Spire (SR) 10-Q 7 May 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Entity Information [Line Items]
Entity Registrant Name	Spire Inc
Entity Central Index Key	0001126956
Current Fiscal Year End Date	--09-30
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
Entity Common Stock, Shares Outstanding (in shares)		51,679,561
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Entity Shell Company	false
Entity File Number	1-16681
Entity Tax Identification Number	74-2976504
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
Document Quarterly Report	true
Document Transition Report	false
Spire Missouri Inc
Entity Information [Line Items]
Entity Registrant Name	Spire Missouri Inc
Entity Central Index Key	0000057183
Current Fiscal Year End Date	--09-30
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
Entity Common Stock, Shares Outstanding (in shares)		24,577
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Entity Shell Company	false
Entity File Number	1-1822
Entity Tax Identification Number	43-0368139
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
Spire Alabama Inc
Entity Information [Line Items]
Entity Registrant Name	Spire Alabama Inc
Entity Central Index Key	0000003146
Current Fiscal Year End Date	--09-30
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
Entity Common Stock, Shares Outstanding (in shares)		1,972,052
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Entity Shell Company	false
Entity File Number	2-38960
Entity Tax Identification Number	63-0022000
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
Common Stock $1.00 par value
Entity Information [Line Items]
Trading Symbol	SR
Title of each class	Common Stock $1.00 par value
Name of each exchange on which registered	NYSE
Depositary Shares, each representing a 1/1,000th interest in a share of 5.90% Series A Cumulative Redeemable Perpetual Preferred Stock, par value $25.00 per share
Entity Information [Line Items]
Trading Symbol	SR.PRA
Title of each class	Depositary Shares
Name of each exchange on which registered	NYSE

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Operating Revenues	$ 1,104.9	$ 715.5	$ 1,617.5	$ 1,282.4
Operating Expenses:
Natural gas	619.1	297.1	800.3	559
Operation and maintenance	119	105.7	230.6	222.3
Depreciation and amortization	51.5	49.2	102.3	96.7
Taxes, other than income taxes	57.9	53	94	91.6
Total Operating Expenses	847.5	505	1,227.2	969.6
Operating Income	257.4	210.5	390.3	312.8
Interest Expense, Net	25.8	27.2	51.5	53.9
Other Income (Expense), Net	1.8	(19.5)	6.1	(13.8)
Income Before Income Taxes	233.4	163.8	344.9	245.1
Income Tax Expense	46	30.2	68.6	44.5
Net Income	187.4	133.6	276.3	200.6
Provision for preferred dividends	3.7	3.7	7.4	7.4
Income allocated to participating securities	0.3	0.2	0.4	0.3
Net Income Available to Common Shareholders	$ 183.4	$ 129.7	$ 268.5	$ 192.9
Weighted Average Number of Common Shares Outstanding:
Basic	51.6	51	51.6	51
Diluted	51.7	51.1	51.7	51.1
Basic Earnings Per Common Share	$ 3.56	$ 2.55	$ 5.21	$ 3.78
Diluted Earnings Per Common Share	$ 3.55	$ 2.54	$ 5.20	$ 3.77
Spire Alabama
Operating Revenues	$ 222.6	$ 185.5	$ 336.2	$ 311.7
Operating Expenses:
Natural gas	69.8	39.4	104.9	86.4
Operation and maintenance	33.7	37.1	66.5	72.3
Depreciation and amortization	15.2	14.6	30.2	28.9
Taxes, other than income taxes	14.7	13.2	22.9	22
Total Operating Expenses	133.4	104.3	224.5	209.6
Operating Income	89.2	81.2	111.7	102.1
Interest Expense, Net	5.3	5.3	10	10.7
Other Income (Expense), Net	0.7	1.2	1.4	3.4
Income Before Income Taxes	84.6	77.1	103.1	94.8
Income Tax Expense	21.3	19.3	26.1	23.8
Net Income	$ 63.3	$ 57.8	$ 77	$ 71

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Net Income	$ 187.4	$ 133.6	$ 276.3	$ 200.6
Cash flow hedging derivative instruments:
Net hedging gain (loss) arising during the period	43.5	(41.1)	60.7	(22.2)
Amounts reclassified into net income	(0.4)	(2.2)	(0.7)	(2.5)
Net gain (loss) on cash flow hedging derivative instruments	43.1	(43.3)	60	(24.7)
Net gain (loss) on defined benefit pension and other postretirement plans	0.2	(0.1)	0.2	(0.1)
Net unrealized loss on available for sale securities	(0.1)		(0.1)
Other Comprehensive Income (Loss), Before Tax	43.2	(43.4)	60.1	(24.8)
Income Tax Expense (Benefit) Related to Items of Other Comprehensive Income	9.8	(9.7)	13.6	(5.5)
Other Comprehensive Income (Loss), Net of Tax	33.4	(33.7)	46.5	(19.3)
Comprehensive Income	220.8	99.9	322.8	181.3
Operating Revenues	1,104.9	715.5	1,617.5	1,282.4
Operating Expenses:
Natural gas	619.1	297.1	800.3	559
Operation and maintenance	119	105.7	230.6	222.3
Depreciation and amortization	51.5	49.2	102.3	96.7
Taxes, other than income taxes	57.9	53	94	91.6
Total Operating Expenses	847.5	505	1,227.2	969.6
Operating Income	257.4	210.5	390.3	312.8
Interest Expense, Net	25.8	27.2	51.5	53.9
Other Income (Expense), Net	1.8	(19.5)	6.1	(13.8)
Income Before Income Taxes	233.4	163.8	344.9	245.1
Income Tax Expense	46	30.2	68.6	44.5
Spire Missouri
Net Income	93.1	74.5	149.7	122.5
Cash flow hedging derivative instruments:
Other Comprehensive Income (Loss), Net of Tax	0.1	(0.2)	0.2	(0.1)
Comprehensive Income	93.2	74.3	149.9	122.4
Operating Revenues	790.9	457.5	1,146.4	831.5
Operating Expenses:
Natural gas	537.4	223.6	699	409.4
Operation and maintenance	62.8	50.8	125.7	116.3
Depreciation and amortization	31	29.3	61.4	58.3
Taxes, other than income taxes	38.9	36.1	64	62.8
Total Operating Expenses	670.1	339.8	950.1	646.8
Operating Income	120.8	117.7	196.3	184.7
Interest Expense, Net	11.7	12.7	23.4	25.9
Other Income (Expense), Net	0.8	(20.9)	3.5	(19.9)
Income Before Income Taxes	109.9	84.1	176.4	138.9
Income Tax Expense	$ 16.8	$ 9.6	$ 26.7	$ 16.4

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020
ASSETS
Utility Plant	$ 6,974.3	$ 6,766.3	$ 6,369.4
Less: Accumulated depreciation and amortization	2,145.1	2,086.2	1,848.4
Net Utility Plant	4,829.2	4,680.1	4,521
Non-utility Property (net of accumulated depreciation and amortization of $25.4, $19.0 and $17.5 at March 31, 2021, September 30, 2020, and March 31, 2020, respectively)	457	432.3	547.4
Other Investments	76.4	71.7	68.1
Total Other Property and Investments	533.4	504	615.5
Current Assets:
Cash and cash equivalents	104	4.1	108.4
Accounts receivable:
Utility	447.7	131.8	248.2
Other	182.3	146.4	132.8
Allowance for credit losses	(34.4)	(24.9)	(28)
Delayed customer billings	20.7	10	16.9
Inventories:
Natural gas	143	154.3	90.3
Propane gas	8.7	10.7	10.7
Materials and supplies	28.3	26.5	26.1
Regulatory assets	60.4	69.5	68
Prepayments	29.4	29.2	27.9
Other	49.9	33	17.5
Total Current Assets	1,040	590.6	718.8
Deferred Charges and Other Assets:
Goodwill	1,171.6	1,171.6	1,171.6
Regulatory assets	1,133.6	1,069.4	770.7
Other	229	225.5	220.4
Total Deferred Charges and Other Assets	2,534.2	2,466.5	2,162.7
Total Assets	8,936.8	8,241.2	8,018
Capitalization:
Preferred stock ($25.00 par value per share; 10.0 million depositary shares authorized, issued and outstanding at March 31, 2021, September 30, 2020, and March 31, 2020)	242	242	242
Common stock (par value $1.00 per share; 70.0 million shares authorized; 51.7 million, 51.6 million, and 51.2 million shares issued and outstanding at March 31, 2021, September 30, 2020, and March 31, 2020, respectively)	51.7	51.6	51.2
Paid-in capital and common stock	1,512.2	1,549.2	1,520.7
Retained earnings	920.1	720.7	902.3
Accumulated other comprehensive gain (loss)	5.3	(41.2)	(50.6)
Total Shareholders' Equity	2,731.3	2,522.3	2,665.6
Temporary equity	8.2	3.4	3.9
Long-term debt (less current portion)	2,692.5	2,423.7	2,484.8
Total Capitalization	5,432	4,949.4	5,154.3
Current Liabilities:
Current portion of long-term debt	110.8	60.4	5.4
Notes payable	653.5	648	560.6
Accounts payable	352.1	243.3	221.4
Advance customer billings	11.4	45.3	11.6
Wages and compensation accrued	43.5	46.3	34
Customer deposits	29.9	30.6	35.9
Taxes accrued	60	71.4	55.1
Regulatory liabilities	56.3	113	31.8
Other	190	190.9	196.7
Total Current Liabilities	1,507.5	1,449.2	1,152.5
Deferred Credits and Other Liabilities:
Deferred income taxes	602.8	511.4	498.1
Pension and postretirement benefit costs	274.4	309	272.1
Asset retirement obligations	551	540.1	344.7
Regulatory liabilities	423.5	343.7	472.3
Other	145.6	138.4	124
Total Deferred Credits and Other Liabilities	1,997.3	1,842.6	1,711.2
Commitments and Contingencies (Note 10)
Total Capitalization and Liabilities	8,936.8	8,241.2	8,018
Spire Missouri
ASSETS
Utility Plant	4,089.1	3,931.2	3,790.8
Less: Accumulated depreciation and amortization	869.9	825.7	795.2
Net Utility Plant	3,219.2	3,105.5	2,995.6
Other Investments	59.4	56.7	53.5
Current Assets:
Cash and cash equivalents	0	0	5.1
Accounts receivable:
Utility	363.9	92.5	169.2
Associated companies	2.8	2.7	3.7
Other	22.2	34.1	22.4
Allowance for credit losses	(26.6)	(18.1)	(20.2)
Delayed customer billings	18.4	2.4	16.9
Inventories:
Natural gas	115.6	95.1	58.5
Propane gas	8.7	10.7	10.7
Materials and supplies	15.8	15.6	15.6
Regulatory assets	37.5	32.1	29.4
Prepayments	18.9	20.7	15.9
Total Current Assets	577.2	287.8	327.2
Deferred Charges and Other Assets:
Goodwill	210.2	210.2	210.2
Regulatory assets	604.3	548.7	512.1
Other	99	96	83.4
Total Deferred Charges and Other Assets	913.5	854.9	805.7
Total Assets	4,769.3	4,304.9	4,182
Capitalization:
Paid-in capital and common stock	765.1	765.1	765.1
Retained earnings	822.6	672.9	676.5
Accumulated other comprehensive gain (loss)	(2.7)	(2.9)	(2.5)
Total Shareholders' Equity	1,585	1,435.1	1,439.1
Long-term debt (less current portion)	1,092.4	1,092	1,098.7
Total Capitalization	2,677.4	2,527.1	2,537.8
Current Liabilities:
Notes payable	250	0	185.1
Notes payable ? associated companies	369.4	301.2	39.6
Accounts payable	87.5	66.7	63.8
Accounts payable ? associated companies	7.7	9.3	5.2
Advance customer billings	2.1	32.7	5.4
Wages and compensation accrued	28	33.3	24.1
Customer deposits	8.2	9.3	13.2
Taxes accrued	29.4	39.1	26.6
Regulatory liabilities	37.6	103.2	24.3
Other	43.4	39.9	32.7
Total Current Liabilities	863.3	634.7	420
Deferred Credits and Other Liabilities:
Deferred income taxes	470.9	434.7	390.6
Pension and postretirement benefit costs	193.7	217.2	205
Asset retirement obligations	156.5	153.4	177.1
Regulatory liabilities	353.5	274.8	400.4
Other	54	63	51.1
Total Deferred Credits and Other Liabilities	1,228.6	1,143.1	1,224.2
Commitments and Contingencies (Note 10)
Total Capitalization and Liabilities	4,769.3	4,304.9	4,182
Spire Alabama
ASSETS
Utility Plant	2,523.4	2,469.9	2,217
Less: Accumulated depreciation and amortization	1,136.5	1,117	904.7
Net Utility Plant	1,386.9	1,352.9	1,312.3
Current Assets:
Cash and cash equivalents	18.2	0	0.1
Accounts receivable:
Utility	66.4	31.4	65.6
Associated companies	0.5	0.6	0.1
Other	5.7	5.8	7.8
Allowance for credit losses	(6.5)	(5.5)	(6.8)
Delayed customer billings	2.3	7.5	0
Inventories:
Natural gas	14.8	22.5	16.3
Materials and supplies	10	8.4	8.3
Regulatory assets	11.8	20.4	23.3
Prepayments	4.7	4.3	5.7
Other	0.1	0.2	0.3
Total Current Assets	148	95.6	120.7
Notes receivable – associated companies	20	0	0
Deferred Charges and Other Assets:
Regulatory assets	501.2	489.9	230.1
Deferred income taxes	33.2	59.3	57.4
Other	53.5	53.7	61
Total Deferred Charges and Other Assets	587.9	602.9	348.5
Total Assets	2,122.8	2,051.4	1,781.5
Capitalization:
Paid-in capital and common stock	328.9	350.9	350.9
Retained earnings	566.8	500.8	518.1
Total Shareholders' Equity	895.7	851.7	869
Long-term debt (less current portion)	571.1	471.8	471.7
Total Capitalization	1,466.8	1,323.5	1,340.7
Current Liabilities:
Current portion of long-term debt	50	0	0
Notes payable	0	0	50
Notes payable ? associated companies	0	121.3	33
Accounts payable	37.4	43.7	48
Accounts payable ? associated companies	8	4.2	4.8
Advance customer billings	5.4	11.5	5.3
Wages and compensation accrued	6.4	8	5.9
Customer deposits	19	18.7	19.9
Taxes accrued	25.1	28	23
Regulatory liabilities	14.2	3.9	2.4
Other	14.8	11.8	9.7
Total Current Liabilities	180.3	251.1	202
Deferred Credits and Other Liabilities:
Pension and postretirement benefit costs	68.2	74.9	54.6
Asset retirement obligations	381.7	374.3	151.7
Regulatory liabilities	18	18.5	21.6
Other	7.8	9.1	10.9
Total Deferred Credits and Other Liabilities	475.7	476.8	238.8
Commitments and Contingencies (Note 10)
Total Capitalization and Liabilities	$ 2,122.8	$ 2,051.4	$ 1,781.5

