023	Mar. 31, 2023
Document Information [Line Items]
Entity Central Index Key	0001126956
Entity Registrant Name	Spire Inc.
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	1-16681
Entity Address, Address Line One	700 Market Street
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63101
City Area Code	314
Local Phone Number	342-0500
Entity Incorporation, State or Country Code	MO
Entity Tax Identification Number	74-2976504
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 3,580,140,878
Entity Common Stock, Shares Outstanding		53,176,840
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	St. Louis, Missouri
Spire Missouri [Member]
Document Information [Line Items]
Entity Central Index Key	0000057183
Entity Registrant Name	Spire Missouri Inc.
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2023
Entity File Number	1-1822
Entity Address, Address Line One	700 Market Street
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63101
City Area Code	314
Local Phone Number	342-0500
Entity Incorporation, State or Country Code	MO
Entity Tax Identification Number	43-0368139
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		25,855
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	St. Louis, Missouri
Spire Alabama Inc [Member]
Document Information [Line Items]
Entity Central Index Key	0000003146
Entity Registrant Name	Spire Alabama Inc.
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2023
Entity File Number	2-38960
Entity Address, Address Line One	605 Richard Arrington Blvd N
Entity Address, City or Town	Birmingham
Entity Address, State or Province	AL
Entity Address, Postal Zip Code	35203
City Area Code	205
Local Phone Number	326-8100
Entity Incorporation, State or Country Code	AL
Entity Tax Identification Number	63-0022000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		1,972,052
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	St. Louis, Missouri
Depositary Shares [Member]
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/1,000th interest in a share of 5.90% Series A Cumulative Redeemable Perpetual
Trading Symbol	SR.PRA
Security Exchange Name	NYSE
Common Stock [Member]
Document Information [Line Items]
Title of 12(b) Security	Common Stock $1.00 par value
Trading Symbol	SR
Security Exchange Name	NYSE

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2023		Sep. 30, 2022		Sep. 30, 2021
Operating Revenues	$ 2,666.3		$ 2,198.5		$ 2,235.5
Operating Expenses:
Natural gas	1,260.8		923.9		946.3
Operation and maintenance	517.6		449.6		465.8
Depreciation and amortization	254.8		237.3		213.1
Taxes, other than income taxes	214.5		179.5		160.1
Total Operating Expenses	2,247.7		1,790.3		1,785.3
Operating Income	418.6		408.2		450.2
Interest Expense	185.7		119.8		106.6
Other Income (Expense), Net	23.4		(8.7)		(3.4)
Income Before Income Taxes	256.3		279.7		340.2
Income Tax Expense	38.8		58.9		68.5
Net Income	217.5		220.8		271.7
Provision for preferred dividends	14.8		14.8		14.8
Income allocated to participating securities	0.3		0.3		0.4
Net Income Available to Common Shareholders	202.4		205.7		256.5
Other Comprehensive Income (Loss), Net of Tax	0.4		43.6		44.8
Comprehensive Income	217.9		264.4		316.5
Operating Revenues	$ 2,666.3		$ 2,198.5		$ 2,235.5
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	52.5		52		51.6
Diluted (in shares)	52.6		52.1		51.7
Basic Earnings Per Share of Common Stock (in dollars per share)	$ 3.86		$ 3.96		$ 4.97
Diluted Earnings Per Share of Common Stock (in dollars per share)	$ 3.85		$ 3.95		$ 4.96
Operating Revenues	$ 2,666.3		$ 2,198.5		$ 2,235.5
Spire Missouri [Member]
Operating Revenues	1,762.9		1,321		1,516.6
Operating Expenses:
Natural gas	943.4		587		786.8
Operation and maintenance	296.2		255.7		261.1
Depreciation and amortization	158.7		145.3		129.2
Taxes, other than income taxes	157.5		129		110.9
Total Operating Expenses	1,555.8		1,117		1,288
Operating Income	207.1		204		228.6
Interest Expense	97.4		60.9		50.3
Other Income (Expense), Net	19.4		(6.9)		(8.9)
Income Before Income Taxes	129.1		136.2		169.4
Income Tax Expense	11.6		21.3		25.3
Net Income	117.5		114.9		144.1	[1]
Other Comprehensive Income (Loss), Net of Tax	0.2	[1]	1.5	[1]	(1.3)
Comprehensive Income	117.7		116.4		142.8
Operating Revenues	1,762.9		1,321		1,516.6
Weighted Average Number of Common Shares Outstanding:
Operating Revenues	1,762.9		1,321		1,516.6
Spire Alabama Inc [Member]
Operating Revenues	571.1		509.1		494
Operating Expenses:
Natural gas	202.7		161.5		145.3
Operation and maintenance	136.4		130.1		132.5
Depreciation and amortization	69.3		66.8		62.1
Taxes, other than income taxes	43		38.1		37.1
Total Operating Expenses	451.4		396.5		377
Operating Income	119.7		112.6		117
Interest Expense	34.9		21.3		20.2
Other Income (Expense), Net	1.5		0.4		2
Income Before Income Taxes	86.3		91.7		98.8
Income Tax Expense	20.3		23.2		25
Net Income	66		68.5		73.8
Operating Revenues	571.1		509.1		494
Weighted Average Number of Common Shares Outstanding:
Operating Revenues	$ 571.1		$ 509.1		$ 494
[1]Accumulated other comprehensive income (loss)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Net Income	$ 217.5	$ 220.8	$ 271.7
Other Comprehensive Income, Before Tax:
Net hedging gain arising during the period	20.1	56.7	61.2
Amounts reclassified into regulatory liabilities	(17.5)	0	0
Amounts reclassified into net income	(2.4)	(1.2)	(1.3)
Net gain on cash flow hedging derivative instruments	0.2	55.5	59.9
Net gain (loss) on defined benefit pension and other postretirement plans	0.2	1.5	(1.3)
Net unrealized gain (loss) on available-for-sale debt securities	0.1	(0.4)	(0.2)
Other Comprehensive Income, Before Tax	0.5	56.6	58.4
Income Tax Expense Related to Items of Other Comprehensive Income	0.1	13	13.6
Other Comprehensive Income, Net of Tax	0.4	43.6	44.8
Comprehensive Income	$ 217.9	$ 264.4	$ 316.5

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Sep. 30, 2023	Sep. 30, 2022
ASSETS
Utility Plant		$ 8,210.1	$ 7,664.9
Less: Accumulated depreciation and amortization		2,431.2	2,294.5
Net Utility Plant		5,778.9	5,370.4
Non-utility Property (net of accumulated depreciation and amortization of $71.1 and $50.7 at September 30, 2023 and 2022, respectively)		628.5	491.4
Other Investments		102.6	87.8
Total Other Property and Investments		731.1	579.2
Other Property and Investments		731.1	579.2
Current Assets:
Cash and cash equivalents		5.6	6.5
Utility		192.4	210.8
Other		128.6	443.8
Allowance for credit losses		(32.5)	(31.9)
Delayed customer billings		22	21.3
Accounts receivable:
Utility		192.4	210.8
Other		128.6	443.8
Allowance for credit losses		(32.5)	(31.9)
Delayed customer billings		22	21.3
Inventories:
Natural gas		223.7	371.8
Propane gas		8.6	8.6
Materials and supplies		47.2	41.9
Regulatory assets		348.3	355.4
Prepayments		48.2	41.1
Other current assets		84.8	122.7
Total Current Assets		1,076.9	1,592
Deferred Charges and Other Assets:
Goodwill		1,171.6	1,171.6
Regulatory assets		1,249.2	1,112.4
Other		305.9	258.1
Total Deferred Charges and Other Assets		2,726.7	2,542.1
Total Assets		10,313.6	10,083.7
Capitalization:
Common stock value		53.2	52.5
Paid-in capital		1,616.5	1,571.3
Retained earnings		958	905.5
Accumulated other comprehensive income		47.6	47.2
Total Shareholders' Equity		2,917.3	2,818.5
Temporary equity		16.5	13.1
Long-term debt (less current portion)		3,554	2,958.5
Total Capitalization		6,487.8	5,790.1
Current Liabilities:
Current portion of long-term debt		156.6	281.2
Notes payable		955.5	1,037.5
Accounts payable		253.1	617.4
Advance customer billings		20.9	18.7
Wages and compensation accrued		47	50.2
Customer deposits		27.7	28.2
Taxes accrued		104.1	90.1
Regulatory liabilities		7.3	3.7
Other current liabilities		183.2	226.6
Total Current Liabilities		1,755.4	2,353.6
Deferred Credits and Other Liabilities:
Deferred income taxes		743.7	675.1
Pension and postretirement benefit costs		137.3	163
Asset retirement obligations		577.4	520.9
Regulatory liabilities		472.4	418.2
Other noncurrent liabilities		139.6	162.8
Total Deferred Credits and Other Liabilities		2,070.4	1,940
Commitments and Contingencies (Note 16)
Total Capitalization and Liabilities		10,313.6	10,083.7
Depositary Shares [Member]
Capitalization:
Preferred stock ($25.00 par value per share; 10.0 million depositary shares authorized, issued and outstanding at September 30, 2023 and 2022)		242	242
Spire Missouri [Member]
ASSETS
Utility Plant		4,964.9	4,550.4
Less: Accumulated depreciation and amortization		1,043.2	982.1
Net Utility Plant		3,921.7	3,568.3
Total Other Property and Investments		65.7	58.9
Other Property and Investments		65.7	58.9
Current Assets:
Cash and cash equivalents		0.8	0
Utility		142.6	131.5
Other		21.1	44.5
Allowance for credit losses		(26.2)	(24.9)
Delayed customer billings		17.9	16.1
Accounts receivable:
Utility		142.6	131.5
Other		21.1	44.5
Allowance for credit losses		(26.2)	(24.9)
Delayed customer billings		17.9	16.1
Inventories:
Natural gas		132.8	215.3
Propane gas		8.6	8.6
Materials and supplies		24.2	22
Regulatory assets		293.1	288.1
Prepayments		26.7	23.3
Total Current Assets		642.9	728.2
Deferred Charges and Other Assets:
Goodwill		210.2	210.2
Regulatory assets		617.6	547.6
Other		147.4	105
Total Deferred Charges and Other Assets		975.2	862.8
Total Assets		5,605.5	5,218.2
Capitalization:
Common stock value		0.1	0.1
Paid-in capital		854.8	816.1
Retained earnings		992.4	931.9
Accumulated other comprehensive income		(2.5)	(2.7)
Total Shareholders' Equity	[1]	1,844.8	1,745.4
Long-term debt (less current portion)		1,785.4	1,387.7
Total Capitalization		3,630.2	3,133.1
Current Liabilities:
Current portion of long-term debt		0	250
Advance customer billings		11	7
Wages and compensation accrued		23.6	33.8
Customer deposits		5.8	6.5
Taxes accrued		60.3	50.4
Regulatory liabilities		0	0
Other current liabilities		48.7	45.6
Total Current Liabilities		786.3	970.9
Deferred Credits and Other Liabilities:
Deferred income taxes		531.8	500.1
Pension and postretirement benefit costs		103.3	115.5
Asset retirement obligations		111.1	110.6
Regulatory liabilities		389.4	331.8
Other noncurrent liabilities		53.4	56.2
Total Deferred Credits and Other Liabilities		1,189	1,114.2
Commitments and Contingencies (Note 16)
Total Capitalization and Liabilities		5,605.5	5,218.2
Spire Missouri [Member] | Related Party [Member]
Current Assets:
Utility		1.3	3.7
Accounts receivable:
Utility		1.3	3.7
Current Liabilities:
Notes payable		540.6	445.3
Accounts payable		10.5	13.3
Spire Missouri [Member] | Nonrelated Party [Member]
Current Liabilities:
Accounts payable		85.8	119
Spire Alabama Inc [Member]
ASSETS
Utility Plant		2,862.6	2,732.6
Less: Accumulated depreciation and amortization		1,273	1,184.1
Net Utility Plant		1,589.6	1,548.5
Current Assets:
Cash and cash equivalents		1.2	2.4
Utility		42.2	69.9
Other		6.6	6.5
Allowance for credit losses		(5.7)	(6.3)
Delayed customer billings		3.6	4.8
Accounts receivable:
Utility		42.2	69.9
Other		6.6	6.5
Allowance for credit losses		(5.7)	(6.3)
Delayed customer billings		3.6	4.8
Inventories:
Natural gas		52.4	72.5
Materials and supplies		19.1	16.3
Regulatory assets		41.6	56.9
Prepayments		6.4	5.8
Total Current Assets		168.6	230.1
Deferred Charges and Other Assets:
Regulatory assets		606.9	538.2
Other		84.2	81.3
Total Deferred Charges and Other Assets		691.1	630.5
Total Assets		2,449.3	2,409.1
Deferred income tax		0	11
Capitalization:
Retained earnings		642.1	589.1
Total Shareholders' Equity		928	906
Long-term debt (less current portion)		745.9	571.5
Total Capitalization		1,673.9	1,477.5
Common stock and paid-in capital (par value $0.01 per share; 3,000,000 shares authorized; 1,972,052 issued and outstanding at September 30, 2023 and 2022)		285.9	316.9
Current Liabilities:
Accounts payable		28.4	85.6
Advance customer billings		8.1	9.9
Wages and compensation accrued		6.6	7.6
Customer deposits		19.3	19
Taxes accrued		34.5	31.3
Regulatory liabilities		0	0
Other current liabilities		14.7	22.4
Total Current Liabilities		240.3	441.1
Deferred Credits and Other Liabilities:
Deferred income taxes		9.1	0
Pension and postretirement benefit costs		27.2	40.5
Asset retirement obligations		451	398.7
Regulatory liabilities		21.2	23
Other noncurrent liabilities		26.6	28.3
Total Deferred Credits and Other Liabilities		535.1	490.5
Commitments and Contingencies (Note 16)
Total Capitalization and Liabilities		2,449.3	2,409.1
Spire Alabama Inc [Member] | Related Party [Member]
Current Assets:
Utility		1.2	1.3
Accounts receivable:
Utility		1.2	1.3
Current Liabilities:
Notes payable		124.1	260.9
Accounts payable		$ 4.6	$ 4.4
[1]Accumulated other comprehensive income (loss)

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Non-utility property, accumulated depreciation and amortization	$ 71.1	$ 50.7
Preferred stock, shares authorized (in shares)	5,000,000
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	70,000,000	70,000,000
Common stock, shares issued (in shares)	53,200,000	52,500,000
Common Stock, shares outstanding (in shares)	53,200,000	52,500,000
Spire Missouri [Member]
Preferred stock, shares authorized (in shares)		1,480,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	25,855	25,325
Common Stock, shares outstanding (in shares)	25,855	25,325
Spire Alabama Inc [Member]
Preferred stock, shares authorized (in shares)	120,000	120,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	3,000,000	3,000,000
Common stock, shares issued (in shares)	1,972,052	1,972,052
Common Stock, shares outstanding (in shares)	1,972,052	1,972,052
Depositary Shares [Member]
Preferred stock, par value (in dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	10,000,000	10,000,000
Preferred stock, shares outstanding (in shares)	10,000,000	10,000,000

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Spire Missouri [Member] Common Stock [Member]	Spire Missouri [Member] Additional Paid-in Capital [Member]	Spire Missouri [Member] Retained Earnings [Member]	Spire Missouri [Member] AOCI Attributable to Parent [Member]	Spire Missouri [Member]		Spire Alabama Inc [Member] Common Stock [Member]	Spire Alabama Inc [Member] Additional Paid-in Capital [Member]	Spire Alabama Inc [Member] Retained Earnings [Member]	Spire Alabama Inc [Member]	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]		Total
Balance (in shares) at Sep. 30, 2020	24,577						1,972,052				51,611,789
Balance at Sep. 30, 2020	$ 0.1	$ 765	$ 672.9	$ (2.9)	$ 1,435.1	[1]	$ 0	$ 350.9	$ 500.8	$ 851.7	$ 51.6	$ 242	$ 1,549.2	$ 720.7	$ (41.2)	[1]	$ 2,522.3
Net Income	0	0	144.1	0	144.1	[1]	0	0	73.8	73.8	$ 0		0	271.7	0	[1]	271.7
Dividend reinvestment plan (in shares)											24,565
Dividend reinvestment plan											$ 0	0	1.6	0	0	[1]	1.6
Stock-based compensation costs											$ 0		9.1	0	0	[1]	9.1
Stock issued under stock-based compensation plans (in shares)											65,316
Stock issued under stock-based compensation plans											$ 0.1	0	(0.1)	0	0		0
Employees’ tax withholding for stock-based compensation (in shares)											(16,787)
Employees’ tax withholding for stock-based compensation											$ 0	0	(1.1)	0	0	[1]	(1.1)
Equity units issued											0	0	(40.8)	0	0		(40.8)
Temporary equity adjustment to redemption value											0		0	1.3	0	[1]	1.3
Common stock, dividends							0	0	(22)	(22)	0		0	(135.9)	0	[1]	(135.9)
Preferred stock dividends											0		0	(14.8)	0	[1]	(14.8)
Other Comprehensive Income (Loss), Net of Tax	$ 0	0	0	(1.3)	(1.3)						$ 0	0	0	0	44.8		44.8
Return of capital to Spire							$ 0	(22)	0	(22)
Balance (in shares) at Sep. 30, 2021	24,577						1,972,052				51,684,883
Balance at Sep. 30, 2021	$ 0.1	765	817	(4.2)	1,577.9	[1]	$ 0	328.9	552.6	881.5	$ 51.7	242	1,517.9	843	3.6	[1]	2,658.2
Net Income	0	0	114.9	0	114.9		0	0	68.5	68.5	$ 0	0	0	220.8	0		220.8
Dividend reinvestment plan (in shares)											24,154
Dividend reinvestment plan											$ 0	0	1.6	0	0		1.6
Stock-based compensation costs											$ 0	0	4.1	0	0		4.1
Stock issued under stock-based compensation plans (in shares)											93,936
Stock issued under stock-based compensation plans											$ 0.1	0	(0.1)	0	0		0
Employees’ tax withholding for stock-based compensation (in shares)											(28,055)
Employees’ tax withholding for stock-based compensation											$ 0	0	(1.8)	0	0		(1.8)
Common stock, dividends							0	0	(32)	(32)	0	0	0	(143.5)	0		(143.5)
Preferred stock dividends											0	0	0	(14.8)	0		(14.8)
Other Comprehensive Income (Loss), Net of Tax	$ 0	0	0	1.5	1.5	[1]					$ 0	0	0	0	43.6		43.6
Common stock issued (in shares)	748										719,625
Common stock issued	$ 0	51.1	0	0	51.1						$ 0.7	0	49.6	0	0		50.3
Return of capital to Spire							$ 0	(12)	0	(12)
Balance (in shares) at Sep. 30, 2022	25,325						1,972,052				52,494,543
Balance at Sep. 30, 2022	$ 0.1	816.1	931.9	(2.7)	1,745.4	[1]	$ 0	316.9	589.1	906	$ 52.5	242	1,571.3	905.5	47.2		2,818.5
Net Income	0	0	117.5	0	117.5		0	0	66	66	$ 0	0	0	217.5	0		217.5
Dividend reinvestment plan (in shares)											22,230
Dividend reinvestment plan											$ 0	0	1.5	0	0		1.5
Stock-based compensation costs											$ 0	0	5.3	0	0		5.3
Stock issued under stock-based compensation plans (in shares)											60,007
Stock issued under stock-based compensation plans											$ 0.1	0	(0.1)	0	0		0
Employees’ tax withholding for stock-based compensation (in shares)											(18,428)
Employees’ tax withholding for stock-based compensation											$ 0	0	(1.4)	0	0		(1.4)
Temporary equity adjustment to redemption value											0	0	0	2.3	0		2.3
Common stock, dividends	0	0	(57)	0	(57)		0	0	(13)	(13)	0	0	0	(152.5)	0		(152.5)
Preferred stock dividends											0	0	0	(14.8)	0		(14.8)
Other Comprehensive Income (Loss), Net of Tax	$ 0	0	0	0.2	0.2	[1]					$ 0	0	0	0	0.4		0.4
Common stock issued (in shares)	530										611,872
Common stock issued	$ 0	38.7	0	0	38.7						$ 0.6	0	39.9	0	0		40.5
Return of capital to Spire							$ 0	(31)	0	(31)
Balance (in shares) at Sep. 30, 2023	25,855						1,972,052				53,170,224
Balance at Sep. 30, 2023	$ 0.1	$ 854.8	$ 992.4	$ (2.5)	$ 1,844.8	[1]	$ 0	$ 285.9	$ 642.1	$ 928	$ 53.2	$ 242	$ 1,616.5	$ 958	$ 47.6		$ 2,917.3
[1]Accumulated other comprehensive income (loss)

Consolidated Statements of Sh_2

Consolidated Statements of Shareholders' Equity (Parentheticals) - $ / shares	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Common stock, dividends per share declared (in dollars per share)	$ 2.88	$ 2.74	$ 2.6
Preferred stock dividends per share declared (in dollars per share)	$ 1.475	$ 1.475	$ 1.475

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Operating Activities:
Net Income	$ 217.5	$ 220.8	$ 271.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	254.8	237.3	213.1
Deferred income taxes and investment tax credits	36.9	57.9	67
Changes in assets and liabilities:
Accounts receivable	334.2	(26.5)	(343)
Inventories	142.8	(117.2)	(111)
Regulatory assets and liabilities	(68.7)	(409)	76.6
Accounts payable	(389.2)	190.7	177.7
Delayed/advance customer billings, net	1.5	(25.5)	(12.4)
Taxes accrued	15	11.2	8.9
Other assets and liabilities	(117.6)	(93.5)	(116.1)
Other	13	8.8	17.3
Net cash provided by operating activities	440.2	55	249.8
Delayed/advance customer billings	1.5	(25.5)	(12.4)
Investing Activities:
Capital expenditures	(662.5)	(552.2)	(624.8)
Business acquisition	(37)	0	0
Other	4	5.5	2.8
Net cash used in investing activities	(695.5)	(546.7)	(622)
Financing Activities:
Issuance of long-term debt	755	300	629.1
Repayment of long-term debt	(281.2)	(55.8)	(115.4)
(Repayment) Issuance of short-term debt, net	(82)	365.5	24
Issuance of common stock	41.9	51.9	1
Dividends paid on common stock	(150.7)	(141.9)	(133.2)
Dividends paid on preferred stock	(14.8)	(14.8)	(14.8)
Other financing activities	(7.6)	(4)	(11.3)
Net cash provided by financing activities	260.6	500.9	379.4
Net Increase in Cash, Cash Equivalents, and Restricted Cash	5.3	9.2	7.2
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	20.5	11.3	4.1
Cash, Cash Equivalents, and Restricted Cash at End of Year	25.8	20.5	11.3
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(177.5)	(119.9)	(98.7)
Income taxes	(2)	(1.8)	(1.5)
Spire Missouri [Member]
Operating Activities:
Net Income	117.5	114.9	144.1	[1]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	158.7	145.3	129.2
Deferred income taxes and investment tax credits	11.6	21.3	25.3
Changes in assets and liabilities:
Accounts receivable	16	163.8	(207.4)
Inventories	80.2	(45.4)	(79)
Regulatory assets and liabilities	(22.4)	(314.3)	35.9
Accounts payable	(45.7)	25.3	23.1
Delayed/advance customer billings, net	2.2	(26.4)	(13)
Taxes accrued	9.7	9.3	2.1
Other assets and liabilities	(108.4)	(48)	(115)
Other	1.7	1.4	0.7
Net cash provided by operating activities	221.1	47.2	(54)
Delayed/advance customer billings	2.2	(26.4)	(13)
Investing Activities:
Capital expenditures	(447.5)	(354.1)	(382.6)
Other	4.1	3.6	1.3
Net cash used in investing activities	(443.4)	(350.5)	(381.3)
Financing Activities:
Issuance of long-term debt	400	300	304.1
Repayment of long-term debt	(250)	0	(55)
(Repayment) Issuance of short-term debt, net	0	(250)	250
Issuance of common stock	38.7	51.1	0
Dividends paid on common stock	(57)	0	0
Other financing activities	(3.9)	(2.2)	(3.5)
Net cash provided by financing activities	223.1	303.3	435.3
Net Increase in Cash, Cash Equivalents, and Restricted Cash	0.8	0	0
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	0	0	0
Cash, Cash Equivalents, and Restricted Cash at End of Year	0.8	0	0
Borrowings from (repayments to) Spire, net	95.3	204.4	(60.3)
(Repayments to) borrowings from Spire, net	95.3	204.4	(60.3)
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(93.8)	(58.9)	(45.9)
Income taxes	(0.2)	0	0
Spire Alabama Inc [Member]
Operating Activities:
Net Income	66	68.5	73.8
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	69.3	66.8	62.1
Deferred income taxes and investment tax credits	20.3	23.2	25
Changes in assets and liabilities:
Accounts receivable	27.1	(21.2)	(17.8)
Inventories	17.2	(42.5)	(15.4)
Regulatory assets and liabilities	(49.5)	(101.7)	29.2
Accounts payable	(42.3)	26.3	14
Delayed/advance customer billings, net	(0.6)	0.5	0.5
Taxes accrued	3.3	0.8	2.5
Other assets and liabilities	18.7	(3.7)	(37.8)
Other	0.4	0.2	0.3
Net cash provided by operating activities	129.9	17.2	136.4
Delayed/advance customer billings	(0.6)	0.5	0.5
Investing Activities:
Capital expenditures	(117.6)	(141.5)	(169.8)
Other	1.3	0.8	0.7
Net cash used in investing activities	(116.3)	(140.7)	(169.1)
Financing Activities:
Issuance of long-term debt	175	0	150
Repayment of long-term debt	0	(50)	0
Dividends paid on common stock	(21)	(24)	(22)
Other financing activities	(1)	0	(0.9)
Net cash provided by financing activities	(14.8)	125.9	32.7
Net Increase in Cash, Cash Equivalents, and Restricted Cash	(1.2)	2.4	0
Cash, Cash Equivalents, and Restricted Cash at Beginning of Year	2.4	0	0
Cash, Cash Equivalents, and Restricted Cash at End of Year	1.2	2.4	0
Borrowings from (repayments to) Spire, net	(136.8)	211.9	(72.4)
(Repayments to) borrowings from Spire, net	(136.8)	211.9	(72.4)
Return of capital to Spire	(31)	(12)	(22)
Supplemental disclosure of cash paid for:
Interest, net of amounts capitalized	(30.1)	(21)	(17.9)
Income taxes	$ 0	$ 0	$ 0
[1]Accumulated other comprehensive income (loss)

Note 1 - Summary of Significant

Note 1 - Summary of Significant Accounting Policies	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Significant Accounting Policies [Text Block]	1. BASIS OF PRESENTATION September 30 The accompanying audited financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). The consolidated financial position, results of operations and cash flows of Spire include the accounts of the Company and all its subsidiaries. Transactions and balances between consolidated entities have been eliminated from the consolidated financial statements of Spire. In compliance with GAAP, transactions between Spire Missouri and Spire Alabama and their affiliates, as well as intercompany balances on their balance sheets, have not NATURE OF OPERATIONS Note 14 USE OF ESTIMATES SYSTEM OF ACCOUNTS REGULATED OPERATIONS 980, Regulated Operations third may Note 15 PROPERTY, PLANT, AND EQUIPMENT Utility Plant Utility plant is depreciated using the composite method on a straight-line basis over the estimated service lives of the various classes of property at rates approved by the applicable regulatory commission. For Spire Missouri and for Spire Alabama, the annual depreciation and amortization expense in fiscal years 2023 2022 2021 Non-utility Property not Accrued Capital Expenditures September 30 2023 2022 2021 Spire $ 104.3 $ 77.8 $ 59.5 Spire Missouri 56.5 45.6 37.1 Spire Alabama 4.6 19.2 13.6 ASSET RETIREMENT OBLIGATIONS not not The following table presents a reconciliation of the beginning and ending balances of asset retirement obligations at September 30, Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Asset retirement obligations, beginning of year $ 520.9 $ 519.6 $ 110.6 $ 143.4 $ 398.7 $ 362.8 Liabilities incurred during the period 7.9 3.2 0.9 1.2 2.0 0.5 Liabilities settled during the period (6.8 ) (9.2 ) (2.5 ) (4.1 ) (2.5 ) (2.0 ) Accretion 21.5 21.1 4.5 5.9 16.5 14.7 Revisions in estimated cash flows 33.9 (13.8 ) (2.4 ) (35.8 ) 36.3 22.7 Asset retirement obligations, end of year $ 577.4 $ 520.9 $ 111.1 $ 110.6 $ 451.0 $ 398.7 NATURAL GAS AND PROPANE GAS first first first September 30, 2023 September 30, 2022 BUSINESS COMBINATIONS AND GOODWILL September 30, 2023 not 2017, no July 1 not September 30, 2023 not A subsidiary of Spire in the Midstream segment acquired a natural gas storage facility in northern Oklahoma, now named Spire Storage Salt Plains LLC, on April 1, 2023. no IMPAIRMENT OF LONG-LIVED ASSETS may not DERIVATIVES 815, Derivatives and Hedging not Note 10 INCOME TAXES not not The Company accounts for uncertain tax positions in accordance with authoritative guidance. The authoritative guidance addresses the determination of whether tax benefits claimed, or expected to be claimed, on a tax return should be recorded in the financial statements. Spire may not Note 12 CASH, CASH EQUIVALENTS, AND RESTRICTED CASH three September 30, 2023 2022 NATURAL GAS RECEIVABLE third third EARNINGS PER COMMON SHARE two Note 4 TRANSACTIONS WITH AFFILIATES Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 Natural gas purchases from Spire Marketing $ 57.4 $ 86.3 $ 92.5 $ 4.7 $ 3.2 $ 10.4 Natural gas sales to Spire Marketing 0.4 — 1.1 — 0.5 0.1 Transportation services from Spire STL Pipeline LLC 32.0 32.0 32.0 — — — Natural gas storage services from Spire Storage Salt Plains LLC 0.7 — — — — — Transportation services from Spire NGL Inc. — — 0.5 — — — ACCOUNTS RECEIVABLE AND ALLOWANCE FOR CREDIT LOSSES not Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Allowance at beginning of year $ 31.9 $ 30.3 $ 24.9 $ 24.9 $ 22.6 $ 18.1 $ 6.3 $ 6.6 $ 5.5 Provision for expected credit losses 16.6 11.6 14.7 13.3 11.2 11.1 2.6 0.3 3.1 Write-offs, net of recoveries (16.0 ) (10.0 ) (9.3 ) (12.0 ) (8.9 ) (6.6 ) (3.2 ) (0.6 ) (2.0 ) Allowance at end of year $ 32.5 $ 31.9 $ 30.3 $ 26.2 $ 24.9 $ 22.6 $ 5.7 $ 6.3 $ 6.6 FINANCE RECEIVABLES third September 30, 2023 2022 90 third 12 third 90 September 30, 2023 2022 GROUP MEDICAL AND WORKERS COMPENSATION RESERVES not FAIR VALUE MEASUREMENTS The levels of the hierarchy are described below: • Level 1 • Level 2 1, • Level 3 Assessment of the significance of a particular input to the fair value measurements may may Note 8 Note 9 Note 13 STOCK-BASED COMPENSATION 718, Compensation - Stock Compensation Note 3

Note 2 - Revenue

Note 2 - Revenue	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Revenue from Contract with Customer [Text Block]	2. The following tables show revenue disaggregated by source and customer type. 2023 2022 2021 Spire Gas Utility: Residential $ 1,648.5 $ 1,416.6 $ 1,234.0 Commercial & industrial 606.0 338.9 586.0 Transportation 121.6 118.0 122.9 Off-system & other incentive 30.0 42.0 152.7 Other customer revenue 16.1 19.9 22.2 Total revenue from contracts with customers 2,422.2 1,935.4 2,117.8 Changes in accrued revenue under alternative revenue programs 34.7 10.7 1.5 Total Gas Utility operating revenues 2,456.9 1,946.1 2,119.3 Gas Marketing 179.1 234.9 96.5 Midstream 66.1 53.1 52.6 Other 16.7 16.1 15.1 Total before eliminations 2,718.8 2,250.2 2,283.5 Intersegment eliminations (see Note 14, Information by Operating Segment) (52.5 ) (51.7 ) (48.0 ) Total Operating Revenues $ 2,666.3 $ 2,198.5 $ 2,235.5 Spire Missouri Residential $ 1,261.3 $ 1,061.4 $ 882.1 Commercial & industrial 411.9 177.2 436.1 Transportation 33.2 33.3 33.5 Off-system & other incentive 20.1 25.2 145.6 Other customer revenue 12.5 11.1 16.3 Total revenue from contracts with customers 1,739.0 1,308.2 1,513.6 Changes in accrued revenue under alternative revenue programs 23.9 12.8 3.0 Total Operating Revenues $ 1,762.9 $ 1,321.0 $ 1,516.6 Spire Alabama Residential $ 322.9 $ 291.6 $ 288.0 Commercial & industrial 150.4 119.1 114.9 Transportation 77.6 74.4 78.7 Off-system & other incentive 9.9 16.8 7.1 Other customer revenue 3.6 5.5 1.9 Total revenue from contracts with customers 564.4 507.4 490.6 Changes in accrued revenue under alternative revenue programs 6.7 1.7 3.4 Total Operating Revenues $ 571.1 $ 509.1 $ 494.0 The Utilities sell natural gas to residential and other customers. The sale of natural gas is governed by the various state utility commissions, which set rates, charges, and terms and conditions of service, collectively included in a “tariff.” The performance obligation, which relates to the promise to provide natural gas, is satisfied over time as the customer simultaneously receives and consumes the natural gas, and revenue is recognized accordingly. The Utilities’ transportation revenue relates to the promise to transport the specified quantities of natural gas at tariff rates. This performance obligation is satisfied over time as the gas is transported, and revenue is recognized as invoiced monthly. The Utilities have alternative revenue programs (ARPs), which represent an agreement between the utility and its regulator, currently consisting of decoupling mechanisms (also known as weather normalization adjustments) and incentive programs (primarily Alabama’s Cost Control Measure). When the criteria to recognize additional (or reduced) revenue from ARPs have been met, the Utilities establish a regulatory asset (or liability). When amounts previously recognized for ARPs are billed, the Utilities reduce the regulatory asset (or liability) and increase (or decrease) accounts receivable. Billed amounts, which are part of the overall tariff paid by customers, are included in revenue from contracts with customers, while the change in the related regulatory asset or liability is presented as revenue from ARPs. Depending on whether the beginning accrued ARP balance was a regulatory asset or liability and depending on the size and direction of the current period accrual, the amount presented as revenue from ARPs could be negative. The Utilities read meters and bill customers on monthly cycles. Spire Missouri, Spire Gulf and Spire Mississippi record their gas utility revenues from gas sales and transportation services on an accrual basis that includes estimated amounts for gas delivered but not not Gas Marketing’s contracts are derivatives. Wholesale contracts (with producers, municipalities, and utility companies) are subject to derivative accounting. Retail contracts (with large commercial and industrial customers) are designated as “normal purchase, normal sale” arrangements and are therefore accounted for as revenue from contracts with customers. The performance obligation is satisfied over time by the transfer of control of natural gas to the customer, and revenue is recognized as invoiced monthly. Payments are generally required within 30 not not Spire, Spire Missouri, and Spire Alabama have elected to apply a “right to invoice” practical expedient, recognizing revenue for volumes delivered for which they have a right to invoice, as long as that amount corresponds with the value to the customer. Disclosures about remaining performance obligations are not one Sales taxes imposed on applicable Spire Alabama and Spire Missouri sales are billed to customers. These amounts are not Gross receipts taxes associated with the Company’s natural gas utility services are imposed on the Company, Spire Missouri, and Spire Alabama and billed to its customers. The expense amounts (shown in the table below) are reported gross in the “Taxes, other than income taxes” line in the statements of income, and corresponding revenues are reported in “Operating Revenues.” 2023 2022 2021 Spire $ 131.8 $ 109.8 $ 94.0 Spire Missouri 96.7 79.6 64.3 Spire Alabama 29.9 25.5 25.1