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020
ASSETS
Non-utility property, accumulated depreciation and amortization	$ 25.4	$ 19	$ 17.5
Capitalization:
Common stock, par value (in dollars per share)	$ 1	$ 1	$ 1
Common stock, authorized (in shares)	70,000,000	70,000,000	70,000,000
Common stock, issued (in shares)	51,700,000	51,600,000	51,200,000
Common stock, outstanding (in shares)	51,700,000	51,600,000	51,200,000
Spire Missouri
Capitalization:
Common stock, par value (in dollars per share)	$ 1	$ 1	$ 1
Common stock, authorized (in shares)	50,000,000	50,000,000	50,000,000
Common stock, issued (in shares)	24,577	24,577	24,577
Common stock, outstanding (in shares)	24,577	24,577	24,577
Spire Alabama
Capitalization:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, authorized (in shares)	3,000,000	3,000,000	3,000,000
Common stock, issued (in shares)	2,000,000	2,000,000	2,000,000
Common stock, outstanding (in shares)	2,000,000	2,000,000	2,000,000
Depositary Shares
Capitalization:
Preferred stock, par value (in dollars per share)	$ 25	$ 25	$ 25
Preferred stock, depositary shares authorized (in shares)	10,000,000	10,000,000	10,000,000
Preferred stock, depositary shares outstanding (in shares)	10,000,000	10,000,000	10,000,000
Preferred stock, depositary shares issued (in shares)	10,000,000	10,000,000	10,000,000

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Spire Missouri	Spire Alabama	Common Stock	Common StockSpire Missouri	Common StockSpire Alabama	Preferred Stock	Paid-in Capital	Paid-in CapitalSpire Missouri	Paid-in CapitalSpire Alabama	Retained Earnings	Retained EarningsSpire Missouri	Retained EarningsSpire Alabama	AOCI	[1]	AOCISpire Missouri	[1]
BALANCE at Sep. 30, 2019	$ 2,543	$ 1,339.3	$ 830	$ 51	$ 0.1		$ 242	$ 1,505.8	$ 765	$ 370.9	$ 775.5	$ 576.6	$ 459.1	$ (31.3)		$ (2.4)
BALANCE (in shares) at Sep. 30, 2019				50,973,515	24,577	1,972,052
Stockholders' Equity Rollforward
Net income	200.6	122.5	71								200.6	122.5	71
Common stock issued	9.5			$ 0.1				9.4
Common stock issued (in shares)				112,758
Dividend reinvestment plan	5.6							5.6
Dividend reinvestment plan (in shares)				73,883
Stock-based compensation costs	3.1							3.1
Stock issued under stock-based compensation plans				$ 0.1				(0.1)
Stock issued under stock-based compensation (in shares)				108,752
Employees’ tax withholding for stock-based compensation	(3.1)							(3.1)
Employee's tax withholding for stock-based compensation (in shares)				(39,847)
Temporary equity adjustment to redemption value	1.1										1.1
Return of capital to Spire			(20)							(20)
Dividends declared on common stock	(63.8)	(22.6)	(12)								(63.8)	(22.6)	(12)
Dividends declared on preferred stock	(11.1)										(11.1)
Other comprehensive income (loss), net of tax	(19.3)	(0.1)												(19.3)		(0.1)
BALANCE at Mar. 31, 2020	2,665.6	1,439.1	869	$ 51.2	$ 0.1		242	1,520.7	765	350.9	902.3	676.5	518.1	$ (50.6)		(2.5)
BALANCE (in shares) at Mar. 31, 2020				51,229,061	24,577	1,972,052								(50,600,000)
BALANCE at Dec. 31, 2019	2,586	1,376.1	837.2	$ 51.1	$ 0.1		242	1,506.7	765	370.9	803.1	613.3	466.3			(2.3)
BALANCE (in shares) at Dec. 31, 2019				51,063,460	24,577	1,972,052								(16,900,000)
Stockholders' Equity Rollforward
Net income	133.6	74.5	57.8								133.6	74.5	57.8
Common stock issued	9.5			$ 0.1				9.4
Common stock issued (in shares)				112,758
Dividend reinvestment plan	3.3							3.3
Dividend reinvestment plan (in shares)				45,119
Stock-based compensation costs	1.5							1.5
Stock issued under stock-based compensation (in shares)				9,626
Employees’ tax withholding for stock-based compensation	(0.2)							(0.2)
Employee's tax withholding for stock-based compensation (in shares)				(1,902)
Temporary equity adjustment to redemption value	1.2										1.2
Return of capital to Spire			(20)							(20)
Dividends declared on common stock	(31.9)	(11.3)	(6)								(31.9)	(11.3)	(6)
Dividends declared on preferred stock	(3.7)										(3.7)
Other comprehensive income (loss), net of tax	(33.7)	(0.2)												$ (33.7)		(0.2)
BALANCE at Mar. 31, 2020	2,665.6	1,439.1	869	$ 51.2	$ 0.1		242	1,520.7	765	350.9	902.3	676.5	518.1	$ (50.6)		(2.5)
BALANCE (in shares) at Mar. 31, 2020				51,229,061	24,577	1,972,052								(50,600,000)
BALANCE at Sep. 30, 2020	2,522.3	1,435.1	851.7	$ 51.6	$ 0.1		242	1,549.2	765	350.9	720.7	672.9	500.8	$ (41.2)		(2.9)
BALANCE (in shares) at Sep. 30, 2020				51,611,789	24,577	1,972,052
Stockholders' Equity Rollforward
Net income	276.3	149.7	77								276.3	149.7	77
Dividend reinvestment plan	0.7							0.7
Dividend reinvestment plan (in shares)				12,545
Stock-based compensation costs	3.4							3.4
Stock issued under stock-based compensation plans				$ 0.1				(0.1)
Stock issued under stock-based compensation (in shares)				64,410
Employees’ tax withholding for stock-based compensation	(0.9)							(0.9)
Employee's tax withholding for stock-based compensation (in shares)				(14,488)
Equity units issued	(40.1)							(40.1)
Temporary equity adjustment to redemption value	(2.1)										(2.1)
Return of capital to Spire			(22)							(22)
Dividends declared on common stock	(67.4)		(11)								(67.4)		(11)
Dividends declared on preferred stock	(7.4)										(7.4)
Other comprehensive income (loss), net of tax	46.5	0.2												46.5		0.2
BALANCE at Mar. 31, 2021	2,731.3	1,585	895.7	$ 51.7	$ 0.1		242	1,512.2	765	328.9	920.1	822.6	566.8	5.3		(2.7)
BALANCE (in shares) at Mar. 31, 2021				51,674,256	24,577	1,972,052
BALANCE at Dec. 31, 2020	2,586.8	1,491.8	848.9	$ 51.7	$ 0.1		242	1,550	765	339.9	771.2	729.5	509	(28.1)		(2.8)
BALANCE (in shares) at Dec. 31, 2020				51,659,473	24,577	1,972,052
Stockholders' Equity Rollforward
Net income	187.4	93.1	63.3								187.4	93.1	63.3
Dividend reinvestment plan	0.3							0.3
Dividend reinvestment plan (in shares)				5,847
Stock-based compensation costs	2							2
Stock issued under stock-based compensation (in shares)				9,249
Employee's tax withholding for stock-based compensation (in shares)				(313)
Equity units issued	(40.1)							(40.1)
Temporary equity adjustment to redemption value	(1.2)										(1.2)
Return of capital to Spire			(11)							(11)
Dividends declared on common stock	(33.6)		(5.5)								(33.6)		(5.5)
Dividends declared on preferred stock	(3.7)										(3.7)
Other comprehensive income (loss), net of tax	33.4	0.1												33.4		0.1
BALANCE at Mar. 31, 2021	$ 2,731.3	$ 1,585	$ 895.7	$ 51.7	$ 0.1		$ 242	$ 1,512.2	$ 765	$ 328.9	$ 920.1	$ 822.6	$ 566.8	$ 5.3		$ (2.7)
BALANCE (in shares) at Mar. 31, 2021				51,674,256	24,577	1,972,052
[1]	Accumulated other comprehensive income (loss)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Statement Of Stockholders Equity [Abstract]
Dividends declared on common stock (in dollars per share)	$ 0.65	$ 0.6225	$ 1.30	$ 1.245
Dividends declared on preferred stock (in dollars per depositary share)	$ 0.36875	$ 0.36875	$ 0.7375	$ 1.10625

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities:
Net Income	$ 276.3	$ 200.6
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	102.3	96.7
Deferred income taxes and investment tax credits	68.5	42.8
Changes in assets and liabilities:
Accounts receivable	(342.3)	(64.4)
Inventories	14	69.5
Regulatory assets and liabilities	(6.7)	74.7
Accounts payable	141.3	(50.5)
Delayed/advance customer billings, net	(44.6)	(33.6)
Taxes accrued	(11.1)	(14.1)
Other assets and liabilities	(44.3)	0.1
Other	5.8	(0.1)
Net cash provided by operating activities	159.2	321.7
Investing Activities:
Capital expenditures	(303.5)	(346.1)
Other	(0.8)	1.5
Net cash used in investing activities	(304.3)	(344.6)
Financing Activities:
Issuance of long-term debt	325	510
Repayment of long-term debt	(5.4)	(140)
Issuance (repayment) of short-term debt, net	5.5	(182.6)
Issuance of common stock	0.7	15.2
Dividends paid on common stock	(65.9)	(63.8)
Dividends paid on preferred stock	(7.4)	(7.4)
Other	(7.5)	(5.9)
Net cash provided by financing activities	245	125.5
Net Increase in Cash, Cash Equivalents, and Restricted Cash	99.9	102.6
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	4.1	5.8
Cash and Cash Equivalents at End of Period	104	108.4
Supplemental disclosure of cash (paid) received for:
Interest, net of amounts capitalized	(48.5)	(46.7)
Income taxes	(1.1)	(1.7)
Spire Missouri
Operating Activities:
Net Income	149.7	122.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	61.4	58.3
Deferred income taxes and investment tax credits	26.7	16.4
Changes in assets and liabilities:
Accounts receivable	(251.1)	(67.6)
Inventories	(18.7)	39.3
Regulatory assets and liabilities	(28.7)	59.8
Accounts payable	32.3	6.8
Delayed/advance customer billings, net	(46.5)	(27.9)
Taxes accrued	(9.7)	(9.8)
Other assets and liabilities	(50.3)	(1.9)
Other	0.3	0.3
Net cash provided by operating activities	(134.6)	196.2
Investing Activities:
Capital expenditures	(184.1)	(183.2)
Other	0.5	0.3
Net cash used in investing activities	(183.6)	(182.9)
Financing Activities:
Issuance of long-term debt	0	275
Repayment of long-term debt	0	(100)
Issuance of short-term debt, net	250	185.1
Repayments to Spire, net	68.2	(346.8)
Dividends paid on common stock	0	(22.6)
Other	0	(1.5)
Net cash provided by financing activities	318.2	(10.8)
Net Increase in Cash, Cash Equivalents, and Restricted Cash	0	2.5
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	0	2.6
Cash and Cash Equivalents at End of Period	0	5.1
Supplemental disclosure of cash (paid) received for:
Interest, net of amounts capitalized	(22.9)	(21.6)
Income taxes	0	0
Spire Alabama
Operating Activities:
Net Income	77	71
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	30.2	28.9
Deferred income taxes and investment tax credits	26.1	23.9
Changes in assets and liabilities:
Accounts receivable	(33.7)	(27.9)
Inventories	6.2	18.3
Regulatory assets and liabilities	14.6	13.7
Accounts payable	9.9	(10.8)
Delayed/advance customer billings, net	(0.9)	(5.3)
Taxes accrued	(2.9)	(4.4)
Other assets and liabilities	(4.6)	(7.8)
Other	0.1	(2.5)
Net cash provided by operating activities	122	97.1
Investing Activities:
Capital expenditures	(78.9)	(75.8)
Lending to Spire, net of repayments	(20)	0
Other	0.3	(3)
Net cash used in investing activities	(98.6)	(78.8)
Financing Activities:
Issuance of long-term debt	150	100
Repayment of long-term debt	0	(40)
Issuance (repayment) of short-term debt, net	0	50
Return of capital to Spire	(22)	(20)
Repayments to Spire, net	(121.3)	(95.7)
Dividends paid on common stock	(11)	(12)
Other	(0.9)	(0.5)
Net cash provided by financing activities	(5.2)	(18.2)
Net Increase in Cash, Cash Equivalents, and Restricted Cash	18.2	0.1
Cash, Cash Equivalents, and Restricted Cash at Beginning of Period	0	0
Cash and Cash Equivalents at End of Period	18.2	0.1
Supplemental disclosure of cash (paid) received for:
Interest, net of amounts capitalized	(8.4)	(9.5)
Income taxes	$ 0	$ 0

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION – These notes are an integral part of the accompanying unaudited financial statements of Spire Inc. (“Spire” or the “Company”) presented on a consolidated basis, Spire Missouri Inc. (“Spire Missouri”) and Spire Alabama Inc. (“Spire Alabama”). Spire Missouri and Spire Alabama are wholly owned subsidiaries of Spire. Spire Missouri, Spire Alabama and the subsidiaries of Spire EnergySouth Inc. (“Spire EnergySouth”) are collectively referred to as the “Utilities.” The subsidiaries of Spire EnergySouth are Spire Gulf Inc. and Spire Mississippi Inc. The accompanying unaudited financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information with the instructions to Form 10-Q and Rule 10-01 of Regulation S‑X. Accordingly, they do not include all the disclosures required for complete financial statements. In the opinion of management, the accompanying unaudited financial statements include all adjustments necessary for the fair presentation of the results of operations for the periods presented. This Form 10-Q should be read in conjunction with the Notes to Financial Statements contained in Spire’s, Spire Missouri’s and Spire Alabama’s combined Annual Report on Form 10-K for the fiscal year ended September 30, 2020. 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 been eliminated from their separate financial statements. NATURE OF OPERATIONS – Spire has two reportable segments: Gas Utility and Gas Marketing. The Gas Utility segment consists of the regulated natural gas distribution operations of the Company and is the core business segment of Spire in terms of revenue and earnings. The Gas Utility segment is comprised of the operations of: Spire Missouri, serving St. Louis, Kansas City, and other areas in Missouri; Spire Alabama, serving central and northern Alabama; and the subsidiaries of Spire EnergySouth, serving southern Alabama and south-central Mississippi. The Gas Marketing segment includes Spire’s largest gas-related business, Spire Marketing Inc. (“Spire Marketing”), which provides non-regulated natural gas services, primarily in the central and southern United States (U.S.). The activities of other subsidiaries are reported as Other and are described in Note 9 , Information by Operating Segment. Spire Missouri and Spire Alabama each have a single reportable segment. Nearly all the Company’s earnings are derived from its Gas Utility segment. Due to the seasonal nature of the Utilities’ business and the Spire Missouri rate design, earnings are typically concentrated during the heating season of November through April each fiscal year. As a result, the interim statements of income for Spire, Spire Missouri and Spire Alabama are not necessarily indicative of annual results or representative of succeeding quarters of the fiscal year. REGULATED OPERATIONS – The Utilities account for their regulated operations in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 980, Regulated Operations . This topic sets forth the application of GAAP for those companies whose rates are established by or are subject to approval by an independent third-party regulator. The provisions of this accounting guidance require, among other things, that financial statements of a regulated enterprise reflect the actions of regulators, where appropriate. These actions may result in the recognition of revenues and expenses in time periods that are different than non-regulated enterprises. When this occurs, costs are deferred as assets in the balance sheet (regulatory assets) and recorded as expenses when those amounts are reflected in rates. In addition, regulators can impose liabilities upon a regulated company for amounts previously collected from customers and for recovery of costs that are expected to be incurred in the future (regulatory liabilities). Management believes that the current regulatory environment supports the continued use of these regulatory accounting principles and that all regulatory assets and regulatory liabilities are recoverable or refundable through the regulatory process. As authorized by the Missouri Public Service Commission (MoPSC), the Mississippi Public Service Commission (MSPSC) and the Alabama Public Service Commission (APSC), 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 liabilities related to the PGA clauses and the GSA riders are both labeled Unamortized Purchased Gas Adjustments herein. See additional information about regulatory assets and liabilities in Note 4 , Regulatory Matters. DERIVATIVES – In the course of their business, certain subsidiaries of Spire enter into commitments associated with the purchase or sale of natural gas. Certain of their derivative natural gas contracts are designated as normal purchases or normal sales and, as such, are excluded from the scope of FASB ASC Topic 815, Derivatives and Hedging . Those contracts are accounted for as executory contracts and recorded on an accrual basis. Revenues and expenses from such contracts are recorded gross. Contracts not designated as normal purchases or normal sales are recorded as derivatives with changes in fair value recognized in earnings in the periods prior to physical delivery. Certain of Spire Marketing’s wholesale purchase and sale transactions are classified as trading activities for financial reporting purposes, with income and expenses presented on a net basis in natural gas expenses in the Condensed Consolidated Statements of Income. TRANSACTIONS WITH AFFILIATES – Transactions between affiliates of the Company have been eliminated from the consolidated financial statements of Spire. As reflected in their separate financial statements, Spire Missouri and Spire Alabama borrowed funds from the Company and incurred related interest, and in 2021, Spire Alabama lent excess funds to the Company and earned related interest. Spire Missouri and Spire Alabama also participated in normal intercompany shared services transactions. Spire Missouri’s and Spire Alabama’s other transactions with affiliates are presented below: Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Missouri Purchases of natural gas from Spire Marketing Inc. $ 57.6 $ 13.3 $ 68.3 $ 32.8 Transportation services received from Spire STL Pipeline LLC 7.9 7.9 16.0 11.8 Sales of natural gas to Spire Marketing Inc. — — 1.1 — Transportation services received from Spire NGL Inc. 0.2 0.2 0.5 0.5 Spire Alabama Purchases of natural gas from Spire Marketing Inc. $ 5.8 $ 1.0 $ 10.6 $ 4.3 Sales of natural gas to Spire Marketing Inc. 0.1 — 0.1 — ACCRUED CAPITAL EXPENDITURES – Accrued capital expenditures, shown in the following table, are excluded from capital expenditures in the statements of cash flows until paid. March 31, September 30, March 31, 2021 2020 2020 Spire $ 36.1 $ 67.6 $ 51.4 Spire Missouri 21.8 34.3 21.5 Spire Alabama 4.7 17.0 17.6 ACCOUNTS RECEIVABLE AND ALLOWANCE FOR CREDIT LOSSES – Trade accounts receivable are recorded at the amounts due from customers, including unbilled amounts. Accounts receivable are written off when they are deemed to be uncollectible. An allowance for expected credit losses is estimated and updated based on relevant data and trends such as accounts receivable aging, historical write-off experience, current write-off trends, economic conditions, and the impact of weather and availability of customer payment assistance on collection trends. For the Utilities, net write-offs as a percentage of revenue has historically been the best predictor of base net write-off experience over time. Management judgment is applied in the development of the allowance due to the complexity of variables and subjective nature of certain relevant factors. For March 31, 2021, and September 30, 2020, the estimates for expected credit losses were increased as a result of considerations related to the outbreak of the novel coronavirus (COVID-19), including trends from previous economic downturns, the effects of moratoriums on gas service cutoffs, and the effects of slower-than-normal disconnection activity in general, offset by the amount subject to specific recovery under Missouri’s deferral order (see Note 4 , Regulatory Matters). The accounts receivable of Spire’s non-utility businesses are evaluated separately from those of the Utilities. The allowance for credit losses for those other businesses is based on a continuous evaluation of the individual counterparty risk and is not significant for the periods presented. Activity in the allowance for credit losses for the three and six months ended March 31, 2021, is shown in the following table. Three Months Ended March 31, 2021 Six Months Ended March 31, 2021 Spire Spire Spire Spire Spire Missouri Alabama Spire Missouri Alabama Allowance at beginning of period $ 28.9 $ 21.4 $ 6.2 $ 24.9 $ 18.1 $ 5.5 Provision for expected credit losses 6.6 5.7 0.6 10.7 9.0 1.3 Write-offs, net of recoveries (1.1 ) (0.5 ) (0.3 ) (1.2 ) (0.5 ) (0.3 ) Allowance at end of period $ 34.4 $ 26.6 $ 6.5 $ 34.4 $ 26.6 $ 6.5 NEW ACCOUNTING PRONOUNCEMENTS – In June 2016, the FASB issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments , which was later supplemented by ASU Nos. 2018-19, 2019-04, 2019-05 and 2019-11. The new standard replaces the current “incurred loss” model with an “expected loss” model for certain instruments, including trade receivables, requiring measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. It also required entities to record credit loss allowances for available-for-sale securities rather than impair the carrying amount of the securities. Spire, Spire Missouri and Spire Alabama adopted the new standard for the quarter ended December 31, 2020. Based on the credit quality of the existing available-for-sale securities portfolio, no allowance for credit losses was recognized for those investments. Application of the new guidance did not result in any significant modifications to the Company’s policies related to recognizing an allowance on trade receivables, and the adoption of the new standard did not have a material impact on Spire’s, Spire Missouri’s and Spire Alabama’s financial statements. RECLASSIFICATIONS – Spire’s consolidated statements of income historically showed Gas Utility operating revenues and expense line items separately from Gas Marketing and other operations. The current presentation shows operating revenues and expense line items on a consolidated basis. Disaggregated data is presented in Note 9 , Information by Operating Segment. Prior period amounts have been reclassified to conform with the current period presentation.