Note 3 - Stock-based Compensati

Note 3 - Stock-based Compensation	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Share-Based Payment Arrangement [Text Block]	3. The Spire 2015 January 29, 2015 November 9, 2018. may may three three The Company allows participants in the EIP the ability to defer a portion or all of their award. As of September 30, 2023, not Restricted Stock Awards During fiscal 2023 ed 116,390 September 30, 2026. no not The number of share units that will ultimately vest is dependent upon the attainment of certain levels of earnings, as well as the Company’s level of total shareholder return (TSR) during the performance period relative to a comparator group of peer companies. This TSR provision is considered a market condition under GAAP and is discussed further below. The maximum amount of shares or share equivalents that can be earned pursuant to the terms of the awards is 200% of the target units granted. The weighted average grant date fair value of performance-contingent restricted share units granted during fiscal years 2022 2021 Fiscal 2023 Weighted Average Grant Date Fair Value Units Per Unit Non-vested at September 30, 2022 343,524 $ 70.14 Granted 116,390 $ 79.88 Adjusted for performance (13,459 ) $ 76.91 Vested (74,556 ) $ 76.91 Forfeited (23,546 ) $ 71.73 Non-vested at September 30, 2023 348,353 $ 71.76 For the year ended September 30, 2023 During fiscal 2023 55,524 2025. not 2022 2021 During fiscal 2023 $75.59 2023 six 2022 2021 Time-vested restricted stock and stock unit activity for fiscal 2023 Weighted Average Grant Date Shares/ Fair Value Units Per Share Non-vested at September 30, 2022 122,245 $ 66.60 Granted 68,244 $ 72.60 Vested (59,040 ) $ 75.27 Forfeited (8,460 ) $ 65.36 Non-vested at September 30, 2023 122,989 $ 65.85 For restricted stock and stock units (performance-contingent and time-vested) that vested during fiscal years 2023 2022 2021 18,428 2023 2022 2021 None Equity Compensation Costs Compensation cost for performance-contingent restricted stock and stock unit awards is based upon the probable outcome of the performance conditions. For shares or units that do not not no The fair value of awards of performance-contingent and time-vested restricted stock and restricted stock units, not not not may not 2023 2022 2021 2023 2022 2021 Risk-free interest rate 4.26% 0.79% 0.22% Expected dividend yield of stock — — — Expected volatility of stock 33.8% 32.2% 31.4% Performance period (in years) 3.0 3.0 3.0 The risk-free interest rate was based on the yield on U.S. Treasury securities matching the vesting period. A zero-percent dividend yield was used, which is mathematically equivalent to the assumption that dividends are reinvested as they are paid. The expected volatility is based on the historical volatility of the Company’s stock. Volatility assumptions were also made for each of the companies included in the comparator group. The vesting period is equal to the performance period set forth in the terms of the award. The amounts of compensation cost recognized for share-based compensation arrangements are presented below: 2023 2022 2021 Total compensation cost $ 11.2 $ 7.5 $ 16.6 Compensation cost capitalized (1.4 ) (1.1 ) (2.7 ) Compensation cost recognized in net income 9.8 6.4 13.9 Income tax benefit recognized in net income (2.2 ) (1.5 ) (3.2 ) Compensation cost recognized in net income, net of income tax $ 7.6 $ 4.9 $ 10.7 As of September 30, 2023

Note 4 - Earnings Per Common Sh

Note 4 - Earnings Per Common Share	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Earnings Per Share [Text Block]	4. 2023 2022 2021 Basic Earnings Per Common Share: Net Income $ 217.5 $ 220.8 $ 271.7 Less: Provision for preferred dividends 14.8 14.8 14.8 Income allocated to participating securities 0.3 0.3 0.4 Net Income Available to Common Shareholders $ 202.4 $ 205.7 $ 256.5 Weighted Average Common Shares Outstanding (in millions) 52.5 52.0 51.6 Basic Earnings Per Share of Common Stock $ 3.86 $ 3.96 $ 4.97 Diluted Earnings per Common Share: Net Income $ 217.5 $ 220.8 $ 271.7 Less: Provision for preferred dividends 14.8 14.8 14.8 Income allocated to participating securities 0.3 0.3 0.4 Net Income Available to Common Shareholders $ 202.4 $ 205.7 $ 256.5 Weighted Average Common Shares Outstanding (in millions) 52.5 52.0 51.6 Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)* 0.1 0.1 0.1 Weighted Average Diluted Common Shares (in millions) 52.6 52.1 51.7 Diluted Earnings Per Share of Common Stock $ 3.85 $ 3.95 $ 4.96 * Calculation excludes certain outstanding common shares (shown in millions by period at the right) attributable to common stock forward contracts, stock units subject to performance or market conditions, and restricted stock, which could have a dilutive effect in the future 1.9 0.1 0.1

Note 5 - Shareholders' Equity

Note 5 - Shareholders' Equity	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Equity [Text Block]	5. EQUITY Spire Preferred Stock At September 30, 2023 2022 On May 21, 2019, 1/1,000th Dividends on the Preferred Stock, when declared by the Board, are payable on the liquidation preference amount, on a cumulative basis, quarterly in arrears on the 15th February, May, August November August 15, 2019. May 21, 2019. Under the terms of the Preferred Stock, the Company’s ability to declare or pay dividends on, or purchase or redeem, shares of its common stock or any class or series of capital stock of the Company that rank junior to the Preferred Stock are subject to certain restrictions in the event that the Company does not Spire may, not August 15, 2024, 120 August 15, 2024, not Shareholders of the Preferred Stock generally have no may not six not two Equity Units In February 2021, 1/20, 2021 March 1, 2026 ( March 1, 2024, If the applicable market value* per share Number of shares to be purchased per of Spire common stock is: stock purchase contract is: Equal to or greater than $78.6906 (“threshold appreciation price”) 0.6354 (“minimum settlement rate”) Less than $78.6906, but greater than $64.24 $50.00 ÷ applicable market value* Less than or equal to $64.24 (“reference price”) 0.7783 (“maximum settlement rate”) *Based on the volume-weighted average price of Spire common stock during the 20 If a holder elects to settle purchase contracts early, the holder would pay fifty The Company makes quarterly interest payments on the RSNs at the rate of 0.75% per year and quarterly contract adjustment payments on the stock purchase contracts at the rate of 6.75%. The RSNs and the contract adjustment payments are structurally subordinated to all liabilities of Spire’s subsidiaries. At issuance, the Company recorded the $35.0 present value of the stock purchase contract payments as a liability (reflected in “Other” current and noncurrent liabilities on the balance sheet) offset by a charge to additional paid-in capital in equity. This noncash financing activity has been excluded from the statement of cash flows. Interest payments on the RSNs are recorded as interest expense and stock purchase contract payments are charged against the liability. Accretion of the stock purchase contract liability is recorded as imputed interest expense. In calculating diluted EPS, the Company applies the treasury stock method to the Corporate Units. These securities have not In order to secure funds necessary for the holders to pay the purchase price of the common stock on the purchase contract settlement date, the remarketing agent will remarket the RSNs on behalf of the current holders to new third ATM Program On February 6, 2019, May 14, 2019, may may April 28, 2022, May 2025. Settled sales under this ATM program are included in “Common stock issued” in the Condensed Consolidated Statements of Shareholders’ Equity. Also, in the second third 2023 , September 27, 2023, third December 28, 2023. September 30, 2023 , As of September 30, 2023 , may Other Equity Information Spire has a shelf registration statement on Form S- 3 September 30, 2023 November 10, 2023, 3. 3 May 9, 2025. Spire Missouri Substantially all of Spire Missouri’s plant is subject to the liens of its first no may September 30, 1953 September 30, 1953 September 30, 2023 2022 Spire Missouri has a universal shelf registration statement on Form S- 3 May 9, 2025. March 5, 2022, first December 31, 2024. September 30, 2023 first At September 30, 2023 2022 Spire Alabama At September 30, 2023 2022 Accumulated Other Comprehensive Income The components of accumulated other comprehensive income (AOCI), net of income taxes, recognized in the balance sheets at September 30 Net Defined Benefit Net Unrealized Unrealized Pension and Gain (Loss) on Gain (Loss) Other Available-for- on Cash Flow Postretirement Sale Debt Hedges Benefit Plans Securities Total Spire Balance at September 30, 2021 $ 7.9 $ (4.2 ) $ (0.1 ) $ 3.6 Other comprehensive income (loss) 42.5 1.5 (0.4 ) 43.6 Balance at September 30, 2022 50.4 (2.7 ) (0.5 ) 47.2 Other comprehensive income 0.1 0.2 0.1 0.4 Balance at September 30, 2023 $ 50.5 $ (2.5 ) $ (0.4 ) $ 47.6 Spire Missouri Balance at September 30, 2021 $ — $ (4.2 ) $ — $ (4.2 ) Other comprehensive income — 1.5 — 1.5 Balance at September 30, 2022 — (2.7 ) — (2.7 ) Other comprehensive income — 0.2 — 0.2 Balance at September 30, 2023 $ — $ (2.5 ) $ — $ (2.5 ) Income tax expense (benefit) recorded for items of other comprehensive income (loss) reported in the statements of comprehensive income is calculated by applying statutory federal, state, and local income tax rates applicable to ordinary income. The tax rates applied to individual items of other comprehensive income (loss) are similar within each reporting period. For the periods presented, Spire Alabama had no

Note 6 - Long-term Debt

Note 6 - Long-term Debt	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Long-Term Debt [Text Block]	6. The composition of long-term debt as of September 30 2023 2022 Spire 3.31 December 15, 2022 $ — $ 25.0 3.54 February 27, 2024 150.0 150.0 0.75 March 1, 2026 175.0 175.0 3.13 September 1, 2026 130.0 130.0 3.93 March 15, 2027 100.0 100.0 5.80 March 15, 2033 150.0 — 4.70 August 15, 2044 250.0 250.0 Total principal of Spire Missouri long-term debt (see below) 1,798.0 1,648.0 Total principal of Spire Alabama long-term debt (see below) 750.0 575.0 Other subsidiaries' long-term debt: 5.00 September 30, 2031 42.0 42.0 2.95 December 2034 117.7 123.9 5.61 October 15, 2037 30.0 — 3.52 September 30, 2049 40.0 40.0 Total principal of long-term debt 3,732.7 3,258.9 Less: Unamortized discounts and debt issuance costs (22.1 ) (19.2 ) Less: Current portion (156.6 ) (281.2 ) Long-term debt, excluding current portion $ 3,554.0 $ 2,958.5 Spire Missouri First Mortgage Bonds: 3.40 August 15, 2023 $ — $ 250.0 Floating Rate Series, due December 2, 2024 300.0 300.0 3.40 March 15, 2028 45.0 45.0 7.00 June 1, 2029 19.3 19.3 2.84 November 15, 2029 275.0 275.0 7.90 September 15, 2030 30.0 30.0 3.68 September 15, 2032 50.0 50.0 4.80 February 15, 2033 400.0 — 6.00 May 1, 2034 99.3 99.3 6.15 June 1, 2036 54.5 54.5 4.63 August 15, 2043 99.9 99.9 4.23 September 15, 2047 70.0 70.0 3.30 June 1, 2051 305.0 305.0 4.38 September 15, 2057 50.0 50.0 Total principal of Spire Missouri long-term debt 1,798.0 1,648.0 Less: Unamortized discounts and debt issuance costs (12.6 ) (10.3 ) Less: Current portion — (250.0 ) Spire Missouri long-term debt, excluding current portion $ 1,785.4 $ 1,387.7 Spire Alabama 3.21 September 15, 2025 $ 35.0 $ 35.0 5.32 October 15, 2029 90.0 — 2.88 December 1, 2029 100.0 100.0 2.04 December 15, 2030 150.0 150.0 5.41 October 15, 2032 85.0 — 5.90 January 15, 2037 45.0 45.0 4.31 December 1, 2045 80.0 80.0 3.92 January 15, 2048 45.0 45.0 4.64 January 15, 2049 90.0 90.0 4.02 January 15, 2058 30.0 30.0 Total principal of Spire Alabama long-term debt 750.0 575.0 Less: Unamortized discounts and debt issuance costs (4.1 ) (3.5 ) Spire Alabama long-term debt, excluding current portion $ 745.9 $ 571.5 Spire Missouri's $300.0 of first December 2, 2024 first Maturities of long-term debt for Spire on a consolidated basis, Spire Missouri and Spire Alabama for the five September 30, 2023 2024 2025 2026 2027 2028 Spire $ 156.6 $ 342.0 $ 312.5 $ 108.1 $ 53.6 Spire Missouri — 300.0 — — 45.0 Spire Alabama — 35.0 — — — The long-term debt agreements of Spire, Spire Missouri and Spire Alabama contain customary financial covenants and default provisions. As of September 30, 2023 no Spire At September 30, 2023 September 30, 2023 2022 2021 As indicated in Note 5 3 Spire Missouri At September 30, 2023 September 30, 2023 2022 2021 As indicated in Note 5 3 May 9, 2025. March 5, 2022, first December 31, 2024. September 30, 2023 first Substantially all of Spire Missouri’s plant is subject to the liens of its first Note 5 Spire Alabama At September 30, 2023 September 30, 2023 2022 2021 Spire Alabama has no

Note 7 - Notes Payable and Cred

Note 7 - Notes Payable and Credit Agreements	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Debt Disclosure [Text Block]	7. Spire, Spire Missouri and Spire Alabama have a syndicated revolving credit facility pursuant to a loan agreement with 12 July 22, 2027. may three may no September 30, 2023 September 30, 2023 2022 Spire has a commercial paper program (“CP Program”) pursuant to which it may may not may 365 On January 5, 2023, October 5, 2023. May 8, 2023. Information about short-term borrowings, including Spire Missouri’s and Spire Alabama’s borrowings from Spire, is presented in the following table. As of September 30, 2023 Spire Spire Spire (Parent Only) Missouri Alabama Spire CP Term Spire Spire Consol- Program Loan Note Note idated Year Ended September 30, 2023 Highest borrowings outstanding $ 1,282.0 $ 250.0 $ 656.9 $ 274.0 $ 1,482.0 Lowest borrowings outstanding 354.4 — 3.8 76.7 489.0 Weighted average borrowings 776.3 66.8 327.9 119.1 843.1 Weighted average interest rate 5.0 % 5.5 % 4.9 % 4.9 % 5.0 % As of September 30, 2023 Borrowings outstanding $ 955.5 $ — $ 540.6 $ 124.1 $ 955.5 Weighted average interest rate 5.6 % 0.0 % 5.6 % 5.6 % 5.6 % As of September 30, 2022 Borrowings outstanding $ 1,037.5 $ — $ 445.3 $ 260.9 $ 1,037.5 Weighted average interest rate 3.3 % 0.0 % 3.3 % 3.3 % 3.3 %

Note 8 - Fair Value of Financia

Note 8 - Fair Value of Financial Instruments	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Fair Value Disclosures [Text Block]	8. The carrying amounts and estimated fair values of financial instruments not Classification of Estimated Fair Value Quoted Prices in Significant Active Observable Carrying Fair Markets Inputs Amount Value (Level 1) (Level 2) Spire As of September 30, 2023 Cash and cash equivalents $ 5.6 $ 5.6 $ 5.6 $ — Notes payable 955.5 955.5 — 955.5 Long-term debt, including current portion 3,710.6 3,270.2 — 3,270.2 As of September 30, 2022 Cash and cash equivalents $ 6.5 $ 6.5 $ 6.5 $ — Notes payable 1,037.5 1,037.5 — 1,037.5 Long-term debt, including current portion 3,239.7 2,851.8 — 2,851.8 Spire Missouri As of September 30, 2023 Cash and cash equivalents $ 0.8 $ 0.8 $ 0.8 $ — Notes payable - associated companies 540.6 540.6 — 540.6 Long-term debt 1,785.4 1,592.4 — 1,592.4 As of September 30, 2022 Notes payable - associated companies $ 445.3 $ 445.3 $ — $ 445.3 Long-term debt, including current portion 1,637.7 1,473.9 — 1,473.9 Spire Alabama As of September 30, 2023 Cash and cash equivalents $ 1.2 $ 1.2 $ 1.2 $ — Notes payable - associated companies 124.1 124.1 — 124.1 Long-term debt 745.9 648.0 — 648.0 As of September 30, 2022 Cash and cash equivalents $ 2.4 $ 2.4 $ 2.4 $ — Notes payable - associated companies 260.9 260.9 — 260.9 Long-term debt 571.5 485.0 — 485.0

Note 9 - Fair Value Measurement

Note 9 - Fair Value Measurements	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block]	9. The information presented below categorizes the assets and liabilities in the balance sheets that are accounted for at fair value on a recurring basis in periods subsequent to initial recognition. The mutual funds included in Level 1 2 Derivative instruments included in Level 1 2 2 3 no 3 September 30, 2023 2022 The mutual funds are included in “Other investments” on the Company’s balance sheets and in “Other Property and Investments” on Spire Missouri’s balance sheets. Changes in their recurring valuations are recorded as unrealized investment gains or losses in the corresponding periodic income statement. Derivative assets and liabilities, including receivables and payables associated with cash margin requirements, are presented net on the balance sheets when a legally enforceable netting agreement exist between the Company, Spire Missouri or Spire Alabama and the counterparty to the derivative contract. For additional information on derivative instruments, see Note 10 Spire Effects of Quoted Netting Prices Significant Significant and Cash in Active Observable Unobservable Margin Markets Inputs Inputs Receivables (Level 1) (Level 2) (Level 3) /Payables Total As of September 30, 2023 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 20.4 $ — $ — $ — $ 20.4 Gasoline and heating oil contracts — 0.1 — (0.1 ) — NYMEX/ICE natural gas contracts 6.3 — — (6.3 ) — Gas Marketing: NYMEX/ICE natural gas contracts 10.1 — — (10.1 ) — Natural gas commodity contracts — 36.7 — (3.6 ) 33.1 Other: U.S. stock/bond mutual funds 37.6 — — — 37.6 Interest rate swaps — 44.2 — — 44.2 Total $ 74.4 $ 81.0 $ — $ (20.1 ) $ 135.3 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 50.8 $ — $ — $ (44.0 ) $ 6.8 Gas Marketing: NYMEX/ICE natural gas contracts 21.8 — — (21.8 ) — Natural gas commodity contracts — 27.6 — (3.6 ) 24.0 Total $ 72.6 $ 27.6 $ — $ (69.4 ) $ 30.8 As of September 30, 2022 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 19.1 $ — $ — $ — $ 19.1 NYMEX/ICE natural gas contracts 57.8 — — (57.8 ) — Gas Marketing: NYMEX/ICE natural gas contracts 91.8 — — (91.8 ) — Natural gas commodity contracts * — 56.6 — (4.0 ) 52.6 Other: U.S. stock/bond mutual funds 29.3 — — — 29.3 Interest rate swaps * — 63.6 — — 63.6 Total $ 198.0 $ 120.2 $ — $ (153.6 ) $ 164.6 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 30.7 $ — $ — $ (30.7 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts 82.3 — — (82.3 ) — Natural gas commodity contracts * — 65.5 — (4.0 ) 61.5 Total $ 113.0 $ 65.5 $ — $ (117.0 ) $ 61.5 * Subsequent to the issuance of its consolidated financial statements for the year ended September 30, 2022, fourth 2023, 2 1 September 30, 2022. not Spire Missouri Effects of Quoted Netting Prices Significant Significant and Cash in Active Observable Unobservable Margin Markets Inputs Inputs Receivables (Level 1) (Level 2) (Level 3) /Payables Total As of September 30, 2023 ASSETS U.S. stock/bond mutual funds $ 20.4 $ — $ — $ — $ 20.4 Gasoline and heating oil contracts — 0.1 — (0.1 ) — NYMEX/ICE natural gas contracts 6.3 — — (6.3 ) — Total $ 26.7 $ 0.1 $ — $ (6.4 ) $ 20.4 LIABILITIES NYMEX/ICE natural gas contracts $ 50.8 $ — $ — $ (44.0 ) $ 6.8 As of September 30, 2022 ASSETS U.S. stock/bond mutual funds $ 19.1 $ — $ — $ — $ 19.1 NYMEX/ICE natural gas contracts 57.8 — — (57.8 ) — Total $ 76.9 $ — $ — $ (57.8 ) $ 19.1 LIABILITIES NYMEX/ICE natural gas contracts $ 30.7 $ — $ — $ (30.7 ) $ — Spire Alabama Spire Alabama occasionally utilizes a gasoline derivative program to stabilize the cost of fuel used in operations. As of September 30, 2023 September 30, 2022 no

Note 10 - Derivative Instrument

Note 10 - Derivative Instruments and Hedging Activities	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Derivative Instruments and Hedging Activities Disclosure [Text Block]	10. Spire Spire Missouri has a risk management policy to utilize various derivatives, including futures contracts, exchange-traded options and swaps for the explicit purpose of managing price risk associated with purchasing and delivering natural gas on a regular basis to customers in accordance with its tariffs. The objective of this policy is to limit Spire Missouri’s exposure to natural gas price volatility and to manage, hedge and mitigate substantial price risk. Further discussion of this policy can be found in the Spire Missouri section. From time to time Spire Missouri and Spire Alabama purchase NYMEX futures and options contracts to help stabilize operating costs associated with forecasted purchases of gasoline and diesel fuels used to power vehicles and equipment. Further information on these derivatives can be found in the Spire Missouri and Spire Alabama sections, respectively. In the course of its business, Spire’s gas marketing subsidiary, Spire Marketing enters into commitments associated with the purchase or sale of natural gas. Certain of Spire Marketing’s derivative natural gas contracts are designated as normal purchases or normal sales and, as such, are excluded from the scope of ASC Topic 815 not September 30, 2023 2024 2025, 2026, 2027, 2028 2030. not Furthermore, Spire Marketing manages the price risk associated with its fixed-priced commitments by either closely matching the offsetting physical purchase or sale of natural gas at fixed prices or through the use of NYMEX or ICE futures, swap, and option contracts to lock in margins. At September 30, 2023 not may Spire enters into cash flow hedges through the execution of interest rate swap contracts to protect itself against adverse movements in interest rates. At September 30, 2023, Period Originated Contract Hedge Term (Years) Notional Amount Fixed Interest Rate Fiscal 2023 Mark-to-Market Gain Quarter 1, fiscal 2022 10 $ 50.0 1.4918 % $ 2.7 Quarter 2, fiscal 2022 10 75.0 1.6475 % 4.0 Quarter 2, fiscal 2022 10 25.0 1.7460 % 1.5 Quarter 1, fiscal 2023 10 50.0 3.4480 % 2.4 Quarter 2, fiscal 2023 10 50.0 3.6850 % 0.9 Quarter 2, fiscal 2023 10 25.0 3.5350 % 0.5 Quarter 2, fiscal 2023 10 25.0 3.3850 % 0.6 Quarter 3, fiscal 2023 30 50.0 2.7470 % 7.8 Quarter 3, fiscal 2023 10 25.0 2.9020 % 2.2 Quarter 3, fiscal 2023 10 25.0 3.0180 % 2.0 $ 400.0 $ 24.6 As of September 30, 2023 The Company’s and Spire Missouri’s exchange-traded/cleared derivative instruments consist primarily of NYMEX and ICE positions. The NYMEX is the primary national commodities exchange on which natural gas derivatives are traded. Open NYMEX and ICE natural gas futures and swap positions at September 30, 2023 2022 September 30, 2023 September 30, 2022 Gas Marketing Notional (MMBtu millions) Maximum Term (Months) Notional (MMBtu millions) Maximum Term (Months) Natural gas futures purchased 61.3 51 76.3 54 Natural gas options purchased, net 4.9 15 3.7 12 Natural gas basis swaps purchased 44.1 51 61.7 39 Gas Utility Natural gas futures purchased 66.5 24 13.0 12 At September 30, 2023 Derivative instruments designated as cash flow hedges of forecasted transactions are recognized on the balance sheets of the Company at fair value, and the change in fair value of the effective portion of these hedge instruments is recorded, net of income tax, in other comprehensive income or loss (OCI). Accumulated other comprehensive income or loss (AOCI) is a component of Total Common Stock Equity. Amounts are reclassified from AOCI into earnings when the hedged items affect net income, using the same revenue or expense category that the hedged item impacts. Based on market prices at September 30, 2023 twelve Effect of Derivative Instruments on the Consolidated Statements of Income and Comprehensive Income Location of Gain (Loss) Recorded in Income 2023 2022 2021 Derivatives in Cash Flow Hedging Relationships Effective portion of gain recognized in OCI on derivatives: Interest rate swaps $ 20.1 $ 56.7 $ 61.2 Effective portion of gain reclassified from AOCI to income: Interest rate swaps Interest Expense $ (2.4 ) $ (1.2 ) $ (1.3 ) Derivatives Not Designated as Hedging Instruments* Gain (Loss) recognized in income on derivatives: Gas / diesel futures Non-Operating Expense: Other Income $ 0.3 $ — $ — Natural gas commodity contracts Operating Expenses: Natural Gas 18.0 52.6 54.1 NYMEX / ICE natural gas contracts Operating Expenses: Natural Gas (35.0 ) 43.3 (77.5 ) Total $ (16.7 ) $ 95.9 $ (23.4 ) * Gains and losses on Spire Missouri’s natural gas derivative instruments, which are not no Fair Value of Derivative Instruments in the Consolidated Balance Sheets Derivative Assets* Derivative Liabilities* September 30, 2023 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Other: Interest rate swaps Current Assets: Other $ 44.2 Current Liabilities: Other $ — Subtotal 44.2 — Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Current Assets: Other 6.3 Current Liabilities: Other 50.8 Gasoline and heating oil contracts Current Assets: Other 0.1 — Gas Marketing: NYMEX / ICE natural gas contracts Current Assets: Other 8.0 Current Liabilities: Other 16.0 Deferred Charges and Other Assets: Other 2.1 Deferred Credits and Other Liabilities: Other 5.7 Natural gas commodity Current Assets: Other 31.2 Current Liabilities: Other 20.1 Deferred Charges and Other Assets: Other 5.5 Deferred Credits and Other Liabilities: Other 7.6 Subtotal 53.2 100.2 Total derivatives $ 97.4 $ 100.2 September 30, 2022 Derivatives designated as hedging instruments Other: Interest rate swaps Current Assets: Other $ 63.6 Current Liabilities: Other $ — Subtotal 63.6 — Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Current Assets: Other 57.8 Current Liabilities: Other 30.7 Gas Marketing: NYMEX / ICE natural gas contracts Current Assets: Other 79.2 Current Liabilities: Other 71.5 Deferred Charges and Other Assets: Other 12.7 Deferred Credits and Other Liabilities: Other 10.8 Natural gas commodity Current Assets: Other 53.4 Current Liabilities: Other 55.1 Deferred Charges and Other Assets: Other 3.1 Deferred Credits and Other Liabilities: Other 10.4 Subtotal 206.2 178.5 Total derivatives $ 269.8 $ 178.5 * The fair values of Derivative Assets and Derivative Liabilities exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the balance sheets. As such, the gross balances presented in the table above are not Note 9 Following is a reconciliation of the amounts in the tables above to the amounts presented in the consolidated balance sheets: 2023 2022 Fair value of derivative assets presented above $ 97.4 $ 269.8 Fair value of cash margin receivable offset with derivatives 49.3 (36.6 ) Netting of assets and liabilities with the same counterparty (69.4 ) (117.0 ) Total $ 77.3 $ 116.2 Derivative Instrument Assets, per Consolidated Balance Sheets: Current Assets: Other $ 71.8 $ 113.1 Deferred Charges and Other Assets: Other 5.5 3.1 Total $ 77.3 $ 116.2 Fair value of derivative liabilities presented above $ 100.2 $ 178.5 Netting of assets and liabilities with the same counterparty (69.4 ) (117.0 ) Total $ 30.8 $ 61.5 Derivative Instrument Liabilities, per Consolidated Balance Sheets: Current Liabilities: Other $ 23.2 $ 51.1 Deferred Credits and Other Liabilities: Other 7.6 10.4 Total $ 30.8 $ 61.5 Additionally, at September 30, 2023 2022 zero not Spire Missouri Spire Missouri has a risk management policy to utilize various derivatives, including futures contracts, exchange-traded options, swaps and over-the-counter instruments for the explicit purpose of managing price risk associated with purchasing and delivering natural gas on a regular basis to customers in accordance with its tariffs. The objective of this policy is to limit Spire Missouri’s exposure to natural gas price volatility and to manage, hedge and mitigate substantial price risk. This policy strictly prohibits speculation and permits Spire Missouri to hedge current physical natural gas purchase commitments or forecasted or anticipated future peak (maximum) physical need for natural gas delivered. Costs and cost reductions, including carrying costs, associated with Spire Missouri’s use of natural gas derivative instruments are allowed to be passed on to Spire Missouri customers through the operation of its PGA clause, through which the MoPSC allows Spire Missouri to recover gas supply costs, subject to prudence review by the MoPSC. Accordingly, Spire Missouri does not Spire Missouri does not 980, Regulated Operations no The timing of the operation of the PGA clause may From time to time, Spire Missouri purchases NYMEX futures and options contracts to help stabilize operating costs associated with forecasted purchases of gasoline and diesel fuels used to power vehicles and equipment used in the course of its business. The gains and losses on these contracts are not September 30, 2023 not Derivative instruments designated as cash flow hedges of forecasted transactions are recognized on the balance sheets at fair value and the change in the fair value of the effective portion of these hedge instruments is recorded, net of income tax, in OCI. AOCI is a component of Total Common Stock Equity. Amounts are reclassified from AOCI into earnings when the hedged items affect net income, using the same revenue or expense category that the hedged item impacts. As in both 2022 2021 no 2024 Spire Missouri’s derivative instruments consist primarily of NYMEX positions. The NYMEX is the primary national commodities exchange on which natural gas derivatives are traded. Open NYMEX natural gas futures positions at September 30, 2023 2022 September 30, 2023 September 30, 2022 Notional (MMBtu millions) Maximum Term (Months) Notional (MMBtu millions) Maximum Term (Months) Natural gas futures purchased 66.5 24 13.0 12 At September 30, 2023 Gains and losses on Spire Missouri’s natural gas derivative instruments, which are not Fair Value of Derivative Instruments in the Balance Sheets Derivative Assets* Derivative Liabilities* September 30, 2023 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives not designated as hedging instruments Natural gas contracts Current Assets: Other $ 6.3 Current Liabilities: Other $ 50.8 Gasoline and heating oil contracts Current Assets: Other 0.1 Total derivatives $ 6.4 $ 50.8 September 30, 2022 Derivatives not designated as hedging instruments Natural gas contracts Current Assets: Other $ 57.8 Current Liabilities: Other $ 30.7 * The fair values of Derivative Assets and Derivative Liabilities exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the balance sheets. As such, the gross balances presented in the table above are not Note 9 Following is a reconciliation of the amounts in the tables above to the amounts presented in Spire Missouri’s balance sheets: 2023 2022 Fair value of derivative assets presented above $ 6.4 $ 57.8 Fair value of cash margin (payable) receivable offset with derivatives 37.6 (27.1 ) Netting of assets and liabilities with the same counterparty (44.0 ) (30.7 ) Total $ — $ — Fair value of derivative liabilities presented above $ 50.8 $ 30.7 Netting of assets and liabilities with the same counterparty (44.0 ) (30.7 ) Total $ 6.8 $ — Derivative Instrument Liabilities, per Balance Sheets: Derivative instrument liabilities $ 6.8 $ — Total $ 6.8 $ — Additionally, at September 30, 2023 2022 not Spire Alabama Spire Alabama periodically employs a gasoline derivative program to help stabilize operating costs associated with forecasted purchases of gasoline and diesel fuels used to power vehicles and equipment used in the course of its business. The gains or losses on these derivative instruments are not no September 30, 2023 2022

Note 11 - Concentrations of Cre

Note 11 - Concentrations of Credit Risk	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Concentration Risk Disclosure [Text Block]	11. Spire’s Gas Utility segment serves 1.7 million customers in three Spire Marketing’s accounts receivable attributable to utility companies and their marketing affiliates totaled $53.4 at September 30, 2023 may September 30, 2023 five five one one one not To manage these risks, Spire Marketing has established procedures to determine the creditworthiness of its counterparties. These procedures include obtaining credit ratings and credit reports, analyzing counterparty financial statements to assess financial condition, and considering the industry environment in which the counterparty operates. This information is monitored on an ongoing basis. In some instances, Spire Marketing may may no

Note 12 - Income Taxes

Note 12 - Income Taxes	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Income Tax Disclosure [Text Block]	12. The Company, Spire Missouri, and Spire Alabama are subject to federal income tax as well as income tax in various state and local jurisdictions. Spire files a consolidated federal income tax return and various state income tax returns and allocates income taxes to Spire Missouri, Spire Alabama and its other subsidiaries as if each entity were a separate taxpayer. The provision for income taxes during the fiscal years ended September 30, 2023 2022 2021 Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Federal: Current $ 0.7 $ 0.5 $ 0.2 $ — $ — $ — $ — $ — $ — Deferred 30.4 47.0 49.5 10.1 18.2 22.0 15.8 18.1 19.8 Investment tax credits (0.2 ) (0.2 ) (0.2 ) (0.2 ) (0.2 ) (0.2 ) — — — State and local: Current 1.2 0.5 1.3 — — — — — — Deferred 6.7 11.1 17.7 1.7 3.3 3.5 4.5 5.1 5.2 Total income tax expense $ 38.8 $ 58.9 $ 68.5 $ 11.6 $ 21.3 $ 25.3 $ 20.3 $ 23.2 $ 25.0 The effective income tax rate varied from the federal statutory income tax rate for each year due to the following: Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Federal income tax statutory rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State and local income taxes, net of federal income tax benefits 3.7 3.6 3.6 2.6 2.6 2.6 4.1 4.1 4.1 Certain expenses capitalized on books and deducted on tax return (1.4 ) (1.6 ) (1.6 ) (2.7 ) (3.2 ) (3.3 ) — — — Taxes related to prior years — (0.3 ) (0.5 ) (0.6 ) (0.2 ) — — — Tax credits * (3.3 ) — — (4.2 ) — — (1.9 ) — — Amortization of excess deferred taxes (5.1 ) (3.5 ) (2.5 ) (7.7 ) (7.3 ) (5.0 ) 0.2 — — Other items – net ** 0.2 1.9 0.1 — 3.1 (0.2 ) 0.1 0.2 0.2 Effective income tax rate 15.1 % 21.1 % 20.1 % 9.0 % 15.6 % 14.9 % 23.5 % 25.3 % 25.3 % * In 2023, 2014 2022. ** Other consists primarily of property adjustments. The significant items comprising the net deferred tax liability or asset as of September 30 Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Deferred tax assets: Reserves not currently deductible $ 27.7 $ 33.5 $ — $ 4.0 $ 3.9 $ 7.4 Pension and other postretirement benefits 64.4 72.6 44.7 52.6 17.0 — Goodwill — — — — 58.8 73.0 Operating losses 239.2 255.1 89.2 116.9 159.8 140.3 Regulatory amount due to customers, net 30.4 34.5 27.6 30.7 — — Other 35.8 24.9 10.5 — 3.0 — Total deferred tax assets 397.5 420.6 172.0 204.2 242.5 220.7 Deferred tax liabilities: Relating to property (788.0 ) (740.0 ) (507.7 ) (489.3 ) (218.7 ) (201.6 ) Regulatory pension and other postretirement benefits (80.6 ) (92.8 ) (53.0 ) (72.3 ) (25.9 ) (1.6 ) Deferred gas costs (67.0 ) (75.8 ) (64.1 ) (74.0 ) — — Other *** (205.6 ) (187.1 ) (79.0 ) (68.7 ) (7.0 ) (6.5 ) Total deferred tax liabilities (1,141.2 ) (1,095.7 ) (703.8 ) (704.3 ) (251.6 ) (209.7 ) Net deferred tax (liability) asset $ (743.7 ) $ (675.1 ) $ (531.8 ) $ (500.1 ) $ (9.1 ) $ 11.0 *** For Spire, Other consists primarily of goodwill-related liabilities. As indicated in Note 1 980, Regulated Operations 2017 2018, 2022. 2023 2022 2021 2023. 2023. On April 14, 2023, 2023 15 may may May 1, 2023. In assessing whether deferred tax assets are realizable, management considers whether it is more likely than not not not As of September 30, 2023 Spire Spire Missouri Spire Alabama Federal and state loss carryforwards $ 1,000.3 $ 352.4 $ 624.1 Contribution carryforwards 6.1 5.6 - Tax credit carryforwards 13.1 8.5 1.6 For federal tax purposes, Spire Missouri’s and Spire Alabama’s loss carryforwards may 2030 2035 The Company, Spire Missouri and Spire Alabama recognize the tax benefit from a tax position only if it is at least more likely than not 2013 11. Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Unrecognized tax benefits, beginning of year $ 19.6 $ 16.4 $ 13.2 $ 19.3 $ 16.1 $ 13.0 $ — $ — $ — Increases related to tax positions taken in current year 4.2 3.3 3.2 3.6 3.2 3.1 0.3 — — Reductions due to lapse of applicable statute of limitations — (0.1 ) — — — — — — — Unrecognized tax benefits, end of year $ 23.8 $ 19.6 $ 16.4 $ 22.9 $ 19.3 $ 16.1 $ 0.3 $ — $ — As of September 30, 2023 2022 12 not 2022 2021 The Company, Spire Missouri, and Spire Alabama record potential interest and penalties related to uncertain tax positions as interest expense and other income deductions, respectively. As of September 30, 2023 2022 The Company, Spire Missouri, and Spire Alabama are no 2020,