Revenue

Revenue	6 Months Ended
	Mar. 31, 2021
Revenue From Contract With Customer [Abstract]
Revenue	2. REVENUE The following tables show revenue disaggregated by source and customer type. Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Gas Utility: Residential $ 537.6 $ 471.9 $ 887.5 $ 840.3 Commercial & industrial 369.2 156.8 472.2 279.3 Transportation 34.2 32.5 66.4 63.5 Off-system & other incentive 130.6 9.3 139.9 18.7 Other customer revenue (11.9 ) 3.2 (9.7 ) 5.6 Total revenue from contracts with customers 1,059.7 673.7 1,556.3 1,207.4 Changes in accrued revenue under alternative revenue programs (6.6 ) 5.3 (5.0 ) 2.3 Total Gas Utility operating revenues 1,053.1 679.0 1,551.3 1,209.7 Gas Marketing 33.4 33.3 58.2 65.6 Other 15.6 14.7 32.3 25.8 Total before eliminations 1,102.1 727.0 1,641.8 1,301.1 Intersegment eliminations (see Note 9, Information by Operating Segment) 2.8 (11.5 ) (24.3 ) (18.7 ) Total Operating Revenues $ 1,104.9 $ 715.5 $ 1,617.5 $ 1,282.4 Spire Missouri Residential $ 365.4 $ 331.1 $ 628.4 $ 607.0 Commercial & industrial 304.0 99.2 373.9 180.0 Transportation 9.9 9.7 18.9 18.7 Off-system & other incentive 128.5 9.3 135.9 18.7 Other customer revenue (17.5 ) 0.9 (14.6 ) 1.4 Total revenue from contracts with customers 790.3 450.2 1,142.5 825.8 Changes in accrued revenue under alternative revenue programs 0.6 7.3 3.9 5.7 Total Operating Revenues $ 790.9 $ 457.5 $ 1,146.4 $ 831.5 Spire Alabama Residential $ 144.8 $ 120.5 $ 214.0 $ 194.8 Commercial & industrial 53.2 46.2 77.5 77.5 Transportation 21.7 19.9 42.2 39.5 Off-system & other incentive 1.9 — 3.9 — Other customer revenue 3.9 1.7 2.0 3.3 Total revenue from contracts with customers 225.5 188.3 339.6 315.1 Changes in accrued revenue under alternative revenue programs (2.9 ) (2.8 ) (3.4 ) (3.4 ) Total Operating Revenues $ 222.6 $ 185.5 $ 336.2 $ 311.7 As discussed in Note 4 , Regulatory Matters, Spire Missouri recorded a $25.0 revenue adjustment related to “Off-system and other incentive” sales during February 2021, resulting in negative “Other customer revenue” for the three and six months ended March 31, 2021. 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.” Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire $ 42.2 $ 37.9 $ 63.9 $ 62.5 Spire Missouri 28.6 26.2 43.8 43.4 Spire Alabama 11.8 9.9 17.1 16.1

Earnings Per Common Share

Earnings Per Common Share	6 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Earnings Per Common Share	3. EARNINGS PER COMMON SHARE Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Basic Earnings Per Common Share: Net Income $ 187.4 $ 133.6 $ 276.3 $ 200.6 Less: Provision for preferred dividends 3.7 3.7 7.4 7.4 Income allocated to participating securities 0.3 0.2 0.4 0.3 Income Available to Common Shareholders $ 183.4 $ 129.7 $ 268.5 $ 192.9 Weighted Average Common Shares Outstanding (in millions) 51.6 51.0 51.6 51.0 Basic Earnings Per Common Share $ 3.56 $ 2.55 $ 5.21 $ 3.78 Diluted Earnings Per Common Share: Net Income $ 187.4 $ 133.6 $ 276.3 $ 200.6 Less: Provision for preferred dividends 3.7 3.7 7.4 7.4 Income allocated to participating securities 0.3 0.2 0.4 0.3 Income Available to Common Shareholders $ 183.4 $ 129.7 $ 268.5 $ 192.9 Weighted Average Common Shares Outstanding (in millions) 51.6 51.0 51.6 51.0 Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)* 0.1 0.1 0.1 0.1 Weighted Average Diluted Common Shares (in millions) 51.7 51.1 51.7 51.1 Diluted Earnings Per Common Share $ 3.55 $ 2.54 $ 5.20 $ 3.77 * 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 0.1 0.1 0.1 0.1

Regulatory Matters

Regulatory Matters	6 Months Ended
	Mar. 31, 2021
Regulated Operations [Abstract]
Regulatory Matters	4. REGULATORY MATTERS As explained in Note 1 , Summary of Significant Accounting Policies, the Utilities account for regulated operations in accordance with FASB ASC Topic 980, Regulated Operations March 31, September 30, March 31, Spire 2021 2020 2020 Regulatory Assets: Current: Pension and postretirement benefit costs $ 30.9 $ 30.6 $ 30.1 Unamortized purchased gas adjustments 0.1 5.5 10.4 Other 29.4 33.4 27.5 Total Current Regulatory Assets 60.4 69.5 68.0 Noncurrent: Pension and postretirement benefit costs 418.3 439.3 415.6 Cost of removal 430.7 395.6 154.3 Future income taxes due from customers 127.4 123.5 113.5 Energy efficiency 43.2 39.6 37.7 Unamortized purchased gas adjustments 51.5 12.1 — Other 62.5 59.3 49.6 Total Noncurrent Regulatory Assets 1,133.6 1,069.4 770.7 Total Regulatory Assets $ 1,194.0 $ 1,138.9 $ 838.7 Regulatory Liabilities: Current: Pension and postretirement benefit costs $ 5.8 $ 5.8 $ 5.8 Unamortized purchased gas adjustments 28.9 73.1 8.0 Other 21.6 34.1 18.0 Total Current Regulatory Liabilities 56.3 113.0 31.8 Noncurrent: Deferred taxes due to customers 133.2 138.8 174.2 Pension and postretirement benefit costs 170.2 157.6 152.5 Accrued cost of removal 28.7 28.6 31.7 Unamortized purchased gas adjustments 49.7 4.4 82.6 Other 41.7 14.3 31.3 Total Noncurrent Regulatory Liabilities 423.5 343.7 472.3 Total Regulatory Liabilities $ 479.8 $ 456.7 $ 504.1 March 31, September 30, March 31, Spire Missouri 2021 2020 2020 Regulatory Assets: Current: Pension and postretirement benefit costs $ 21.9 $ 21.9 $ 21.9 Other 15.6 10.2 7.5 Total Current Regulatory Assets 37.5 32.1 29.4 Noncurrent: Future income taxes due from customers 118.6 114.6 106.8 Pension and postretirement benefit costs 324.6 332.6 337.5 Energy efficiency 43.2 39.6 37.7 Unamortized purchased gas adjustments 51.5 12.1 — Cost of removal 21.3 7.1 — Other 45.1 42.7 30.1 Total Noncurrent Regulatory Assets 604.3 548.7 512.1 Total Regulatory Assets $ 641.8 $ 580.8 $ 541.5 Regulatory Liabilities: Current: Pension and postretirement benefit costs $ 3.6 $ 3.6 $ 3.6 Unamortized purchased gas adjustments 17.0 72.3 7.1 Other 17.0 27.3 13.6 Total Current Regulatory Liabilities 37.6 103.2 24.3 Noncurrent: Deferred taxes due to customers 115.8 121.4 156.8 Pension and postretirement benefit costs 151.9 140.4 130.7 Accrued cost of removal — — 4.8 Unamortized purchased gas adjustments 49.7 4.4 82.6 Other 36.1 8.6 25.5 Total Noncurrent Regulatory Liabilities 353.5 274.8 400.4 Total Regulatory Liabilities $ 391.1 $ 378.0 $ 424.7 March 31, September 30, March 31, Spire Alabama 2021 2020 2020 Regulatory Assets: Current: Pension and postretirement benefit costs $ 8.0 $ 7.7 $ 7.2 Unamortized purchased gas adjustments — 5.5 10.4 Other 3.8 7.2 5.7 Total Current Regulatory Assets 11.8 20.4 23.3 Noncurrent: Pension and postretirement benefit costs 88.5 98.2 72.6 Cost of removal 409.4 388.6 154.3 Future income taxes due from customers 2.2 2.2 — Other 1.1 0.9 3.2 Total Noncurrent Regulatory Assets 501.2 489.9 230.1 Total Regulatory Assets $ 513.0 $ 510.3 $ 253.4 Regulatory Liabilities: Current: Pension and postretirement benefit costs $ 2.2 $ 2.2 $ 2.2 Unamortized purchased gas adjustments 10.6 — — Other 1.4 1.7 0.2 Total Current Regulatory Liabilities 14.2 3.9 2.4 Noncurrent: Pension and postretirement benefit costs 14.3 14.8 17.8 Other 3.7 3.7 3.8 Total Noncurrent Regulatory Liabilities 18.0 18.5 21.6 Total Regulatory Liabilities $ 32.2 $ 22.4 $ 24.0 A portion of the Company’s and Spire Missouri’s regulatory assets are not earning a return, as shown in the table below: March 31, September 30, March 31, 2021 2020 2020 Spire Pension and postretirement benefit costs $ 226.3 $ 232.3 $ 226.2 Future income taxes due from customers 125.1 121.3 113.5 Other 122.9 12.9 13.7 Total Regulatory Assets Not Earning a Return $ 474.3 $ 366.5 $ 353.4 Spire Missouri Pension and postretirement benefit costs $ 226.3 $ 232.3 $ 226.2 Future income taxes due from customers 118.6 114.6 106.8 Other 122.9 12.9 13.7 Total Regulatory Assets Not Earning a Return $ 467.8 $ 359.8 $ 346.7 Like all the Company’s regulatory assets, these regulatory assets are expected to be recovered from customers in future rates. The recovery period for the future income taxes due from customers and pension and other postretirement benefit costs could be 20 years or longer, based on current Internal Revenue Service guidelines and average remaining service life of active participants, respectively. The other items not earning a return are expected to be recovered over a period not to exceed 15 years, consistent with precedent set by the MoPSC. Spire Alabama does not have any regulatory assets that are not earning a return. On March 7, 2018, the MoPSC issued its order in two general rate cases (docketed as GR-2017-0215 and GR-2017-0216), approving new tariffs that became effective on April 19, 2018. Certain provisions of the order allow less future recovery of certain deferred or capitalized costs than estimated based upon previous rate proceedings, and management determined that the related regulatory assets should be written down or off in connection with the preparation of the financial statements for the second quarter of 2018. Spire Missouri filed an appeal of portions of the MoPSC’s order, including the disallowance of certain pension costs ($28.8). On February 9, 2021, the Missouri Supreme Court issued its decision, reversing the MoPSC’s order with respect to certain pension costs and affirming the MoPSC’s order in all other respects. The case will now be remanded back to the MoPSC with directions that $9.0 in pension assets that accrued between 1994 and 1996 be added to the Company’s prepaid pension asset. The MoPSC has not yet opened a remand docket in the case, but based on the court’s decision, the Company increased its noncurrent regulatory asset for “Pension and postretirement benefit costs” and reduced operation and maintenance expense for the three and six months ended March 31, 2021. Like the original write-down in 2018, this adjustment is excluded for the net economic earnings financial measure. In the first half of fiscal 2020, provisions totaling $4.2 were recorded to Spire Missouri’s regulatory liability for Infrastructure System Replacement Surcharge (ISRS) revenues related to customer billings recorded during the period under a disputed ISRS filing, along with a $0.6 provision for interest due on all ISRS revenues in dispute. The after-tax impact of these provisions reduced net income for the six months ended March 31, 2020, by $3.7, which was excluded for the net economic earnings financial measure. As previously disclosed, these matters were settled by the end of fiscal 2020. In September 2020, Spire Missouri, the MoPSC staff and the OPC reached a Unanimous Stipulation and Agreement regarding Spire Missouri’s request for an Accounting Authority Order (AAO) pertaining to certain costs and lost customer fee revenue related to the COVID-19 pandemic. In October 2020, the MoPSC issued an order approving that agreement and granting an AAO effective through March 31, 2021. Accordingly, Spire Missouri recorded a net regulatory asset of $3.4 and $3.8 as of March 31, 2021, and September 30, 2020, respectively, related to the deferral of applicable costs and has tracked lost customer fee revenue. All ratemaking treatment of the deferrals and any revenue recoveries is reserved for consideration in Spire Missouri’s ongoing general rate case. On December 11, 2020, Spire Missouri filed a general rate case with the MoPSC that includes new proposed rates for its service areas. The case proposes an increase in base rates, reflecting recovery of system investments and operating costs necessary to maintain the safety and reliability of its natural gas distribution systems as well as to support enhancements to customer service. The request, if approved, represents a net base rate increase of $64.2. Spire Missouri is already recovering $47.3 from customers through the ISRS, resulting in a total base rate increase request of $111.5. The ISRS cap would then be reset in order to continue the timely recovery of the investment in pipeline upgrades. The proposed rates are calculated on a filed rate base of $2,780 based on the end of fiscal year 2020, reflecting the significant investment made in infrastructure upgrades and other systems. Among other things, the filing changes rate design, proposes new customer programs, and aligns the tariffs of the company’s service areas. The filing assumes a common equity ratio of 54.25% and a 9.95% return on equity. Management anticipates that certain measures, such as rate base, capital structure and operating costs will be updated through May 31, 2021. In accordance with Missouri law, the MoPSC has up to 11 months to consider this filing. Direct testimony of other parties is due to be filed in May 2021, local public hearings will take place June 21–25, 2021, and evidentiary hearings are scheduled for late July and early August 2021. In mid-February 2021, the central U.S. experienced a period of unusually severe cold weather, and Spire Missouri implemented an Operational Flow Order (OFO) to preserve the integrity of its distribution system. During this time, Spire Missouri was required to purchase additional natural gas supply, both to ensure adequate supply for its firm utility customers, and to cover the shortfall created when third-party marketers failed to deliver natural gas supply to its city gates on behalf of their customers. In accordance with its tariffs, Spire Missouri invoiced the cost of gas and associated penalties totaling $195.8 to non-compliant marketers pursuant to the MoPSC-approved OFO tariff. Recoveries collected will be an offset to cost of natural gas for firm utility customers through the Purchased Gas Adjustment (PGA) and Actual Cost Adjustment. The three largest counterparties did not remit payment when due, so Spire Missouri filed suit against them in federal court to recover the invoiced amounts. The marketers have filed complaints with the MoPSC requesting review of the transactions between them and Spire; at this time, the Company has no reason to believe the MoPSC will not follow the tariff and has determined collection is probable. The MoPSC has also opened a working case to investigate the effects of the February cold weather event on all Missouri utilities. Spire Missouri is not subject to any upstream OFO penalties on any interstate pipelines. Spire Missouri is able to sell excess natural gas supply and capacity to third parties off system, resulting in significant savings to its firm utility customers through the gas incentive mechanisms of its PGA. Spire Missouri normally retains 25% and passes 75% through to its customers. During the February cold weather event, Spire Missouri had an unusually large off-system sale resulting in $100.0 of incremental gross revenue. Due to the nature and magnitude of this particular transaction, Spire Missouri anticipates distributing all or a portion of its usual 25% share to customers and plans to work with the MoPSC and community partners over the rest of the fiscal year to determine the method and timing. Accordingly, a $25.0 regulatory liability has been recorded, with a corresponding reduction in revenue. Spire Missouri’s net deferred gas costs and average inventory cost in the quarter increased by approximately $110 primarily due to the February weather event, including projected offsets of off-system sales and tariff-based OFO penalties. In August 2018, the Federal Energy Regulatory Commission (FERC) approved an order issuing a Certificate of Public Convenience and Necessity for the Spire STL Pipeline (“August 2018 Order”), and in November 2018, the FERC issued a Notice to Proceed, allowing construction to begin. In November 2019, Spire STL Pipeline received FERC authorization to place the pipeline into service. Also, in November 2019, the FERC issued an Order on Rehearing of the August 2018 Order dismissing or denying the outstanding requests for rehearing filed by several parties, dismissing the request for stay filed by one party, and noting the withdrawal of the request for rehearing by another party. On January 21, 2020, two of the rehearing parties filed petitions for review of the FERC’s orders with the U.S. Court of Appeals for the District of Columbia Circuit. Spire STL Pipeline and Spire Missouri have intervened and filed responsive briefs in this proceeding, which remains pending. On October 9, 2020, Spire Storage filed with the FERC an Abbreviated Application for an Amendment of Certificate of Public Convenience and Necessity, Reaffirmation of Market-Based Rate Authority, and Related Authorizations pursuant to Section 7(c) of the Natural Gas Act. The application, which requests authorization to expand capacity and increase pipeline connectivity at certain of Spire Storage’s natural gas storage facilities in Wyoming, remains pending.

Financing

Financing	6 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Financing	5. FINANCING Short-term Spire, Spire Missouri and Spire Alabama have a syndicated revolving credit facility pursuant to a loan agreement with 11 banks, expiring October 31, 2023. The loan agreement has an aggregate credit commitment of $975.0, including sublimits of $300.0 for Spire, $475.0 for Spire Missouri, and $200.0 for Spire Alabama. These sublimits may be reallocated from time to time among the three borrowers within the $975.0 aggregate commitment, with commitments fees applied for each borrower relative to its credit rating. Spire may use its line to provide for the funding needs of various subsidiaries. The agreement also contains financial covenants limiting each borrower’s consolidated total debt, including short-term debt, to no more than 70% of its total capitalization. As defined in the line of credit, on March 31, 2021, total debt was less than 60% of total capitalization for each borrower. Spire has a commercial paper program (“CP Program”) pursuant to which Spire may issue short-term, unsecured commercial paper notes. Amounts available under the CP Program may be borrowed, repaid and re-borrowed from time to time, with the aggregate face or principal amount of the notes outstanding under the CP Program at any time not to exceed $975.0. The notes may have maturities of up to 365 days from date of issue. On March 26, 2020, Spire entered into a loan agreement with two banks providing for a term loan of $150.0, which was immediately fully funded. It was repaid on December 16, 2020. The term loan bore interest at the LIBOR Rate (as defined in the loan agreement) plus 0.85% per annum. On March 23, 2021, Spire Missouri entered into a loan agreement with several banks for a $250.0, 364-day unsecured term loan with an interest rate based on LIBOR plus 65 basis points. The loan carries no prepayment penalty and has the same covenants as the revolving credit facility. Information about Spire’s consolidated short-term borrowings and about Spire Missouri’s and Spire Alabama’s borrowings from Spire is presented in the following table. As of March 31, 2021, $398.1 of Spire’s short-term borrowings were used to support lending to the Utilities. Spire (Parent Only) Spire Missouri Spire Alabama Spire Credit Term CP Credit Term Spire Credit Spire Consol- Facility Loan Program Facility Loan Note Facility Note idated Six Months Ended March 31, 2021 Weighted average borrowings $ — $ 63.5 $ 606.9 $ — $ 11.0 $ 360.8 $ — $ 59.6 $ 681.4 Lowest borrowings outstanding — — 403.5 — — 277.2 — — 455.5 Highest borrowings outstanding — 150.0 775.0 — 250.0 441.9 — 152.2 850.5 Weighted average interest rate n/a 1.1 % 0.3 % n/a 0.8 % 0.3 % n/a 0.2 % 0.4 % As of March 31, 2021 Borrowings outstanding $ — $ — $ 403.5 $ — $ 250.0 $ 369.4 $ — $ — $ 653.5 Weighted average interest rate n/a n/a 0.2 % n/a 0.8 % 0.2 % n/a n/a 0.4 % As of September 30, 2020 Borrowings outstanding $ — $ 150.0 $ 498.0 $ — $ — $ 301.2 $ — $ 121.3 $ 648.0 Weighted average interest rate n/a 1.1 % 0.2 % n/a n/a 0.2 % n/a 0.2 % 0.6 % As of March 31, 2020 Borrowings outstanding $ — $ 150.0 $ 175.5 $ 185.1 $ — $ 39.6 $ 50.0 $ 33.0 $ 560.6 Weighted average interest rate n/a 2.1 % 1.8 % 1.8 % n/a 1.9 % 1.9 % 1.9 % 1.9 % Long-term Debt The long-term debt agreements of Spire, Spire Missouri and Spire Alabama contain customary financial covenants and default provisions. As of March 31, 2021, there were no events of default under these financial covenants. Interest expense shown on Spire’s consolidated statements of income and Spire Missouri’s statements of comprehensive income is net of the capitalized interest amounts shown in the following table. Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire $ 1.1 $ 1.4 $ 2.0 $ 3.6 Spire Missouri 0.1 0.3 0.1 0.6 Spire Alabama 0.7 0.4 1.3 1.0 On December 15, 2020, Spire Alabama issued and sold to certain institutional investors in a private placement $150.0 of 2.04% Series 2020 Senior Notes due December 15, 2030. Interest is payable semi-annually. The notes are senior unsecured obligations of Spire Alabama and rank equal in right to payment with all its other senior unsecured indebtedness. Spire Alabama used the proceeds to repay short-term debt. In February 2021, Spire issued $175.0 of 2021 Series A 0.75% Remarketable Senior Notes as part of the equity units described in the next section. Equity Units In February 2021, Spire issued 3.5 million equity units, initially in the form of Corporate Units, for an aggregate stated amount of $175.0, resulting in net proceeds (after underwriting fees and other issuance costs) of $169.3. Each “Corporate Unit” has a stated amount of fifty dollars fifty dollars If the applicable market value * of Spire common stock is: Number of shares to be purchased per 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 trading days before settlement. If a holder elects to settle purchase contracts early, the holder would pay fifty dollars per unit and receive 0.6354 shares per unit. The Company will make 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. The Company has 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 had an effect on diluted EPS. 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-party investors. Following any successful remarketing of the RSNs, the interest rate on the RSNs will be reset, interest will be payable on a semi-annual basis, and Spire will cease to have the option to redeem the RSNs, other than in connection with the occurrence or continuance of certain special events.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	6. FAIR VALUE OF FINANCIAL INSTRUMENTS The carrying amounts of cash and cash equivalents, notes receivable, and short-term debt approximate fair value due to the short maturity of these instruments. The fair values of long-term debt are estimated based on market prices for similar issues. Refer to Note 7 , Fair Value Measurements, for information on financial instruments measured at fair value on a recurring basis. The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis are shown in the following tables, classified according to the fair value hierarchy. There were no such instruments classified as Level 3 (significant unobservable inputs) as of March 31, 2021, September 30, 2020, and March 31, 2020. Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Spire As of March 31, 2021 Cash and cash equivalents $ 104.0 $ 104.0 $ 104.0 $ — Notes payable 653.5 653.5 — 653.5 Long-term debt, including current portion 2,803.3 3,090.9 — 3,090.9 As of September 30, 2020 Cash and cash equivalents $ 4.1 $ 4.1 $ 4.1 $ — Notes payable 648.0 648.0 — 648.0 Long-term debt, including current portion 2,484.1 2,908.6 — 2,908.6 As of March 31, 2020 Cash and cash equivalents $ 108.4 $ 108.4 $ 108.4 $ — Notes payable 560.6 560.6 — 560.6 Long-term debt, including current portion 2,490.2 2,671.0 — 2,671.0 Spire Missouri As of March 31, 2021 Notes payable $ 250.0 $ 250.0 $ — $ 250.0 Notes payable – associated companies 369.4 369.4 — 369.4 Long-term debt 1,092.4 1,254.2 — 1,254.2 As of September 30, 2020 Notes payable – $ 301.2 $ 301.2 $ — $ 301.2 Long-term debt 1,092.0 1,313.5 — 1,313.5 As of March 31, 2020 Cash and cash equivalents $ 5.1 $ 5.1 $ 5.1 $ — Notes payable 185.1 185.1 — 185.1 Notes payable – 39.6 39.6 — 39.6 Long-term debt 1,098.7 1,231.2 — 1,231.2 Spire Alabama As of March 31, 2021 Cash and cash equivalents $ 18.2 $ 18.2 $ 18.2 $ — Notes receivable – associated companies 20.0 20.0 — 20.0 Long-term debt, including current portion 621.1 682.3 — 682.3 As of September 30, 2020 Notes payable – $ 121.3 $ 121.3 $ — $ 121.3 Long-term debt, including current portion 471.8 576.9 — 576.9 As of March 31, 2020 Cash and cash equivalents $ 0.1 $ 0.1 $ 0.1 $ — Notes payable 50.0 50.0 — 50.0 Notes payable – 33.0 33.0 — 33.0 Long-term debt 471.7 535.1 — 535.1