Note 13 - Pension Plans and Oth

Note 13 - Pension Plans and Other Postretirement Benefits	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Retirement Benefits [Text Block]	13. Pension Plans Spire and the Utilities maintain pension plans for their employees. Spire Missouri and Spire Alabama have non-contributory, defined benefit, trusteed forms of pension plans covering the majority of their employees. Qualified plan assets are comprised of mutual and commingled funds consisting of U.S. equities with varying strategies, global equities, alternative investments, and fixed income investments. The net periodic pension cost includes components shown in the following table. The components other than the service costs and regulatory adjustment are presented in “Other Income, Net” in the income statement, except for Spire Alabama’s losses on lump-sum settlements. Such losses are capitalized in regulatory balances and amortized over the remaining actuarial life of individuals in the plan, and that amortization is presented in “Other Income, Net.” Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Service cost – benefits earned during the period $ 16.3 $ 20.0 $ 21.7 $ 11.4 $ 14.4 $ 15.4 $ 4.2 $ 4.8 $ 5.5 Interest cost on projected benefit obligation 25.1 21.5 20.7 17.8 14.7 14.2 4.8 4.7 4.6 Expected return on plan assets (24.5 ) (31.3 ) (31.6 ) (18.0 ) (22.7 ) (22.5 ) (3.5 ) (5.2 ) (5.8 ) Amortization of prior service credit (4.5 ) (4.5 ) (3.1 ) (1.9 ) (1.9 ) (0.6 ) (2.4 ) (2.4 ) (2.3 ) Amortization of actuarial loss 6.6 11.9 14.9 6.1 9.6 11.0 0.9 2.4 3.9 Loss on lump-sum settlements and curtailments 9.7 33.6 18.2 0.6 27.3 11.6 9.1 6.3 6.6 Subtotal 28.7 51.2 40.8 16.0 41.4 29.1 13.1 10.6 12.5 Regulatory adjustment 26.3 12.5 20.6 27.1 9.9 19.0 (1.7 ) 1.7 0.7 Net pension cost $ 55.0 $ 63.7 $ 61.4 $ 43.1 $ 51.3 $ 48.1 $ 11.4 $ 12.3 $ 13.2 Other changes in plan assets and pension benefit obligations recognized in other comprehensive income or loss include the following: Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Current year actuarial loss (gain) $ 14.5 $ (16.9 ) $ (8.1 ) $ 5.7 $ 0.9 $ (0.9 ) $ 9.0 $ (16.0 ) $ (1.5 ) Amortization of actuarial loss (6.6 ) (11.9 ) (14.9 ) (6.1 ) (9.6 ) (11.0 ) (0.9 ) (2.4 ) (3.9 ) Acceleration of loss recognized due to settlement (9.7 ) (33.6 ) (18.2 ) (0.6 ) (27.3 ) (11.6 ) (9.1 ) (6.3 ) (6.6 ) Current year service credit — — (17.9 ) — — (17.9 ) — — — Amortization of prior service credit 4.5 4.5 3.1 1.9 1.9 0.6 2.4 2.4 2.3 Subtotal 2.7 (57.9 ) (56.0 ) 0.9 (34.1 ) (40.8 ) 1.4 (22.3 ) (9.7 ) Regulatory adjustment (2.8 ) 56.3 57.3 (1.0 ) 32.5 42.1 (1.4 ) 22.3 9.7 Total recognized in OCI $ (0.1 ) $ (1.6 ) $ 1.3 $ (0.1 ) $ (1.6 ) $ 1.3 $ — $ — $ — Spire pension obligations are driven by separate plan and regulatory provisions governing Spire Missouri, Spire Alabama and Spire EnergySouth pension plans. Pursuant to the provisions of Spire Missouri’s and Spire Alabama’s pension plans, pension obligations may In the fiscal year ended September 30, 2023 one two September 30, 2023 September 30, 2022 2023 2023 September 30, 2023 In the fiscal year ended September 30, 2022, two two September 30, 2022 ( September 30, 2021), 2022 2022 12.3 September 30, 2022. Effective December 23, 2021, December 26, 2022, Also effective December 23, 2021, eight eight eight eight December 26, 2022, The following table shows the reconciliation of the beginning and ending balances of the pension benefit obligation at September 30: Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Benefit obligation, beginning of year $ 464.4 $ 689.6 $ 320.6 $ 479.0 $ 97.8 $ 149.4 Service cost 16.3 20.0 11.4 14.4 4.2 4.8 Interest cost 25.1 21.5 17.8 14.7 4.8 4.7 Actuarial (gain) loss (1.1 ) (173.9 ) (4.9 ) (116.2 ) 5.4 (42.4 ) Settlement loss 9.7 33.4 0.6 27.9 9.1 5.6 Settlement benefits paid (48.8 ) (109.3 ) (9.9 ) (87.0 ) (38.8 ) (22.3 ) Regular benefits paid (26.9 ) (16.9 ) (22.4 ) (12.2 ) (1.9 ) (2.0 ) Benefit obligation, end of year $ 438.7 $ 464.4 $ 313.2 $ 320.6 $ 80.6 $ 97.8 Accumulated benefit obligation, end of year $ 433.1 $ 457.1 $ 309.5 $ 315.0 $ 78.8 $ 96.2 In 2023, The following table sets forth the reconciliation of the beginning and ending balances of the fair value of plan assets at September 30: Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Fair value of plan assets, beginning of year $ 332.7 $ 498.9 $ 235.9 $ 364.0 $ 57.3 $ 82.8 Actual return on plan assets 9.1 (92.5 ) 7.5 (66.7 ) — (15.6 ) Employer contributions 58.9 52.4 30.3 37.8 27.9 14.4 Settlement benefits paid (39.1 ) (109.3 ) (9.3 ) (87.0 ) (29.7 ) (22.3 ) Regular benefits paid (26.9 ) (16.8 ) (22.4 ) (12.2 ) (1.9 ) (2.0 ) Fair value of plan assets, end of year $ 334.7 $ 332.7 $ 242.0 $ 235.9 $ 53.6 $ 57.3 Funded status of plans, end of year $ (104.0 ) $ (131.7 ) $ (71.2 ) $ (84.7 ) $ (27.0 ) $ (40.5 ) The following table sets forth the amounts recognized in the balance sheets at September 30: Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Current liabilities $ (1.6 ) $ (1.1 ) $ (1.6 ) $ (1.1 ) $ — $ — Noncurrent liabilities (102.4 ) (130.6 ) (69.6 ) (83.6 ) (27.0 ) (40.5 ) Total $ (104.0 ) $ (131.7 ) $ (71.2 ) $ (84.7 ) $ (27.0 ) $ (40.5 ) Pre-tax amounts recognized in accumulated other comprehensive loss not Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Net actuarial loss $ 130.1 $ 132.0 $ 92.5 $ 93.6 $ 40.2 $ 41.2 Prior service credit (31.2 ) (35.7 ) (16.2 ) (18.1 ) (13.9 ) (16.3 ) Subtotal 98.9 96.3 76.3 75.5 26.3 24.9 Adjustments for amounts included in regulatory assets (95.9 ) (93.1 ) (73.3 ) (72.3 ) (26.3 ) (24.9 ) Total $ 3.0 $ 3.2 $ 3.0 $ 3.2 $ — $ — The assumptions used to calculate net periodic pension costs for Spire Missouri are as follows: 2023 2022 2021 Weighted average discount rate - Spire Missouri East plan 5.70% 3.00% 2.85% Weighted average discount rate - Spire Missouri West plan 5.80% 3.00% 2.75% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets 6.50% 6.75% 6.75% The assumptions used to calculate net periodic pension costs for Spire Alabama are as follows: 2023 2022 2021 Weighted average discount rate 5.65%/5.7% 3.10%/3.0% 2.95%/2.80% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets 6.50% 6.75% 6.75% The discount rate is based on long-term, high quality bond indices at the measurement date. The expected long-term rate of return on plan assets is based on historical and projected rates of return for current and planned asset classes in the investment portfolio. Assumed projected rates of return for each asset class were selected after analyzing historical experience and future expectations of the returns. The overall expected rate of return for the portfolio was developed based on the target allocation for each class. The assumptions used to calculate the benefit obligations are as follows: 2023 2022 Weighted average discount rate - Spire Missouri East plan 6.25% 5.70% Weighted average discount rate - Spire Missouri West plan 6.30% 5.80% Weighted average discount rate - Spire Alabama plans 6.2%/6.25% 5.70%/5.65% Weighted average rate of future compensation increase 3.00% 3.00% Cash balance interest crediting rate - Spire Alabama / Spire Missouri 4.25% 4.25% The following table sets forth the year-end projected benefit obligation, accumulated benefit obligation, and fair value of plan assets for plans that have a projected benefit obligation and an accumulated benefit obligation in excess of plan assets: Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Projected benefit obligation $ 438.7 $ 464.4 $ 313.2 $ 320.6 $ 80.6 $ 97.8 Accumulated benefit obligation 433.1 457.1 309.5 315.0 78.8 96.2 Fair value of plan assets 334.7 332.7 242.0 235.9 53.6 57.3 The following tables set forth the targeted and actual plan assets by category as of September 30 Spire Missouri 2023 Target 2023 Actual 2022 Target 2022 Actual Return seeking assets 70.0 % 77.0 % 70.0 % 74.3 % Liability hedging assets 30.0 % 20.0 % 30.0 % 22.8 % Cash and cash equivalents — % 3.0 % — % 2.9 % Total 100.0 % 100.0 % 100.0 % 100.0 % Spire Alabama 2023 Target 2023 Actual 2022 Target 2022 Actual Return seeking assets 75.0 % 76.0 % 70.0 % 68.7 % Liability hedging assets 25.0 % 15.0 % 30.0 % 25.3 % Cash and cash equivalents — % 9.0 % — % 6.0 % Total 100.0 % 100.0 % 100.0 % 100.0 % The Spire Inc. Retirement Plans Committee is responsible for the administration of the various plans, and all payments under the plans require direction of that committee. The Spire Inc. Defined Benefit Plan Investment Review Committee utilizes an Outsourced Chief Investment Officer (OCIO) model where investment decisions are outsourced to investment consultants (Willis Towers Watson), who in turn become co-fiduciaries with the committee. For all plans, the Company employs a total return investment approach whereby a mix of equities and fixed income investments are used to maximize the long-term return of plan assets with a prudent level of risk. Risk tolerance is established through consideration of plan liabilities, plan funded status, corporate financial condition and market conditions. The Company has developed an investment strategy that focuses on asset allocation, diversification and quality guidelines. The investment goals are to obtain an adequate level of return to meet future obligations of the plan by providing above average risk-adjusted returns with a risk exposure in the mid-range of comparable funds. Comparative market and peer group benchmarks are utilized to ensure that investment managers are performing satisfactorily. The Company seeks to maintain an appropriate level of diversification to minimize the risk of large losses in a single asset class. Accordingly, plan assets for the pension plans do not The following table sets forth expected pension benefit payments for the succeeding five five 2024 2025 2026 2027 2028 2029 2032 Spire $ 52.4 $ 45.3 $ 41.8 $ 41.8 $ 43.3 $ 202.8 Spire Missouri 41.0 34.1 30.4 29.4 30.5 139.1 Spire Alabama 8.0 7.7 7.8 8.7 8.9 44.1 The funding policy of Spire Missouri and Spire Alabama is to contribute an amount not 2024 2024 Other Postretirement Benefits Spire and the Utilities provide certain life insurance benefits at retirement. Spire Missouri plans provide for medical insurance after early retirement until age 65. January 1, 2015, Net periodic postretirement benefit costs consist of the following components: Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Service cost – benefits earned during the period $ 4.8 $ 7.5 $ 7.3 $ 4.0 $ 6.3 $ 6.2 $ 0.7 $ 1.1 $ 0.9 Interest cost on accumulated postretirement benefit obligation 8.5 6.0 6.0 6.5 4.5 4.5 1.8 1.4 1.3 Expected return on plan assets (15.8 ) (16.8 ) (16.1 ) (10.5 ) (11.3 ) (10.9 ) (5.0 ) (5.2 ) (4.9 ) Amortization of prior service cost (credit) 0.3 1.0 1.0 0.6 0.7 0.7 (0.3 ) 0.3 0.3 Amortization of actuarial gain (4.0 ) (2.2 ) (1.6 ) (3.2 ) (1.9 ) (1.5 ) (0.5 ) — — Subtotal (6.2 ) (4.5 ) (3.4 ) (2.6 ) (1.7 ) (1.0 ) (3.3 ) (2.4 ) (2.4 ) Regulatory adjustment 0.6 3.3 13.2 1.8 5.0 15.0 (1.3 ) (1.8 ) (1.8 ) Net postretirement benefit (income) cost $ (5.6 ) $ (1.2 ) $ 9.8 $ (0.8 ) $ 3.3 $ 14.0 $ (4.6 ) $ (4.2 ) $ (4.2 ) Other changes in plan assets and postretirement benefit obligations recognized in OCI include the following: Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Current year actuarial (gain) loss $ (24.4 ) $ 15.8 $ (41.0 ) $ (21.5 ) $ 9.8 $ (29.0 ) $ (1.1 ) $ 5.9 $ (9.9 ) Amortization of actuarial gain 4.0 2.2 1.6 3.2 1.9 1.5 0.5 — — Current year prior service cost — (6.3 ) — (1.1 ) — — (5.2 ) — Amortization of prior service (cost) credit (0.3 ) (1.0 ) (1.0 ) (0.6 ) (0.7 ) (0.7 ) 0.3 (0.3 ) (0.3 ) Subtotal (20.7 ) 10.7 (40.4 ) (18.9 ) 9.9 (28.2 ) (0.3 ) 0.4 (10.2 ) Regulatory adjustment 20.7 (10.7 ) 40.4 18.9 (9.9 ) 28.2 0.3 (0.4 ) 10.2 Total recognized in OCI $ — $ — $ — $ — $ — $ — $ — $ — $ — Pursuant to a MoPSC Order, the return on plan assets is based on the market-related value of plan assets implemented prospectively over a four not December 23, 2021, no 2022 December 2022, The following table sets forth the reconciliation of the beginning and ending balances of the postretirement benefit obligation at September 30: Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Benefit obligation, beginning of year $ 148.1 $ 204.2 $ 114.8 $ 151.7 $ 29.9 $ 48.0 Service cost 4.8 7.5 4.0 6.3 0.7 1.1 Interest cost 8.5 6.0 6.5 4.5 1.8 1.4 Actuarial (gain) loss (10.6 ) (52.6 ) (13.4 ) (37.7 ) 4.2 (13.6 ) Plan amendments — (6.2 ) — (1.0 ) — (5.2 ) Retiree drug subsidy program 0.2 0.2 0.2 0.2 — — Benefits paid (8.4 ) (11.0 ) (6.8 ) (9.2 ) (1.5 ) (1.8 ) Benefit obligation, end of year $ 142.6 $ 148.1 $ 105.3 $ 114.8 $ 35.1 $ 29.9 In fiscal 2023 The following table sets forth the reconciliation of the beginning and ending balances of the fair value of plan assets at September 30: Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Fair value of plan assets at beginning of year $ 264.7 $ 326.9 $ 176.7 $ 221.7 $ 83.3 $ 99.4 Actual return on plan assets 29.9 (51.6 ) 18.8 (36.2 ) 10.2 (14.3 ) Employer contributions 0.1 0.4 0.1 0.4 — — Benefits paid (8.4 ) (11.0 ) (6.8 ) (9.2 ) (1.5 ) (1.8 ) Fair value of plan assets, end of year $ 286.3 $ 264.7 $ 188.8 $ 176.7 $ 92.0 $ 83.3 Funded status of plans, end of year $ 143.7 $ 116.6 $ 83.5 $ 61.9 $ 56.9 $ 53.4 The following table sets forth the amounts recognized in the balance sheets at September 30: Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Noncurrent assets $ 180.7 $ 151.6 $ 120.5 $ 96.9 $ 56.9 $ 53.4 Current liabilities (0.4 ) (0.3 ) (0.4 ) (0.3 ) — — Noncurrent liabilities (36.6 ) (34.7 ) (36.6 ) (34.7 ) — — Total $ 143.7 $ 116.6 $ 83.5 $ 61.9 $ 56.9 $ 53.4 Pre-tax amounts recognized in accumulated other comprehensive loss not Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Net actuarial gain $ (103.3 ) $ (83.3 ) $ (92.3 ) $ (74.2 ) $ (6.1 ) $ (5.6 ) Prior service cost (credit) 7.0 7.1 7.4 7.9 (0.4 ) (0.8 ) Subtotal (96.3 ) (76.2 ) (84.9 ) (66.3 ) (6.5 ) (6.4 ) Adjustments for amounts included in regulatory assets 96.3 76.2 84.9 66.3 6.5 6.4 Total $ — $ — $ — $ — $ — $ — The assumptions used to calculate net periodic postretirement benefit costs for Spire Missouri are as follows: 2023 2022 2021 Weighted average discount rate - Spire Missouri plans 5.80% 2.95% 2.75% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets - Spire Missouri plans 5.50% 5.75% 5.75% The assumptions used to calculate net periodic postretirement benefit costs for Spire Alabama are as follows: 2023 2022 2021 Weighted average discount rate 5.80% 2.95% 2.75% Expected long-term rate of return on plan assets 4.75%/6.0% 5.00%/6.25% 5.00%/6.25% The discount rate is based on long-term, high quality bond indices at the measurement date. The expected long-term rate of return on plan assets is based on historical and projected rates of return for current and planned asset classes in the investment portfolio. Assumed projected rates of return for each asset class were selected after analyzing historical experience and future expectations of the returns. The overall expected rate of return for the portfolio was developed based on the target allocation for each class. The assumptions used to calculate the accumulated postretirement benefit obligations are as follows: 2023 2022 Weighted average discount rate - Spire Alabama plans and Spire Missouri Plans 6.30% 5.80% Weighted average rate of future compensation increase - Spire Missouri East plans 3.00% 3.00% The assumed medical cost trend rates at September 30 2023 2022 Medical cost trend assumed for next year - Spire Alabama and Spire Missouri 6.50% 6.75% Rate to which the medical cost trend rate is assumed to decline (the ultimate medical cost trend rate) 5.00% 5.00% Year the rate reaches the ultimate trend 2030 2028 The following tables set forth the targeted and actual plan assets by category as of September 30 Spire Missouri Target 2023 Actual 2022 Actual Equity securities 60.0 % 58.9 % 58.7 % Debt securities 40.0 % 38.1 % 40.5 % Cash and cash equivalents — % 3.0 % 0.8 % Total 100.0 % 100.0 % 100.0 % Spire Alabama Target 2023 Actual 2022 Actual Equity securities 60.5 % 59.9 % 57.7 % Debt securities 39.5 % 40.1 % 42.3 % Total 100.0 % 100.0 % 100.0 % Missouri and Alabama state laws provide for the recovery in rates of costs accrued pursuant to GAAP provided that such costs are funded through an independent, external funding mechanism. The Utilities have established Voluntary Employees’ Beneficiary Association and Rabbi Trusts as external funding mechanisms. Their investment policies seek to maximize investment returns consistent with their tolerance for risk. Outside investment management specialists are utilized in each asset class. Such specialists are provided with guidelines, where appropriate, designed to ensure that the investment portfolio is managed in accordance with policy. Performance and compliance with the guidelines is regularly monitored. Spire Missouri and Spire Alabama currently invest in mutual funds which are rebalanced periodically to the target allocation. The mutual funds are diversified across U.S. stock and bond markets, and for Spire Alabama, international stock markets. The following table sets forth expected postretirement benefit payments for the succeeding five five 2024 2025 2026 2027 2028 2029 2032 Spire $ 14.6 $ 14.8 $ 14.9 $ 14.8 $ 14.5 $ 68.6 Spire Missouri 11.6 11.8 11.8 11.7 11.4 52.2 Spire Alabama 2.9 2.9 2.9 2.9 2.9 15.0 The Utilities’ funding policy is to contribute amounts to the trusts equal to the periodic benefit cost calculated pursuant to GAAP as recovered in rates. For both Spire Missouri and Spire Alabama there are no anticipated contributions to the postretirement plans in fiscal 2024 Other Plans Spire Services Inc. sponsors a 401 2023 2022 2021 2023 2022 2021 2023 2022 2021 Fair Value Measurements of Pension and Other Postretirement Plan Assets Spire The table below categorizes the fair value measurements of the Spire pension plan assets: As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 14.8 $ — $ 14.8 $ 11.5 $ — $ 11.5 Equity funds - global (including U.S.) — 139.0 139.0 — 122.2 122.2 Real asset funds — 55.2 55.2 — 61.0 61.0 Debt securities: U.S. bond funds 27.8 — 27.8 42.3 — 42.3 U.S. government index funds 36.2 — 36.2 36.1 — 36.1 Global funds (including U.S.) — 61.7 61.7 — 59.6 59.6 Total $ 78.8 $ 255.9 $ 334.7 $ 89.9 $ 242.8 $ 332.7 The table below categorizes the fair value measurements of Spire’s postretirement plan assets: As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 5.1 $ — $ 5.1 $ 3.5 $ — $ 3.5 U.S. stock/bond mutual funds 188.2 76.5 264.7 177.1 69.4 246.5 International fund — 16.5 16.5 0.8 13.9 14.7 Total $ 193.3 $ 93.0 $ 286.3 $ 181.4 $ 83.3 $ 264.7 Cash and cash equivalents include money market mutual funds valued based on quoted market prices. Debt securities are valued based on broker/dealer quotations or by using observable market inputs. The stock and bond mutual funds are valued at the quoted market price of the identical securities. Spire Missouri The table below categorizes the fair value measurements of Spire Missouri’s pension plan assets: As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 6.8 $ — $ 6.8 $ 5.7 $ — $ 5.7 Equity funds - global (including U.S.) — 99.4 99.4 — 85.7 85.7 Real asset funds — 40.2 40.2 — 47.2 47.2 Debt securities: U.S. bond funds 20.9 — 20.9 29.4 — 29.4 U.S. government index funds 28.7 — 28.7 24.6 — 24.6 Global funds (including U.S.) — 46.0 46.0 — 43.3 43.3 Total $ 56.4 $ 185.6 $ 242.0 $ 59.7 $ 176.2 $ 235.9 The table below categorizes the fair value measurements of Spire Missouri’s postretirement plan assets: As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 4.3 $ — $ 4.3 $ 2.7 $ — $ 2.7 U.S. stock/bond mutual funds 184.5 — 184.5 174.0 — 174.0 Total $ 188.8 $ — $ 188.8 $ 176.7 $ — $ 176.7 Cash and cash equivalents include money market mutual funds valued based on quoted market prices. Debt securities are valued based on broker/dealer quotations or by using observable market inputs. The stock and bond mutual funds are valued at the quoted market price of the identical securities. Spire Alabama The table below categorizes the fair value measurements of Spire Alabama’s pension plan assets: As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 4.6 $ — $ 4.6 $ 3.5 $ — $ 3.5 Equity funds - global (including U.S.) — 22.9 22.9 — 21.6 21.6 Real asset funds — 8.7 8.7 — 8.1 8.1 Debt securities: U.S. bond funds 4.0 — 4.0 7.7 — 7.7 U.S. government index funds 4.3 — 4.3 6.8 — 6.8 Global funds (including U.S.) — 9.1 9.1 — 9.6 9.6 Total $ 12.9 $ 40.7 $ 53.6 $ 18.0 $ 39.3 $ 57.3 The table below categorizes the fair value measurements of Spire Alabama’s postretirement plan assets: As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total U.S. stock/bond mutual funds $ — $ 76.5 $ 76.5 $ — $ 69.4 $ 69.4 International fund — 15.5 15.5 — 13.9 13.9 Total $ — $ 92.0 $ 92.0 $ — $ 83.3 $ 83.3 Cash and cash equivalents include money market mutual funds valued based on quoted market prices. Debt securities are valued based on broker/dealer quotations or by using observable market inputs. The stock and bond mutual funds are valued at the quoted market price of the identical securities.

Note 14 - Information by Operat

Note 14 - Information by Operating Segment	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Segment Reporting Disclosure [Text Block]	14. The Company has three Accounting policies are described in Note 1 Management evaluates the performance of the operating segments based on the computation of net economic earnings. Net economic earnings exclude from reported net income, as applicable, the after-tax impacts of fair value accounting and timing adjustments associated with energy-related transactions, the impacts of acquisition, divestiture and restructuring activities, and the largely non-cash impacts of other non-recurring or unusual items such as certain regulatory, legislative or GAAP standard-setting actions. Gas Gas 2023 Utility Marketing Midstream Other Eliminations Consolidated Revenues from external customers $ 2,456.6 $ 179.1 $ 29.9 $ 0.7 $ — $ 2,666.3 Intersegment revenues 0.3 — 36.2 16.0 (52.5 ) — Total Operating Revenues 2,456.9 179.1 66.1 16.7 (52.5 ) 2,666.3 Depreciation and amortization expense 244.4 1.5 8.4 0.5 — 254.8 Interest expense 139.9 — 8.6 72.1 (34.9 ) 185.7 Income tax expense (benefit) 32.7 12.8 3.8 (10.5 ) — 38.8 Net economic earnings (loss) 200.5 47.6 14.1 (34.1 ) — 228.1 Capital expenditures 588.6 0.4 73.6 (0.1 ) — 662.5 Gas Gas 2022 Utility Marketing Midstream Other Eliminations Consolidated Revenues from external customers $ 1,945.6 $ 234.9 $ 17.4 $ 0.6 $ — $ 2,198.5 Intersegment revenues 0.5 — 35.7 15.5 (51.7 ) — Total Operating Revenues 1,946.1 234.9 53.1 16.1 (51.7 ) 2,198.5 Depreciation and amortization expense 227.9 1.4 7.5 0.5 — 237.3 Interest expense 86.4 — 4.9 37.3 (8.8 ) 119.8 Income tax expense (benefit) 49.6 11.9 4.5 (7.1 ) — 58.9 Net economic earnings (loss) 202.7 27.0 11.1 (24.5 ) — 216.3 Capital expenditures 528.6 0.9 22.6 0.1 — 552.2 Gas Gas 2021 Utility Marketing Midstream Other Eliminations Consolidated Revenues from external customers $ 2,118.2 $ 96.5 $ 19.9 $ 0.9 $ — $ 2,235.5 Intersegment revenues 1.1 — 32.7 14.2 (48.0 ) — Total Operating Revenues 2,119.3 96.5 52.6 15.1 (48.0 ) 2,235.5 Depreciation and amortization expense 204.4 1.2 6.9 0.6 — 213.1 Interest expense 74.7 — 4.0 29.3 (1.4 ) 106.6 Income tax expense (benefit) 56.9 13.4 4.4 (6.2 ) — 68.5 Net economic earnings (loss) 230.6 47.0 11.1 (22.4 ) — 266.3 Capital expenditures 590.4 0.7 33.0 0.7 — 624.8 Total Assets at End of Year 2023 2022 2021 Gas Utility $ 8,486.7 $ 8,042.8 $ 7,615.4 Gas Marketing 332.0 638.7 466.1 Midstream 574.3 446.0 413.8 Other 2,533.3 2,705.5 2,193.3 Eliminations (1,612.7 ) (1,749.3 ) (1,332.2 ) Total Assets $ 10,313.6 $ 10,083.7 $ 9,356.4 Reconciliation of Consolidated Net Income to Consolidated Net Economic Earnings 2023 2022 2021 Net Income $ 217.5 $ 220.8 $ 271.7 Adjustments, pre-tax: Missouri regulatory adjustments — — (9.0 ) Fair value and timing adjustments 11.4 (11.4 ) 3.3 Acquisition and divestiture activities 2.5 — (1.3 ) Income tax adjustments (3.3 ) 6.9 1.6 Net Economic Earnings $ 228.1 $ 216.3 $ 266.3

Note 15 - Regulatory Matters

Note 15 - Regulatory Matters	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Public Utilities Disclosure [Text Block]	15. As discussed below for Spire Missouri and Spire Alabama, the Purchased Gas Adjustment (PGA) clauses and Gas Supply Adjustment (GSA) riders allow the Utilities to pass through to customers the cost of purchased gas supplies. Regulatory assets and regulatory liabilities related to the PGA clauses and the GSA rider are both labeled Unamortized Purchased Gas Adjustments herein. The following regulatory assets and regulatory liabilities were reflected in the balance sheets of the Company, Spire Missouri and Spire Alabama as of September 30, 2023 2022 Spire Spire Missouri Spire Alabama September 30 2023 2022 2023 2022 2023 2022 Regulatory Assets: Current: Unamortized purchased gas adjustments $ 293.2 $ 322.2 $ 269.4 $ 275.1 $ 21.7 $ 43.8 Other 55.1 33.2 23.7 13.0 19.9 13.1 Total Current Regulatory Assets 348.3 355.4 293.1 288.1 41.6 56.9 Noncurrent: Future income taxes due from customers 144.5 137.8 136.2 129.2 2.0 2.2 Pension and postretirement benefit costs 261.0 294.5 189.1 222.9 67.8 66.5 Cost of removal 633.2 493.7 97.0 25.2 536.2 468.5 Unamortized purchased gas adjustments 23.0 — 23.0 — — — Energy efficiency 56.3 57.2 56.3 57.2 — — Other 131.2 129.2 116.0 113.1 0.9 1.0 Total Noncurrent Regulatory Assets 1,249.2 1,112.4 617.6 547.6 606.9 538.2 Total Regulatory Assets $ 1,597.5 $ 1,467.8 $ 910.7 $ 835.7 $ 648.5 $ 595.1 Regulatory Liabilities: Current: Other $ 7.3 $ 3.7 $ — $ — $ — $ — Total Current Regulatory Liabilities 7.3 3.7 — — — — Noncurrent: Deferred taxes due to customers 128.0 145.3 114.8 127.9 — — Pension and postretirement benefit costs 185.2 172.6 156.5 143.6 17.9 19.4 Accrued cost of removal 126.6 32.9 90.4 — — — Unamortized purchased gas adjustments 11.2 53.0 11.2 53.0 — — Other 21.4 14.4 16.5 7.3 3.3 3.6 Total Noncurrent Regulatory Liabilities 472.4 418.2 389.4 331.8 21.2 23.0 Total Regulatory Liabilities $ 479.7 $ 421.9 $ 389.4 $ 331.8 $ 21.2 $ 23.0 A portion of the Company’s and Spire Missouri's regulatory assets are not Spire Spire Missouri September 30 2023 2022 2023 2022 Pension and postretirement benefit costs $ 133.4 $ 152.9 $ 133.4 $ 152.9 Future income taxes due from customers 142.5 135.6 136.2 129.2 Unamortized purchase gas adjustments 292.4 275.1 292.4 275.1 Other 104.2 122.7 104.2 122.7 Total Regulatory Assets Not Earning a Return $ 672.5 $ 686.3 $ 666.2 $ 679.9 Like all the Company’s regulatory assets, these regulatory assets as of September 30, 2023 two not not 35 not not Spire Missouri As authorized by the MoPSC, the PGA clause allows Spire Missouri to flow through to customers, subject to prudence review by the MoPSC, the cost of purchased gas supplies. To better match customer billings with market natural gas prices, Spire Missouri is allowed to file to modify, on a periodic basis, the level of gas costs in its PGA. Certain provisions of the PGA clause are included below: • Spire Missouri has a risk management policy that allows for the purchase of natural gas derivative instruments with the goal of managing price risk associated with purchasing natural gas on behalf of its customers. The MoPSC clarified that costs, cost reductions, and carrying costs associated with the Utility’s use of natural gas derivative instruments are gas costs recoverable through the PGA mechanism. • The tariffs allow Spire Missouri flexibility to make up to three November two • Spire Missouri is authorized to apply carrying costs to all over- or under-recoveries of gas costs, including cost increases and cost reductions associated with the use of derivative instruments, including cash payments for margin deposits. • Pre-tax income from off-system sales and capacity release revenues is shared with customers (such that customers receive 75% and Spire Missouri receives 25%). Pursuant to the provisions of the PGA clause, the difference between actual costs incurred and costs recovered through the application of the PGA clause, as well as the actual amount of off-system sales and capacity release revenues allocated to customers, are reflected as a regulatory asset or liability at the end of the fiscal year. At that time, the balance is classified as a current asset or current liability and recovered from, or credited to, customers over an annual period commencing in the subsequent November. 2023, two November 29, 2022 January 19, 2023. In mid- February 2021, third three not February 2022, second 2022. three May 2022, As a result of the significant net deferred gas costs and average inventory cost in the second 2021, three In the first 2022, December 23, 2021, December 23, 2021 September 30, 2022 April 1, 2022, November 4, 2022. November 18, 2022, December 26, 2022. ISRS allows Spire Missouri expedited recovery for its investment to replace qualifying components of its infrastructure without the necessity of a formal rate case. As noted above, all prior ISRS revenues were reset to zero December 26, 2022 April 20, 2023, May 6, 2023, October 2022 February 2023. October 4, 2023, October 23, 2023, March 2023 August 2023. On May 27, 2022, first no July 11, 2022, July 29 August 1, 2022, January 6, 2023, January 25, 2023, July 25- 26, 2023; July 21, 2023, August 23, 2023 In 2022, 2022 0135 2022 0136 2020 2021 December 15, 2022, January 19, 2023, no July 12, 2023, May 2024. November 2, 2023, Spire Alabama In September 2022, September 30, 2025, March, June September December 1, October 1, 2022, 2022, 2023, 2024, 2023 2025. The inflation-based Cost Control Measure (CCM) established by the APSC allows for annual changes in operation and maintenance (“O&M”) expense relative to an index range. Effective October 1, 2022, 2020, 2021, 2022. August 2020, 2021, 2022. August no three one three not not may The RSE reduction for September 30, 2021 2021 2021 five 24 December 29, 2021, 2022 2021 five 2021 January 1, 2022. no 2022 January 31, April 30, July 31 September 30 2022 2021 2022 five October 26, 2022, September 30, 2023, 2017 January 1, 2023. no 2023 March 31, June 30 September 30 2023 October 26, 2023, September 30, 2024, December 1, 2023. Spire Alabama’s rate schedules for natural gas distribution charges contain a GSA rider which permits the pass-through to customers of changes in the cost of gas supply. Spire Alabama’s tariff provides a temperature adjustment mechanism, also included in the GSA rider, which is designed to moderate the impact of departures from normal temperatures on Spire Alabama’s earnings. The temperature adjustment applies primarily to residential, small commercial and small industrial customers. Other non-temperature weather-related conditions that may not April 2022, first December 1, 2022 January 1, 2023, October 1, 2023 December 1, 2023, The APSC approved an Enhanced Stability Reserve (ESR) in 1998, 2010. 1 2 3 4 may five Spire In addition to those discussed above for Spire Missouri and Spire Alabama, Spire is affected by the following regulatory matters. Spire Gulf has similar rate regulation to Spire Alabama. Its RSE rate-setting mechanism was renewed in September 2021 four September 2025. 2021, 2022 2025. October 2021 2022, January 2022 2023, 2023 April 30, 2023 July 1, 2023. September 30, 2023, December 1, 2023. 2017 2021 2021 2022. 2022, 2023 2025 2022 2021 2022 2023 10 not 2019 two not Spire Mississippi utilizes a formula rate-making process under the Rate Stabilization Adjustment Rider (RSA). An allowed return on equity (currently 10.04%) is computed annually and compared to the actual return on equity based on a rate year ending June 30. may 12 months ended June 30, September 15 November 1, January 15 February 1, 2022 January 1, 2023. September 1, 2023 In August 2018, “August 2018 June 2021, September December 2021, December 15, 2022, no

Note 16 - Commitments and Conti

Note 16 - Commitments and Contingencies	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Commitments and Contingencies Disclosure [Text Block]	16. Commitments The Company and the Utilities have entered into contracts with various counterparties, expiring on dates through calendar 2039, September 30, 2023 November April. In May 2023, second 2024 A consolidated subsidiary of Spire is a limited partner in Inter-Atlantic Energy Capital Ventures, L.P., an unconsolidated partnership focusing on sustainability initiatives largely tied to the natural gas utility sector. Spire committed to contribute a total of $10.0 of capital to the partnership as and when requested by the general partner. As of September 30, 2023 Contingencies The Company and the Utilities account for contingencies, including environmental liabilities, in accordance with accounting standards under the loss contingency guidance of ASC Topic 450, Contingencies In addition to matters noted below, the Company and the Utilities are involved in other litigation, claims, and investigations arising in the normal course of business. Management, after discussion with counsel, believes the final outcome will not The Company and the Utilities own and operate natural gas distribution, transmission, and storage facilities, the operations of which are subject to various environmental laws, regulations, and interpretations. While environmental issues resulting from such operations arise in the ordinary course of business, such issues have not may may may In the natural gas industry, many gas distribution companies have incurred environmental liabilities associated with sites they or their predecessor companies formerly owned or operated where manufactured gas operations took place. The Utilities each have former manufactured gas plant (MGP) operations in their respective service territories, some of which are discussed under the Spire Missouri and Spire Alabama headings below. To the extent costs are incurred associated with environmental remediation activities, the Utilities would request authority from their respective regulators to defer such costs (less any amounts received from insurance proceeds or as contributions from other potentially responsible parties (PRPs)) and collect them through future rates. To date, costs incurred for all Spire MGP sites for investigation, remediation and monitoring have not may may In 2020, March 2021, not may Spire Missouri Spire Missouri has identified three two third In conjunction with redevelopment of the Carondelet Coke site, Spire Missouri and another former owner of the site entered into an agreement (the “Remediation Agreement”) with the City development agencies, the developer, and an environmental consultant that obligates one No December 20, 2010, seven six In a letter dated June 29, 2011, second January 10, 2012, no Additionally, in correspondence dated November 30, 2016, 7 107 1980 third not March 2017 Spire Missouri has notified its insurers that it seeks reimbursement for costs incurred in the past and future potential liabilities associated with these MGP sites. While some of the insurers have denied coverage and reserved their rights, Spire Missouri retains the right to seek potential reimbursements from them. On March 10, 2015, 104 7 April 3, 2015, July 15, 2015, August 15, 2015. no In its western service area, Spire Missouri has six #1, #1, #2. 2003 September 15, 2016, six May 11, 2015, Spire Alabama Spire Alabama is in the chain of title of nine four five one In 2011, In 2012, 104 35th not 35th Assessments were performed by the EPA of the former MGP sites in Gadsden and Anniston, and NFA letters were received after each assessment. Spire In addition to those discussed above for Spire Missouri and Spire Alabama, Spire is aware of the following contingent matters. Spire Marketing, along with many natural gas industry participants, faced the unprecedented effects of Winter Storm Uri in February 2021. may

Note 17 - Leases

Note 17 - Leases	12 Months Ended
	Sep. 30, 2023
Notes to Financial Statements
Lessee, Operating Leases [Text Block]	17. The lease agreement covering the Company’s primary office space in St. Louis extends through February 2035, five January 2037, two five December 2028, three five ten Operating lease cost, cash flow and noncash information are shown in the following table. Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Operating lease cost, including amounts capitalized $ 7.3 $ 7.4 $ 7.2 $ 0.5 $ 0.5 $ 0.4 $ 2.0 $ 2.1 $ 2.1 Cash flow and noncash information about operating leases: Operating cash flows representing cash paid for amounts included in the measurement of lease liabilities 7.3 7.3 7.2 0.5 0.5 0.4 2.1 2.1 2.1 Right-of-use assets obtained in exchange for lease liabilities 0.8 24.6 — 0.8 1.1 — — 23.5 — The following table shows year-end balance sheet and weighted-average information about operating leases. Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Right-of-use assets $ 70.6 $ 73.7 $ 2.1 $ 1.7 $ 19.2 $ 20.2 Lease liabilities, current 6.8 6.5 0.5 0.4 1.9 1.9 Lease liabilities, noncurrent 70.2 73.7 1.8 1.5 23.5 24.6 Weighted-average remaining lease term (in years) 14.1 15.0 5.6 5.1 13.3 14.3 Weighted-average discount rate 4.2 % 4.1 % 3.3 % 2.2 % 3.7 % 3.7 % On the balance sheets, right-of-use assets are included in “Deferred Charges and Other Assets: Other,” current lease liabilities are in “Current Liabilities: Other,” and noncurrent lease liabilities are in “Deferred Credits and Other Liabilities: Other.” Following is a maturity analysis by fiscal year for operating lease liabilities as of September 30, 2023 Spire Spire Missouri Spire Alabama 2024 $ 6.9 $ 0.5 $ 1.9 2025 7.5 0.6 2.2 2026 7.5 0.4 2.2 2027 7.4 0.3 2.3 2028 7.4 0.3 2.3 Thereafter 65.9 0.5 21.7 Total undiscounted lease payments 102.6 2.6 32.6 Less present value discount (25.6 ) (0.3 ) (7.2 ) Total current and noncurrent lease liabilities $ 77.0 $ 2.3 $ 25.4 There are no The Company elected, for all asset classes, not not The discount rate used for all the leases is the applicable incremental borrowing rate, which is the rate of interest that a lessee would have to pay to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. For a subsidiary lessee, the rate applicable to the subsidiary is used unless the lease terms are influenced by parent credit.

Insider Trading Arrangements

Insider Trading Arrangements	12 Months Ended
	Sep. 30, 2023
Insider Trading Arr Line Items
Material Terms of Trading Arrangement [Text Block]	9B. During the quarterly period ended September 30, 2023 no 10b5 1 10b5 1
Rule 10b5-1 Arrangement Adopted [Flag]	false
Non-Rule 10b5-1 Arrangement Adopted [Flag]	false
Rule 10b5-1 Arrangement Terminated [Flag]	false
Non-Rule 10b5-1 Arrangement Terminated [Flag]	false

Significant Accounting Policies

Significant Accounting Policies (Policies)	12 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	BASIS OF PRESENTATION September 30 The accompanying audited financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). The consolidated financial position, results of operations and cash flows of Spire include the accounts of the Company and all its subsidiaries. Transactions and balances between consolidated entities have been eliminated from the consolidated financial statements of Spire. In compliance with GAAP, transactions between Spire Missouri and Spire Alabama and their affiliates, as well as intercompany balances on their balance sheets, have not NATURE OF OPERATIONS Note 14
Use of Estimates, Policy [Policy Text Block]	USE OF ESTIMATES
System Of Accounts Policy [Policy Text Block]	SYSTEM OF ACCOUNTS
Public Utilities, Policy [Policy Text Block]	REGULATED OPERATIONS 980, Regulated Operations third may Note 15
Property, Plant and Equipment, Policy [Policy Text Block]	PROPERTY, PLANT, AND EQUIPMENT Utility Plant Utility plant is depreciated using the composite method on a straight-line basis over the estimated service lives of the various classes of property at rates approved by the applicable regulatory commission. For Spire Missouri and for Spire Alabama, the annual depreciation and amortization expense in fiscal years 2023 2022 2021 Non-utility Property not
Accrued Capital Expenditures [Policy Text Block]	Accrued Capital Expenditures September 30 2023 2022 2021 Spire $ 104.3 $ 77.8 $ 59.5 Spire Missouri 56.5 45.6 37.1 Spire Alabama 4.6 19.2 13.6
Asset Retirement Obligation [Policy Text Block]	ASSET RETIREMENT OBLIGATIONS not not The following table presents a reconciliation of the beginning and ending balances of asset retirement obligations at September 30, Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Asset retirement obligations, beginning of year $ 520.9 $ 519.6 $ 110.6 $ 143.4 $ 398.7 $ 362.8 Liabilities incurred during the period 7.9 3.2 0.9 1.2 2.0 0.5 Liabilities settled during the period (6.8 ) (9.2 ) (2.5 ) (4.1 ) (2.5 ) (2.0 ) Accretion 21.5 21.1 4.5 5.9 16.5 14.7 Revisions in estimated cash flows 33.9 (13.8 ) (2.4 ) (35.8 ) 36.3 22.7 Asset retirement obligations, end of year $ 577.4 $ 520.9 $ 111.1 $ 110.6 $ 451.0 $ 398.7
Inventory, Policy [Policy Text Block]	NATURAL GAS AND PROPANE GAS first first first September 30, 2023 September 30, 2022
Business Combinations and Goodwill [Policy Text Block]	BUSINESS COMBINATIONS AND GOODWILL September 30, 2023 not 2017, no July 1 not September 30, 2023 not A subsidiary of Spire in the Midstream segment acquired a natural gas storage facility in northern Oklahoma, now named Spire Storage Salt Plains LLC, on April 1, 2023. no
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	IMPAIRMENT OF LONG-LIVED ASSETS may not
Derivatives, Policy [Policy Text Block]	DERIVATIVES 815, Derivatives and Hedging not Note 10
Income Tax, Policy [Policy Text Block]	INCOME TAXES not not The Company accounts for uncertain tax positions in accordance with authoritative guidance. The authoritative guidance addresses the determination of whether tax benefits claimed, or expected to be claimed, on a tax return should be recorded in the financial statements. Spire may not Note 12
Cash and Cash Equivalents, Policy [Policy Text Block]	CASH, CASH EQUIVALENTS, AND RESTRICTED CASH three September 30, 2023 2022
Accounts Receivable [Policy Text Block]	NATURAL GAS RECEIVABLE third third
Earnings Per Share, Policy [Policy Text Block]	EARNINGS PER COMMON SHARE two Note 4
Transactions With Affiliates [Policy Text Block]	TRANSACTIONS WITH AFFILIATES Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 Natural gas purchases from Spire Marketing $ 57.4 $ 86.3 $ 92.5 $ 4.7 $ 3.2 $ 10.4 Natural gas sales to Spire Marketing 0.4 — 1.1 — 0.5 0.1 Transportation services from Spire STL Pipeline LLC 32.0 32.0 32.0 — — — Natural gas storage services from Spire Storage Salt Plains LLC 0.7 — — — — — Transportation services from Spire NGL Inc. — — 0.5 — — —
Receivable [Policy Text Block]	ACCOUNTS RECEIVABLE AND ALLOWANCE FOR CREDIT LOSSES not Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Allowance at beginning of year $ 31.9 $ 30.3 $ 24.9 $ 24.9 $ 22.6 $ 18.1 $ 6.3 $ 6.6 $ 5.5 Provision for expected credit losses 16.6 11.6 14.7 13.3 11.2 11.1 2.6 0.3 3.1 Write-offs, net of recoveries (16.0 ) (10.0 ) (9.3 ) (12.0 ) (8.9 ) (6.6 ) (3.2 ) (0.6 ) (2.0 ) Allowance at end of year $ 32.5 $ 31.9 $ 30.3 $ 26.2 $ 24.9 $ 22.6 $ 5.7 $ 6.3 $ 6.6 FINANCE RECEIVABLES third September 30, 2023 2022 90 third 12 third 90 September 30, 2023 2022
Liability Reserve Estimate, Policy [Policy Text Block]	GROUP MEDICAL AND WORKERS COMPENSATION RESERVES not
Fair Value of Financial Instruments, Policy [Policy Text Block]	FAIR VALUE MEASUREMENTS The levels of the hierarchy are described below: • Level 1 • Level 2 1, • Level 3 Assessment of the significance of a particular input to the fair value measurements may may Note 8 Note 9 Note 13
Share-Based Payment Arrangement [Policy Text Block]	STOCK-BASED COMPENSATION 718, Compensation - Stock Compensation Note 3

Note 1 - Summary of Significa_2

Note 1 - Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule Of Capital Expenditure Excluded From Statement Of Cash Flow [Table Text Block]	September 30 2023 2022 2021 Spire $ 104.3 $ 77.8 $ 59.5 Spire Missouri 56.5 45.6 37.1 Spire Alabama 4.6 19.2 13.6
Schedule of Asset Retirement Obligations [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Asset retirement obligations, beginning of year $ 520.9 $ 519.6 $ 110.6 $ 143.4 $ 398.7 $ 362.8 Liabilities incurred during the period 7.9 3.2 0.9 1.2 2.0 0.5 Liabilities settled during the period (6.8 ) (9.2 ) (2.5 ) (4.1 ) (2.5 ) (2.0 ) Accretion 21.5 21.1 4.5 5.9 16.5 14.7 Revisions in estimated cash flows 33.9 (13.8 ) (2.4 ) (35.8 ) 36.3 22.7 Asset retirement obligations, end of year $ 577.4 $ 520.9 $ 111.1 $ 110.6 $ 451.0 $ 398.7
Schedule of Related Party Transactions [Table Text Block]	Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 Natural gas purchases from Spire Marketing $ 57.4 $ 86.3 $ 92.5 $ 4.7 $ 3.2 $ 10.4 Natural gas sales to Spire Marketing 0.4 — 1.1 — 0.5 0.1 Transportation services from Spire STL Pipeline LLC 32.0 32.0 32.0 — — — Natural gas storage services from Spire Storage Salt Plains LLC 0.7 — — — — — Transportation services from Spire NGL Inc. — — 0.5 — — —
Accounts Receivable, Allowance for Credit Loss [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Allowance at beginning of year $ 31.9 $ 30.3 $ 24.9 $ 24.9 $ 22.6 $ 18.1 $ 6.3 $ 6.6 $ 5.5 Provision for expected credit losses 16.6 11.6 14.7 13.3 11.2 11.1 2.6 0.3 3.1 Write-offs, net of recoveries (16.0 ) (10.0 ) (9.3 ) (12.0 ) (8.9 ) (6.6 ) (3.2 ) (0.6 ) (2.0 ) Allowance at end of year $ 32.5 $ 31.9 $ 30.3 $ 26.2 $ 24.9 $ 22.6 $ 5.7 $ 6.3 $ 6.6

Note 2 - Revenue (Tables)

Note 2 - Revenue (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Disaggregation of Revenue [Table Text Block]	2023 2022 2021 Spire Gas Utility: Residential $ 1,648.5 $ 1,416.6 $ 1,234.0 Commercial & industrial 606.0 338.9 586.0 Transportation 121.6 118.0 122.9 Off-system & other incentive 30.0 42.0 152.7 Other customer revenue 16.1 19.9 22.2 Total revenue from contracts with customers 2,422.2 1,935.4 2,117.8 Changes in accrued revenue under alternative revenue programs 34.7 10.7 1.5 Total Gas Utility operating revenues 2,456.9 1,946.1 2,119.3 Gas Marketing 179.1 234.9 96.5 Midstream 66.1 53.1 52.6 Other 16.7 16.1 15.1 Total before eliminations 2,718.8 2,250.2 2,283.5 Intersegment eliminations (see Note 14, Information by Operating Segment) (52.5 ) (51.7 ) (48.0 ) Total Operating Revenues $ 2,666.3 $ 2,198.5 $ 2,235.5 Spire Missouri Residential $ 1,261.3 $ 1,061.4 $ 882.1 Commercial & industrial 411.9 177.2 436.1 Transportation 33.2 33.3 33.5 Off-system & other incentive 20.1 25.2 145.6 Other customer revenue 12.5 11.1 16.3 Total revenue from contracts with customers 1,739.0 1,308.2 1,513.6 Changes in accrued revenue under alternative revenue programs 23.9 12.8 3.0 Total Operating Revenues $ 1,762.9 $ 1,321.0 $ 1,516.6 Spire Alabama Residential $ 322.9 $ 291.6 $ 288.0 Commercial & industrial 150.4 119.1 114.9 Transportation 77.6 74.4 78.7 Off-system & other incentive 9.9 16.8 7.1 Other customer revenue 3.6 5.5 1.9 Total revenue from contracts with customers 564.4 507.4 490.6 Changes in accrued revenue under alternative revenue programs 6.7 1.7 3.4 Total Operating Revenues $ 571.1 $ 509.1 $ 494.0
Schedule Of Taxes On Revenues [Table Text Block]	2023 2022 2021 Spire $ 131.8 $ 109.8 $ 94.0 Spire Missouri 96.7 79.6 64.3 Spire Alabama 29.9 25.5 25.1

Note 3 - Stock-based Compensa_2

Note 3 - Stock-based Compensation (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Share-Based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]	Weighted Average Grant Date Fair Value Units Per Unit Non-vested at September 30, 2022 343,524 $ 70.14 Granted 116,390 $ 79.88 Adjusted for performance (13,459 ) $ 76.91 Vested (74,556 ) $ 76.91 Forfeited (23,546 ) $ 71.73 Non-vested at September 30, 2023 348,353 $ 71.76 Weighted Average Grant Date Shares/ Fair Value Units Per Share Non-vested at September 30, 2022 122,245 $ 66.60 Granted 68,244 $ 72.60 Vested (59,040 ) $ 75.27 Forfeited (8,460 ) $ 65.36 Non-vested at September 30, 2023 122,989 $ 65.85
Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	2023 2022 2021 Risk-free interest rate 4.26% 0.79% 0.22% Expected dividend yield of stock — — — Expected volatility of stock 33.8% 32.2% 31.4% Performance period (in years) 3.0 3.0 3.0
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]	2023 2022 2021 Total compensation cost $ 11.2 $ 7.5 $ 16.6 Compensation cost capitalized (1.4 ) (1.1 ) (2.7 ) Compensation cost recognized in net income 9.8 6.4 13.9 Income tax benefit recognized in net income (2.2 ) (1.5 ) (3.2 ) Compensation cost recognized in net income, net of income tax $ 7.6 $ 4.9 $ 10.7

Note 4 - Earnings Per Common _2

Note 4 - Earnings Per Common Share (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	2023 2022 2021 Basic Earnings Per Common Share: Net Income $ 217.5 $ 220.8 $ 271.7 Less: Provision for preferred dividends 14.8 14.8 14.8 Income allocated to participating securities 0.3 0.3 0.4 Net Income Available to Common Shareholders $ 202.4 $ 205.7 $ 256.5 Weighted Average Common Shares Outstanding (in millions) 52.5 52.0 51.6 Basic Earnings Per Share of Common Stock $ 3.86 $ 3.96 $ 4.97 Diluted Earnings per Common Share: Net Income $ 217.5 $ 220.8 $ 271.7 Less: Provision for preferred dividends 14.8 14.8 14.8 Income allocated to participating securities 0.3 0.3 0.4 Net Income Available to Common Shareholders $ 202.4 $ 205.7 $ 256.5 Weighted Average Common Shares Outstanding (in millions) 52.5 52.0 51.6 Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)* 0.1 0.1 0.1 Weighted Average Diluted Common Shares (in millions) 52.6 52.1 51.7 Diluted Earnings Per Share of Common Stock $ 3.85 $ 3.95 $ 4.96 * Calculation excludes certain outstanding common shares (shown in millions by period at the right) attributable to common stock forward contracts, stock units subject to performance or market conditions, and restricted stock, which could have a dilutive effect in the future 1.9 0.1 0.1

Note 5 - Shareholders' Equity (

Note 5 - Shareholders' Equity (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Stock Purchase Contract Obligation, Number of Shares to be Purchased [Table Text Block]	If the applicable market value* per share Number of shares to be purchased per of Spire common stock is: stock purchase contract is: Equal to or greater than $78.6906 (“threshold appreciation price”) 0.6354 (“minimum settlement rate”) Less than $78.6906, but greater than $64.24 $50.00 ÷ applicable market value* Less than or equal to $64.24 (“reference price”) 0.7783 (“maximum settlement rate”)
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Net Defined Benefit Net Unrealized Unrealized Pension and Gain (Loss) on Gain (Loss) Other Available-for- on Cash Flow Postretirement Sale Debt Hedges Benefit Plans Securities Total Spire Balance at September 30, 2021 $ 7.9 $ (4.2 ) $ (0.1 ) $ 3.6 Other comprehensive income (loss) 42.5 1.5 (0.4 ) 43.6 Balance at September 30, 2022 50.4 (2.7 ) (0.5 ) 47.2 Other comprehensive income 0.1 0.2 0.1 0.4 Balance at September 30, 2023 $ 50.5 $ (2.5 ) $ (0.4 ) $ 47.6 Spire Missouri Balance at September 30, 2021 $ — $ (4.2 ) $ — $ (4.2 ) Other comprehensive income — 1.5 — 1.5 Balance at September 30, 2022 — (2.7 ) — (2.7 ) Other comprehensive income — 0.2 — 0.2 Balance at September 30, 2023 $ — $ (2.5 ) $ — $ (2.5 )

Note 6 - Long-term Debt (Tables

Note 6 - Long-term Debt (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Long-Term Debt Instruments [Table Text Block]	2023 2022 Spire 3.31 December 15, 2022 $ — $ 25.0 3.54 February 27, 2024 150.0 150.0 0.75 March 1, 2026 175.0 175.0 3.13 September 1, 2026 130.0 130.0 3.93 March 15, 2027 100.0 100.0 5.80 March 15, 2033 150.0 — 4.70 August 15, 2044 250.0 250.0 Total principal of Spire Missouri long-term debt (see below) 1,798.0 1,648.0 Total principal of Spire Alabama long-term debt (see below) 750.0 575.0 Other subsidiaries' long-term debt: 5.00 September 30, 2031 42.0 42.0 2.95 December 2034 117.7 123.9 5.61 October 15, 2037 30.0 — 3.52 September 30, 2049 40.0 40.0 Total principal of long-term debt 3,732.7 3,258.9 Less: Unamortized discounts and debt issuance costs (22.1 ) (19.2 ) Less: Current portion (156.6 ) (281.2 ) Long-term debt, excluding current portion $ 3,554.0 $ 2,958.5 Spire Missouri First Mortgage Bonds: 3.40 August 15, 2023 $ — $ 250.0 Floating Rate Series, due December 2, 2024 300.0 300.0 3.40 March 15, 2028 45.0 45.0 7.00 June 1, 2029 19.3 19.3 2.84 November 15, 2029 275.0 275.0 7.90 September 15, 2030 30.0 30.0 3.68 September 15, 2032 50.0 50.0 4.80 February 15, 2033 400.0 — 6.00 May 1, 2034 99.3 99.3 6.15 June 1, 2036 54.5 54.5 4.63 August 15, 2043 99.9 99.9 4.23 September 15, 2047 70.0 70.0 3.30 June 1, 2051 305.0 305.0 4.38 September 15, 2057 50.0 50.0 Total principal of Spire Missouri long-term debt 1,798.0 1,648.0 Less: Unamortized discounts and debt issuance costs (12.6 ) (10.3 ) Less: Current portion — (250.0 ) Spire Missouri long-term debt, excluding current portion $ 1,785.4 $ 1,387.7 Spire Alabama 3.21 September 15, 2025 $ 35.0 $ 35.0 5.32 October 15, 2029 90.0 — 2.88 December 1, 2029 100.0 100.0 2.04 December 15, 2030 150.0 150.0 5.41 October 15, 2032 85.0 — 5.90 January 15, 2037 45.0 45.0 4.31 December 1, 2045 80.0 80.0 3.92 January 15, 2048 45.0 45.0 4.64 January 15, 2049 90.0 90.0 4.02 January 15, 2058 30.0 30.0 Total principal of Spire Alabama long-term debt 750.0 575.0 Less: Unamortized discounts and debt issuance costs (4.1 ) (3.5 ) Spire Alabama long-term debt, excluding current portion $ 745.9 $ 571.5
Schedule of Maturities of Long-Term Debt [Table Text Block]	2024 2025 2026 2027 2028 Spire $ 156.6 $ 342.0 $ 312.5 $ 108.1 $ 53.6 Spire Missouri — 300.0 — — 45.0 Spire Alabama — 35.0 — — —

Note 7 - Notes Payable and Cr_2

Note 7 - Notes Payable and Credit Agreements (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Short-Term Debt [Table Text Block]	Spire Spire Spire (Parent Only) Missouri Alabama Spire CP Term Spire Spire Consol- Program Loan Note Note idated Year Ended September 30, 2023 Highest borrowings outstanding $ 1,282.0 $ 250.0 $ 656.9 $ 274.0 $ 1,482.0 Lowest borrowings outstanding 354.4 — 3.8 76.7 489.0 Weighted average borrowings 776.3 66.8 327.9 119.1 843.1 Weighted average interest rate 5.0 % 5.5 % 4.9 % 4.9 % 5.0 % As of September 30, 2023 Borrowings outstanding $ 955.5 $ — $ 540.6 $ 124.1 $ 955.5 Weighted average interest rate 5.6 % 0.0 % 5.6 % 5.6 % 5.6 % As of September 30, 2022 Borrowings outstanding $ 1,037.5 $ — $ 445.3 $ 260.9 $ 1,037.5 Weighted average interest rate 3.3 % 0.0 % 3.3 % 3.3 % 3.3 %

Note 8 - Fair Value of Financ_2

Note 8 - Fair Value of Financial Instruments (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Fair Value, by Balance Sheet Grouping [Table Text Block]	Classification of Estimated Fair Value Quoted Prices in Significant Active Observable Carrying Fair Markets Inputs Amount Value (Level 1) (Level 2) Spire As of September 30, 2023 Cash and cash equivalents $ 5.6 $ 5.6 $ 5.6 $ — Notes payable 955.5 955.5 — 955.5 Long-term debt, including current portion 3,710.6 3,270.2 — 3,270.2 As of September 30, 2022 Cash and cash equivalents $ 6.5 $ 6.5 $ 6.5 $ — Notes payable 1,037.5 1,037.5 — 1,037.5 Long-term debt, including current portion 3,239.7 2,851.8 — 2,851.8 Spire Missouri As of September 30, 2023 Cash and cash equivalents $ 0.8 $ 0.8 $ 0.8 $ — Notes payable - associated companies 540.6 540.6 — 540.6 Long-term debt 1,785.4 1,592.4 — 1,592.4 As of September 30, 2022 Notes payable - associated companies $ 445.3 $ 445.3 $ — $ 445.3 Long-term debt, including current portion 1,637.7 1,473.9 — 1,473.9 Spire Alabama As of September 30, 2023 Cash and cash equivalents $ 1.2 $ 1.2 $ 1.2 $ — Notes payable - associated companies 124.1 124.1 — 124.1 Long-term debt 745.9 648.0 — 648.0 As of September 30, 2022 Cash and cash equivalents $ 2.4 $ 2.4 $ 2.4 $ — Notes payable - associated companies 260.9 260.9 — 260.9 Long-term debt 571.5 485.0 — 485.0

Note 9 - Fair Value Measureme_2

Note 9 - Fair Value Measurements (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	Effects of Quoted Netting Prices Significant Significant and Cash in Active Observable Unobservable Margin Markets Inputs Inputs Receivables (Level 1) (Level 2) (Level 3) /Payables Total As of September 30, 2023 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 20.4 $ — $ — $ — $ 20.4 Gasoline and heating oil contracts — 0.1 — (0.1 ) — NYMEX/ICE natural gas contracts 6.3 — — (6.3 ) — Gas Marketing: NYMEX/ICE natural gas contracts 10.1 — — (10.1 ) — Natural gas commodity contracts — 36.7 — (3.6 ) 33.1 Other: U.S. stock/bond mutual funds 37.6 — — — 37.6 Interest rate swaps — 44.2 — — 44.2 Total $ 74.4 $ 81.0 $ — $ (20.1 ) $ 135.3 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 50.8 $ — $ — $ (44.0 ) $ 6.8 Gas Marketing: NYMEX/ICE natural gas contracts 21.8 — — (21.8 ) — Natural gas commodity contracts — 27.6 — (3.6 ) 24.0 Total $ 72.6 $ 27.6 $ — $ (69.4 ) $ 30.8 As of September 30, 2022 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 19.1 $ — $ — $ — $ 19.1 NYMEX/ICE natural gas contracts 57.8 — — (57.8 ) — Gas Marketing: NYMEX/ICE natural gas contracts 91.8 — — (91.8 ) — Natural gas commodity contracts * — 56.6 — (4.0 ) 52.6 Other: U.S. stock/bond mutual funds 29.3 — — — 29.3 Interest rate swaps * — 63.6 — — 63.6 Total $ 198.0 $ 120.2 $ — $ (153.6 ) $ 164.6 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 30.7 $ — $ — $ (30.7 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts 82.3 — — (82.3 ) — Natural gas commodity contracts * — 65.5 — (4.0 ) 61.5 Total $ 113.0 $ 65.5 $ — $ (117.0 ) $ 61.5 Effects of Quoted Netting Prices Significant Significant and Cash in Active Observable Unobservable Margin Markets Inputs Inputs Receivables (Level 1) (Level 2) (Level 3) /Payables Total As of September 30, 2023 ASSETS U.S. stock/bond mutual funds $ 20.4 $ — $ — $ — $ 20.4 Gasoline and heating oil contracts — 0.1 — (0.1 ) — NYMEX/ICE natural gas contracts 6.3 — — (6.3 ) — Total $ 26.7 $ 0.1 $ — $ (6.4 ) $ 20.4 LIABILITIES NYMEX/ICE natural gas contracts $ 50.8 $ — $ — $ (44.0 ) $ 6.8 As of September 30, 2022 ASSETS U.S. stock/bond mutual funds $ 19.1 $ — $ — $ — $ 19.1 NYMEX/ICE natural gas contracts 57.8 — — (57.8 ) — Total $ 76.9 $ — $ — $ (57.8 ) $ 19.1 LIABILITIES NYMEX/ICE natural gas contracts $ 30.7 $ — $ — $ (30.7 ) $ —

Note 10 - Derivative Instrume_2

Note 10 - Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Derivative Instruments [Table Text Block]	September 30, 2023 September 30, 2022 Gas Marketing Notional (MMBtu millions) Maximum Term (Months) Notional (MMBtu millions) Maximum Term (Months) Natural gas futures purchased 61.3 51 76.3 54 Natural gas options purchased, net 4.9 15 3.7 12 Natural gas basis swaps purchased 44.1 51 61.7 39 Gas Utility Natural gas futures purchased 66.5 24 13.0 12 September 30, 2023 September 30, 2022 Notional (MMBtu millions) Maximum Term (Months) Notional (MMBtu millions) Maximum Term (Months) Natural gas futures purchased 66.5 24 13.0 12
Derivative Instruments, Gain (Loss) [Table Text Block]	Effect of Derivative Instruments on the Consolidated Statements of Income and Comprehensive Income Location of Gain (Loss) Recorded in Income 2023 2022 2021 Derivatives in Cash Flow Hedging Relationships Effective portion of gain recognized in OCI on derivatives: Interest rate swaps $ 20.1 $ 56.7 $ 61.2 Effective portion of gain reclassified from AOCI to income: Interest rate swaps Interest Expense $ (2.4 ) $ (1.2 ) $ (1.3 ) Derivatives Not Designated as Hedging Instruments* Gain (Loss) recognized in income on derivatives: Gas / diesel futures Non-Operating Expense: Other Income $ 0.3 $ — $ — Natural gas commodity contracts Operating Expenses: Natural Gas 18.0 52.6 54.1 NYMEX / ICE natural gas contracts Operating Expenses: Natural Gas (35.0 ) 43.3 (77.5 ) Total $ (16.7 ) $ 95.9 $ (23.4 )
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]	Fair Value of Derivative Instruments in the Consolidated Balance Sheets Derivative Assets* Derivative Liabilities* September 30, 2023 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives designated as hedging instruments Other: Interest rate swaps Current Assets: Other $ 44.2 Current Liabilities: Other $ — Subtotal 44.2 — Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Current Assets: Other 6.3 Current Liabilities: Other 50.8 Gasoline and heating oil contracts Current Assets: Other 0.1 — Gas Marketing: NYMEX / ICE natural gas contracts Current Assets: Other 8.0 Current Liabilities: Other 16.0 Deferred Charges and Other Assets: Other 2.1 Deferred Credits and Other Liabilities: Other 5.7 Natural gas commodity Current Assets: Other 31.2 Current Liabilities: Other 20.1 Deferred Charges and Other Assets: Other 5.5 Deferred Credits and Other Liabilities: Other 7.6 Subtotal 53.2 100.2 Total derivatives $ 97.4 $ 100.2 September 30, 2022 Derivatives designated as hedging instruments Other: Interest rate swaps Current Assets: Other $ 63.6 Current Liabilities: Other $ — Subtotal 63.6 — Derivatives not designated as hedging instruments Gas Utility: Natural gas contracts Current Assets: Other 57.8 Current Liabilities: Other 30.7 Gas Marketing: NYMEX / ICE natural gas contracts Current Assets: Other 79.2 Current Liabilities: Other 71.5 Deferred Charges and Other Assets: Other 12.7 Deferred Credits and Other Liabilities: Other 10.8 Natural gas commodity Current Assets: Other 53.4 Current Liabilities: Other 55.1 Deferred Charges and Other Assets: Other 3.1 Deferred Credits and Other Liabilities: Other 10.4 Subtotal 206.2 178.5 Total derivatives $ 269.8 $ 178.5 Fair Value of Derivative Instruments in the Balance Sheets Derivative Assets* Derivative Liabilities* September 30, 2023 Balance Sheet Location Fair Value Balance Sheet Location Fair Value Derivatives not designated as hedging instruments Natural gas contracts Current Assets: Other $ 6.3 Current Liabilities: Other $ 50.8 Gasoline and heating oil contracts Current Assets: Other 0.1 Total derivatives $ 6.4 $ 50.8 September 30, 2022 Derivatives not designated as hedging instruments Natural gas contracts Current Assets: Other $ 57.8 Current Liabilities: Other $ 30.7
Derivative Instrument Reconciliation [Table Text Block]	2023 2022 Fair value of derivative assets presented above $ 97.4 $ 269.8 Fair value of cash margin receivable offset with derivatives 49.3 (36.6 ) Netting of assets and liabilities with the same counterparty (69.4 ) (117.0 ) Total $ 77.3 $ 116.2 Derivative Instrument Assets, per Consolidated Balance Sheets: Current Assets: Other $ 71.8 $ 113.1 Deferred Charges and Other Assets: Other 5.5 3.1 Total $ 77.3 $ 116.2 Fair value of derivative liabilities presented above $ 100.2 $ 178.5 Netting of assets and liabilities with the same counterparty (69.4 ) (117.0 ) Total $ 30.8 $ 61.5 Derivative Instrument Liabilities, per Consolidated Balance Sheets: Current Liabilities: Other $ 23.2 $ 51.1 Deferred Credits and Other Liabilities: Other 7.6 10.4 Total $ 30.8 $ 61.5 2023 2022 Fair value of derivative assets presented above $ 6.4 $ 57.8 Fair value of cash margin (payable) receivable offset with derivatives 37.6 (27.1 ) Netting of assets and liabilities with the same counterparty (44.0 ) (30.7 ) Total $ — $ — Fair value of derivative liabilities presented above $ 50.8 $ 30.7 Netting of assets and liabilities with the same counterparty (44.0 ) (30.7 ) Total $ 6.8 $ — Derivative Instrument Liabilities, per Balance Sheets: Derivative instrument liabilities $ 6.8 $ — Total $ 6.8 $ —
Interest Rate Swap [Member]
Notes Tables
Schedule of Derivative Instruments [Table Text Block]	Period Originated Contract Hedge Term (Years) Notional Amount Fixed Interest Rate Fiscal 2023 Mark-to-Market Gain Quarter 1, fiscal 2022 10 $ 50.0 1.4918 % $ 2.7 Quarter 2, fiscal 2022 10 75.0 1.6475 % 4.0 Quarter 2, fiscal 2022 10 25.0 1.7460 % 1.5 Quarter 1, fiscal 2023 10 50.0 3.4480 % 2.4 Quarter 2, fiscal 2023 10 50.0 3.6850 % 0.9 Quarter 2, fiscal 2023 10 25.0 3.5350 % 0.5 Quarter 2, fiscal 2023 10 25.0 3.3850 % 0.6 Quarter 3, fiscal 2023 30 50.0 2.7470 % 7.8 Quarter 3, fiscal 2023 10 25.0 2.9020 % 2.2 Quarter 3, fiscal 2023 10 25.0 3.0180 % 2.0 $ 400.0 $ 24.6

Note 12 - Income Taxes (Tables)