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. FAIR VALUE MEASUREMENTS 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 are valued based on exchange-quoted market prices of individual securities. Derivative instruments included in Level 1 are valued using quoted market prices on the New York Mercantile Exchange (NYMEX) or the Intercontinental Exchange (ICE). Derivative instruments classified in Level 2 include physical commodity derivatives that are valued using broker or dealer quotation services whose prices are derived principally from, or are corroborated by, observable market inputs. Also included in Level 2 are certain derivative instruments that have values that are similar to, and correlate with, quoted prices for exchange-traded instruments in active markets. Derivative instruments included in Level 3 are valued using generally unobservable inputs that are based upon the best information available and reflect management’s assumptions about how market participants would price the asset or liability. There were no Level 3 balances as of March 31, 2021, and those Level 3 balances at September 30, 2020, and March 31, 2020, consisted of gas commodity contracts. The Company’s and the Utilities’ policy is to recognize transfers between the levels of the fair value hierarchy, if any, as of the beginning of the interim reporting period in which circumstances change or events occur to cause the transfer. 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. Derivative assets and liabilities, including receivables and payables associated with cash margin requirements, are presented net in the balance sheets when a legally enforceable netting agreement exists between the Company, Spire Missouri, or Spire Alabama and the counterparty to a derivative contract. Spire Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of March 31, 2021 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 23.5 $ — $ — $ — $ 23.5 NYMEX/ICE natural gas contracts 0.4 — — (0.4 ) — Gasoline and heating oil contracts 0.3 — — (0.3 ) — Gas Marketing: NYMEX/ICE natural gas contracts — 15.1 — (12.3 ) 2.8 Natural gas commodity contracts — 9.3 — — 9.3 Other: U.S. stock/bond mutual funds 22.9 — — — 22.9 Interest rate swaps — 27.9 — — 27.9 Total $ 47.1 $ 52.3 $ — $ (13.0 ) $ 86.4 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 1.8 $ — $ — $ (1.8 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts — 4.7 — (4.7 ) — Natural gas commodity contracts — 24.5 — — 24.5 Other: Interest rate swaps — 21.4 — — 21.4 Total $ 1.8 $ 50.6 $ — $ (6.5 ) $ 45.9 Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of September 30, 2020 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 21.9 $ — $ — $ — $ 21.9 NYMEX/ICE natural gas contracts 6.3 — — (6.3 ) — Gasoline and heating oil contracts 0.3 — — (0.3 ) — Gas Marketing: NYMEX/ICE natural gas contracts — 27.7 — (25.4 ) 2.3 Natural gas commodity contracts — 14.5 0.4 — 14.9 Other: U.S. stock/bond mutual funds 18.6 — — — 18.6 Total $ 47.1 $ 42.2 $ 0.4 $ (32.0 ) $ 57.7 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 0.9 $ — $ — $ (0.9 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts 0.7 21.4 — (22.1 ) — Natural gas commodity contracts — 22.3 — — 22.3 Other: Interest rate swaps — 54.2 — — 54.2 Total $ 1.6 $ 97.9 $ — $ (23.0 ) $ 76.5 As of March 31, 2020 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 18.1 $ — $ — $ — $ 18.1 NYMEX/ICE natural gas contracts 0.1 — — (0.1 ) — Gas Marketing: NYMEX/ICE natural gas contracts 0.2 6.8 — (7.0 ) — Natural gas commodity contracts — 17.5 — (4.8 ) 12.7 Other: U.S. stock/bond mutual funds 17.6 — — — 17.6 Total $ 36.0 $ 24.3 $ — $ (11.9 ) $ 48.4 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 12.2 $ — $ — $ (12.2 ) $ — Gasoline and heating oil contracts 0.4 — — (0.4 ) — Gas Marketing: NYMEX/ICE natural gas contracts 0.5 8.4 — (8.9 ) — Natural gas commodity contracts — 27.7 1.1 (4.8 ) 24.0 Other: Interest rate swaps — 66.9 — — 66.9 Total $ 13.1 $ 103.0 $ 1.1 $ (26.3 ) $ 90.9 Spire Missouri Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of March 31, 2021 ASSETS U.S. stock/bond mutual funds $ 23.5 $ — $ — $ — $ 23.5 NYMEX/ICE natural gas contracts 0.4 — — (0.4 ) — Gasoline and heating oil contracts 0.3 — — (0.3 ) — Total $ 24.2 $ — $ — $ (0.7 ) $ 23.5 LIABILITIES NYMEX/ICE natural gas contracts $ 1.8 $ — $ — $ (1.8 ) $ — As of September 30, 2020 ASSETS U.S. stock/bond mutual funds $ 21.9 $ — $ — $ — $ 21.9 NYMEX/ICE natural gas contracts 6.3 — — (6.3 ) — Gasoline and heating oil contracts 0.3 — — (0.3 ) — Total $ 28.5 $ — $ — $ (6.6 ) $ 21.9 LIABILITIES NYMEX/ICE natural gas contracts $ 0.9 $ — $ — $ (0.9 ) $ — As of March 31, 2020 ASSETS U.S. stock/bond mutual funds $ 18.1 $ — $ — $ — $ 18.1 NYMEX/ICE natural gas contracts 0.1 — — (0.1 ) — Total $ 18.2 $ — $ — $ (0.1 ) $ 18.1 LIABILITIES NYMEX/ICE natural gas contracts $ 12.2 $ — $ — $ (12.2 ) $ — Gasoline and heating oil contracts 0.4 — — (0.4 ) — Total $ 12.6 $ — $ — $ (12.6 ) $ —

Pension Plans and Other Postret

Pension Plans and Other Postretirement Benefits	6 Months Ended
	Mar. 31, 2021
Compensation And Retirement Disclosure [Abstract]
Pension Plans and Other Postretirement Benefits	8. PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS Pension Plans Spire and the Utilities maintain pension plans for their employees. Spire Missouri has non-contributory, defined benefit, trusteed forms of pension plans covering the majority of its employees. Plan assets consist primarily of corporate and U.S. government obligations and a growth segment consisting of exposure to equity markets, commodities, real estate and inflation-indexed securities, achieved through derivative instruments. Spire Alabama has non-contributory, defined benefit, trusteed forms of pension plans covering the majority of its 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 tables. The components other than the service costs and regulatory adjustment are presented in “Other Income (Expense), 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 (Expense), Net.” Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Service cost – benefits earned during the period $ 5.3 $ 5.6 $ 10.9 $ 11.1 Interest cost on projected benefit obligation 4.6 5.8 9.8 11.7 Expected return on plan assets (7.1 ) (9.0 ) (15.1 ) (18.2 ) Amortization of prior service credit (0.7 ) (0.6 ) (1.5 ) (1.2 ) Amortization of actuarial loss 3.8 3.9 7.8 7.6 Loss on lump-sum settlements 3.8 21.0 3.8 21.0 Subtotal 9.7 26.7 15.7 32.0 Regulatory adjustment 5.2 (11.3 ) 14.8 (1.7 ) Net pension cost $ 14.9 $ 15.4 $ 30.5 $ 30.3 Spire Missouri Service cost – benefits earned during the period $ 3.9 $ 3.9 $ 7.8 $ 7.7 Interest cost on projected benefit obligation 3.5 4.0 7.0 8.2 Expected return on plan assets (5.6 ) (6.3 ) (11.2 ) (12.9 ) Amortization of prior service (credit) cost (0.1 ) 0.1 (0.3 ) 0.1 Amortization of actuarial loss 2.8 3.1 5.7 6.0 Loss on lump-sum settlements — 21.0 — 21.0 Subtotal 4.5 25.8 9.0 30.1 Regulatory adjustment 7.5 (13.2 ) 15.1 (5.5 ) Net pension cost $ 12.0 $ 12.6 $ 24.1 $ 24.6 Spire Alabama Service cost – benefits earned during the period $ 1.4 $ 1.5 $ 2.9 $ 3.0 Interest cost on projected benefit obligation 1.2 1.3 2.4 2.5 Expected return on plan assets (1.5 ) (1.8 ) (3.1 ) (3.5 ) Amortization of prior service credit (0.6 ) (0.6 ) (1.2 ) (1.2 ) Amortization of actuarial loss 1.0 0.8 2.1 1.6 Loss on lump-sum settlements 3.8 — 3.8 — Subtotal 5.3 1.2 6.9 2.4 Regulatory adjustment (2.5 ) 1.7 (0.7 ) 3.4 Net pension cost $ 2.8 $ 2.9 $ 6.2 $ 5.8 Pursuant to the provisions of Spire Missouri’s and Spire Alabama’s pension plans, pension obligations may be satisfied by monthly annuities, lump-sum cash payments, or special termination benefits. Lump-sum payments are recognized as settlements (which can result in gains or losses) only if the total of such payments exceeds the sum of service and interest costs in a specific year. Special termination benefits, when offered, are also recognized as settlements which can result in Alabama plan met the criteria for settlement recognition. The lump-sum payments recognized as settlements for the remeasurement were $12.9. The lump-sum settlement resulted in a loss of $3.8. For the remeasurement, the discount rate for the Alabama plan was updated to 3.2% from 2.95% at September 30, 2020. The Alabama regulatory tariff requires that settlement losses be amortized over the remaining actuarial life of the individuals in the plan— in this case, 11.4 years. Therefore, no lump sum settlement expense was recorded in the period ended March 31, 2021. In the quarter ended March 31, 2020, two Spire Missouri plans met the criteria for settlement recognition. The lump-sum payments recognized as settlements for the remeasurement were $59.1. The lump-sum settlement resulted in a loss of $21.0. For the remeasurements, the discount rates for the Missouri plans were updated to 2.85% from 3.2% at September 30, 2019. The funding policy of the Utilities is to contribute an amount not less than the minimum required by government funding standards, nor more than the maximum deductible amount for federal income tax purposes. Fiscal 2021 contributions to Spire Missouri’s pension plans through March 31, 2021 were $28.3 to the qualified trusts and none to non-qualified plans. There were $4.5 of fiscal 2021 contributions to the Spire Alabama pension plans through March 31, 2021. Contributions to the qualified trusts of Spire Missouri’s pension plans for the remainder of fiscal 2021 are anticipated to be $13.7. Contributions to Spire Alabama’s pension plans for the remainder of fiscal 2021 are anticipated to be $6.6. 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. For retirements prior to January 1, 2015, certain Spire Missouri plans provided medical insurance after retirement until death. The Spire Alabama plans provide medical insurance upon retirement until death for certain retirees depending on the type of employee and the date the employee was originally hired. The net periodic postretirement benefit cost includes components shown in the following tables. The components other than the service costs and regulatory adjustment are presented in “Other Income (Expense), Net” in the income statement, except in the event Spire Alabama incurs losses on lump-sum settlements. Any 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 (Expense), Net.” Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Service cost – benefits earned during the period $ 1.9 $ 1.5 $ 3.7 $ 2.9 Interest cost on accumulated postretirement benefit obligation 1.6 1.5 3.0 3.1 Expected return on plan assets (4.1 ) (4.1 ) (8.1 ) (8.2 ) Amortization of prior service cost (credit) 0.2 (0.1 ) 0.5 (0.3 ) Amortization of actuarial gain (0.4 ) (0.5 ) (0.8 ) (1.0 ) Subtotal (0.8 ) (1.7 ) (1.7 ) (3.5 ) Regulatory adjustment 3.2 4.0 6.6 8.0 Net postretirement benefit cost $ 2.4 $ 2.3 $ 4.9 $ 4.5 Spire Missouri Service cost – benefits earned during the period $ 1.5 $ 1.3 $ 3.1 $ 2.6 Interest cost on accumulated postretirement benefit obligation 1.1 1.1 2.2 2.3 Expected return on plan assets (2.8 ) (2.9 ) (5.5 ) (5.7 ) Amortization of prior service cost (credit) 0.2 — 0.4 (0.1 ) Amortization of actuarial gain (0.3 ) (0.5 ) (0.7 ) (1.0 ) Subtotal (0.3 ) (1.0 ) (0.5 ) (1.9 ) Regulatory adjustment 3.7 4.5 7.5 8.9 Net postretirement benefit cost $ 3.4 $ 3.5 $ 7.0 $ 7.0 Spire Alabama Service cost – benefits earned during the period $ 0.3 $ 0.1 $ 0.5 $ 0.2 Interest cost on accumulated postretirement benefit obligation 0.4 0.4 0.7 0.7 Expected return on plan assets (1.3 ) (1.2 ) (2.5 ) (2.4 ) Amortization of prior service (credit) cost — (0.1 ) 0.1 (0.2 ) Subtotal (0.6 ) (0.8 ) (1.2 ) (1.7 ) Regulatory adjustment (0.5 ) (0.5 ) (0.9 ) (0.9 ) Net postretirement benefit income $ (1.1 ) $ (1.3 ) $ (2.1 ) $ (2.6 ) 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 (VEBA) and Rabbi Trusts as external funding mechanisms. The assets of the VEBA and Rabbi Trusts consist primarily of money market securities and mutual funds invested in stocks and bonds. 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. There have been no