Note 12 - Income Taxes (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Federal: Current $ 0.7 $ 0.5 $ 0.2 $ — $ — $ — $ — $ — $ — Deferred 30.4 47.0 49.5 10.1 18.2 22.0 15.8 18.1 19.8 Investment tax credits (0.2 ) (0.2 ) (0.2 ) (0.2 ) (0.2 ) (0.2 ) — — — State and local: Current 1.2 0.5 1.3 — — — — — — Deferred 6.7 11.1 17.7 1.7 3.3 3.5 4.5 5.1 5.2 Total income tax expense $ 38.8 $ 58.9 $ 68.5 $ 11.6 $ 21.3 $ 25.3 $ 20.3 $ 23.2 $ 25.0
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Federal income tax statutory rate 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % 21.0 % State and local income taxes, net of federal income tax benefits 3.7 3.6 3.6 2.6 2.6 2.6 4.1 4.1 4.1 Certain expenses capitalized on books and deducted on tax return (1.4 ) (1.6 ) (1.6 ) (2.7 ) (3.2 ) (3.3 ) — — — Taxes related to prior years — (0.3 ) (0.5 ) (0.6 ) (0.2 ) — — — Tax credits * (3.3 ) — — (4.2 ) — — (1.9 ) — — Amortization of excess deferred taxes (5.1 ) (3.5 ) (2.5 ) (7.7 ) (7.3 ) (5.0 ) 0.2 — — Other items – net ** 0.2 1.9 0.1 — 3.1 (0.2 ) 0.1 0.2 0.2 Effective income tax rate 15.1 % 21.1 % 20.1 % 9.0 % 15.6 % 14.9 % 23.5 % 25.3 % 25.3 %
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Deferred tax assets: Reserves not currently deductible $ 27.7 $ 33.5 $ — $ 4.0 $ 3.9 $ 7.4 Pension and other postretirement benefits 64.4 72.6 44.7 52.6 17.0 — Goodwill — — — — 58.8 73.0 Operating losses 239.2 255.1 89.2 116.9 159.8 140.3 Regulatory amount due to customers, net 30.4 34.5 27.6 30.7 — — Other 35.8 24.9 10.5 — 3.0 — Total deferred tax assets 397.5 420.6 172.0 204.2 242.5 220.7 Deferred tax liabilities: Relating to property (788.0 ) (740.0 ) (507.7 ) (489.3 ) (218.7 ) (201.6 ) Regulatory pension and other postretirement benefits (80.6 ) (92.8 ) (53.0 ) (72.3 ) (25.9 ) (1.6 ) Deferred gas costs (67.0 ) (75.8 ) (64.1 ) (74.0 ) — — Other *** (205.6 ) (187.1 ) (79.0 ) (68.7 ) (7.0 ) (6.5 ) Total deferred tax liabilities (1,141.2 ) (1,095.7 ) (703.8 ) (704.3 ) (251.6 ) (209.7 ) Net deferred tax (liability) asset $ (743.7 ) $ (675.1 ) $ (531.8 ) $ (500.1 ) $ (9.1 ) $ 11.0
Summary of Federal and State Loss and Contribution and Tax Credit Carryforwards[Table Text Block]	Spire Spire Missouri Spire Alabama Federal and state loss carryforwards $ 1,000.3 $ 352.4 $ 624.1 Contribution carryforwards 6.1 5.6 - Tax credit carryforwards 13.1 8.5 1.6
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Unrecognized tax benefits, beginning of year $ 19.6 $ 16.4 $ 13.2 $ 19.3 $ 16.1 $ 13.0 $ — $ — $ — Increases related to tax positions taken in current year 4.2 3.3 3.2 3.6 3.2 3.1 0.3 — — Reductions due to lapse of applicable statute of limitations — (0.1 ) — — — — — — — Unrecognized tax benefits, end of year $ 23.8 $ 19.6 $ 16.4 $ 22.9 $ 19.3 $ 16.1 $ 0.3 $ — $ —

Note 13 - Pension Plans and O_2

Note 13 - Pension Plans and Other Postretirement Benefits (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Net Benefit Costs [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Service cost – benefits earned during the period $ 16.3 $ 20.0 $ 21.7 $ 11.4 $ 14.4 $ 15.4 $ 4.2 $ 4.8 $ 5.5 Interest cost on projected benefit obligation 25.1 21.5 20.7 17.8 14.7 14.2 4.8 4.7 4.6 Expected return on plan assets (24.5 ) (31.3 ) (31.6 ) (18.0 ) (22.7 ) (22.5 ) (3.5 ) (5.2 ) (5.8 ) Amortization of prior service credit (4.5 ) (4.5 ) (3.1 ) (1.9 ) (1.9 ) (0.6 ) (2.4 ) (2.4 ) (2.3 ) Amortization of actuarial loss 6.6 11.9 14.9 6.1 9.6 11.0 0.9 2.4 3.9 Loss on lump-sum settlements and curtailments 9.7 33.6 18.2 0.6 27.3 11.6 9.1 6.3 6.6 Subtotal 28.7 51.2 40.8 16.0 41.4 29.1 13.1 10.6 12.5 Regulatory adjustment 26.3 12.5 20.6 27.1 9.9 19.0 (1.7 ) 1.7 0.7 Net pension cost $ 55.0 $ 63.7 $ 61.4 $ 43.1 $ 51.3 $ 48.1 $ 11.4 $ 12.3 $ 13.2 Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Service cost – benefits earned during the period $ 4.8 $ 7.5 $ 7.3 $ 4.0 $ 6.3 $ 6.2 $ 0.7 $ 1.1 $ 0.9 Interest cost on accumulated postretirement benefit obligation 8.5 6.0 6.0 6.5 4.5 4.5 1.8 1.4 1.3 Expected return on plan assets (15.8 ) (16.8 ) (16.1 ) (10.5 ) (11.3 ) (10.9 ) (5.0 ) (5.2 ) (4.9 ) Amortization of prior service cost (credit) 0.3 1.0 1.0 0.6 0.7 0.7 (0.3 ) 0.3 0.3 Amortization of actuarial gain (4.0 ) (2.2 ) (1.6 ) (3.2 ) (1.9 ) (1.5 ) (0.5 ) — — Subtotal (6.2 ) (4.5 ) (3.4 ) (2.6 ) (1.7 ) (1.0 ) (3.3 ) (2.4 ) (2.4 ) Regulatory adjustment 0.6 3.3 13.2 1.8 5.0 15.0 (1.3 ) (1.8 ) (1.8 ) Net postretirement benefit (income) cost $ (5.6 ) $ (1.2 ) $ 9.8 $ (0.8 ) $ 3.3 $ 14.0 $ (4.6 ) $ (4.2 ) $ (4.2 )
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Current year actuarial loss (gain) $ 14.5 $ (16.9 ) $ (8.1 ) $ 5.7 $ 0.9 $ (0.9 ) $ 9.0 $ (16.0 ) $ (1.5 ) Amortization of actuarial loss (6.6 ) (11.9 ) (14.9 ) (6.1 ) (9.6 ) (11.0 ) (0.9 ) (2.4 ) (3.9 ) Acceleration of loss recognized due to settlement (9.7 ) (33.6 ) (18.2 ) (0.6 ) (27.3 ) (11.6 ) (9.1 ) (6.3 ) (6.6 ) Current year service credit — — (17.9 ) — — (17.9 ) — — — Amortization of prior service credit 4.5 4.5 3.1 1.9 1.9 0.6 2.4 2.4 2.3 Subtotal 2.7 (57.9 ) (56.0 ) 0.9 (34.1 ) (40.8 ) 1.4 (22.3 ) (9.7 ) Regulatory adjustment (2.8 ) 56.3 57.3 (1.0 ) 32.5 42.1 (1.4 ) 22.3 9.7 Total recognized in OCI $ (0.1 ) $ (1.6 ) $ 1.3 $ (0.1 ) $ (1.6 ) $ 1.3 $ — $ — $ — Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Current year actuarial (gain) loss $ (24.4 ) $ 15.8 $ (41.0 ) $ (21.5 ) $ 9.8 $ (29.0 ) $ (1.1 ) $ 5.9 $ (9.9 ) Amortization of actuarial gain 4.0 2.2 1.6 3.2 1.9 1.5 0.5 — — Current year prior service cost — (6.3 ) — (1.1 ) — — (5.2 ) — Amortization of prior service (cost) credit (0.3 ) (1.0 ) (1.0 ) (0.6 ) (0.7 ) (0.7 ) 0.3 (0.3 ) (0.3 ) Subtotal (20.7 ) 10.7 (40.4 ) (18.9 ) 9.9 (28.2 ) (0.3 ) 0.4 (10.2 ) Regulatory adjustment 20.7 (10.7 ) 40.4 18.9 (9.9 ) 28.2 0.3 (0.4 ) 10.2 Total recognized in OCI $ — $ — $ — $ — $ — $ — $ — $ — $ —
Schedule of Accumulated and Projected Benefit Obligations [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Benefit obligation, beginning of year $ 464.4 $ 689.6 $ 320.6 $ 479.0 $ 97.8 $ 149.4 Service cost 16.3 20.0 11.4 14.4 4.2 4.8 Interest cost 25.1 21.5 17.8 14.7 4.8 4.7 Actuarial (gain) loss (1.1 ) (173.9 ) (4.9 ) (116.2 ) 5.4 (42.4 ) Settlement loss 9.7 33.4 0.6 27.9 9.1 5.6 Settlement benefits paid (48.8 ) (109.3 ) (9.9 ) (87.0 ) (38.8 ) (22.3 ) Regular benefits paid (26.9 ) (16.9 ) (22.4 ) (12.2 ) (1.9 ) (2.0 ) Benefit obligation, end of year $ 438.7 $ 464.4 $ 313.2 $ 320.6 $ 80.6 $ 97.8 Accumulated benefit obligation, end of year $ 433.1 $ 457.1 $ 309.5 $ 315.0 $ 78.8 $ 96.2 Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Benefit obligation, beginning of year $ 148.1 $ 204.2 $ 114.8 $ 151.7 $ 29.9 $ 48.0 Service cost 4.8 7.5 4.0 6.3 0.7 1.1 Interest cost 8.5 6.0 6.5 4.5 1.8 1.4 Actuarial (gain) loss (10.6 ) (52.6 ) (13.4 ) (37.7 ) 4.2 (13.6 ) Plan amendments — (6.2 ) — (1.0 ) — (5.2 ) Retiree drug subsidy program 0.2 0.2 0.2 0.2 — — Benefits paid (8.4 ) (11.0 ) (6.8 ) (9.2 ) (1.5 ) (1.8 ) Benefit obligation, end of year $ 142.6 $ 148.1 $ 105.3 $ 114.8 $ 35.1 $ 29.9
Schedule of Changes in Fair Value of Plan Assets [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Fair value of plan assets, beginning of year $ 332.7 $ 498.9 $ 235.9 $ 364.0 $ 57.3 $ 82.8 Actual return on plan assets 9.1 (92.5 ) 7.5 (66.7 ) — (15.6 ) Employer contributions 58.9 52.4 30.3 37.8 27.9 14.4 Settlement benefits paid (39.1 ) (109.3 ) (9.3 ) (87.0 ) (29.7 ) (22.3 ) Regular benefits paid (26.9 ) (16.8 ) (22.4 ) (12.2 ) (1.9 ) (2.0 ) Fair value of plan assets, end of year $ 334.7 $ 332.7 $ 242.0 $ 235.9 $ 53.6 $ 57.3 Funded status of plans, end of year $ (104.0 ) $ (131.7 ) $ (71.2 ) $ (84.7 ) $ (27.0 ) $ (40.5 ) Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Fair value of plan assets at beginning of year $ 264.7 $ 326.9 $ 176.7 $ 221.7 $ 83.3 $ 99.4 Actual return on plan assets 29.9 (51.6 ) 18.8 (36.2 ) 10.2 (14.3 ) Employer contributions 0.1 0.4 0.1 0.4 — — Benefits paid (8.4 ) (11.0 ) (6.8 ) (9.2 ) (1.5 ) (1.8 ) Fair value of plan assets, end of year $ 286.3 $ 264.7 $ 188.8 $ 176.7 $ 92.0 $ 83.3 Funded status of plans, end of year $ 143.7 $ 116.6 $ 83.5 $ 61.9 $ 56.9 $ 53.4
Schedule of Amounts Recognized in Balance Sheet [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Current liabilities $ (1.6 ) $ (1.1 ) $ (1.6 ) $ (1.1 ) $ — $ — Noncurrent liabilities (102.4 ) (130.6 ) (69.6 ) (83.6 ) (27.0 ) (40.5 ) Total $ (104.0 ) $ (131.7 ) $ (71.2 ) $ (84.7 ) $ (27.0 ) $ (40.5 ) Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Noncurrent assets $ 180.7 $ 151.6 $ 120.5 $ 96.9 $ 56.9 $ 53.4 Current liabilities (0.4 ) (0.3 ) (0.4 ) (0.3 ) — — Noncurrent liabilities (36.6 ) (34.7 ) (36.6 ) (34.7 ) — — Total $ 143.7 $ 116.6 $ 83.5 $ 61.9 $ 56.9 $ 53.4
Schedule of Amounts in Accumulated Other Comprehensive Income (Loss) to be Recognized over Next Fiscal Year [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Net actuarial loss $ 130.1 $ 132.0 $ 92.5 $ 93.6 $ 40.2 $ 41.2 Prior service credit (31.2 ) (35.7 ) (16.2 ) (18.1 ) (13.9 ) (16.3 ) Subtotal 98.9 96.3 76.3 75.5 26.3 24.9 Adjustments for amounts included in regulatory assets (95.9 ) (93.1 ) (73.3 ) (72.3 ) (26.3 ) (24.9 ) Total $ 3.0 $ 3.2 $ 3.0 $ 3.2 $ — $ — Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Net actuarial gain $ (103.3 ) $ (83.3 ) $ (92.3 ) $ (74.2 ) $ (6.1 ) $ (5.6 ) Prior service cost (credit) 7.0 7.1 7.4 7.9 (0.4 ) (0.8 ) Subtotal (96.3 ) (76.2 ) (84.9 ) (66.3 ) (6.5 ) (6.4 ) Adjustments for amounts included in regulatory assets 96.3 76.2 84.9 66.3 6.5 6.4 Total $ — $ — $ — $ — $ — $ —
Defined Benefit Plan, Assumptions [Table Text Block]	2023 2022 2021 Weighted average discount rate - Spire Missouri East plan 5.70% 3.00% 2.85% Weighted average discount rate - Spire Missouri West plan 5.80% 3.00% 2.75% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets 6.50% 6.75% 6.75% 2023 2022 2021 Weighted average discount rate 5.65%/5.7% 3.10%/3.0% 2.95%/2.80% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets 6.50% 6.75% 6.75% 2023 2022 Weighted average discount rate - Spire Missouri East plan 6.25% 5.70% Weighted average discount rate - Spire Missouri West plan 6.30% 5.80% Weighted average discount rate - Spire Alabama plans 6.2%/6.25% 5.70%/5.65% Weighted average rate of future compensation increase 3.00% 3.00% Cash balance interest crediting rate - Spire Alabama / Spire Missouri 4.25% 4.25% 2023 2022 2021 Weighted average discount rate - Spire Missouri plans 5.80% 2.95% 2.75% Weighted average rate of future compensation increase 3.00% 3.00% 3.00% Expected long-term rate of return on plan assets - Spire Missouri plans 5.50% 5.75% 5.75% 2023 2022 2021 Weighted average discount rate 5.80% 2.95% 2.75% Expected long-term rate of return on plan assets 4.75%/6.0% 5.00%/6.25% 5.00%/6.25% 2023 2022 Weighted average discount rate - Spire Alabama plans and Spire Missouri Plans 6.30% 5.80% Weighted average rate of future compensation increase - Spire Missouri East plans 3.00% 3.00%
Defined Benefit Plan, Plan with Projected Benefit Obligation in Excess of Plan Assets [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Projected benefit obligation $ 438.7 $ 464.4 $ 313.2 $ 320.6 $ 80.6 $ 97.8 Accumulated benefit obligation 433.1 457.1 309.5 315.0 78.8 96.2 Fair value of plan assets 334.7 332.7 242.0 235.9 53.6 57.3
Schedule of Allocation of Plan Assets [Table Text Block]	Spire Missouri 2023 Target 2023 Actual 2022 Target 2022 Actual Return seeking assets 70.0 % 77.0 % 70.0 % 74.3 % Liability hedging assets 30.0 % 20.0 % 30.0 % 22.8 % Cash and cash equivalents — % 3.0 % — % 2.9 % Total 100.0 % 100.0 % 100.0 % 100.0 % Spire Alabama 2023 Target 2023 Actual 2022 Target 2022 Actual Return seeking assets 75.0 % 76.0 % 70.0 % 68.7 % Liability hedging assets 25.0 % 15.0 % 30.0 % 25.3 % Cash and cash equivalents — % 9.0 % — % 6.0 % Total 100.0 % 100.0 % 100.0 % 100.0 % Spire Missouri Target 2023 Actual 2022 Actual Equity securities 60.0 % 58.9 % 58.7 % Debt securities 40.0 % 38.1 % 40.5 % Cash and cash equivalents — % 3.0 % 0.8 % Total 100.0 % 100.0 % 100.0 % Spire Alabama Target 2023 Actual 2022 Actual Equity securities 60.5 % 59.9 % 57.7 % Debt securities 39.5 % 40.1 % 42.3 % Total 100.0 % 100.0 % 100.0 %
Schedule of Expected Benefit Payments [Table Text Block]	2024 2025 2026 2027 2028 2029 2032 Spire $ 52.4 $ 45.3 $ 41.8 $ 41.8 $ 43.3 $ 202.8 Spire Missouri 41.0 34.1 30.4 29.4 30.5 139.1 Spire Alabama 8.0 7.7 7.8 8.7 8.9 44.1 2024 2025 2026 2027 2028 2029 2032 Spire $ 14.6 $ 14.8 $ 14.9 $ 14.8 $ 14.5 $ 68.6 Spire Missouri 11.6 11.8 11.8 11.7 11.4 52.2 Spire Alabama 2.9 2.9 2.9 2.9 2.9 15.0
Schedule of Health Care Cost Trend Rates [Table Text Block]	2023 2022 Medical cost trend assumed for next year - Spire Alabama and Spire Missouri 6.50% 6.75% Rate to which the medical cost trend rate is assumed to decline (the ultimate medical cost trend rate) 5.00% 5.00% Year the rate reaches the ultimate trend 2030 2028
Fair Value, Assets Measured on Recurring Basis [Table Text Block]	As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 14.8 $ — $ 14.8 $ 11.5 $ — $ 11.5 Equity funds - global (including U.S.) — 139.0 139.0 — 122.2 122.2 Real asset funds — 55.2 55.2 — 61.0 61.0 Debt securities: U.S. bond funds 27.8 — 27.8 42.3 — 42.3 U.S. government index funds 36.2 — 36.2 36.1 — 36.1 Global funds (including U.S.) — 61.7 61.7 — 59.6 59.6 Total $ 78.8 $ 255.9 $ 334.7 $ 89.9 $ 242.8 $ 332.7 As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 5.1 $ — $ 5.1 $ 3.5 $ — $ 3.5 U.S. stock/bond mutual funds 188.2 76.5 264.7 177.1 69.4 246.5 International fund — 16.5 16.5 0.8 13.9 14.7 Total $ 193.3 $ 93.0 $ 286.3 $ 181.4 $ 83.3 $ 264.7 As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 6.8 $ — $ 6.8 $ 5.7 $ — $ 5.7 Equity funds - global (including U.S.) — 99.4 99.4 — 85.7 85.7 Real asset funds — 40.2 40.2 — 47.2 47.2 Debt securities: U.S. bond funds 20.9 — 20.9 29.4 — 29.4 U.S. government index funds 28.7 — 28.7 24.6 — 24.6 Global funds (including U.S.) — 46.0 46.0 — 43.3 43.3 Total $ 56.4 $ 185.6 $ 242.0 $ 59.7 $ 176.2 $ 235.9 As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 4.3 $ — $ 4.3 $ 2.7 $ — $ 2.7 U.S. stock/bond mutual funds 184.5 — 184.5 174.0 — 174.0 Total $ 188.8 $ — $ 188.8 $ 176.7 $ — $ 176.7 As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total Cash and cash equivalents $ 4.6 $ — $ 4.6 $ 3.5 $ — $ 3.5 Equity funds - global (including U.S.) — 22.9 22.9 — 21.6 21.6 Real asset funds — 8.7 8.7 — 8.1 8.1 Debt securities: U.S. bond funds 4.0 — 4.0 7.7 — 7.7 U.S. government index funds 4.3 — 4.3 6.8 — 6.8 Global funds (including U.S.) — 9.1 9.1 — 9.6 9.6 Total $ 12.9 $ 40.7 $ 53.6 $ 18.0 $ 39.3 $ 57.3 As of September 30, 2023 As of September 30, 2022 Quoted Prices Significant Quoted Prices Significant in Active Observable in Active Observable Markets Inputs Markets Inputs (Level 1) (Level 2) Total (Level 1) (Level 2) Total U.S. stock/bond mutual funds $ — $ 76.5 $ 76.5 $ — $ 69.4 $ 69.4 International fund — 15.5 15.5 — 13.9 13.9 Total $ — $ 92.0 $ 92.0 $ — $ 83.3 $ 83.3

Note 14 - Information by Oper_2

Note 14 - Information by Operating Segment (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Segment Reporting Information, by Segment [Table Text Block]	Gas Gas 2023 Utility Marketing Midstream Other Eliminations Consolidated Revenues from external customers $ 2,456.6 $ 179.1 $ 29.9 $ 0.7 $ — $ 2,666.3 Intersegment revenues 0.3 — 36.2 16.0 (52.5 ) — Total Operating Revenues 2,456.9 179.1 66.1 16.7 (52.5 ) 2,666.3 Depreciation and amortization expense 244.4 1.5 8.4 0.5 — 254.8 Interest expense 139.9 — 8.6 72.1 (34.9 ) 185.7 Income tax expense (benefit) 32.7 12.8 3.8 (10.5 ) — 38.8 Net economic earnings (loss) 200.5 47.6 14.1 (34.1 ) — 228.1 Capital expenditures 588.6 0.4 73.6 (0.1 ) — 662.5 Gas Gas 2022 Utility Marketing Midstream Other Eliminations Consolidated Revenues from external customers $ 1,945.6 $ 234.9 $ 17.4 $ 0.6 $ — $ 2,198.5 Intersegment revenues 0.5 — 35.7 15.5 (51.7 ) — Total Operating Revenues 1,946.1 234.9 53.1 16.1 (51.7 ) 2,198.5 Depreciation and amortization expense 227.9 1.4 7.5 0.5 — 237.3 Interest expense 86.4 — 4.9 37.3 (8.8 ) 119.8 Income tax expense (benefit) 49.6 11.9 4.5 (7.1 ) — 58.9 Net economic earnings (loss) 202.7 27.0 11.1 (24.5 ) — 216.3 Capital expenditures 528.6 0.9 22.6 0.1 — 552.2 Gas Gas 2021 Utility Marketing Midstream Other Eliminations Consolidated Revenues from external customers $ 2,118.2 $ 96.5 $ 19.9 $ 0.9 $ — $ 2,235.5 Intersegment revenues 1.1 — 32.7 14.2 (48.0 ) — Total Operating Revenues 2,119.3 96.5 52.6 15.1 (48.0 ) 2,235.5 Depreciation and amortization expense 204.4 1.2 6.9 0.6 — 213.1 Interest expense 74.7 — 4.0 29.3 (1.4 ) 106.6 Income tax expense (benefit) 56.9 13.4 4.4 (6.2 ) — 68.5 Net economic earnings (loss) 230.6 47.0 11.1 (22.4 ) — 266.3 Capital expenditures 590.4 0.7 33.0 0.7 — 624.8
Reconciliation of Assets from Segment to Consolidated [Table Text Block]	Total Assets at End of Year 2023 2022 2021 Gas Utility $ 8,486.7 $ 8,042.8 $ 7,615.4 Gas Marketing 332.0 638.7 466.1 Midstream 574.3 446.0 413.8 Other 2,533.3 2,705.5 2,193.3 Eliminations (1,612.7 ) (1,749.3 ) (1,332.2 ) Total Assets $ 10,313.6 $ 10,083.7 $ 9,356.4
Reconciliation Of Consolidated Net Economic Earnings To Consolidated Net Income [Table Text Block]	Reconciliation of Consolidated Net Income to Consolidated Net Economic Earnings 2023 2022 2021 Net Income $ 217.5 $ 220.8 $ 271.7 Adjustments, pre-tax: Missouri regulatory adjustments — — (9.0 ) Fair value and timing adjustments 11.4 (11.4 ) 3.3 Acquisition and divestiture activities 2.5 — (1.3 ) Income tax adjustments (3.3 ) 6.9 1.6 Net Economic Earnings $ 228.1 $ 216.3 $ 266.3

Note 15 - Regulatory Matters (T

Note 15 - Regulatory Matters (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Regulatory Assets and Liabilities [Table Text Block]	Spire Spire Missouri Spire Alabama September 30 2023 2022 2023 2022 2023 2022 Regulatory Assets: Current: Unamortized purchased gas adjustments $ 293.2 $ 322.2 $ 269.4 $ 275.1 $ 21.7 $ 43.8 Other 55.1 33.2 23.7 13.0 19.9 13.1 Total Current Regulatory Assets 348.3 355.4 293.1 288.1 41.6 56.9 Noncurrent: Future income taxes due from customers 144.5 137.8 136.2 129.2 2.0 2.2 Pension and postretirement benefit costs 261.0 294.5 189.1 222.9 67.8 66.5 Cost of removal 633.2 493.7 97.0 25.2 536.2 468.5 Unamortized purchased gas adjustments 23.0 — 23.0 — — — Energy efficiency 56.3 57.2 56.3 57.2 — — Other 131.2 129.2 116.0 113.1 0.9 1.0 Total Noncurrent Regulatory Assets 1,249.2 1,112.4 617.6 547.6 606.9 538.2 Total Regulatory Assets $ 1,597.5 $ 1,467.8 $ 910.7 $ 835.7 $ 648.5 $ 595.1 Regulatory Liabilities: Current: Other $ 7.3 $ 3.7 $ — $ — $ — $ — Total Current Regulatory Liabilities 7.3 3.7 — — — — Noncurrent: Deferred taxes due to customers 128.0 145.3 114.8 127.9 — — Pension and postretirement benefit costs 185.2 172.6 156.5 143.6 17.9 19.4 Accrued cost of removal 126.6 32.9 90.4 — — — Unamortized purchased gas adjustments 11.2 53.0 11.2 53.0 — — Other 21.4 14.4 16.5 7.3 3.3 3.6 Total Noncurrent Regulatory Liabilities 472.4 418.2 389.4 331.8 21.2 23.0 Total Regulatory Liabilities $ 479.7 $ 421.9 $ 389.4 $ 331.8 $ 21.2 $ 23.0
Schedule of Regulatory Assets Not Earning Return [Table Text Block]	Spire Spire Missouri September 30 2023 2022 2023 2022 Pension and postretirement benefit costs $ 133.4 $ 152.9 $ 133.4 $ 152.9 Future income taxes due from customers 142.5 135.6 136.2 129.2 Unamortized purchase gas adjustments 292.4 275.1 292.4 275.1 Other 104.2 122.7 104.2 122.7 Total Regulatory Assets Not Earning a Return $ 672.5 $ 686.3 $ 666.2 $ 679.9

Note 17 - Leases (Tables)

Note 17 - Leases (Tables)	12 Months Ended
	Sep. 30, 2023
Notes Tables
Schedule of Operating Lease Cost, Cash Flow and Non Cash Information [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2021 2023 2022 2021 2023 2022 2021 Operating lease cost, including amounts capitalized $ 7.3 $ 7.4 $ 7.2 $ 0.5 $ 0.5 $ 0.4 $ 2.0 $ 2.1 $ 2.1 Cash flow and noncash information about operating leases: Operating cash flows representing cash paid for amounts included in the measurement of lease liabilities 7.3 7.3 7.2 0.5 0.5 0.4 2.1 2.1 2.1 Right-of-use assets obtained in exchange for lease liabilities 0.8 24.6 — 0.8 1.1 — — 23.5 —
Schedule of Balance Sheet and Weighted Average Information About Operating Leases [Table Text Block]	Spire Spire Missouri Spire Alabama 2023 2022 2023 2022 2023 2022 Right-of-use assets $ 70.6 $ 73.7 $ 2.1 $ 1.7 $ 19.2 $ 20.2 Lease liabilities, current 6.8 6.5 0.5 0.4 1.9 1.9 Lease liabilities, noncurrent 70.2 73.7 1.8 1.5 23.5 24.6 Weighted-average remaining lease term (in years) 14.1 15.0 5.6 5.1 13.3 14.3 Weighted-average discount rate 4.2 % 4.1 % 3.3 % 2.2 % 3.7 % 3.7 %
Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block]	Spire Spire Missouri Spire Alabama 2024 $ 6.9 $ 0.5 $ 1.9 2025 7.5 0.6 2.2 2026 7.5 0.4 2.2 2027 7.4 0.3 2.3 2028 7.4 0.3 2.3 Thereafter 65.9 0.5 21.7 Total undiscounted lease payments 102.6 2.6 32.6 Less present value discount (25.6 ) (0.3 ) (7.2 ) Total current and noncurrent lease liabilities $ 77.0 $ 2.3 $ 25.4

Note 1 - Summary of Significa_3

Note 1 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Millions		12 Months Ended
	Apr. 01, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Number of Reportable Segments		3
Difference Between Replacement Cost of Gas Storage and Inventory Basis Amount		$ 21.1	$ 37.3
Goodwill		1,171.6	1,171.6
Payments to Acquire Businesses, Gross	$ 37	37	0	$ 0
Restricted Cash		20.2	$ 14
Gas Utility [Member]
Goodwill		$ 210.2
Spire Alabama Inc [Member]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service		3%	3%	3%
Financing Receivable, after Allowance for Credit Loss		$ 6.7	$ 7.1
Spire Alabama Inc [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, before Allowance for Credit Loss		$ 0.3	$ 0.3
Spire Missouri [Member]
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service		3%	3%	3%
Goodwill		$ 210.2	$ 210.2

Note 1 - Summary of Significa_4

Note 1 - Summary of Significant Accounting Policies - Accrued Capital Expenditures Excluded from Capital Expenditures in the Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Accrued capital expenditures	$ 104.3	$ 77.8	$ 59.5
Spire Missouri [Member]
Accrued capital expenditures	56.5	45.6	37.1
Spire Alabama Inc [Member]
Accrued capital expenditures	$ 4.6	$ 19.2	$ 13.6

Note 1 - Summary of Significa_5

Note 1 - Summary of Significant Accounting Policies - Schedule of Asset Retirement Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Asset retirement obligations, beginning of year	$ 520.9	$ 519.6
Liabilities incurred during the period	7.9	3.2
Liabilities settled during the period	(6.8)	(9.2)
Accretion	21.5	21.1
Revisions in estimated cash flows	33.9	(13.8)
Asset retirement obligations, end of year	577.4	520.9
Spire Missouri [Member]
Asset retirement obligations, beginning of year	110.6	143.4
Liabilities incurred during the period	0.9	1.2
Liabilities settled during the period	(2.5)	(4.1)
Accretion	4.5	5.9
Revisions in estimated cash flows	(2.4)	(35.8)
Asset retirement obligations, end of year	111.1	110.6
Spire Alabama Inc [Member]
Asset retirement obligations, beginning of year	398.7	362.8
Liabilities incurred during the period	2	0.5
Liabilities settled during the period	(2.5)	(2)
Accretion	16.5	14.7
Revisions in estimated cash flows	36.3	22.7
Asset retirement obligations, end of year	$ 451	$ 398.7

Note 1 - Summary of Significa_6

Note 1 - Summary of Significant Accounting Policies - Transactions With Affiliates (Details) - Affiliated Entity [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Regulated Operation [Member] | Spire Marketing [Member] | Spire Missouri [Member]
Natural gas purchases from Spire Marketing	$ 57.4	$ 86.3	$ 92.5
Transaction amount	0.4	0	1.1
Regulated Operation [Member] | Spire Marketing [Member] | Spire Alabama Inc [Member]
Natural gas purchases from Spire Marketing	4.7	3.2	10.4
Transaction amount	0	0.5	0.1
Unregulated Operation [Member] | Spire S T L Pipeline L L C [Member] | Spire Missouri [Member]
Transaction amount	32	32	32
Unregulated Operation [Member] | Spire S T L Pipeline L L C [Member] | Spire Alabama Inc [Member]
Transaction amount	0	0	0
Unregulated Operation [Member] | Spire Storage Salt Plains LLC [Member] | Spire Missouri [Member]
Transaction amount	0.7	0	0
Unregulated Operation [Member] | Spire Storage Salt Plains LLC [Member] | Spire Alabama Inc [Member]
Transaction amount	0	0	0
Unregulated Operation [Member] | Spire N G L Inc [Member] | Spire Missouri [Member]
Transaction amount	0	0	0.5
Unregulated Operation [Member] | Spire N G L Inc [Member] | Spire Alabama Inc [Member]
Transaction amount	$ 0	$ 0	$ 0

Note 1 - Summary of Significa_7

Note 1 - Summary of Significant Accounting Policies - Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Allowance at beginning of year	$ 31.9	$ 30.3	$ 24.9
Provision for expected credit losses	16.6	11.6	14.7
Write-offs, net of recoveries	(16)	(10)	(9.3)
Allowance at end of year	32.5	31.9	30.3
Spire Missouri [Member]
Allowance at beginning of year	24.9	22.6	18.1
Provision for expected credit losses	13.3	11.2	11.1
Write-offs, net of recoveries	(12)	(8.9)	(6.6)
Allowance at end of year	26.2	24.9	22.6
Spire Alabama Inc [Member]
Allowance at beginning of year	6.3	6.6	5.5
Provision for expected credit losses	2.6	0.3	3.1
Write-offs, net of recoveries	(3.2)	(0.6)	(2)
Allowance at end of year	$ 5.7	$ 6.3	$ 6.6

Note 2 - Revenue - Disaggregate

Note 2 - Revenue - Disaggregated of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Operating Revenues	$ 2,666.3	$ 2,198.5	$ 2,235.5
Consolidation, Eliminations [Member]
Operating Revenues	(52.5)	(51.7)	(48)
Gas Utility [Member] | Operating Segments [Member]
Operating Revenues	2,456.9	1,946.1	2,119.3
Gas Marketing [Member] | Operating Segments [Member]
Operating Revenues	179.1	234.9	96.5
Midstream [Member] | Operating Segments [Member]
Operating Revenues	66.1	53.1	52.6
Other Segments [Member] | Consolidation, Eliminations [Member]
Operating Revenues	16.7	16.1	15.1
Spire [Member]
Operating Revenues	2,666.3	2,198.5	2,235.5
Spire [Member] | Operating Segments [Member]
Operating Revenues	2,718.8	2,250.2	2,283.5
Spire [Member] | Consolidation, Eliminations [Member]
Operating Revenues	(52.5)		(48)
Spire [Member] | Segment Reconciling Items [Member]
Operating Revenues		(51.7)
Spire [Member] | Gas Utility [Member] | Operating Segments [Member]
Revenue	2,422.2	1,935.4	2,117.8
Changes in accrued revenue under alternative revenue programs	34.7	10.7	1.5
Total Gas Utility operating revenues	2,456.9	1,946.1	2,119.3
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Residential [Member]
Revenue	1,648.5	1,416.6	1,234
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Commercial and Industrial [Member]
Revenue	606	338.9	586
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Transportation [Member]
Revenue	121.6	118	122.9
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Off-system and Other Incentive [Member]
Revenue	30	42	152.7
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Other Customer Revenue [Member]
Revenue	16.1	19.9	22.2
Spire [Member] | Gas Marketing [Member] | Operating Segments [Member]
Unregulated Operating Revenue	179.1	234.9	96.5
Spire [Member] | Midstream [Member] | Operating Segments [Member]
Unregulated Operating Revenue	66.1	53.1	52.6
Spire [Member] | Other Segments [Member] | Operating Segments [Member]
Unregulated Operating Revenue	16.7	16.1	15.1
Spire Missouri [Member]
Changes in accrued revenue under alternative revenue programs	23.9	12.8	3
Operating Revenues	1,762.9	1,321	1,516.6
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member]
Revenue	1,739	1,308.2	1,513.6
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Residential [Member]
Revenue	1,261.3	1,061.4	882.1
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Commercial and Industrial [Member]
Revenue	411.9	177.2	436.1
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Transportation [Member]
Revenue	33.2	33.3	33.5
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Off-system and Other Incentive [Member]
Revenue	20.1	25.2	145.6
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Other Customer Revenue [Member]
Revenue	12.5	11.1	16.3
Spire Alabama Inc [Member]
Changes in accrued revenue under alternative revenue programs	6.7	1.7	3.4
Operating Revenues	571.1	509.1	494
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member]
Revenue	564.4	507.4	490.6
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Residential [Member]
Revenue	322.9	291.6	288
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Commercial and Industrial [Member]
Revenue	150.4	119.1	114.9
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Transportation [Member]
Revenue	77.6	74.4	78.7
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Off-system and Other Incentive [Member]
Revenue	9.9	16.8	7.1
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Other Customer Revenue [Member]
Revenue	$ 3.6	$ 5.5	$ 1.9

Note 2 - Revenue - Taxes Associ

Note 2 - Revenue - Taxes Associated with Natural Gas Utility Services (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Gross Receipts Tax Amounts	$ 131.8	$ 109.8	$ 94
Spire Missouri [Member]
Gross Receipts Tax Amounts	96.7	79.6	64.3
Spire Alabama Inc [Member]
Gross Receipts Tax Amounts	$ 29.9	$ 25.5	$ 25.1

Note 3 - Stock-based Compensa_3

Note 3 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)	3 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)	1,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Deferred (in shares)	244,618
Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Dividend Rate	0%	0%	0%
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 12.1
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)	1 year 8 months 12 days
Performance-contingent Restricted Share Units [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	116,390
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 79.88
Performance-contingent Restricted Share Units [Member] | Executive Officers and Key Employees [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	116,390
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 79.88	$ 67.43	$ 68.69
Share Based Compensation Arrangement By Share Based Payment Award, Maximum Target Award Percentage	200%
Share Based Compensation Arrangement By Share Based Payment Award, Number of Shares to Be Issued at Maximum Performance Target (in shares)	696,706
Time-vested Restricted Stock [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	68,244
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 72.6
Time-vested Restricted Stock [Member] | Executive Officers and Key Employees [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	55,524
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 71.91	63.57	64.29
Time-vested Restricted Stock [Member] | Non Employee Directors [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)	12,720
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)	$ 75.59	$ 66.31	$ 62.35
Performance-contingent Restricted Stock Unit and Time-vested Restricted Stocks [Member]
Share-Based Payment Arrangement, Shares Withheld for Tax Withholding Obligation (in shares)	18,428	28,055	16,787
Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Withheld for Tax Withholding Obligations, Weighted Average Price Per Share (in dollars per share)	$ 72.03	$ 63.97	$ 65.99
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value	$ 8.6	$ 10.1	$ 6.5
Share Based Compensation Tax Benefit Realized From Exercise Of Equity Instruments Other Than Stock Options	$ 3.2	$ 3.8	$ 2.5