Information by Operating Segmen

Information by Operating Segment	6 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Information by Operating Segment	9. INFORMATION BY OPERATING SEGMENT The Company has two reportable segments: Gas Utility and Gas Marketing. The Gas Utility segment is the aggregation of the operations of the Utilities. The Gas Marketing segment includes the results of Spire Marketing, a subsidiary engaged in the non-regulated marketing of natural gas and related activities, including utilizing natural gas storage contracts for providing natural gas sales. Other components of the Company’s consolidated information include: • unallocated corporate items, including certain debt and associated interest costs; • Spire STL Pipeline, a subsidiary of Spire providing interstate natural gas pipeline transportation services; • Spire Storage, a subsidiary of Spire providing interstate natural gas storage services; and • Spire’s subsidiaries engaged in the operation of a propane pipeline, the compression of natural gas, and risk management, among other activities. Accounting policies are described in Note 1 , Summary of Significant Accounting Policies. Intersegment transactions include sales of natural gas from Spire Marketing to Spire Missouri, Spire Alabama and Spire Storage, sales of natural gas from Spire Missouri and Spire Alabama to Spire Marketing, propane transportation services provided by Spire NGL Inc. to Spire Missouri, and propane storage services provided by Spire Missouri to Spire NGL Inc. Management evaluates the performance of the operating segments based on the computation of net economic earnings. Net economic earnings exclude from reported net income 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 impairments and other non-recurring or unusual items such as certain regulatory, legislative, or GAAP standard-setting actions. Gas Utility Gas Marketing Other Eliminations Consolidated Three Months Ended March 31, 2021 Operating Revenues: Revenues from external customers $ 1,053.0 $ 47.4 $ 4.5 $ — $ 1,104.9 Intersegment revenues 0.1 (14.0 ) 11.1 2.8 — Total Operating Revenues 1,053.1 33.4 15.6 2.8 1,104.9 Operating Expenses: Natural gas 619.2 (6.2 ) 0.1 6.0 619.1 Operation and maintenance 104.0 7.1 11.1 (3.2 ) 119.0 Depreciation and amortization 49.5 0.3 1.7 — 51.5 Taxes, other than income taxes 56.4 0.5 1.0 — 57.9 Total Operating Expenses 829.1 1.7 13.9 2.8 847.5 Operating Income $ 224.0 $ 31.7 $ 1.7 $ — $ 257.4 Net Economic Earnings (Loss) $ 159.7 $ 39.8 $ (3.9 ) $ — $ 195.6 Gas Utility Gas Marketing Other Eliminations Consolidated Three Months Ended March 31, 2020 Operating Revenues: Revenues from external customers $ 679.1 $ 33.3 $ 3.1 $ — $ 715.5 Intersegment revenues (0.1 ) — 11.6 (11.5 ) — Total Operating Revenues 679.0 33.3 14.7 (11.5 ) 715.5 Operating Expenses: Natural gas 271.6 33.6 0.1 (8.2 ) 297.1 Operation and maintenance 95.8 3.6 9.6 (3.3 ) 105.7 Depreciation and amortization 47.0 0.1 2.1 — 49.2 Taxes, other than income taxes 51.7 0.4 0.9 — 53.0 Total Operating Expenses 466.1 37.7 12.7 (11.5 ) 505.0 Operating Income $ 212.9 $ (4.4 ) $ 2.0 $ — $ 210.5 Net Economic Earnings (Loss) $ 144.3 $ 5.1 $ (5.4 ) $ — $ 144.0 Gas Utility Gas Marketing Other Eliminations Consolidated Six Months Ended March 31, 2021 Operating Revenues: Revenues from external customers $ 1,550.2 $ 58.1 $ 9.2 $ — $ 1,617.5 Intersegment revenues 1.1 0.1 23.1 (24.3 ) — Total Operating Revenues 1,551.3 58.2 32.3 (24.3 ) 1,617.5 Operating Expenses: Natural gas 823.5 (5.5 ) 0.1 (17.8 ) 800.3 Operation and maintenance 207.0 10.4 19.7 (6.5 ) 230.6 Depreciation and amortization 98.1 0.6 3.6 — 102.3 Taxes, other than income taxes 91.9 0.7 1.4 — 94.0 Total Operating Expenses 1,220.5 6.2 24.8 (24.3 ) 1,227.2 Operating Income $ 330.8 $ 52.0 $ 7.5 $ — $ 390.3 Net Economic Earnings (Loss) $ 236.1 $ 43.1 $ (6.7 ) $ — $ 272.5 Gas Utility Gas Marketing Other Eliminations Consolidated Six Months Ended March 31, 2020 Operating Revenues: Revenues from external customers $ 1,209.7 $ 65.6 $ 7.1 $ — $ 1,282.4 Intersegment revenues — — 18.7 (18.7 ) — Total Operating Revenues 1,209.7 65.6 25.8 (18.7 ) 1,282.4 Operating Expenses: Natural gas 513.1 58.1 0.2 (12.4 ) 559.0 Operation and maintenance 204.4 6.7 17.5 (6.3 ) 222.3 Depreciation and amortization 93.4 0.1 3.2 — 96.7 Taxes, other than income taxes 89.6 0.7 1.3 — 91.6 Total Operating Expenses 900.5 65.6 22.2 (18.7 ) 969.6 Operating Income $ 309.2 $ — $ 3.6 $ — $ 312.8 Net Economic Earnings (Loss) $ 213.4 $ 11.2 $ (8.8 ) $ — $ 215.8 The following table reconciles the Company’s net economic earnings to net income. For information about the Missouri regulatory adjustment for $9.0 of pension costs in fiscal 2021 and the provision for ISRS rulings in fiscal 2020, see Note 4 , Regulatory Matters. Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Net Income $ 187.4 $ 133.6 $ 276.3 $ 200.6 Adjustments, pre-tax: Missouri regulatory adjustment (9.0 ) — (9.0 ) — Provision for ISRS rulings — 2.2 — 4.8 Fair value and timing adjustments 20.1 11.6 4.1 15.3 Income tax effect of adjustments (2.9 ) (3.4 ) 1.1 (4.9 ) Net Economic Earnings $ 195.6 $ 144.0 $ 272.5 $ 215.8 The Company’s total assets by segment were as follows: March 31, September 30, March 31, 2021 2020 2020 Total Assets: Gas Utility $ 7,265.0 $ 6,716.2 $ 6,311.6 Gas Marketing 341.0 182.7 159.3 Other 2,513.7 2,443.5 2,214.7 Eliminations (1,182.9 ) (1,101.2 ) (667.6 ) Total Assets $ 8,936.8 $ 8,241.2 $ 8,018.0