Note 3 - Stock-based Compensa_4

Note 3 - Stock-based Compensation - Activity of Restricted Stock Units (Details)	12 Months Ended
	Sep. 30, 2023 $ / shares shares
Performance-contingent Restricted Share Units [Member]
Nonvested, units (in shares) | shares	343,524
Nonvested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 70.14
Granted, units (in shares) | shares	116,390
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 79.88
Adjusted for performance, units (in shares) | shares	(13,459)
Adjusted for performance, weighted average grant date fair value (in dollars per share) | $ / shares	$ 76.91
Vested, units (in shares) | shares	(74,556)
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 76.91
Forfeited, units (in shares) | shares	(23,546)
Forfeited, weighted average grant date fair value (in dollars per share) | $ / shares	$ 71.73
Nonvested, units (in shares) | shares	348,353
Nonvested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 71.76
Time-vested Restricted Stock [Member]
Nonvested, units (in shares) | shares	122,245
Nonvested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 66.6
Granted, units (in shares) | shares	68,244
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 72.6
Vested, units (in shares) | shares	(59,040)
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 75.27
Forfeited, units (in shares) | shares	(8,460)
Forfeited, weighted average grant date fair value (in dollars per share) | $ / shares	$ 65.36
Nonvested, units (in shares) | shares	122,989
Nonvested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 65.85

Note 3 - Stock-based Compensa_5

Note 3 - Stock-based Compensation - Schedule of Significant Assumptions (Details)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Risk-free interest rate	4.26%	0.79%	0.22%
Expected dividend yield of stock	0%	0%	0%
Expected volatility of stock	33.80%	32.20%	31.40%
Performance period (in years) (Year)	3 years	3 years	3 years

Note 3 - Stock-based Compensa_6

Note 3 - Stock-based Compensation - Compensation Cost of Share-based Compensation Arrangements (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Total compensation cost	$ 11.2	$ 7.5	$ 16.6
Compensation cost capitalized	(1.4)	(1.1)	(2.7)
Compensation cost recognized in net income	9.8	6.4	13.9
Income tax benefit recognized in net income	(2.2)	(1.5)	(3.2)
Compensation cost recognized in net income, net of income tax	$ 7.6	$ 4.9	$ 10.7

Note 4 - Earnings Per Common _3

Note 4 - Earnings Per Common Share - Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Net Income		$ 217.5	$ 220.8	$ 271.7
Provision for preferred dividends		14.8	14.8	14.8
Income allocated to participating securities		0.3	0.3	0.4
Net Income Available to Common Shareholders		$ 202.4	$ 205.7	$ 256.5
Basic (in shares)		52.5	52	51.6
Basic Earnings Per Share of Common Stock (in dollars per share)		$ 3.86	$ 3.96	$ 4.97
Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)* (in shares)	[1]	0.1	0.1	0.1
Weighted Average Diluted Common Shares (in millions) (in shares)		52.6	52.1	51.7
Diluted Earnings Per Share of Common Stock (in dollars per share)		$ 3.85	$ 3.95	$ 4.96
* Calculation excludes certain outstanding common shares (shown in millions by period at the right) attributable to common stock forward contracts, stock units subject to performance or market conditions, and restricted stock, which could have a dilutive effect in the future (in shares)		1.9	0.1	0.1
[1]Calculation excludes certain outstanding common shares (shown in millions by period at the right) attributable to stock units subject to performance or market conditions and restricted stock, which could have a dilutive effect in the future

Note 5 - Shareholders' Equity_2

Note 5 - Shareholders' Equity (Details Textual) - USD ($)			1 Months Ended	3 Months Ended		12 Months Ended		19 Months Ended
	Sep. 27, 2023	May 21, 2019	Feb. 28, 2021	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Mar. 01, 2024	Nov. 10, 2023	Apr. 28, 2022
Preferred Stock, Shares Authorized (in shares)						5,000,000		5,000,000
Number of Shares Authorized for Issuance (in shares)						250,000		250,000
Number Of Shares Remaining and Available for Issuance (in shares)						244,182		244,182
Retained Earnings Dividend Restrictions Formula Component Fixed Amount							$ 8,000,000
Retained Earnings, Unappropriated						$ 1,678,500,000	1,579,400,000	$ 1,678,500,000
Stock Issued During Period, Value, New Issues						$ 40,500,000	$ 50,300,000
Spire Missouri [Member]
Preferred Stock, Shares Authorized (in shares)							1,480,000
Preferred Stock, Shares Outstanding, Ending Balance (in shares)						0	0	0
Regulatory Preferred Stock and Debt Securities Issuance Amount Authorized						$ 800,000,000		$ 800,000,000
Stock Issued During Period, Value, New Issues						$ 38,700,000	$ 51,100,000
Preferred Stock, Shares Issued (in shares)						0	0	0
Spire Alabama Inc [Member]
Preferred Stock, Shares Authorized (in shares)						120,000	120,000	120,000
Preferred Stock, Shares Outstanding, Ending Balance (in shares)						0	0	0
Preferred Stock, Shares Issued (in shares)						0	0	0
Forecast [Member]
Number Of Shares Remaining and Available for Issuance (in shares)										237,891
At The Market Program [Member]
Number of Shares Authorized for Issuance (in shares)						17,900,000		17,900,000			200,000,000
Forward Sales Agreements, Shares (in shares)				2,087,231	228,690
Forward Sales Agreements, Shares Settled (in shares)	571,372
Proceeds from Shares Settled	$ 38,500,000
Forward Sales Agreements, Block Sales, Shares (in shares)						1,744,549
Forward Sales Agreements, Proceeds If Settled						$ 111,200,000		$ 111,200,000
Universal Shelf Registration [Member] | Spire Missouri [Member]
Stock Issued During Period, Value, New Issues						$ 79,100,000		79,100,000
Common Stock [Member]
Stock Issued During Period, Shares, New Issues (in shares)						611,872	719,625
Stock Issued During Period, Value, New Issues						$ 600,000	$ 700,000
Common Stock [Member] | Spire Missouri [Member]
Stock Issued During Period, Shares, New Issues (in shares)						530	748
Stock Issued During Period, Value, New Issues						$ 0	$ 0
First Mortgage Bond [Member] | Spire Missouri [Member]
Debt Instrument, Face Amount						400,000,000		400,000,000
Parent Company [Member]
Present Value of Stock Purchase Contract Payment						$ 35,000,000		$ 35,000,000
Parent Company [Member] | Common Stock [Member] | Minimum [Member]
Number of Shares to Be Purchased Per Stock Purchase Contract Settlement Rate (in shares)			0.6354
Parent Company [Member] | Common Stock [Member] | Minimum [Member] | Forecast [Member]
Number of Shares to Be Purchased Per Stock Purchase Contract Settlement Rate (in shares)									0.6354
Parent Company [Member] | Two Thousand Twenty One Series A Zero Point Seven Five Percentage Remarketable Senior Notes [Member]
Debt Instrument, Face Amount			$ 1,000
Debt Instrument, Interest Rate, Stated Percentage			0.75%
Stock Purchase Contracts Rate			6.75%
Redemption Prior to August Fifteen Two Thousand Twenty Four [Member]
Preferred Stock, Redemption Price Per Share (in dollars per share)						$ 25,500		$ 25,500
Redemption on Or After August Fifteen Two Thousand Twenty Four [Member]
Preferred Stock, Redemption Price Per Share (in dollars per share)						$ 25,000		$ 25,000
Depositary Shares [Member]
Preferred Stock, Shares Authorized (in shares)						10,000,000	10,000,000	10,000,000
Preferred Stock, Shares Outstanding, Ending Balance (in shares)		10,000,000				10,000,000	10,000,000	10,000,000
Preferred Stock, Share Interest Rate		0.001%
Preferred Stock, Dividend Rate, Percentage		5.90%
Preferred Stock, Par or Stated Value Per Share (in dollars per share)		$ 25				$ 25	$ 25	$ 25
Preferred Stock, Liquidation Preference Per Share (in dollars per share)		$ 25,000
Proceeds from Issuance of Preferred Stock and Preference Stock		$ 242,000,000
Preferred Stock, Shares Issued (in shares)						10,000,000	10,000,000	10,000,000
Series A Preferred Stock [Member]
Preferred Stock, Dividend Rate, Percentage		5.90%
Corporate Unit [Member] | Parent Company [Member]
Stock Issued During Period, Shares, New Issues (in shares)			3,500,000
Equity Stock Units Issued			$ 175,000,000
Proceeds from Issuance or Sale of Equity, Total			$ 169,300,000
Equity Units, Stated Value (in dollars per share)			$ 50
Percentage of Undivided Beneficial Ownership Interest			5%
Shares Issued, Price Per Share (in dollars per share)			$ 50

Note 5 - Shareholders' Equity -

Note 5 - Shareholders' Equity - Number of Shares to be Purchased Per Stock Purchase Contract (Details) - Common Stock [Member] - Parent Company [Member] - $ / shares	Mar. 01, 2024	Feb. 28, 2021
Forecast [Member]
Less than $78.6906, but greater than $64.24 (in dollars per share)	$ 50
Minimum [Member]
Equal to or greater than $78.6906 (“threshold appreciation price”) (in shares)		0.6354
Minimum [Member] | Forecast [Member]
Equal to or greater than $78.6906 (“threshold appreciation price”) (in shares)	0.6354
Maximum [Member] | Forecast [Member]
Equal to or greater than $78.6906 (“threshold appreciation price”) (in shares)	0.7783

Note 5 - Shareholders' Equity_3

Note 5 - Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2023		Sep. 30, 2022		Sep. 30, 2021
Balance		$ 2,818.5		$ 2,658.2		$ 2,522.3
Other Comprehensive Income (Loss), Net of Tax		0.4		43.6		44.8
Balance		2,917.3		2,818.5		2,658.2
Spire Missouri [Member]
Balance	[1]	1,745.4		1,577.9		1,435.1
Other Comprehensive Income (Loss), Net of Tax		0.2	[1]	1.5	[1]	(1.3)
Balance	[1]	1,844.8		1,745.4		1,577.9
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Balance		50.4		7.9
Other Comprehensive Income (Loss), Net of Tax		0.1		42.5
Balance		50.5		50.4		7.9
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Spire Missouri [Member]
Balance		0		0
Other Comprehensive Income (Loss), Net of Tax		0		0
Balance		0		0		0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance		(2.7)		(4.2)
Other Comprehensive Income (Loss), Net of Tax		0.2		1.5
Balance		(2.5)		(2.7)		(4.2)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] | Spire Missouri [Member]
Balance		(2.7)		(4.2)
Other Comprehensive Income (Loss), Net of Tax		0.2		1.5
Balance		(2.5)		(2.7)		(4.2)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
Balance		(0.5)		(0.1)
Other Comprehensive Income (Loss), Net of Tax		0.1		(0.4)
Balance		(0.4)		(0.5)		(0.1)
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member] | Spire Missouri [Member]
Balance		0		0
Other Comprehensive Income (Loss), Net of Tax		0		0
Balance		0		0		0
AOCI Attributable to Parent [Member]
Balance		47.2		3.6	[1]	(41.2)	[1]
Other Comprehensive Income (Loss), Net of Tax		0.4		43.6		44.8
Balance		47.6		47.2		3.6	[1]
AOCI Attributable to Parent [Member] | Spire Missouri [Member]
Balance		(2.7)		(4.2)		(2.9)
Other Comprehensive Income (Loss), Net of Tax		0.2		1.5		(1.3)
Balance		$ (2.5)		$ (2.7)		$ (4.2)
[1]Accumulated other comprehensive income (loss)

Note 6 - Long-term Debt (Detail

Note 6 - Long-term Debt (Details Textual) - USD ($) $ in Millions		12 Months Ended			19 Months Ended
	Dec. 07, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2023
Long-Term Debt, Gross		$ 3,732.7	$ 3,258.9		$ 3,732.7
Interest Paid, Capitalized, Investing Activities		8.6	4.5	$ 4.4
Stock Issued During Period, Value, New Issues		40.5	50.3
Subsidiaries [Member]
Long-Term Debt, Gross		229.7			229.7
Spire Missouri [Member]
Long-Term Debt, Gross		1,798	1,648		1,798
Interest Paid, Capitalized, Investing Activities		3.1	0.6	0.2
Regulatory Preferred Stock and Debt Securities Issuance Amount Authorized		800			800
Stock Issued During Period, Value, New Issues		38.7	51.1
Spire Missouri [Member] | Universal Shelf Registration [Member]
Stock Issued During Period, Value, New Issues		79.1			79.1
Spire Missouri [Member] | First Mortgage Bonds Due December Two Two Thousand Twenty Four [Member]
Long-Term Debt, Gross	$ 300
Debt Instrument, Interest Rate, Stated Percentage	8%
Spire Missouri [Member] | First Mortgage Bonds Due December Two Two Thousand Twenty Four [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Spire Missouri [Member] | Floating Rate Series Due December 2, 2024 [Member]
Long-Term Debt, Gross		300			300
Spire Missouri [Member] | First Mortgage Bond [Member]
Debt Instrument, Face Amount		400			400
Spire Alabama Inc [Member]
Long-Term Debt, Gross		750	575		$ 750
Interest Paid, Capitalized, Investing Activities		$ 2.3	$ 3.2	$ 3.2

Note 6 - Long-term Debt - Compo

Note 6 - Long-term Debt - Composition of Long-term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Total principal of long-term debt	$ 3,732.7	$ 3,258.9
Less: Unamortized discounts and debt issuance costs	(22.1)	(19.2)
Less: Current portion	(156.6)	(281.2)
Long-term debt (less current portion)	3,554	2,958.5
Spire Missouri [Member]
Total principal of long-term debt	1,798	1,648
Less: Unamortized discounts and debt issuance costs	(12.6)	(10.3)
Less: Current portion	0	(250)
Long-term debt (less current portion)	1,785.4	1,387.7
Spire Alabama Inc [Member]
Total principal of long-term debt	750	575
Less: Unamortized discounts and debt issuance costs	(4.1)	(3.5)
Long-term debt (less current portion)	745.9	571.5
First Mortgage Bonds Three Point Four Percentage Series Due August152023 [Member] | Spire Missouri [Member]
Total principal of long-term debt	0	250
Floating Rate Series Due December 2, 2024 [Member] | Spire Missouri [Member]
Total principal of long-term debt	300
First Mortgage Bonds Three Point Four Percentage Series Due March152028 [Member] | Spire Missouri [Member]
Total principal of long-term debt	45	45
First Mortgage Bonds Seven Percentage Series Due June12029 [Member] | Spire Missouri [Member]
Total principal of long-term debt	19.3	19.3
First Mortgage Bonds Two Point Eight Four Percentage Series Due November152029 [Member] | Spire Missouri [Member]
Total principal of long-term debt	275	275
First Mortgage Bonds Seven Point Nine Percentage Series Due September152030 [Member] | Spire Missouri [Member]
Total principal of long-term debt	30	30
First Mortgage Bonds Three Point Six Eight Percentage Series Due September152032 [Member] | Spire Missouri [Member]
Total principal of long-term debt	50	50
First Mortgage Bonds Four Point Eight Zero Percentage Series Due February 152033 [Member] | Spire Missouri [Member]
Total principal of long-term debt	400	0
First Mortgage Bonds Six Percentage Series Due May12034 [Member] | Spire Missouri [Member]
Total principal of long-term debt	99.3	99.3
First Mortgage Bonds Six Point One Five Percentage Series Due June12036 [Member] | Spire Missouri [Member]
Total principal of long-term debt	54.5	54.5
First Mortgage Bonds Four Point Six Three Percentage Series Due August152043 [Member] | Spire Missouri [Member]
Total principal of long-term debt	99.9	99.9
First Mortgage Bonds Four Point Two Three Percentage Series Due September152047 [Member] | Spire Missouri [Member]
Total principal of long-term debt	70	70
First Mortgage Bonds Three Point Three Zero Percentage Series Due June12051 [Member] | Spire Missouri [Member]
Total principal of long-term debt	305	305
First Mortgage Bonds Four Point Three Eight Percentage Series Due September152057 [Member] | Spire Missouri [Member]
Total principal of long-term debt	50	50
Three Point Two One Percentage Notes Due September152025 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	35	35
Five Point Three Two Percentage Notes Due October152029 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	90	0
Two Point Eight Eight Percentage Notes Due December12029 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	100	100
Two Point Zero Four Percentage Notes Due December152030 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	150	150
Five Point Four One Percentage Notes Due October152032[Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	85	0
Five Point Nine Zero Percentage Notes Due January152037 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	45	45
Four Point Three One Percentage Notes Due December12045 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	80	80
Three Point Nine Two Percentage Notes Due January152048 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	45	45
Four Point Six Four Percentage Notes Due January152049 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	90	90
Four Point Zero Two Percentage Notes Due January152058 [Member] | Spire Alabama Inc [Member]
Total principal of long-term debt	30	30
Parent Company [Member] | Three Point Three One Percent Notes Payable Due December152022 [Member]
Total principal of long-term debt	0	25
Parent Company [Member] | Three Point Five Four Percent Senior Notes Due February272024 [Member]
Total principal of long-term debt	150	150
Parent Company [Member] | Zero Point Seven Five Percent Remarketable Senior Notes Due March12026 [Member]
Total principal of long-term debt	175	175
Parent Company [Member] | Three Point One Three Percent Senior Notes Due September12026 [Member]
Total principal of long-term debt	130	130
Parent Company [Member] | Three Point Nine Three Percent Senior Notes Due March152027 [Member]
Total principal of long-term debt	100	100
Parent Company [Member] | Five Point Eight Percent Senior Notes Due March152033 [Member]
Total principal of long-term debt	150	0
Parent Company [Member] | Four Point Seven Zero Percent Senior Notes Due August152044 [Member]
Total principal of long-term debt	250	250
Subsidiaries [Member]
Total principal of long-term debt	229.7
Subsidiaries [Member] | Five Point Zero Zero Percent First Mortgage Bonds Due September302031 [Member]
Total principal of long-term debt	42	42
Subsidiaries [Member] | Two Nine Five Percent Notes With Annual Principal Payments Through December2034 [Member]
Total principal of long-term debt	117.7	123.9
Subsidiaries [Member] | Five Point Six One Percent First Mortgage Bonds Due October 152037 [Member]
Total principal of long-term debt	30	0
Subsidiaries [Member] | Three Point Five Two Percent First Mortgage Bonds Due September302049 [Member]
Total principal of long-term debt	$ 40	$ 40

Note 6 - Long-term Debt - Com_2

Note 6 - Long-term Debt - Composition of Long-term Debt (Details) (Parentheticals)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
First Mortgage Bonds Three Point Four Percentage Series Due August152023 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	3.40%	3.40%
Debt Instrument Maturity Date	Aug. 15, 2023	Aug. 15, 2023
Floating Rate Series Due December 2, 2024 [Member] | Spire Missouri [Member]
Debt Instrument Maturity Date	Dec. 02, 2024
First Mortgage Bonds Three Point Four Percentage Series Due March152028 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	3.40%	3.40%
Debt Instrument Maturity Date	Mar. 15, 2028	Mar. 15, 2028
First Mortgage Bonds Seven Percentage Series Due June12029 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	7%	7%
Debt Instrument Maturity Date	Jun. 01, 2029	Jun. 01, 2029
First Mortgage Bonds Two Point Eight Four Percentage Series Due November152029 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	2.84%	2.84%
Debt Instrument Maturity Date	Nov. 15, 2029	Nov. 15, 2029
First Mortgage Bonds Seven Point Nine Percentage Series Due September152030 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	7.90%	7.90%
Debt Instrument Maturity Date	Sep. 15, 2030	Sep. 15, 2030
First Mortgage Bonds Three Point Six Eight Percentage Series Due September152032 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	3.68%	3.68%
Debt Instrument Maturity Date	Sep. 15, 2032	Sep. 15, 2032
First Mortgage Bonds Four Point Eight Zero Percentage Series Due February 152033 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	4.80%	4.80%
Debt Instrument Maturity Date	Feb. 15, 2033	Feb. 15, 2033
First Mortgage Bonds Six Percentage Series Due May12034 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	6%	6%
Debt Instrument Maturity Date	May 01, 2034	May 01, 2034
First Mortgage Bonds Six Point One Five Percentage Series Due June12036 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	6.15%	6.15%
Debt Instrument Maturity Date	Jun. 01, 2036	Jun. 01, 2036
First Mortgage Bonds Four Point Six Three Percentage Series Due August152043 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	4.63%	4.63%
Debt Instrument Maturity Date	Aug. 15, 2043	Aug. 15, 2043
First Mortgage Bonds Four Point Two Three Percentage Series Due September152047 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	4.23%	4.23%
Debt Instrument Maturity Date	Sep. 15, 2047	Sep. 15, 2047
First Mortgage Bonds Three Point Three Zero Percentage Series Due June12051 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	3.30%	3.30%
Debt Instrument Maturity Date	Jun. 01, 2051	Jun. 01, 2051
First Mortgage Bonds Four Point Three Eight Percentage Series Due September152057 [Member] | Spire Missouri [Member]
Debt Instrument Interest Rate	4.38%	4.38%
Debt Instrument Maturity Date	Sep. 15, 2057	Sep. 15, 2057
Three Point Two One Percentage Notes Due September152025 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	3.21%	3.21%
Debt Instrument Maturity Date	Sep. 15, 2025	Sep. 15, 2025
Five Point Three Two Percentage Notes Due October152029 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	5.32%	5.32%
Debt Instrument Maturity Date	Oct. 15, 2029	Oct. 15, 2029
Two Point Eight Eight Percentage Notes Due December12029 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	2.88%	2.88%
Debt Instrument Maturity Date	Dec. 01, 2029	Dec. 01, 2029
Two Point Zero Four Percentage Notes Due December152030 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	2.04%	2.04%
Debt Instrument Maturity Date	Dec. 15, 2030	Dec. 15, 2030
Five Point Four One Percentage Notes Due October152032[Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	5.41%	5.41%
Debt Instrument Maturity Date	Oct. 15, 2032	Oct. 15, 2032
Five Point Nine Zero Percentage Notes Due January152037 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	5.90%	5.90%
Debt Instrument Maturity Date	Jan. 15, 2037	Jan. 15, 2037
Four Point Three One Percentage Notes Due December12045 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	4.31%	4.31%
Debt Instrument Maturity Date	Dec. 01, 2045	Dec. 01, 2045
Three Point Nine Two Percentage Notes Due January152048 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	3.92%	3.92%
Debt Instrument Maturity Date	Jan. 15, 2048	Jan. 15, 2048
Four Point Six Four Percentage Notes Due January152049 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	4.64%	4.64%
Debt Instrument Maturity Date	Jan. 15, 2049	Jan. 15, 2049
Four Point Zero Two Percentage Notes Due January152058 [Member] | Spire Alabama Inc [Member]
Debt Instrument Interest Rate	4.02%	4.02%
Debt Instrument Maturity Date	Jan. 15, 2058	Jan. 15, 2058
Parent Company [Member] | Three Point Three One Percent Notes Payable Due December152022 [Member]
Debt Instrument Interest Rate	3.31%	3.31%
Debt Instrument Maturity Date	Dec. 15, 2022	Dec. 15, 2022
Parent Company [Member] | Three Point Five Four Percent Senior Notes Due February272024 [Member]
Debt Instrument Interest Rate	3.54%	3.54%
Debt Instrument Maturity Date	Feb. 27, 2024	Feb. 27, 2024
Parent Company [Member] | Zero Point Seven Five Percent Remarketable Senior Notes Due March12026 [Member]
Debt Instrument Interest Rate	0.75%	0.75%
Debt Instrument Maturity Date	Mar. 01, 2026	Mar. 01, 2026
Parent Company [Member] | Three Point One Three Percent Senior Notes Due September12026 [Member]
Debt Instrument Interest Rate	3.13%	3.13%
Debt Instrument Maturity Date	Sep. 01, 2026	Sep. 01, 2026
Parent Company [Member] | Three Point Nine Three Percent Senior Notes Due March152027 [Member]
Debt Instrument Interest Rate	3.93%	3.93%
Debt Instrument Maturity Date	Mar. 15, 2027	Mar. 15, 2027
Parent Company [Member] | Five Point Eight Percent Senior Notes Due March152033 [Member]
Debt Instrument Interest Rate	5.80%	5.80%
Debt Instrument Maturity Date	Mar. 15, 2033	Mar. 15, 2033
Parent Company [Member] | Four Point Seven Zero Percent Senior Notes Due August152044 [Member]
Debt Instrument Interest Rate	4.70%	4.70%
Debt Instrument Maturity Date	Aug. 15, 2044	Aug. 15, 2044
Subsidiaries [Member] | Five Point Zero Zero Percent First Mortgage Bonds Due September302031 [Member]
Debt Instrument Interest Rate	5%	5%
Debt Instrument Maturity Date	Sep. 30, 2031	Sep. 30, 2031
Subsidiaries [Member] | Two Nine Five Percent Notes With Annual Principal Payments Through December2034 [Member]
Debt Instrument Interest Rate	2.95%	2.95%
Debt Instrument Maturity Date	Dec. 31, 2034	Dec. 31, 2034
Subsidiaries [Member] | Five Point Six One Percent First Mortgage Bonds Due October 152037 [Member]
Debt Instrument Interest Rate	5.61%	5.61%
Debt Instrument Maturity Date	Oct. 15, 2037	Oct. 15, 2037
Subsidiaries [Member] | Three Point Five Two Percent First Mortgage Bonds Due September302049 [Member]
Debt Instrument Interest Rate	3.52%	3.52%
Debt Instrument Maturity Date	Sep. 30, 2049	Sep. 30, 2049

Note 6 - Long-term Debt - Matur

Note 6 - Long-term Debt - Maturities of Long-term Debt (Details) $ in Millions	Sep. 30, 2023 USD ($)
2023	$ 156.6
2024	342
2025	312.5
2026	108.1
2027	53.6
Spire Missouri [Member]
2023	0
2024	300
2025	0
2026	0
2027	45
Spire Alabama Inc [Member]
2023	0
2024	35
2025	0
2026	0
2027	$ 0

Note 7 - Notes Payable and Cr_3

Note 7 - Notes Payable and Credit Agreements (Details Textual) - USD ($) $ in Thousands	Jan. 05, 2023	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2021
Commercial Paper [Member] | Parent Company [Member]
Short Term Borrowings Used to Support Lending to Utilities		$ 706,900
Spire Missouri [Member] | Unsecured Term Loan [Member]
Debt Instrument, Face Amount				$ 250,000
Debt Instrument, Interest Rate, Stated Percentage	0.10%
Spire Missouri [Member] | Unsecured Term Loan [Member] | London Interbank Offered Rate LIBOR 1 [Member]
Line of Credit Facility, Covenant, Percentage of Total Capitalization		65%
Debt Instrument, Basis Spread on Variable Rate	0.80%
Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,300,000
Long-Term Line of Credit		$ 0	$ 0
Revolving Credit Facility [Member] | Maximum [Member]
Line of Credit Facility, Covenant, Percentage of Total Capitalization		70%
Revolving Credit Facility [Member] | Spire [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 450,000
Revolving Credit Facility [Member] | Spire Missouri [Member]
Line of Credit Facility, Maximum Borrowing Capacity		575,000
Revolving Credit Facility [Member] | Spire Alabama Inc [Member]
Line of Credit Facility, Maximum Borrowing Capacity		$ 275,000

Note 7 - Notes Payable and Cr_4

Note 7 - Notes Payable and Credit Agreements - Short-term Borrowings (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Term Loan [Member] | Spire Missouri [Member]
Highest borrowings outstanding	$ 656.9
Lowest borrowings outstanding	3.8
Weighted average borrowings	$ 327.9
Weighted average interest rate	4.90%
Borrowings outstanding	$ 540.6	$ 445.3
Weighted average interest rate	5.60%
Spire Note [Member] | Spire Missouri [Member]
Highest borrowings outstanding	$ 274
Lowest borrowings outstanding	76.7
Weighted average borrowings	$ 119.1
Weighted average interest rate	4.90%
Borrowings outstanding	$ 124.1	$ 260.9
Weighted average interest rate	5.60%	3.30%
Spire Note [Member] | Spire Alabama Inc [Member]
Highest borrowings outstanding	$ 1,482
Lowest borrowings outstanding	489
Weighted average borrowings	$ 843.1
Weighted average interest rate	5%
Borrowings outstanding	$ 955.5	$ 1,037.5
Weighted average interest rate	5.60%	3.30%
Parent Company [Member] | Term Loan [Member]
Highest borrowings outstanding	$ 250
Lowest borrowings outstanding	0
Weighted average borrowings	$ 66.8
Weighted average interest rate	5.50%
Borrowings outstanding	$ 0	$ 0
Weighted average interest rate		0%
Parent Company [Member] | Commercial Paper [Member]
Highest borrowings outstanding	1,282
Lowest borrowings outstanding	354.4
Weighted average borrowings	$ 776.3
Weighted average interest rate	5%
Borrowings outstanding	$ 955.5	$ 1,037.5
Weighted average interest rate	5.60%	3.30%

Note 8 - Fair Value of Financ_3

Note 8 - Fair Value of Financial Instruments - Estimated Fair Value of Financial Instruments Not Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Reported Value Measurement [Member]
Cash and cash equivalents	$ 5.6	$ 6.5
Notes payable	955.5	1,037.5
Long-term debt, including current portion	3,710.6	3,239.7
Reported Value Measurement [Member] | Spire Missouri [Member]
Cash and cash equivalents	0.8
Long-term debt, including current portion	1,785.4	1,637.7
Notes payable - associated companies	540.6	445.3
Reported Value Measurement [Member] | Spire Alabama Inc [Member]
Cash and cash equivalents	1.2	2.4
Long-term debt, including current portion	745.9	571.5
Notes payable - associated companies	124.1	260.9
Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	5.6	6.5
Notes payable	955.5	1,037.5
Long-term debt, including current portion	3,270.2	2,851.8
Estimate of Fair Value Measurement [Member] | Spire Missouri [Member]
Cash and cash equivalents	0.8
Long-term debt, including current portion	1,592.4	1,473.9
Notes payable - associated companies	540.6	445.3
Estimate of Fair Value Measurement [Member] | Spire Alabama Inc [Member]
Cash and cash equivalents	1.2	2.4
Long-term debt, including current portion	648	485
Notes payable - associated companies	124.1	260.9
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	5.6	6.5
Notes payable	0	0
Long-term debt, including current portion	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Cash and cash equivalents	0.8
Long-term debt, including current portion	0	0
Notes payable - associated companies	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Cash and cash equivalents	1.2	2.4
Long-term debt, including current portion	0	0
Notes payable - associated companies	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents	0	0
Notes payable	955.5	1,037.5
Long-term debt, including current portion	3,270.2	2,851.8
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Cash and cash equivalents	0
Long-term debt, including current portion	1,592.4	1,473.9
Notes payable - associated companies	540.6	445.3
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Cash and cash equivalents	0	0
Long-term debt, including current portion	648	485
Notes payable - associated companies	$ 124.1	$ 260.9

Note 9 - Fair Value Measureme_3

Note 9 - Fair Value Measurements - Schedule of Derivative Assets and Liabilities, Including Receivables and Payables (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Derivative Assets	$ 77.3	$ 116.2
Derivative Liabilities	30.8	61.5
Fair Value, Recurring [Member]
Effects of netting, asset	(20.1)	(153.6)
Derivative Assets	135.3	164.6
Effects of netting, liability	(69.4)	(117)
Derivative Liabilities	30.8	61.5
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative Asset Fair Value Gross Asset	74.4	198
Derivative Liability Fair Value Gross Liability	72.6	113
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Asset Fair Value Gross Asset	81	120.2
Derivative Liability Fair Value Gross Liability	27.6	65.5
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	0	0
U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Gas Utility [Member]
Effects of netting, asset	0	0
Derivative Assets	20.4	19.1
U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Other Segments [Member]
Effects of netting, asset	0	0
Derivative Assets	37.6	29.3
U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	20.4	19.1
U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Segments [Member]
Derivative Asset Fair Value Gross Asset	37.6	29.3
U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	0	0
U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Segments [Member]
Derivative Asset Fair Value Gross Asset	0	0
U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	0	0
U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Segments [Member]
Derivative Asset Fair Value Gross Asset	0	0
Gasoline And Heating Oil Contracts [Member] | Fair Value, Recurring [Member] | Gas Utility [Member]
Effects of netting, asset	(0.1)
Derivative Assets	0
Gasoline And Heating Oil Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	0
Gasoline And Heating Oil Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	0.1
Gasoline And Heating Oil Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	0
N Y M E X And I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Gas Utility [Member]
Effects of netting, asset	(6.3)	(57.8)
Derivative Assets	0	0
Effects of netting, liability	(44)	(30.7)
Derivative Liabilities	6.8	0
N Y M E X And I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Gas Marketing [Member]
Effects of netting, asset	(10.1)	(91.8)
Derivative Assets	0	0
Effects of netting, liability	(21.8)	(82.3)
Derivative Liabilities	0	0
N Y M E X And I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	6.3	57.8
Derivative Liability Fair Value Gross Liability	50.8	30.7
N Y M E X And I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Gas Marketing [Member]
Derivative Asset Fair Value Gross Asset	10.1	91.8
Derivative Liability Fair Value Gross Liability	21.8	82.3
N Y M E X And I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	0	0
N Y M E X And I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Marketing [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	0	0
N Y M E X And I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Utility [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	0	0
N Y M E X And I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Marketing [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	0	0
Natural Gas Commodity Contracts [Member] | Fair Value, Recurring [Member] | Gas Marketing [Member]
Effects of netting, asset	(3.6)	(4)
Derivative Assets	33.1	52.6
Effects of netting, liability	(3.6)	(4)
Derivative Liabilities	24	61.5
Natural Gas Commodity Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Gas Marketing [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	0	0
Natural Gas Commodity Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Gas Marketing [Member]
Derivative Asset Fair Value Gross Asset	36.7	56.6
Derivative Liability Fair Value Gross Liability	27.6	65.5
Natural Gas Commodity Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Gas Marketing [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	0	0
Interest Rate Swap [Member] | Fair Value, Recurring [Member] | Other Segments [Member]
Effects of netting, asset	0	0
Derivative Assets	44.2	63.6
Interest Rate Swap [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Segments [Member]
Derivative Asset Fair Value Gross Asset	0	0
Interest Rate Swap [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Segments [Member]
Derivative Asset Fair Value Gross Asset	44.2	63.6
Interest Rate Swap [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Segments [Member]
Derivative Asset Fair Value Gross Asset	0	0
Spire Missouri [Member]
Derivative Assets	0	0
Derivative Liabilities	6.8	0
Spire Missouri [Member] | Fair Value, Recurring [Member]
Effects of netting, asset	(6.4)	(57.8)
Derivative Assets	20.4	19.1
Spire Missouri [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative Asset Fair Value Gross Asset	26.7	76.9
Spire Missouri [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Asset Fair Value Gross Asset	0.1	0
Spire Missouri [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative Asset Fair Value Gross Asset	0	0
Spire Missouri [Member] | U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member]
Effects of netting, asset	0	0
Derivative Assets	20.4	19.1
Spire Missouri [Member] | U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative Asset Fair Value Gross Asset	20.4	19.1
Spire Missouri [Member] | U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Asset Fair Value Gross Asset	0	0
Spire Missouri [Member] | U S Stock And Bond Mutual Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative Asset Fair Value Gross Asset	0	0
Spire Missouri [Member] | Gasoline And Heating Oil Contracts [Member] | Fair Value, Recurring [Member]
Effects of netting, asset	(0.1)
Derivative Assets	0
Spire Missouri [Member] | Gasoline And Heating Oil Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative Asset Fair Value Gross Asset	0
Spire Missouri [Member] | Gasoline And Heating Oil Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Asset Fair Value Gross Asset	0.1
Spire Missouri [Member] | Gasoline And Heating Oil Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative Asset Fair Value Gross Asset	0
Spire Missouri [Member] | N Y M E X I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member]
Effects of netting, asset	(6.3)	(57.8)
Derivative Assets	0	0
Effects of netting, liability	(44)	(30.7)
Derivative Liabilities	6.8	0
Spire Missouri [Member] | N Y M E X I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative Asset Fair Value Gross Asset	6.3	57.8
Derivative Liability Fair Value Gross Liability	50.8	30.7
Spire Missouri [Member] | N Y M E X I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	0	0
Spire Missouri [Member] | N Y M E X I C E Natural Gas Contracts [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative Asset Fair Value Gross Asset	0	0
Derivative Liability Fair Value Gross Liability	$ 0	$ 0

Note 10 - Derivative Instrume_3

Note 10 - Derivative Instruments and Hedging Activities (Details Textual) $ in Thousands	12 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($) MMBoe	Sep. 30, 2022 USD ($)
Nonmonetary Notional Amount of Natural Gas Derivative Contracts Not Designated As Normal Purchases Or Normal Sales (Millions of Barrels of Oil Equivalent)		567,000,000
Notional Amount of Non Exchange Traded Natural Gas Commodity Contracts To Be Settled In Next Twelve Months (Millions of Barrels of Oil Equivalent)		379.1
Notional Amount of Non Exchange Traded Natural Gas Commodity Contracts To Be Settled In Year Two (Millions of Barrels of Oil Equivalent)		151.1
Notional Amount of Non Exchange Traded Natural Gas Commodity Contracts To Be Settled In Year Three (Millions of Barrels of Oil Equivalent)		26.4
Notional Amount of Non Exchange Traded Natural Gas Commodity Contracts To Be Settled In Year Four (Millions of Barrels of Oil Equivalent)		3.8
Notional Amount of Non Exchange Traded Natural Gas Commodity Contracts To Be Settled In Year Five (Millions of Barrels of Oil Equivalent)		6.6
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax | $		$ 44,200
Other Receivable from Broker-Dealer and Clearing Organization | $		$ 0	$ 49,800
Forecast [Member]
Reclassification from AOCI, Current Period, before Tax, Attributable to Parent | $	$ 2,800
Spire Missouri [Member]
Nonmonetary Notional Amount of Other Price Mitigation in Place Not Designated As Normal Purchases Or Normal Sales (Millions of Barrels of Oil Equivalent)		16,300,000
Other Receivable from Broker-Dealer and Clearing Organization | $		$ 0	$ 24,000

Note 10 - Derivative Instrume_4

Note 10 - Derivative Instruments and Hedging Activities - Interest Swap Contracts (Details) - Cash Flow Hedging [Member] $ in Millions	12 Months Ended
	Sep. 30, 2023 USD ($)
Interest Rate Swap Agreement One [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 50
Derivative, fixed interest rate	1.4918%
Derivative, mark-to-market gain	$ 2.7
Interest Rate Swap Agreement Two [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 75
Derivative, fixed interest rate	1.6475%
Derivative, mark-to-market gain	$ 4
Interest Rate Swap Agreement Three [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25
Derivative, fixed interest rate	1.746%
Derivative, mark-to-market gain	$ 1.5
Interest Rate Swap Agreement Four [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 50
Derivative, fixed interest rate	3.448%
Derivative, mark-to-market gain	$ 2.4
Interest Rate Swap Agreement Five [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 50
Derivative, fixed interest rate	3.685%
Derivative, mark-to-market gain	$ 0.9
Interest Rate Swap Agreement Six [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25
Derivative, fixed interest rate	3.535%
Derivative, mark-to-market gain	$ 0.5
Interest Rate Swap Agreement Seven [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25
Derivative, fixed interest rate	3.385%
Derivative, mark-to-market gain	$ 0.6
Interest Rate Swap Agreement Eight [Member]
Derivative, hedge term (Year)	30 years
Derivative, notional amount	$ 50
Derivative, fixed interest rate	2.747%
Derivative, mark-to-market gain	$ 7.8
Interest Rate Swap Agreement Nine [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25
Derivative, fixed interest rate	2.902%
Derivative, mark-to-market gain	$ 2.2
Interest Rate Swap Agreement Ten [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25
Derivative, fixed interest rate	3.018%
Derivative, mark-to-market gain	$ 2
Interest Rate Swap [Member]
Derivative, notional amount	400
Derivative, mark-to-market gain	$ 24.6

Note 10 - Derivative Instrume_5

Note 10 - Derivative Instruments and Hedging Activities - Summary of NYMEX and ICE Natural Gas Futures and Swap Positions (Details) - MMBTU MMBTU in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Natural Gas Futures Purchased [Member] | Spire Missouri [Member]
Notional Amount, Energy Measure (Millions of British Thermal Unit)	66.5	13
Derivative, hedge term (Year)	24 months	12 months
Natural Gas Futures Purchased [Member] | Gas Marketing [Member]
Notional Amount, Energy Measure (Millions of British Thermal Unit)	61.3	76.3
Derivative, hedge term (Year)	51 months	54 months
Natural Gas Futures Purchased [Member] | Gas Utility [Member]
Notional Amount, Energy Measure (Millions of British Thermal Unit)	66.5	13
Derivative, hedge term (Year)	24 months	12 months
Natural Gas Options Purchased Net [Member] | Gas Marketing [Member]
Notional Amount, Energy Measure (Millions of British Thermal Unit)	4.9	3.7
Derivative, hedge term (Year)	15 months	12 months
Natural Gas Basis Swaps Purchased [Member] | Gas Marketing [Member]
Notional Amount, Energy Measure (Millions of British Thermal Unit)	44.1	61.7
Derivative, hedge term (Year)	51 months	39 months

Note 10 - Derivative Instrume_6

Note 10 - Derivative Instruments and Hedging Activities - Effect of Derivative Instruments on the Consolidated Statements of Income and Comprehensive Income (Details) - USD ($) $ in Millions		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Net hedging gain arising during the period		$ 20.1	$ 56.7	$ 61.2
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Other Comprehensive Income (Loss) [Member]
Net hedging gain arising during the period		(16.7)	95.9	(23.4)
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Other Comprehensive Income (Loss) [Member]
Net hedging gain arising during the period		20.1	56.7	61.2
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Interest Expense [Member]
Effective portion of (loss) gain reclassified from AOCI to income:		(2.4)	(1.2)	(1.3)
Not Designated as Hedging Instrument [Member] | Gasoline And Heating Oil Contracts [Member] | Non Regulated Gas Marketing Operating Revenue [Member]
Derivatives Not Designated as Hedging Instrument		0.3	0	0
Not Designated as Hedging Instrument [Member] | Natural Gas Commodity Contracts [Member] | Non Regulated Gas Marketing Operating Revenue [Member]
Derivatives Not Designated as Hedging Instrument	[1]	18	52.6	54.1
Not Designated as Hedging Instrument [Member] | N Y M E X And I C E Natural Gas Contracts [Member] | Non Regulated Gas Marketing Operating Revenue [Member]
Derivatives Not Designated as Hedging Instrument	[1]	$ (35)	$ 43.3	$ (77.5)
[1]Gains and losses on Spire Missouri’s natural gas derivative instruments, which are not designated as hedging instruments for financial reporting purposes, are deferred pursuant to the Missouri Utilities’ PGA clauses and initially recorded as regulatory assets or regulatory liabilities. These gains and losses are excluded from the table above because they have no direct impact on the statements of income. Such amounts are recognized in the statements of income as a component of natural gas operating expenses when they are recovered through the PGA clause and reflected in customer billings.

Note 10 - Derivative Instrume_7

Note 10 - Derivative Instruments and Hedging Activities - Fair Value of Derivative Instruments in the Consolidated Balance Sheets (Details) - USD ($) $ in Millions		Sep. 30, 2023	Sep. 30, 2022
Fair value of derivative assets presented above		$ 97.4	$ 269.8
Fair Value Of Derivative Liability	[1]	100.2	178.5
Spire Missouri [Member]
Fair value of derivative assets presented above		6.4	57.8
Fair Value Of Derivative Liability		50.8	30.7
Designated as Hedging Instrument [Member]
Fair value of derivative assets presented above		44.2	63.6
Fair Value Of Derivative Liability	[1]	0	0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Derivative Instruments Assets [Member] | Corporate, Non-Segment [Member]
Fair value of derivative assets presented above		44.2
Fair Value Of Derivative Liability	[1]	0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Derivative Instruments Liability [Member] | Corporate, Non-Segment [Member]
Fair value of derivative assets presented above			63.6
Fair Value Of Derivative Liability	[1]		0
Not Designated as Hedging Instrument [Member]
Fair value of derivative assets presented above		53.2	206.2
Fair Value Of Derivative Liability	[1]	100.2	178.5
Not Designated as Hedging Instrument [Member] | Gas Utility [Member] | Spire Missouri [Member]
Fair value of derivative assets presented above		6.4
Fair Value Of Derivative Liability		50.8
Not Designated as Hedging Instrument [Member] | N Y M E X Natural Gas Contracts [Member] | Accounts Receivable Other [Member] | Gas Utility [Member] | Spire Missouri [Member]
Fair value of derivative assets presented above		6.3	57.8
Fair Value Of Derivative Liability	[2]	50.8	30.7
Not Designated as Hedging Instrument [Member] | N Y M E X Natural Gas Contracts [Member] | Accounts Receivable Other [Member] | Operating Segments [Member] | Gas Utility [Member]
Fair value of derivative assets presented above		6.3	57.8
Fair Value Of Derivative Liability	[1]	50.8	30.7
Not Designated as Hedging Instrument [Member] | Gasoline And Heating Oil Contracts [Member] | Accounts Receivable Other [Member] | Gas Utility [Member] | Spire Missouri [Member]
Fair value of derivative assets presented above		0.1
Not Designated as Hedging Instrument [Member] | Gasoline And Heating Oil Contracts [Member] | Accounts Receivable Other [Member] | Operating Segments [Member] | Gas Utility [Member]
Fair value of derivative assets presented above		0.1
Fair Value Of Derivative Liability		0
Not Designated as Hedging Instrument [Member] | N Y M E X And I C E Natural Gas Contracts [Member] | Derivative Instruments Liability [Member] | Operating Segments [Member] | Gas Marketing [Member]
Fair value of derivative assets presented above		8
Fair Value Of Derivative Liability	[1]	16
Not Designated as Hedging Instrument [Member] | N Y M E X And I C E Natural Gas Contracts [Member] | Other Deferred Charges [Member] | Operating Segments [Member] | Gas Marketing [Member]
Fair value of derivative assets presented above		2.1
Fair Value Of Derivative Liability	[1]	5.7
Not Designated as Hedging Instrument [Member] | Natural Gas Commodity Contracts [Member] | Derivative Instruments Assets [Member] | Operating Segments [Member] | Gas Marketing [Member]
Fair value of derivative assets presented above		31.2	53.4
Fair Value Of Derivative Liability	[1]		55.1
Not Designated as Hedging Instrument [Member] | Natural Gas Commodity Contracts [Member] | Other Deferred Charges [Member] | Operating Segments [Member] | Gas Marketing [Member]
Fair value of derivative assets presented above		5.5	3.1
Fair Value Of Derivative Liability	[1]		10.4
Not Designated as Hedging Instrument [Member] | Natural Gas Commodity Contracts [Member] | Other Current Liabilities [Member] | Operating Segments [Member] | Gas Marketing [Member]
Fair Value Of Derivative Liability	[1]	20.1
Not Designated as Hedging Instrument [Member] | Natural Gas Commodity Contracts [Member] | Deferred Credits And Other Liabilities [Member] | Operating Segments [Member] | Gas Marketing [Member]
Fair Value Of Derivative Liability	[1]	$ 7.6
Not Designated as Hedging Instrument [Member] | N Y M E X I C E Natural Gas Contracts [Member] | Derivative Instruments Assets [Member] | Operating Segments [Member] | Gas Marketing [Member]
Fair value of derivative assets presented above			79.2
Fair Value Of Derivative Liability	[1]		71.5
Not Designated as Hedging Instrument [Member] | N Y M E X I C E Natural Gas Contracts [Member] | Other Deferred Charges [Member] | Operating Segments [Member] | Gas Marketing [Member]
Fair value of derivative assets presented above			12.7
Fair Value Of Derivative Liability	[1]		$ 10.8
[1]The fair values of Derivative Assets and Derivative Liabilities exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the balance sheets. As such, the gross balances presented in the table above are not indicative of the Company’s net economic exposure. Refer to Note 9, Fair Value Measurements, for information on the valuation of derivative instruments.[2]The fair values of Derivative Assets and Derivative Liabilities exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the Balance Sheets. As such, the gross balances presented in the table above are not indicative of Spire Missouri’s net economic exposure. Refer to Note 9, Fair Value Measurements, for information on the valuation of derivative instruments.

Note 10 - Derivative Instrume_8

Note 10 - Derivative Instruments and Hedging Activities - Reconciliation of Amounts in the Consolidated Balance Sheet (Details) - USD ($) $ in Millions		Sep. 30, 2023	Sep. 30, 2022
Fair value of derivative assets presented above		$ 97.4	$ 269.8
Fair value of cash margin receivable offset with derivatives		49.3	(36.6)
Netting of assets and liabilities with the same counterparty		(69.4)	(117)
Total		77.3	116.2
Derivative Assets		77.3	116.2
Fair value of derivative liabilities presented above	[1]	100.2	178.5
Netting of assets and liabilities with the same counterparty		(69.4)	(117)
Total		30.8	61.5
Derivative Liabilities		30.8	61.5
Other Current Assets [Member]
Total		71.8	113.1
Derivative Assets		71.8	113.1
Deferred Charges and Other Assets, Other [Member]
Total		5.5	3.1
Derivative Assets		5.5	3.1
Other Current Liabilities [Member]
Total		23.2	51.1
Derivative Liabilities		23.2	51.1
Deferred Credits And Other Liabilities [Member]
Total		7.6	10.4
Derivative Liabilities		7.6	10.4
Spire Missouri [Member]
Fair value of derivative assets presented above		6.4	57.8
Netting of assets and liabilities with the same counterparty		(44)	(30.7)
Total		0	0
Derivative Assets		0	0
Fair value of derivative liabilities presented above		50.8	30.7
Netting of assets and liabilities with the same counterparty		(44)	(30.7)
Total		6.8	0
Derivative Liabilities		6.8	0
Fair value of cash margin (payable) receivable offset with derivatives		$ 37.6	$ (27.1)
[1]The fair values of Derivative Assets and Derivative Liabilities exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the balance sheets. As such, the gross balances presented in the table above are not indicative of the Company’s net economic exposure. Refer to Note 9, Fair Value Measurements, for information on the valuation of derivative instruments.

Note 11 - Concentrations of C_2

Note 11 - Concentrations of Credit Risk (Details Textual) Pure in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2023 USD ($)
Customer Concentration Risk [Member] | Utility Companies and Their Marketing Affiliates [Member]
Accounts Receivable, after Allowance for Credit Loss	$ 53.4
Customer Concentration Risk [Member] | Five Largest Counterparties [Member]
Accounts Receivable, after Allowance for Credit Loss	$ 26.7
Gas Utility [Member]
Number of Customer Serves	1.7

Note 12 - Income Taxes (Details

Note 12 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 5,900	$ 4,000
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	0	0
Spire Missouri [Member]
Regulatory Order, Excess Deferred Income Tax Returned to Customers	10,000	9,900	$ 8,400
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	5,100	3,700
Unrecognized Tax Benefits	22,900	19,300	16,100	$ 13,000
Spire Gulf [Member]
Regulatory Order, Excess Deferred Income Tax Returned to Customers	3,100
Spire Mississippi [Member]
Regulatory Order, Excess Deferred Income Tax Returned to Customers	100
Spire Alabama Inc [Member]
Regulatory Order, Excess Deferred Income Tax Returned to Customers	200
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	300	0
Unrecognized Tax Benefits	$ 300	$ 0	$ 0	$ 0

Note 12 - Income Taxes - Provis

Note 12 - Income Taxes - Provision (Benefit) for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Total income tax expense	$ 38.8	$ 58.9	$ 68.5
Spire Missouri [Member]
Current	0	0	0
Deferred	10.1	18.2	22
Investment tax credits	(0.2)	(0.2)	(0.2)
Current	0	0	0
Deferred	1.7	3.3	3.5
Total income tax expense	11.6	21.3	25.3
Spire Alabama Inc [Member]
Current	0	0	0
Deferred	15.8	18.1	19.8
Investment tax credits	0	0	0
Current	0	0	0
Deferred	4.5	5.1	5.2
Total income tax expense	20.3	23.2	25
Parent Company [Member]
Current	0.7	0.5	0.2
Deferred	30.4	47	49.5
Investment tax credits	(0.2)	(0.2)	(0.2)
Current	1.2	0.5	1.3
Deferred	6.7	11.1	17.7
Total income tax expense	$ 38.8	$ 58.9	$ 68.5

Note 12 - Income Taxes - Effect

Note 12 - Income Taxes - Effective Income Tax Rate (Details)		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Spire Missouri [Member]
Federal income tax statutory rate		21%	21%	21%
State and local income taxes, net of federal income tax benefits		2.60%	2.60%	2.60%
Certain expenses capitalized on books and deducted on tax return		(2.70%)	(3.20%)	(3.30%)
Taxes related to prior years			(0.60%)	(0.20%)
Tax credits *		(4.20%)	0%	0%
Amortization of excess deferred taxes		(7.70%)	(7.30%)	(5.00%)
Other items – net **	[1]	0%	3.10%	(0.20%)
Effective income tax rate		9%	15.60%	14.90%
Spire Alabama Inc [Member]
Federal income tax statutory rate		21%	21%	21%
State and local income taxes, net of federal income tax benefits		4.10%	4.10%	4.10%
Certain expenses capitalized on books and deducted on tax return		0%	0%	0%
Taxes related to prior years		0%	0%	0%
Tax credits *		(1.90%)	0%	0%
Amortization of excess deferred taxes		0.20%	0%	0%
Other items – net **	[1]	0.10%	0.20%	0.20%
Effective income tax rate		23.50%	25.30%	25.30%
Parent Company [Member]
Federal income tax statutory rate		21%	21%	21%
State and local income taxes, net of federal income tax benefits		3.70%	3.60%	3.60%
Certain expenses capitalized on books and deducted on tax return		(1.40%)	(1.60%)	(1.60%)
Taxes related to prior years		0%	(0.30%)	(0.50%)
Tax credits *		(3.30%)	0%	0%
Amortization of excess deferred taxes		(5.10%)	(3.50%)	(2.50%)
Other items – net **	[1]	0.20%	1.90%	0.10%
Effective income tax rate		15.10%	21.10%	20.10%
[1]Other consists primarily of property adjustments.

Note 12 - Income Taxes - Signif

Note 12 - Income Taxes - Significant Items Comprising the Net Deferred Tax Liability or Asset (Details) - USD ($) $ in Millions		Sep. 30, 2023	Sep. 30, 2022
Reserves not currently deductible		$ 27.7	$ 33.5
Pension and other postretirement benefits		64.4	72.6
Goodwill		0	0
Operating losses		239.2	255.1
Regulatory amount due to customers, net		30.4	34.5
Other		35.8	24.9
Total deferred tax assets		397.5	420.6
Relating to property		(788)	(740)
Regulatory pension and other postretirement benefits		(80.6)	(92.8)
Deferred gas costs		(67)	(75.8)
Other ***	[1]	(205.6)	(187.1)
Total deferred tax liabilities		(1,141.2)	(1,095.7)
Net deferred tax (liability) asset		(743.7)	(675.1)
Spire Missouri [Member]
Reserves not currently deductible		0	4
Pension and other postretirement benefits		44.7	52.6
Goodwill		0	0
Operating losses		89.2	116.9
Regulatory amount due to customers, net		27.6	30.7
Other		10.5	0
Total deferred tax assets		172	204.2
Relating to property		(507.7)	(489.3)
Regulatory pension and other postretirement benefits		(53)	(72.3)
Deferred gas costs		(64.1)	(74)
Other ***	[1]	(79)	(68.7)
Total deferred tax liabilities		(703.8)	(704.3)
Net deferred tax (liability) asset		(531.8)	(500.1)
Spire Alabama Inc [Member]
Reserves not currently deductible		3.9	7.4
Pension and other postretirement benefits		17	0
Goodwill		58.8	73
Operating losses		159.8	140.3
Regulatory amount due to customers, net		0	0
Other		3	0
Total deferred tax assets		242.5	220.7
Relating to property		(218.7)	(201.6)
Regulatory pension and other postretirement benefits		(25.9)	(1.6)
Deferred gas costs		0	0
Other ***	[1]	(7)	(6.5)
Total deferred tax liabilities		(251.6)	(209.7)
Net deferred tax (liability) asset		(9.1)
Net deferred tax (liability) asset		$ 0	$ 11
[1]For Spire, Other consists primarily of goodwill-related liabilities.

Note 12 - Income Taxes - Summar

Note 12 - Income Taxes - Summary of Federal and State Loss and Contribution and Tax Credit Carryforwards (Details) $ in Millions	Sep. 30, 2023 USD ($)
Federal and state loss carryforwards	$ 1,000.3
Contribution carryforwards	6.1
Tax credit carryforwards	13.1
Spire Missouri [Member]
Federal and state loss carryforwards	352.4
Contribution carryforwards	5.6
Tax credit carryforwards	8.5
Spire Alabama Inc [Member]
Federal and state loss carryforwards	624.1
Contribution carryforwards	0
Tax credit carryforwards	$ 1.6

Note 12 - Income Taxes - Reconc

Note 12 - Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Spire Missouri [Member]
Unrecognized tax benefits, beginning of year	$ 19,300	$ 16,100	$ 13,000
Increases related to tax positions taken in current year	3,600	3,200	3,100
Reductions due to lapse of applicable statute of limitations	0	0	0
Unrecognized tax benefits, end of year	22,900	19,300	16,100
Spire Alabama Inc [Member]
Unrecognized tax benefits, beginning of year	0	0	0
Increases related to tax positions taken in current year	300	0	0
Reductions due to lapse of applicable statute of limitations	0	0	0
Unrecognized tax benefits, end of year	300	0	0
Parent Company [Member]
Unrecognized tax benefits, beginning of year	19,600	16,400	13,200
Increases related to tax positions taken in current year	4,200	3,300	3,200
Reductions due to lapse of applicable statute of limitations	0	(100)	0
Unrecognized tax benefits, end of year	$ 23,800	$ 19,600	$ 16,400

Note 13 - Pension Plans and O_3

Note 13 - Pension Plans and Other Postretirement Benefits (Details Textual) - USD ($) $ in Thousands				12 Months Ended
	Dec. 26, 2022	Dec. 23, 2021	Dec. 22, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement				$ 0	$ 0
Regulatory Asset, Total				$ 1,597,500	1,467,800
Implementation Period Used To Calculate Return On Plan Assets (Year)				4 years
Gains Or Losses Includible In Cost Amortized To Extent Exceeds Projected Benefit Obligations or Market Related Value of Plan Assets Percentage				10%
Regulatory Liability				$ 479,700	421,900
Defined Contribution Plan, Cost				$ 15,500	15,500	$ 15,500
Minimum [Member]
Defined Benefit Plan, Benefit Obligation, Actuarial Gains From Prior Years, Percent				0.50%
Maximum [Member]
Defined Benefit Plan, Benefit Obligation, Actuarial Gains From Prior Years, Percent				0.55%
Pension Plan [Member]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement				$ 48,800	$ 109,300
Spire Missouri [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				6.30%	5.80%
Regulatory Asset, Total				$ 910,700	$ 835,700
Regulatory Liability				389,400	331,800
Defined Contribution Plan, Cost				9,100	$ 10,900	$ 10,900
Spire Missouri [Member] | Pension Costs [Member] | Missouri West [Member]
Regulatory Asset, Total		$ 4,400	$ 5,500
Spire Missouri [Member] | Pension Costs [Member] | Missouri East [Member]
Regulatory Asset, Total	$ 29,900	32,400	29,000
Spire Missouri [Member] | Pension and Other Postretirement Plans Costs [Member] | Missouri West [Member]
Regulatory Liabilities For Which No Return On Investment During Recovery Period Is Provided	800	$ 1,100	$ 3,300
Remaining Recovery Period of Regulatory Liabilities for which No Return on Investment During Recovery Period is Provided (Year)		8 years	8 years
Spire Missouri [Member] | Pension and Other Postretirement Plans Costs [Member] | Missouri East [Member]
Regulatory Assets for Which No Return on Investment During Recovery Period Is Provided	6,900	$ 11,000	$ 21,600
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided (Year)			8 years
Additional Remaining Recovery Period of Regulatory Assets for Which No Return on Investment During Recovery Period Is Provided (Year)		8 years
Spire Missouri [Member] | Pension Plan One [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate					5.70%
Spire Missouri [Member] | Pension Plan Two [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate					5.80%
Spire Missouri [Member] | Pension Plan [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate						3%
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement				9,900	$ 87,000
Anticipated Contributions to Pension Plans Qualified Trusts				21,600
Anticipated Contributions To Pension Plans Non Qualified Trusts				0
Spire Missouri [Member] | Other Postretirement Benefits Plan [Member]
Anticipated Contributions to Pension Plans Qualified Trusts				0
Postretirement Benefit Plans, Recovery in Rates Base Allowance		$ 8,600
Spire Missouri [Member] | Other Postretirement Benefits Plan [Member] | Missouri West [Member]
Regulatory Liability	100
Spire Missouri [Member] | Other Postretirement Benefits Plan [Member] | Missouri East [Member]
Regulatory Liability	$ 900
Spire Alabama Inc [Member]
Regulatory Asset, Total				648,500	595,100
Regulatory Liability				21,200	23,000
Defined Contribution Plan, Cost				$ 3,100	$ 3,600	$ 2,900
Spire Alabama Inc [Member] | Pension Plan One [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				6.20%	5.70%	3.10%
Spire Alabama Inc [Member] | Pension Plan Two [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				6.25%	5.65%	3%
Spire Alabama Inc [Member] | Pension Plan [Member]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement				$ 38,800	$ 22,300
Anticipated Contributions to Pension Plans Qualified Trusts				$ 16,400
Spire Alabama Inc [Member] | Pension Plan [Member] | Minimum [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				6.25%	5.65%
Defined Benefit Plan, Benefit Obligation, Settlement Losses Amortized Over Remaining Actuarial Life (Year)				11 years 9 months 18 days	11 years 4 months 24 days
Spire Alabama Inc [Member] | Pension Plan [Member] | Maximum [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				6.20%	5.70%
Defined Benefit Plan, Benefit Obligation, Settlement Losses Amortized Over Remaining Actuarial Life (Year)				13 years 4 months 24 days	12 years 3 months 18 days
Spire Alabama Inc [Member] | Other Postretirement Benefits Plan [Member]
Anticipated Contributions to Pension Plans Qualified Trusts				$ 0
Spire Alabama And Spire Missouri [Member] | Pension Plan [Member]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Remeasurement due to Settlement				$ 48,700	$ 109,300
Spire Alabama And Spire Missouri [Member] | Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				6.30%	5.80%

Note 13 - Pension Plans and O_4

Note 13 - Pension Plans and Other Postretirement Benefits - Net Pension Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Pension Plan [Member]
Service cost – benefits earned during the period	$ 16.3	$ 20	$ 21.7
Interest cost on projected benefit obligation	25.1	21.5	20.7
Expected return on plan assets	(24.5)	(31.3)	(31.6)
Amortization of prior service credit	(4.5)	(4.5)	(3.1)
Amortization of actuarial loss	6.6	11.9	14.9
Loss on lump-sum settlements and curtailments	9.7	33.6	18.2
Subtotal	28.7	51.2	40.8
Regulatory adjustment	26.3	12.5	20.6
Net pension cost	55	63.7	61.4
Pension Plan [Member] | Spire Missouri [Member]
Service cost – benefits earned during the period	11.4	14.4	15.4
Interest cost on projected benefit obligation	17.8	14.7	14.2
Expected return on plan assets	(18)	(22.7)	(22.5)
Amortization of prior service credit	(1.9)	(1.9)	(0.6)
Amortization of actuarial loss	6.1	9.6	11
Loss on lump-sum settlements and curtailments	0.6	27.3	11.6
Subtotal	16	41.4	29.1
Regulatory adjustment	27.1	9.9	19
Net pension cost	43.1	51.3	48.1
Pension Plan [Member] | Spire Alabama Inc [Member]
Service cost – benefits earned during the period	4.2	4.8	5.5
Interest cost on projected benefit obligation	4.8	4.7	4.6
Expected return on plan assets	(3.5)	(5.2)	(5.8)
Amortization of prior service credit	(2.4)	(2.4)	(2.3)
Amortization of actuarial loss	0.9	2.4	3.9
Loss on lump-sum settlements and curtailments	9.1	6.3	6.6
Subtotal	13.1	10.6	12.5
Regulatory adjustment	(1.7)	1.7	0.7
Net pension cost	11.4	12.3	13.2
Other Postretirement Benefits Plan [Member]
Service cost – benefits earned during the period	4.8	7.5	7.3
Interest cost on projected benefit obligation	8.5	6	6
Expected return on plan assets	(15.8)	(16.8)	(16.1)
Amortization of prior service credit	0.3	1	1
Amortization of actuarial loss	(4)	(2.2)	(1.6)
Subtotal	(6.2)	(4.5)	(3.4)
Regulatory adjustment	0.6	3.3	13.2
Net pension cost	(5.6)	(1.2)	9.8
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
Service cost – benefits earned during the period	4	6.3	6.2
Interest cost on projected benefit obligation	6.5	4.5	4.5
Expected return on plan assets	(10.5)	(11.3)	(10.9)
Amortization of prior service credit	0.6	0.7	0.7
Amortization of actuarial loss	(3.2)	(1.9)	(1.5)
Subtotal	(2.6)	(1.7)	(1)
Regulatory adjustment	1.8	5	15
Net pension cost	(0.8)	3.3	14
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
Service cost – benefits earned during the period	0.7	1.1	0.9
Interest cost on projected benefit obligation	1.8	1.4	1.3
Expected return on plan assets	(5)	(5.2)	(4.9)
Amortization of prior service credit	(0.3)	0.3	0.3
Amortization of actuarial loss	(0.5)	0	0
Subtotal	(3.3)	(2.4)	(2.4)
Regulatory adjustment	(1.3)	(1.8)	(1.8)
Net pension cost	$ (4.6)	$ (4.2)	$ (4.2)

Note 13 - Pension Plans and O_5

Note 13 - Pension Plans and Other Postretirement Benefits - Other Changes in Plan Assets and Pension Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Pension Plan [Member]
Current year actuarial loss (gain)	$ 14.5	$ (16.9)	$ (8.1)
Amortization of actuarial loss	(6.6)	(11.9)	(14.9)
Acceleration of loss recognized due to settlement	(9.7)	(33.6)	(18.2)
Current year service credit	0	0	(17.9)
Amortization of prior service credit	4.5	4.5	3.1
Subtotal	2.7	(57.9)	(56)
Regulatory adjustment	(2.8)	56.3	57.3
Total recognized in OCI	(0.1)	(1.6)	1.3
Pension Plan [Member] | Spire Missouri [Member]
Current year actuarial loss (gain)	5.7	0.9	(0.9)
Amortization of actuarial loss	(6.1)	(9.6)	(11)
Acceleration of loss recognized due to settlement	(0.6)	(27.3)	(11.6)
Current year service credit	0	0	(17.9)
Amortization of prior service credit	1.9	1.9	0.6
Subtotal	0.9	(34.1)	(40.8)
Regulatory adjustment	(1)	32.5	42.1
Total recognized in OCI	(0.1)	(1.6)	1.3
Pension Plan [Member] | Spire Alabama Inc [Member]
Current year actuarial loss (gain)	9	(16)	(1.5)
Amortization of actuarial loss	(0.9)	(2.4)	(3.9)
Acceleration of loss recognized due to settlement	(9.1)	(6.3)	(6.6)
Current year service credit	0	0	0
Amortization of prior service credit	2.4	2.4	2.3
Subtotal	1.4	(22.3)	(9.7)
Regulatory adjustment	(1.4)	22.3	9.7
Total recognized in OCI	0	0	0
Other Postretirement Benefits Plan [Member]
Current year actuarial loss (gain)	(24.4)	15.8	(41)
Amortization of actuarial loss	4	2.2	1.6
Amortization of prior service credit	(0.3)	(1)	(1)
Subtotal	(20.7)	10.7	(40.4)
Regulatory adjustment	20.7	(10.7)	40.4
Total recognized in OCI	0	0	0
Current year prior service cost	0	(6.3)	0
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
Current year actuarial loss (gain)	(21.5)	9.8	(29)
Amortization of actuarial loss	3.2	1.9	1.5
Amortization of prior service credit	(0.6)	(0.7)	(0.7)
Subtotal	(18.9)	9.9	(28.2)
Regulatory adjustment	18.9	(9.9)	28.2
Total recognized in OCI	0	0	0
Current year prior service cost		(1.1)	0
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
Current year actuarial loss (gain)	(1.1)	5.9	(9.9)
Amortization of actuarial loss	0.5	0	0
Amortization of prior service credit	0.3	(0.3)	(0.3)
Subtotal	(0.3)	0.4	(10.2)
Regulatory adjustment	0.3	(0.4)	10.2
Total recognized in OCI	0	0	0
Current year prior service cost	$ 0	$ (5.2)	$ 0

Note 13 - Pension Plans and O_6

Note 13 - Pension Plans and Other Postretirement Benefits - Reconciliation of Pension Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Settlement benefits paid	$ 0	$ 0
Pension Plan [Member]
Benefit obligation, beginning of year	464,400	689,600
Service cost – benefits earned during the period	16,300	20,000	$ 21,700
Interest cost on projected benefit obligation	25,100	21,500	20,700
Actuarial (gain) loss	(1,100)	(173,900)
Settlement loss	9,700	33,400
Settlement benefits paid	(48,800)	(109,300)
Regular benefits paid	(26,900)	(16,900)
Benefit obligation, end of year	438,700	464,400	689,600
Accumulated benefit obligation, end of year	433,100	457,100
Pension Plan [Member] | Spire Missouri [Member]
Benefit obligation, beginning of year	320,600	479,000
Service cost – benefits earned during the period	11,400	14,400	15,400
Interest cost on projected benefit obligation	17,800	14,700	14,200
Actuarial (gain) loss	(4,900)	(116,200)
Settlement loss	600	27,900
Settlement benefits paid	(9,900)	(87,000)
Regular benefits paid	(22,400)	(12,200)
Benefit obligation, end of year	313,200	320,600	479,000
Accumulated benefit obligation, end of year	309,500	315,000
Pension Plan [Member] | Spire Alabama Inc [Member]
Benefit obligation, beginning of year	97,800	149,400
Service cost – benefits earned during the period	4,200	4,800	5,500
Interest cost on projected benefit obligation	4,800	4,700	4,600
Actuarial (gain) loss	5,400	(42,400)
Settlement loss	9,100	5,600
Settlement benefits paid	(38,800)	(22,300)
Regular benefits paid	(1,900)	(2,000)
Benefit obligation, end of year	80,600	97,800	149,400
Accumulated benefit obligation, end of year	78,800	96,200
Other Postretirement Benefits Plan [Member]
Benefit obligation, beginning of year	148,100	204,200
Service cost – benefits earned during the period	4,800	7,500	7,300
Interest cost on projected benefit obligation	8,500	6,000	6,000
Actuarial (gain) loss	(10,600)	(52,600)
Regular benefits paid	(8,400)	(11,000)
Benefit obligation, end of year	142,600	148,100	204,200
Plan amendments	0	(6,200)
Retiree drug subsidy program	200	200
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
Benefit obligation, beginning of year	114,800	151,700
Service cost – benefits earned during the period	4,000	6,300	6,200
Interest cost on projected benefit obligation	6,500	4,500	4,500
Actuarial (gain) loss	(13,400)	(37,700)
Regular benefits paid	(6,800)	(9,200)
Benefit obligation, end of year	105,300	114,800	151,700
Plan amendments	0	(1,000)
Retiree drug subsidy program	200	200
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
Benefit obligation, beginning of year	29,900	48,000
Service cost – benefits earned during the period	700	1,100	900
Interest cost on projected benefit obligation	1,800	1,400	1,300
Actuarial (gain) loss	4,200	(13,600)
Regular benefits paid	(1,500)	(1,800)
Benefit obligation, end of year	35,100	29,900	$ 48,000
Plan amendments	0	(5,200)
Retiree drug subsidy program	$ 0	$ 0

Note 13 - Pension Plans and O_7

Note 13 - Pension Plans and Other Postretirement Benefits - Reconciliation of Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Spire Missouri [Member]
Fair value of plan assets, beginning of year	$ 235.9	$ 364
Actual return on plan assets		(66.7)
Employer contributions		37.8
Settlement benefits paid		(87)
Regular benefits paid		(12.2)
Fair value of plan assets, end of year		235.9
Funded status of plans, end of year		(84.7)
Spire Alabama Inc [Member]
Fair value of plan assets, beginning of year	57.3	82.8
Actual return on plan assets		(15.6)
Employer contributions		14.4
Settlement benefits paid		(22.3)
Regular benefits paid		(2)
Fair value of plan assets, end of year		57.3
Funded status of plans, end of year		(40.5)
Pension Plan [Member]
Fair value of plan assets, beginning of year	332.7	498.9
Actual return on plan assets	9.1	(92.5)
Employer contributions	58.9	52.4
Settlement benefits paid	(39.1)	(109.3)
Regular benefits paid	(26.9)	(16.8)
Fair value of plan assets, end of year	334.7	332.7
Funded status of plans, end of year	(104)	(131.7)
Pension Plan [Member] | Spire Missouri [Member]
Fair value of plan assets, beginning of year	235.9
Actual return on plan assets	7.5
Employer contributions	30.3
Settlement benefits paid	(9.3)
Regular benefits paid	(22.4)
Fair value of plan assets, end of year	242	235.9
Funded status of plans, end of year	(71.2)
Pension Plan [Member] | Spire Alabama Inc [Member]
Fair value of plan assets, beginning of year	57.3
Actual return on plan assets	0
Employer contributions	27.9
Settlement benefits paid	(29.7)
Regular benefits paid	(1.9)
Fair value of plan assets, end of year	53.6	57.3
Funded status of plans, end of year	(27)
Other Postretirement Benefits Plan [Member]
Fair value of plan assets, beginning of year	264.7	326.9
Actual return on plan assets	29.9	(51.6)
Employer contributions	0.1	0.4
Regular benefits paid	(8.4)	(11)
Fair value of plan assets, end of year	286.3	264.7
Funded status of plans, end of year	143.7	116.6
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
Fair value of plan assets, beginning of year	176.7	221.7
Actual return on plan assets	18.8	(36.2)
Employer contributions	0.1	0.4
Regular benefits paid	(6.8)	(9.2)
Fair value of plan assets, end of year	188.8	176.7
Funded status of plans, end of year	83.5	61.9
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
Fair value of plan assets, beginning of year	83.3	99.4
Actual return on plan assets	10.2	(14.3)
Employer contributions	0	0
Regular benefits paid	(1.5)	(1.8)
Fair value of plan assets, end of year	92	83.3
Funded status of plans, end of year	$ 56.9	$ 53.4

Note 13 - Pension Plans and O_8

Note 13 - Pension Plans and Other Postretirement Benefits - Amounts Recognized in the Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Noncurrent liabilities	$ (137.3)	$ (163)
Spire Missouri [Member]
Noncurrent liabilities	(103.3)	(115.5)
Spire Alabama Inc [Member]
Noncurrent liabilities	(27.2)	(40.5)
Pension Plan [Member]
Current liabilities	(1.6)	(1.1)
Noncurrent liabilities	(102.4)	(130.6)
Total	(104)	(131.7)
Pension Plan [Member] | Spire Missouri [Member]
Current liabilities	(1.6)	(1.1)
Noncurrent liabilities	(69.6)	(83.6)
Total	(71.2)	(84.7)
Pension Plan [Member] | Spire Alabama Inc [Member]
Current liabilities	0	0
Noncurrent liabilities	(27)	(40.5)
Total	(27)	(40.5)
Other Postretirement Benefits Plan [Member]
Current liabilities	(0.4)	(0.3)
Noncurrent liabilities	(36.6)	(34.7)
Noncurrent assets	180.7	151.6
Total	143.7	116.6
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
Current liabilities	(0.4)	(0.3)
Noncurrent liabilities	(36.6)	(34.7)
Noncurrent assets	120.5	96.9
Total	83.5	61.9
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
Current liabilities	0	0
Noncurrent liabilities	0	0
Noncurrent assets	56.9	53.4
Total	$ 56.9	$ 53.4

Note 13 - Pension Plans and O_9

Note 13 - Pension Plans and Other Postretirement Benefits - Amounts Recognized in AOCI Not Yet Recognized As Components of Net Periodic Pension Costs (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Spire Missouri [Member]
Net actuarial loss		$ 93.6
Prior service credit		(18.1)
Subtotal		75.5
Adjustments for amounts included in regulatory assets		(72.3)
Total		3.2
Spire Alabama Inc [Member]
Net actuarial loss		41.2
Prior service credit		(16.3)
Subtotal		24.9
Adjustments for amounts included in regulatory assets		(24.9)
Total		0
Pension Plan [Member]
Net actuarial loss	$ 130.1	132
Prior service credit	(31.2)	(35.7)
Subtotal	98.9	96.3
Adjustments for amounts included in regulatory assets	(95.9)	(93.1)
Total	3	3.2
Pension Plan [Member] | Spire Missouri [Member]
Net actuarial loss	92.5
Prior service credit	(16.2)
Subtotal	76.3
Adjustments for amounts included in regulatory assets	(73.3)
Total	3
Pension Plan [Member] | Spire Alabama Inc [Member]
Net actuarial loss	40.2
Prior service credit	(13.9)
Subtotal	26.3
Adjustments for amounts included in regulatory assets	(26.3)
Total	0
Other Postretirement Benefits Plan [Member]
Net actuarial loss	(103.3)	(83.3)
Prior service credit	7	7.1
Subtotal	(96.3)	(76.2)
Adjustments for amounts included in regulatory assets	96.3	76.2
Total	0	0
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
Net actuarial loss	(92.3)	(74.2)
Prior service credit	7.4	7.9
Subtotal	(84.9)	(66.3)
Adjustments for amounts included in regulatory assets	84.9	66.3
Total	0	0
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
Net actuarial loss	(6.1)	(5.6)
Prior service credit	(0.4)	(0.8)
Subtotal	(6.5)	(6.4)
Adjustments for amounts included in regulatory assets	6.5	6.4
Total	$ 0	$ 0

Note 13 - Pension Plans and _10

Note 13 - Pension Plans and Other Postretirement Benefits - Assumption Used (Details)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Pension Plan [Member]
Weighted average rate of future compensation increase	3%	3%
Spire Missouri East [Member] | Pension Plan [Member]
Weighted average discount rate	5.70%	3%	2.85%
Weighted average discount rate	6.25%	5.70%
Spire Missouri East [Member] | Other Postretirement Benefits Plan [Member]
Weighted average rate of future compensation increase	3%	3%
Spire Alabama Inc [Member] | Pension Plan [Member]
Weighted average rate of future compensation increase	3%	3%	3%
Expected long-term rate of return on plan assets	6.50%	6.75%	6.75%
Spire Alabama Inc [Member] | Pension Plan [Member] | Maximum [Member]
Weighted average discount rate	5.65%	3.10%	2.80%
Weighted average discount rate	6.20%	5.70%
Spire Alabama Inc [Member] | Pension Plan [Member] | Minimum [Member]
Weighted average discount rate	5.65%	3.10%	2.95%
Weighted average discount rate	6.25%	5.65%
Spire Alabama Inc [Member] | Other Postretirement Benefits Plan [Member]
Weighted average discount rate	5.80%	2.95%	2.75%
Spire Alabama Inc [Member] | Other Postretirement Benefits Plan [Member] | Maximum [Member]
Expected long-term rate of return on plan assets	6%	6.25%	6.25%
Spire Alabama Inc [Member] | Other Postretirement Benefits Plan [Member] | Minimum [Member]
Expected long-term rate of return on plan assets	4.75%	5%	5%
Spire Missouri [Member]
Weighted average discount rate	6.30%	5.80%
Spire Missouri [Member] | Pension Plan [Member]
Weighted average rate of future compensation increase	3%	3%	3%
Expected long-term rate of return on plan assets	6.50%	6.75%	6.75%
Weighted average discount rate			3%
Spire Missouri [Member] | Other Postretirement Benefits Plan [Member]
Weighted average discount rate	5.80%	2.95%	2.75%
Weighted average rate of future compensation increase	3%	3%	3%
Expected long-term rate of return on plan assets	5.50%	5.75%	5.75%
Spire Alabama And Spire Missouri [Member] | Other Postretirement Benefits Plan [Member]
Weighted average discount rate	6.30%	5.80%
Spire Missouri West [Member] | Pension Plan [Member]
Weighted average discount rate	5.80%	3%	2.75%
Weighted average discount rate	6.30%	5.80%
Spire Alabama or Spire Missouri [Member] | Pension Plan [Member]
Cash balance interest crediting rate - Spire Alabama / Spire Missouri	4.25%	4.25%

Note 13 - Pension Plans and _11

Note 13 - Pension Plans and Other Postretirement Benefits - PBO, ABO, and Fair Value of Plan Assets for Plans in Excess of Plan Assets (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Projected benefit obligation	$ 438.7	$ 464.4
Accumulated benefit obligation	433.1	457.1
Fair value of plan assets	334.7	332.7
Spire Missouri [Member]
Projected benefit obligation	313.2	320.6
Accumulated benefit obligation	309.5	315
Fair value of plan assets	242	235.9
Spire Alabama Inc [Member]
Projected benefit obligation	80.6	97.8
Accumulated benefit obligation	78.8	96.2
Fair value of plan assets	$ 53.6	$ 57.3

Note 13 - Pension Plans and _12

Note 13 - Pension Plans and Other Postretirement Benefits - Targeted and Actual Plan Assets by Category (Details)	Sep. 30, 2023	Sep. 30, 2022
Pension Plan [Member] | Spire Missouri [Member]
Return seeking assets, target	100%	100%
Return seeking assets, actual	100%	100%
Pension Plan [Member] | Spire Missouri [Member] | Return Seeking Assets [Member]
Return seeking assets, target	70%	70%
Return seeking assets, actual	77%	74.30%
Pension Plan [Member] | Spire Missouri [Member] | Liability Hedging Assets [Member]
Return seeking assets, target	30%	30%
Return seeking assets, actual	20%	22.80%
Pension Plan [Member] | Spire Missouri [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member]
Return seeking assets, target	0%	0%
Return seeking assets, actual	3%	2.90%
Pension Plan [Member] | Spire Alabama Inc [Member]
Return seeking assets, target	100%	100%
Return seeking assets, actual	100%	100%
Pension Plan [Member] | Spire Alabama Inc [Member] | Return Seeking Assets [Member]
Return seeking assets, target	75%	70%
Return seeking assets, actual	76%	68.70%
Pension Plan [Member] | Spire Alabama Inc [Member] | Liability Hedging Assets [Member]
Return seeking assets, target	25%	30%
Return seeking assets, actual	15%	25.30%
Pension Plan [Member] | Spire Alabama Inc [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member]
Return seeking assets, target	0%	0%
Return seeking assets, actual	9%	6%
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
Return seeking assets, target	100%
Return seeking assets, actual	100%	100%
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member] | Defined Benefit Plan, Equity Securities [Member]
Return seeking assets, target	60%
Return seeking assets, actual	58.90%	58.70%
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member] | Debt Securities [Member]
Return seeking assets, target	40%
Return seeking assets, actual	38.10%	40.50%
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member]
Return seeking assets, target	0%
Return seeking assets, actual	3%	0.80%
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
Return seeking assets, target	100%
Return seeking assets, actual	100%	100%
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member] | Defined Benefit Plan, Equity Securities [Member]
Return seeking assets, target	60.50%
Return seeking assets, actual	59.90%	57.70%
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member] | Debt Securities [Member]
Return seeking assets, target	39.50%
Return seeking assets, actual	40.10%	42.30%

Note 13 - Pension Plans and _13

Note 13 - Pension Plans and Other Postretirement Benefits - Expected Pension Benefit Payments for Succeeding Fiscal Years (Details) $ in Millions	Sep. 30, 2023 USD ($)
Pension Plan [Member]
2024	$ 52.4
2025	45.3
2026	41.8
2027	41.8
2028	43.3
2029-2032	202.8
Pension Plan [Member] | Spire Missouri [Member]
2024	41
2025	34.1
2026	30.4
2027	29.4
2028	30.5
2029-2032	139.1
Pension Plan [Member] | Spire Alabama Inc [Member]
2024	8
2025	7.7
2026	7.8
2027	8.7
2028	8.9
2029-2032	44.1
Other Postretirement Benefits Plan [Member]
2024	14.6
2025	14.8
2026	14.9
2027	14.8
2028	14.5
2029-2032	68.6
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
2024	11.6
2025	11.8
2026	11.8
2027	11.7
2028	11.4
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
2024	2.9
2025	2.9
2026	2.9
2027	2.9
2028	$ 2.9

Note 13 - Pension Plans and _14

Note 13 - Pension Plans and Other Postretirement Benefits - Assumed Medical Cost Trend Rates (Details) - Other Postretirement Benefits Plan [Member]	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Rate to which the medical cost trend rate is assumed to decline (the ultimate medical cost trend rate)	5%	5%
Year the rate reaches the ultimate trend	2030	2028
Spire Alabama And Spire Missouri [Member]
Medical cost trend assumed for next year - Spire Alabama and Spire Missouri	6.50%	6.75%

Note 13 - Pension Plans and _15

Note 13 - Pension Plans and Other Postretirement Benefits - Fair Value Measurements of Pension Plan Assets (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Spire Missouri [Member]
Defined Benefit Plan Assets		$ 235.9	$ 364
Spire Alabama Inc [Member]
Defined Benefit Plan Assets		57.3	82.8
Pension Plan [Member]
Defined Benefit Plan Assets	$ 334.7	332.7	498.9
Pension Plan [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	242	235.9
Pension Plan [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	53.6	57.3
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	78.8	89.9
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	56.4	59.7
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	12.9	18
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	255.9	242.8
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	185.6	176.2
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	40.7	39.3
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	334.7	332.7
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	242	235.9
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	53.6	57.3
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	14.8	11.5
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	6.8	5.7
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	4.6	3.5
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	14.8	11.5
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	6.8	5.7
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	4.6	3.5
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	139	122.2
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	99.4	85.7
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	22.9	21.6
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	139	122.2
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	99.4	85.7
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	22.9	21.6
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	55.2	61
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	40.2	47.2
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	8.7	8.1
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	55.2	61
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	40.2	47.2
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	8.7	8.1
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	27.8	42.3
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	20.9	29.4
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	4	7.7
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	27.8	42.3
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	20.9	29.4
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	4	7.7
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	36.2	36.1
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	28.7	24.6
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	4.3	6.8
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	36.2	36.1
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	28.7	24.6
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	4.3	6.8
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	61.7	59.6
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	46	43.3
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	9.1	9.6
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	61.7	59.6
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	46	43.3
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	9.1	9.6
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Assets	286.3	264.7	326.9
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	188.8	176.7	221.7
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	92	83.3	$ 99.4
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	193.3	181.4
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	188.8	176.7
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	93	83.3
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	92	83.3
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	286.3	264.7
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	188.8	176.7
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	92	83.3
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	5.1	3.5
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	4.3	2.7
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	5.1	3.5
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	4.3	2.7
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	188.2	177.1
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	184.5	174
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	76.5	69.4
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	76.5	69.4
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	264.7	246.5
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member]
Defined Benefit Plan Assets	184.5	174
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	76.5	69.4
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Assets	0	0.8
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	0	0
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Assets	16.5	13.9
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	15.5	13.9
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Assets	16.5	14.7
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member]
Defined Benefit Plan Assets	$ 15.5	$ 13.9

Note 14 - Information by Oper_3

Note 14 - Information by Operating Segment (Details Textual)	12 Months Ended
	Sep. 30, 2023
Number of Reportable Segments	3

Note 14 - Information by Oper_4

Note 14 - Information by Operating Segment - Segment Information by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Revenues from external customers	$ 2,666.3	$ 2,198.5	$ 2,235.5
Intersegment revenues	0	0	0
Operating Revenues	2,666.3	2,198.5	2,235.5
Depreciation and amortization	254.8	237.3	213.1
Interest Expense	185.7	119.8	106.6
Income Tax Expense	38.8	58.9	68.5
Net economic earnings (loss)	228.1	216.3	266.3
Capital expenditures	662.5	552.2	624.8
Consolidation, Eliminations [Member]
Revenues from external customers	0	0	0
Intersegment revenues	(52.5)	(51.7)	(48)
Operating Revenues	(52.5)	(51.7)	(48)
Depreciation and amortization	0	0	0
Interest Expense	(34.9)	(8.8)	(1.4)
Income Tax Expense	0	0	0
Net economic earnings (loss)	0	0	0
Capital expenditures	0	0	0
Gas Utility [Member] | Operating Segments [Member]
Revenues from external customers	2,456.6	1,945.6	2,118.2
Intersegment revenues	0.3	0.5	1.1
Operating Revenues	2,456.9	1,946.1	2,119.3
Depreciation and amortization	244.4	227.9	204.4
Interest Expense	139.9	86.4	74.7
Income Tax Expense	32.7	49.6	56.9
Net economic earnings (loss)	200.5	202.7	230.6
Capital expenditures	588.6	528.6	590.4
Gas Marketing [Member] | Operating Segments [Member]
Revenues from external customers	179.1	234.9	96.5
Intersegment revenues	0	0	0
Operating Revenues	179.1	234.9	96.5
Depreciation and amortization	1.5	1.4	1.2
Interest Expense	0	0	0
Income Tax Expense	12.8	11.9	13.4
Net economic earnings (loss)	47.6	27	47
Capital expenditures	0.4	0.9	0.7
Midstream [Member] | Operating Segments [Member]
Revenues from external customers	29.9	17.4	19.9
Intersegment revenues	36.2	35.7	32.7
Operating Revenues	66.1	53.1	52.6
Depreciation and amortization	8.4	7.5	6.9
Interest Expense	8.6	4.9	4
Income Tax Expense	3.8	4.5	4.4
Net economic earnings (loss)	14.1	11.1	11.1
Capital expenditures	73.6	22.6	33
Other Segments [Member]
Depreciation and amortization	0.5	0.5	0.6
Interest Expense	72.1	37.3	29.3
Income Tax Expense	(10.5)	(7.1)	(6.2)
Other Segments [Member] | Consolidation, Eliminations [Member]
Revenues from external customers	0.7	0.6	0.9
Intersegment revenues	16	15.5	14.2
Operating Revenues	16.7	16.1	15.1
Net economic earnings (loss)	(34.1)	(24.5)	(22.4)
Capital expenditures	$ (0.1)	$ 0.1	$ 0.7

Note 14 - Information by Oper_5

Note 14 - Information by Operating Segment - Total Assets by Segment (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Total Assets	$ 10,313.6	$ 10,083.7	$ 9,356.4
Operating Segments [Member] | Gas Utility [Member]
Total Assets	8,486.7	8,042.8	7,615.4
Operating Segments [Member] | Gas Marketing [Member]
Total Assets	332	638.7	466.1
Operating Segments [Member] | Midstream [Member]
Total Assets	574.3	446	413.8
Operating Segments [Member] | Other Segments [Member]
Total Assets	2,533.3	2,705.5	2,193.3
Consolidation, Eliminations [Member]
Total Assets	$ (1,612.7)	$ (1,749.3)	$ (1,332.2)

Note 14 - Information by Oper_6

Note 14 - Information by Operating Segment - Net Economic Earnings to Net Income (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Net Income	$ 217.5	$ 220.8	$ 271.7
Missouri regulatory adjustments	0	0	(9)
Fair value and timing adjustments	11.4	(11.4)	3.3
Acquisition and divestiture activities	2.5	0	(1.3)
Income tax adjustments	(3.3)	6.9	1.6
Net Economic Earnings	$ 228.1	$ 216.3	$ 266.3

Note 15 - Regulatory Matters (D

Note 15 - Regulatory Matters (Details Textual) - USD ($) $ in Thousands															1 Months Ended			3 Months Ended	12 Months Ended
	Dec. 01, 2023	Oct. 04, 2023	Sep. 01, 2023	Apr. 30, 2023	Apr. 20, 2023	Jan. 01, 2023	Nov. 18, 2022	Apr. 22, 2022	Feb. 01, 2022	Jan. 01, 2022	Dec. 29, 2021	Dec. 23, 2021	Oct. 26, 2021	Oct. 01, 2018	Sep. 30, 2022	Feb. 28, 2021	Nov. 30, 2019	Mar. 31, 2022	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021	Jan. 25, 2023
Customer Share																				75%
Utilities Operating Expense, Gas and Petroleum Purchased																				$ 1,260,800	$ 923,900	$ 946,300
Missouri Public Service Commission [Member] | Infrastructure System Replacement Surcharge [Member]
Public Utilities, Requested Rate Increase (Decrease), Amount												$ 47,300
Alabama Public Service Commission [Member] | Enhanced Stability Reserve [Member]
Utilities Operating Expense Maintenance and Operations Self Insurance Cost Deferred Amount																					1,000
Utilities Operating Expense Maintenance and Operations Self Insurance Cost Single Force Majeure Event Deferred Amount																				300
Utilities Operating Expense Maintenance and Operations Self Insurance Cost Multiple Force Majeure Events Deferred Amount																				400
Regulated Operating Revenue Variances Amount																				$ 400
Regulated Operations Enhanced Stability Reserve Underfunded Balances Amortization Term (Year)																				5 years
Regulated Operations, Enhanced Stability Reserve, Unfunded Balances, Amortization, Annual Limitation																				$ 700
Spire Missouri [Member]
Customer Share																				25%
Utilities Operating Expense, Gas and Petroleum Purchased																$ 195,800				$ 943,400	587,000	786,800
Public Utilities, Reduced Revenue Accounts Receivable Cost Of Gas and Regulatory Liabilities																		$ 150,000
Utilities Operating, Due From Other Parties																		$ 42,000
Spire Missouri [Member] | Missouri Public Service Commission [Member]
Public Utilities, Approved Rate Increase (Decrease), Amount							$ 78,000					72,200
Public Utilities, Requested Rate Increase (Decrease), Amount												$ 24,900
Public Utilities, Deferred Amount Under Order Authorizing Accounting Treatment															$ 42,800						42,800
Public Utilities, Approved Rate, Increase Decrease Annualized Revenue					$ 7,700
Public Utilities, Disallowance From ACA Balance																							$ 600
Spire Missouri [Member] | Missouri Public Service Commission [Member] | Subsequent Event [Member]
Public Utilities, Approved Rate, Increase Decrease Annualized Revenue		$ 12,400
Spire Missouri [Member] | Missouri Public Service Commission [Member] | Infrastructure System Replacement Surcharge [Member]
Public Utilities, Approved Rate Increase (Decrease), Amount							$ 19,000
Spire Alabama Inc [Member]
Utilities Operating Expense, Gas and Petroleum Purchased																				202,700	$ 161,500	145,300
Public Utilities, Rate Increase Decrease Index Range Margin															1.50%						1.50%
Public Utilities, Approved Point of Test Giveback Under Rate Stabilization and Equalization															$ 2,200						$ 2,200	2,200
Financing Receivable, after Allowance for Credit Loss															$ 7,100					6,700	7,100
Spire Alabama Inc [Member] | Maximum [Member] | Spire [Member] | Related Party [Member]
Financing Receivable, after Allowance for Credit Loss																				25,000
Spire Alabama Inc [Member] | Alabama Public Service Commission [Member]
Public Utilities, Approved Rate Increase (Decrease), Amount										$ 5,300										4,400		8,800
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 5,300										$ 17,200
Public Utilities Maximum Return on Equity Percentage of Prior Year Revenues															4%						4%
Public Utilities, Approved Return on Equity, Percentage														10.40%	9.70%
Public Utilities, Rate Increase Decrease Index Range Margin															0.10%						0.10%
Public Utilities, Equity Limitation as Percent of Total Capitalization															55.50%						55.50%
Public Utilities, Equity Limitation as Percent of Average Common Equity Growth															6%						6%
Annual Revenue Increase From Rates, Amount						$ 15,000
Public Utilities Approved Percentage of Excess Natural Gas Supply and Capacity to Customers																	75%
Public Utilities Approved Percentage of Excess Natural Gas Supply and Capacity To Retain								25%									25%
Public Utilities, Value From Capacity Release, Threshold								$ 1,600
Spire Alabama Inc [Member] | Alabama Public Service Commission [Member] | Forecast [Member]
Annual Revenue Increase From Rates, Amount	$ 15,800
Spire Alabama Inc [Member] | Alabama Public Service Commission [Member] | Minimum [Member]
Public Utilities, Approved Return on Equity, Percentage														10.15%	9.50%
Spire Alabama Inc [Member] | Alabama Public Service Commission [Member] | Maximum [Member]
Public Utilities, Approved Return on Equity, Percentage														10.65%	9.90%
Spire Gulf [Member]
Public Utilities, Approved Rate Increase (Decrease), Amount																					$ 1,700	2,300
Public Utilities, Approved Rate, Increase Decrease Annualized Revenue				$ 1,800		2,500				$ 1,000
Public Utilities, Approved Return on Equity, Percentage													9.95%								10.70%
Public Utilities, Rate Increase Decrease Index Range Margin															1.50%						1.50%
Utilities Operating Expense Maintenance and Operations Self Insurance Cost Single Force Majeure Event Deferred Amount																				100
Utilities Operating Expense Maintenance and Operations Self Insurance Cost Multiple Force Majeure Events Deferred Amount																				150
Regulated Operating Revenue Variances Amount																				$ 100
Public Utilities, Approved Rate, Net Income Benefit																						$ 1,600
Public Utilities, Approved Return on Equity, Pro-Rata, Percentage																				75%
Regulated Operations, Recovery of Incurred Costs, Percentage																				90%
Spire Gulf [Member] | Forecast [Member]
Public Utilities, Approved Rate, Increase Decrease Annualized Revenue	$ 2,000
Public Utilities, Approved Return on Equity, Percentage																			9.95%
Spire Gulf [Member] | Minimum [Member]
Public Utilities, Approved Return on Equity, Percentage																					10.45%
Spire Gulf [Member] | Minimum [Member] | Forecast [Member]
Public Utilities, Approved Return on Equity, Percentage																			9.70%
Spire Gulf [Member] | Maximum [Member]
Public Utilities, Approved Return on Equity, Percentage																					10.95%
Spire Gulf [Member] | Maximum [Member] | Forecast [Member]
Public Utilities, Approved Return on Equity, Percentage																			10.30%
Spire [Member] | Alabama Public Service Commission [Member]
Line of Credit Facility, Maximum Borrowing Capacity																				$ 75,000
Spire Mississippi [Member]
Public Utilities, Approved Rate Increase (Decrease), Amount			$ 1,300
Public Utilities, Approved Rate, Increase Decrease Annualized Revenue						$ 800			$ 800
Public Utilities, Approved Return on Equity, Percentage																				10.04%
Public Utilities, Approved Return on Equity, Excess of Allowed Return, Percentage																				1%
Public Utilities, Approved Return on Equity Shortfall Percentage																				75%
Public Utilities, Approved Return On Equity, Excess, Percentage																				50%
Future Income Taxes Due From Customers and Pension and Other Postretirement Benefit Costs [Member]
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided (Year)																				20 years
PGA Assets [Member]
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided (Year)																				2 years
PGA Assets Not Earning A Return [Member]
Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided (Year)																				15 years

Note 15 - Regulatory Matters -

Note 15 - Regulatory Matters - Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Regulatory assets	$ 348.3	$ 355.4
Regulatory Assets Noncurrent	1,249.2	1,112.4
Total Regulatory Assets	1,597.5	1,467.8
Regulatory Liability Current	7.3	3.7
Regulatory Liability Noncurrent	472.4	418.2
Total Regulatory Liabilities	479.7	421.9
Spire Missouri [Member]
Regulatory assets	293.1	288.1
Regulatory Assets Noncurrent	617.6	547.6
Total Regulatory Assets	910.7	835.7
Regulatory Liability Current	0	0
Regulatory Liability Noncurrent	389.4	331.8
Total Regulatory Liabilities	389.4	331.8
Spire Alabama Inc [Member]
Regulatory assets	41.6	56.9
Regulatory Assets Noncurrent	606.9	538.2
Total Regulatory Assets	648.5	595.1
Regulatory Liability Current	0	0
Regulatory Liability Noncurrent	21.2	23
Total Regulatory Liabilities	21.2	23
Unamortized Purchased Gas Adjustments Asset [Member]
Regulatory assets	293.2	322.2
Regulatory Assets Noncurrent	23	0
Regulatory Liability Current	11.2	53
Unamortized Purchased Gas Adjustments Asset [Member] | Spire Missouri [Member]
Regulatory assets	269.4	275.1
Regulatory Assets Noncurrent	23	0
Regulatory Liability Current	11.2	53
Unamortized Purchased Gas Adjustments Asset [Member] | Spire Alabama Inc [Member]
Regulatory assets	21.7	43.8
Regulatory Assets Noncurrent	0	0
Regulatory Liability Current	0	0
Other Regulatory Assets (Liabilities) [Member]
Regulatory assets	55.1	33.2
Regulatory Assets Noncurrent	131.2	129.2
Regulatory Liability Current	7.3	3.7
Regulatory Liability Noncurrent	21.4	14.4
Other Regulatory Assets (Liabilities) [Member] | Spire Missouri [Member]
Regulatory assets	23.7	13
Regulatory Assets Noncurrent	116	113.1
Regulatory Liability Current	0	0
Regulatory Liability Noncurrent	16.5	7.3
Other Regulatory Assets (Liabilities) [Member] | Spire Alabama Inc [Member]
Regulatory assets	19.9	13.1
Regulatory Assets Noncurrent	0.9	1
Regulatory Liability Current	0	0
Regulatory Liability Noncurrent	3.3	3.6
Deferred Income Tax Charge [Member]
Regulatory Assets Noncurrent	144.5	137.8
Deferred Income Tax Charge [Member] | Spire Missouri [Member]
Regulatory Assets Noncurrent	136.2	129.2
Deferred Income Tax Charge [Member] | Spire Alabama Inc [Member]
Regulatory Assets Noncurrent	2	2.2
Pension and Other Postretirement Plans Costs [Member]
Regulatory assets	261	294.5
Regulatory Assets Noncurrent	185.2	172.6
Pension and Other Postretirement Plans Costs [Member] | Spire Missouri [Member]
Regulatory assets	189.1	222.9
Regulatory Assets Noncurrent	156.5	143.6
Pension and Other Postretirement Plans Costs [Member] | Spire Alabama Inc [Member]
Regulatory assets	67.8	66.5
Regulatory Assets Noncurrent	17.9	19.4
Removal Costs [Member]
Regulatory Assets Noncurrent	633.2	493.7
Regulatory Liability Noncurrent	126.6	32.9
Removal Costs [Member] | Spire Missouri [Member]
Regulatory Assets Noncurrent	97	25.2
Regulatory Liability Noncurrent	90.4	0
Removal Costs [Member] | Spire Alabama Inc [Member]
Regulatory Assets Noncurrent	536.2	468.5
Regulatory Liability Noncurrent	0	0
Renewable Energy Program [Member]
Regulatory Assets Noncurrent	56.3	57.2
Renewable Energy Program [Member] | Spire Missouri [Member]
Regulatory Assets Noncurrent	56.3	57.2
Renewable Energy Program [Member] | Spire Alabama Inc [Member]
Regulatory Assets Noncurrent	0	0
Estimated Deferred Taxes Due to Customers [Member]
Regulatory Liability Noncurrent	128	145.3
Estimated Deferred Taxes Due to Customers [Member] | Spire Missouri [Member]
Regulatory Liability Noncurrent	114.8	127.9
Estimated Deferred Taxes Due to Customers [Member] | Spire Alabama Inc [Member]
Regulatory Liability Noncurrent	$ 0	$ 0

Note 15 - Regulatory Matters _2

Note 15 - Regulatory Matters - Regulatory Assets Not Earning a Return (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Regulatory assets not earning a return	$ 672.5	$ 686.3
Spire Missouri [Member]
Regulatory assets not earning a return	666.2	679.9
Pension and Other Postretirement Plans Costs [Member]
Regulatory assets not earning a return	133.4	152.9
Pension and Other Postretirement Plans Costs [Member] | Spire Missouri [Member]
Regulatory assets not earning a return	133.4	152.9
Deferred Income Tax Charge [Member]
Regulatory assets not earning a return	142.5	135.6
Deferred Income Tax Charge [Member] | Spire Missouri [Member]
Regulatory assets not earning a return	136.2	129.2
Unamortized Purchased Gas Adjustments Asset [Member]
Regulatory assets not earning a return	292.4	275.1
Unamortized Purchased Gas Adjustments Asset [Member] | Spire Missouri [Member]
Regulatory assets not earning a return	292.4	275.1
Other Regulatory Assets (Liabilities) [Member]
Regulatory assets not earning a return	104.2	122.7
Other Regulatory Assets (Liabilities) [Member] | Spire Missouri [Member]
Regulatory assets not earning a return	$ 104.2	$ 122.7

Note 16 - Commitments and Con_2

Note 16 - Commitments and Contingencies (Details Textual) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2023	Sep. 30, 2023
Long-Term Purchase Commitment, Amount		$ 1,613.2
Capital Committed to Contribute to Partnership		10
Remaining Unfunded Capital Commitment		4.9
MoGas Pipeline and Omega Pipeline [Member]
Business Combination, Price of Acquisition, Expected	$ 175
Spire Missouri [Member]
Long-Term Purchase Commitment, Amount		1,182
Spire Alabama Inc [Member]
Long-Term Purchase Commitment, Amount		$ 251.6

Note 17 - Leases - Operating Le

Note 17 - Leases - Operating Lease Cost, Cash Flow and Noncash Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Operating lease cost, including amounts capitalized	$ 7.3	$ 7.4	$ 7.2
Operating cash flows representing cash paid for amounts included in the measurement of lease liabilities	7.3	7.3	7.2
Right-of-use assets obtained in exchange for lease liabilities	0.8	24.6	0
Spire Missouri [Member]
Operating lease cost, including amounts capitalized	0.5	0.5	0.4
Operating cash flows representing cash paid for amounts included in the measurement of lease liabilities	0.5	0.5	0.4
Right-of-use assets obtained in exchange for lease liabilities	0.8	1.1	0
Spire Alabama Inc [Member]
Operating lease cost, including amounts capitalized	2	2.1	2.1
Operating cash flows representing cash paid for amounts included in the measurement of lease liabilities	2.1	2.1	2.1
Right-of-use assets obtained in exchange for lease liabilities	$ 0	$ 23.5	$ 0

Note 17 - Leases - Year-end Bal

Note 17 - Leases - Year-end Balance Sheet and Weighted-average Information About Operating Lease (Details) - USD ($) $ in Millions	Sep. 30, 2023	Sep. 30, 2022
Weighted-average remaining lease term (in years) (Year)	14 years 1 month 6 days	15 years
Weighted-average discount rate	4.20%	4.10%
Spire Missouri [Member]
Weighted-average remaining lease term (in years) (Year)	5 years 7 months 6 days	5 years 1 month 6 days
Weighted-average discount rate	3.30%	2.20%
Spire Alabama Inc [Member]
Weighted-average remaining lease term (in years) (Year)	13 years 3 months 18 days	14 years 3 months 18 days
Weighted-average discount rate	3.70%	3.70%
Deferred Charges and Other Assets, Other [Member]
Right-of-use assets	$ 70.6	$ 73.7
Deferred Charges and Other Assets, Other [Member] | Spire Missouri [Member]
Right-of-use assets	2.1	1.7
Deferred Charges and Other Assets, Other [Member] | Spire Alabama Inc [Member]
Right-of-use assets	19.2	20.2
Other Current Liabilities [Member]
Lease liabilities, current	6.8	6.5
Other Current Liabilities [Member] | Spire Missouri [Member]
Lease liabilities, current	0.5	0.4
Other Current Liabilities [Member] | Spire Alabama Inc [Member]
Lease liabilities, current	1.9	1.9
Deferred Credits and Other Liabilities, Other [Member]
Lease liabilities, noncurrent	70.2	73.7
Deferred Credits and Other Liabilities, Other [Member] | Spire Missouri [Member]
Lease liabilities, noncurrent	1.8	1.5
Deferred Credits and Other Liabilities, Other [Member] | Spire Alabama Inc [Member]
Lease liabilities, noncurrent	$ 23.5	$ 24.6

Note 17 - Leases - Maturity of

Note 17 - Leases - Maturity of Operating Lease Liabilities (Details) $ in Millions	Sep. 30, 2023 USD ($)
2024	$ 6.9
2025	7.5
2026	7.5
2027	7.4
2028	7.4
Thereafter	65.9
Total undiscounted lease payments	102.6
Less present value discount	(25.6)
Total current and noncurrent lease liabilities	77
Spire Missouri [Member]
2024	0.5
2025	0.6
2026	0.4
2027	0.3
2028	0.3
Thereafter	0.5
Total undiscounted lease payments	2.6
Less present value discount	(0.3)
Total current and noncurrent lease liabilities	2.3
Spire Alabama Inc [Member]
2024	1.9
2025	2.2
2026	2.2
2027	2.3
2028	2.3
Thereafter	21.7
Total undiscounted lease payments	32.6
Less present value discount	(7.2)
Total current and noncurrent lease liabilities	$ 25.4