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. COMMITMENTS AND CONTINGENCIES Commitments The Company and the Utilities have entered into contracts with various counterparties, expiring on dates through 2039, for the storage, transportation, and supply of natural gas. Minimum payments required under the contracts in place at March 31, 2021, are estimated at $1,632.2, $1,264.6, and $244.7 for the Company, Spire Missouri, and Spire Alabama, respectively. Additional contracts are generally entered into prior to or during the heating season of November through April. The Utilities recover their costs from customers in accordance with their PGA clauses or GSA riders. 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 have a material effect on the statements of income, balance sheets, and statements of cash flows of the Company, Spire Missouri, or Spire Alabama. However, there is uncertainty in the valuation of pending claims and prediction of litigation results. 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 materially affected the Company’s or Utilities’ financial position and results of operations. As environmental laws, regulations, and their interpretations change, the Company or the Utilities may incur additional environmental liabilities that may result in additional costs, which may be material. 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 been material. However, the amount of costs relative to future remedial actions at these and other sites is unknown and may be material. The actual future costs that Spire Missouri and Spire Alabama may incur could be materially higher or lower depending upon several factors, including whether remediation will be required, final selection and regulatory approval of any remedial actions, changing technologies and government regulations, the ultimate ability of other PRPs to pay, and any insurance recoveries. In 2020, Spire retained an outside consultant to conduct probabilistic cost modeling of its former MGP sites in Missouri and Alabama. The purpose of this analysis was to develop an estimated range of probabilistic future liability for each of their MGP sites. That analysis, completed in March 2021, provided a range of demonstrated possible future expenditures to investigate, monitor and remediate the former MGP sites. Spire Missouri and Spire Alabama have recorded their best estimates of the probable expenditures that relate to these matters. The amount remains immaterial, and Spire Missouri, Spire Alabama and the Company do not expect potential liabilities that may arise from remediating these sites to have a material impact on their future financial condition or results of operations. Spire Missouri Spire Missouri has identified three former MGP sites in the city of St. Louis, Missouri (the “City”) where costs have been incurred and claims have been asserted. Spire Missouri has enrolled two of the sites in the Missouri Department of Natural Resources (MDNR) Brownfields/Voluntary Cleanup Program (BVCP). The third site is the result of a relatively new claim assertion by the United States Environmental Protection Agency (EPA). In conjunction with redevelopment of one of the sites, 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 of the City agencies and the environmental consultant to remediate the site and obtain a No Further Action letter from the MDNR. The Remediation Agreement also provides for a release of Spire Missouri and the other former site owner from certain liabilities related to the past and current environmental condition of the site and requires the developer and the environmental consultant to maintain certain insurance coverage, including remediation cost containment, premises pollution liability, and professional liability. The operative provisions of the Remediation Agreement were triggered on December 20, 2010, on which date Spire Missouri and the other former site owner, as full consideration under the Remediation Agreement, paid a small percentage of the cost of remediation of the site. Spire Missouri has not owned the second site for many years. In a letter dated June 29, 2011, the Attorney General for the State of Missouri informed Spire Missouri that the MDNR had completed an investigation of the site. The Attorney General requested that Spire Missouri participate in the follow up investigations of the site. In a letter dated January 10, 2012, Spire Missouri stated that it would participate in future environmental response activities at the site in conjunction with other PRPs that are willing to contribute to such efforts in a meaningful and equitable fashion. Accordingly, Spire Missouri entered into a cost sharing agreement for remedial investigation with other PRPs. To date, MDNR has not approved the agreement, so remedial investigation has not yet occurred. Additionally, in correspondence dated November 30, 2016, Region 7 of the EPA has asserted that Spire Missouri is liable under Section 107(a) of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) for alleged coal gas waste contamination at a third site in the northern portion of the City on which Spire Missouri operated a MGP. Spire Missouri has not owned or operated the site (also known as Station “B”) for over 70 years. Spire Missouri and the site owner have met with the EPA and reviewed its assertions. Both Spire Missouri and the site owner have notified the EPA that information and data provided by the EPA to date does not rise to the level of documenting a threat to the public health or environment. As such, Spire Missouri requested more information from the EPA, some of which would also be utilized to identify other former owners and operators of the site that could be added as PRPs. To date, Spire Missouri has not received a response from the EPA. 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, Spire Missouri received a Section 104(e) information request under CERCLA from EPA Region 7 regarding the former Thompson Chemical/Superior Solvents site in the City. In turn, Spire Missouri issued a Freedom of Information Act (FOIA) request to the EPA on April 3, 2015, in an effort to identify the basis of the inquiry. The FOIA response from the EPA was received on July 15, 2015, and a response was provided to the EPA on August 15, 2015. Spire Missouri has received no further inquiry from the EPA regarding this matter. In its western service area, Spire Missouri has six owned MGP sites enrolled in the BVCP, including Joplin MGP #1, St. Joseph MGP #1, Kansas City Coal Gas Station B, Kansas City Station A Railroad area, Kansas City Coal Gas Station A, and Independence MGP #2. Source removal has been conducted at all of the owned sites since 2003 with the exception of Joplin. On September 15, 2016, a request was made with the MDNR for a restrictive covenant use limitation with respect to Joplin. Remediation efforts at the six sites are at various stages of completion, ranging from groundwater monitoring and sampling following source removal activities to the aforementioned request in respect to Joplin. As part of its participation in the BVCP, Spire Missouri communicates regularly with the MDNR with respect to its remediation efforts and monitoring activities at these sites. On May 11, 2015, MDNR approved the next phase of investigation at the Kansas City Station A and Railroad areas. Spire Alabama Spire Alabama is in the chain of title of nine former MGP sites, four of which it still owns, and five former manufactured gas distribution sites, one of which it still owns. In 2012, Spire Alabama responded to an EPA Request for Information Pursuant to Section 104 of CERCLA relating to the 35th Avenue Superfund Site located in North Birmingham, Jefferson County, Alabama. Spire Alabama was identified as a PRP under CERCLA for the cleanup of the site or costs the EPA incurs in cleaning up the site. At this point, Spire Alabama has not been provided information that would allow it to determine the extent, if any, of its potential liability with respect to the 35th Avenue Superfund Site and vigorously denies its inclusion as a PRP. 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 the February 2021 cold weather event. Numerous natural gas producers and midstream operators were unable to deliver natural gas to market as they experienced wellhead freeze-offs, power outages and equipment failure from the extreme weather. These events resulted in supply curtailments, and related notices of force majeure to excuse performance, from and to certain counterparties. Further, these events have made Spire Marketing subject to various commercial disputes (including regarding force majeure) and a regulatory dispute regarding tariff obligations as a shipper on an interstate pipeline. As such, Spire Marketing has recorded an estimate of potential liabilities for damages based on communications with counterparties to date and the facts and circumstances surrounding each transaction. It is expected that the estimate will change as new facts emerge or settlements are reached, and it is possible that final settlement amounts may materially differ from the current estimate. In February 2018, the Company was made aware of a complaint filed with the U.S. Department of Housing and Urban Development (HUD) by the South Alabama Center for Fair Housing and the National Community Reinvestment Coalition. The complaint alleged that Spire Gulf discriminated against unspecified residents of Eight Mile, Alabama, on the basis of race in violation of the Fair Housing Act by failing to adequately address the odorant release that occurred in 2008. On December 2, 2020, HUD issued a determination that found no reasonable cause exists that Spire Gulf discriminated against residents in Eight Mile, Alabama.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	BASIS OF PRESENTATION – These notes are an integral part of the accompanying unaudited financial statements of Spire Inc. (“Spire” or the “Company”) presented on a consolidated basis, Spire Missouri Inc. (“Spire Missouri”) and Spire Alabama Inc. (“Spire Alabama”). Spire Missouri and Spire Alabama are wholly owned subsidiaries of Spire. Spire Missouri, Spire Alabama and the subsidiaries of Spire EnergySouth Inc. (“Spire EnergySouth”) are collectively referred to as the “Utilities.” The subsidiaries of Spire EnergySouth are Spire Gulf Inc. and Spire Mississippi Inc. The accompanying unaudited financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information with the instructions to Form 10-Q and Rule 10-01 of Regulation S‑X. Accordingly, they do not include all the disclosures required for complete financial statements. In the opinion of management, the accompanying unaudited financial statements include all adjustments necessary for the fair presentation of the results of operations for the periods presented. This Form 10-Q should be read in conjunction with the Notes to Financial Statements contained in Spire’s, Spire Missouri’s and Spire Alabama’s combined Annual Report on Form 10-K for the fiscal year ended September 30, 2020. 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 been eliminated from their separate financial statements.
Regulated Operations	REGULATED OPERATIONS – The Utilities account for their regulated operations in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Topic 980, Regulated Operations . This topic sets forth the application of GAAP for those companies whose rates are established by or are subject to approval by an independent third-party regulator. The provisions of this accounting guidance require, among other things, that financial statements of a regulated enterprise reflect the actions of regulators, where appropriate. These actions may result in the recognition of revenues and expenses in time periods that are different than non-regulated enterprises. When this occurs, costs are deferred as assets in the balance sheet (regulatory assets) and recorded as expenses when those amounts are reflected in rates. In addition, regulators can impose liabilities upon a regulated company for amounts previously collected from customers and for recovery of costs that are expected to be incurred in the future (regulatory liabilities). Management believes that the current regulatory environment supports the continued use of these regulatory accounting principles and that all regulatory assets and regulatory liabilities are recoverable or refundable through the regulatory process. As authorized by the Missouri Public Service Commission (MoPSC), the Mississippi Public Service Commission (MSPSC) and the Alabama Public Service Commission (APSC), 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 liabilities related to the PGA clauses and the GSA riders are both labeled Unamortized Purchased Gas Adjustments herein. See additional information about regulatory assets and liabilities in Note 4 , Regulatory Matters.
Derivatives	DERIVATIVES – In the course of their business, certain subsidiaries of Spire enter into commitments associated with the purchase or sale of natural gas. Certain of their derivative natural gas contracts are designated as normal purchases or normal sales and, as such, are excluded from the scope of FASB ASC Topic 815, Derivatives and Hedging . Those contracts are accounted for as executory contracts and recorded on an accrual basis. Revenues and expenses from such contracts are recorded gross. Contracts not designated as normal purchases or normal sales are recorded as derivatives with changes in fair value recognized in earnings in the periods prior to physical delivery. Certain of Spire Marketing’s wholesale purchase and sale transactions are classified as trading activities for financial reporting purposes, with income and expenses presented on a net basis in natural gas expenses in the Condensed Consolidated Statements of Income.
Transactions with Affiliates	TRANSACTIONS WITH AFFILIATES – Transactions between affiliates of the Company have been eliminated from the consolidated financial statements of Spire. As reflected in their separate financial statements, Spire Missouri and Spire Alabama borrowed funds from the Company and incurred related interest, and in 2021, Spire Alabama lent excess funds to the Company and earned related interest. Spire Missouri and Spire Alabama also participated in normal intercompany shared services transactions. Spire Missouri’s and Spire Alabama’s other transactions with affiliates are presented below: Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Missouri Purchases of natural gas from Spire Marketing Inc. $ 57.6 $ 13.3 $ 68.3 $ 32.8 Transportation services received from Spire STL Pipeline LLC 7.9 7.9 16.0 11.8 Sales of natural gas to Spire Marketing Inc. — — 1.1 — Transportation services received from Spire NGL Inc. 0.2 0.2 0.5 0.5 Spire Alabama Purchases of natural gas from Spire Marketing Inc. $ 5.8 $ 1.0 $ 10.6 $ 4.3 Sales of natural gas to Spire Marketing Inc. 0.1 — 0.1 —
Accrued Capital Expenditures	ACCRUED CAPITAL EXPENDITURES – Accrued capital expenditures, shown in the following table, are excluded from capital expenditures in the statements of cash flows until paid. March 31, September 30, March 31, 2021 2020 2020 Spire $ 36.1 $ 67.6 $ 51.4 Spire Missouri 21.8 34.3 21.5 Spire Alabama 4.7 17.0 17.6
Accounts Receivable and Allowance For Credit Losses	ACCOUNTS RECEIVABLE AND ALLOWANCE FOR CREDIT LOSSES – Trade accounts receivable are recorded at the amounts due from customers, including unbilled amounts. Accounts receivable are written off when they are deemed to be uncollectible. An allowance for expected credit losses is estimated and updated based on relevant data and trends such as accounts receivable aging, historical write-off experience, current write-off trends, economic conditions, and the impact of weather and availability of customer payment assistance on collection trends. For the Utilities, net write-offs as a percentage of revenue has historically been the best predictor of base net write-off experience over time. Management judgment is applied in the development of the allowance due to the complexity of variables and subjective nature of certain relevant factors. For March 31, 2021, and September 30, 2020, the estimates for expected credit losses were increased as a result of considerations related to the outbreak of the novel coronavirus (COVID-19), including trends from previous economic downturns, the effects of moratoriums on gas service cutoffs, and the effects of slower-than-normal disconnection activity in general, offset by the amount subject to specific recovery under Missouri’s deferral order (see Note 4 , Regulatory Matters). The accounts receivable of Spire’s non-utility businesses are evaluated separately from those of the Utilities. The allowance for credit losses for those other businesses is based on a continuous evaluation of the individual counterparty risk and is not significant for the periods presented. Activity in the allowance for credit losses for the three and six months ended March 31, 2021, is shown in the following table. Three Months Ended March 31, 2021 Six Months Ended March 31, 2021 Spire Spire Spire Spire Spire Missouri Alabama Spire Missouri Alabama Allowance at beginning of period $ 28.9 $ 21.4 $ 6.2 $ 24.9 $ 18.1 $ 5.5 Provision for expected credit losses 6.6 5.7 0.6 10.7 9.0 1.3 Write-offs, net of recoveries (1.1 ) (0.5 ) (0.3 ) (1.2 ) (0.5 ) (0.3 ) Allowance at end of period $ 34.4 $ 26.6 $ 6.5 $ 34.4 $ 26.6 $ 6.5
New Accounting Pronouncements	NEW ACCOUNTING PRONOUNCEMENTS – In June 2016, the FASB issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments , which was later supplemented by ASU Nos. 2018-19, 2019-04, 2019-05 and 2019-11. The new standard replaces the current “incurred loss” model with an “expected loss” model for certain instruments, including trade receivables, requiring measurement of all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. It also required entities to record credit loss allowances for available-for-sale securities rather than impair the carrying amount of the securities. Spire, Spire Missouri and Spire Alabama adopted the new standard for the quarter ended December 31, 2020. Based on the credit quality of the existing available-for-sale securities portfolio, no allowance for credit losses was recognized for those investments. Application of the new guidance did not result in any significant modifications to the Company’s policies related to recognizing an allowance on trade receivables, and the adoption of the new standard did not have a material impact on Spire’s, Spire Missouri’s and Spire Alabama’s financial statements.
Reclassifications	RECLASSIFICATIONS – Spire’s consolidated statements of income historically showed Gas Utility operating revenues and expense line items separately from Gas Marketing and other operations. The current presentation shows operating revenues and expense line items on a consolidated basis. Disaggregated data is presented in Note 9 , Information by Operating Segment. Prior period amounts have been reclassified to conform with the current period presentation.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Schedule of Inter-Company Transactions	Spire Missouri’s and Spire Alabama’s other transactions with affiliates are presented below Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Missouri Purchases of natural gas from Spire Marketing Inc. $ 57.6 $ 13.3 $ 68.3 $ 32.8 Transportation services received from Spire STL Pipeline LLC 7.9 7.9 16.0 11.8 Sales of natural gas to Spire Marketing Inc. — — 1.1 — Transportation services received from Spire NGL Inc. 0.2 0.2 0.5 0.5 Spire Alabama Purchases of natural gas from Spire Marketing Inc. $ 5.8 $ 1.0 $ 10.6 $ 4.3 Sales of natural gas to Spire Marketing Inc. 0.1 — 0.1 —
Schedule of Capital Expenditures Excluded from Statement of Cash Flow	Accrued capital expenditures, shown in the following table, are excluded from capital expenditures in the statements of cash flows until paid. March 31, September 30, March 31, 2021 2020 2020 Spire $ 36.1 $ 67.6 $ 51.4 Spire Missouri 21.8 34.3 21.5 Spire Alabama 4.7 17.0 17.6
Schedule of Allowance for Credit Losses	Three Months Ended March 31, 2021 Six Months Ended March 31, 2021 Spire Spire Spire Spire Spire Missouri Alabama Spire Missouri Alabama Allowance at beginning of period $ 28.9 $ 21.4 $ 6.2 $ 24.9 $ 18.1 $ 5.5 Provision for expected credit losses 6.6 5.7 0.6 10.7 9.0 1.3 Write-offs, net of recoveries (1.1 ) (0.5 ) (0.3 ) (1.2 ) (0.5 ) (0.3 ) Allowance at end of period $ 34.4 $ 26.6 $ 6.5 $ 34.4 $ 26.6 $ 6.5

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Mar. 31, 2021
Revenue From Contract With Customer [Abstract]
Schedule of Revenue Disaggregated by Source and Customer Type	The following tables show revenue disaggregated by source and customer type. Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Gas Utility: Residential $ 537.6 $ 471.9 $ 887.5 $ 840.3 Commercial & industrial 369.2 156.8 472.2 279.3 Transportation 34.2 32.5 66.4 63.5 Off-system & other incentive 130.6 9.3 139.9 18.7 Other customer revenue (11.9 ) 3.2 (9.7 ) 5.6 Total revenue from contracts with customers 1,059.7 673.7 1,556.3 1,207.4 Changes in accrued revenue under alternative revenue programs (6.6 ) 5.3 (5.0 ) 2.3 Total Gas Utility operating revenues 1,053.1 679.0 1,551.3 1,209.7 Gas Marketing 33.4 33.3 58.2 65.6 Other 15.6 14.7 32.3 25.8 Total before eliminations 1,102.1 727.0 1,641.8 1,301.1 Intersegment eliminations (see Note 9, Information by Operating Segment) 2.8 (11.5 ) (24.3 ) (18.7 ) Total Operating Revenues $ 1,104.9 $ 715.5 $ 1,617.5 $ 1,282.4 Spire Missouri Residential $ 365.4 $ 331.1 $ 628.4 $ 607.0 Commercial & industrial 304.0 99.2 373.9 180.0 Transportation 9.9 9.7 18.9 18.7 Off-system & other incentive 128.5 9.3 135.9 18.7 Other customer revenue (17.5 ) 0.9 (14.6 ) 1.4 Total revenue from contracts with customers 790.3 450.2 1,142.5 825.8 Changes in accrued revenue under alternative revenue programs 0.6 7.3 3.9 5.7 Total Operating Revenues $ 790.9 $ 457.5 $ 1,146.4 $ 831.5 Spire Alabama Residential $ 144.8 $ 120.5 $ 214.0 $ 194.8 Commercial & industrial 53.2 46.2 77.5 77.5 Transportation 21.7 19.9 42.2 39.5 Off-system & other incentive 1.9 — 3.9 — Other customer revenue 3.9 1.7 2.0 3.3 Total revenue from contracts with customers 225.5 188.3 339.6 315.1 Changes in accrued revenue under alternative revenue programs (2.9 ) (2.8 ) (3.4 ) (3.4 ) Total Operating Revenues $ 222.6 $ 185.5 $ 336.2 $ 311.7
Schedule of Gross Receipts Taxes	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.” Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire $ 42.2 $ 37.9 $ 63.9 $ 62.5 Spire Missouri 28.6 26.2 43.8 43.4 Spire Alabama 11.8 9.9 17.1 16.1

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	6 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Earnings Per Share	Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Basic Earnings Per Common Share: Net Income $ 187.4 $ 133.6 $ 276.3 $ 200.6 Less: Provision for preferred dividends 3.7 3.7 7.4 7.4 Income allocated to participating securities 0.3 0.2 0.4 0.3 Income Available to Common Shareholders $ 183.4 $ 129.7 $ 268.5 $ 192.9 Weighted Average Common Shares Outstanding (in millions) 51.6 51.0 51.6 51.0 Basic Earnings Per Common Share $ 3.56 $ 2.55 $ 5.21 $ 3.78 Diluted Earnings Per Common Share: Net Income $ 187.4 $ 133.6 $ 276.3 $ 200.6 Less: Provision for preferred dividends 3.7 3.7 7.4 7.4 Income allocated to participating securities 0.3 0.2 0.4 0.3 Income Available to Common Shareholders $ 183.4 $ 129.7 $ 268.5 $ 192.9 Weighted Average Common Shares Outstanding (in millions) 51.6 51.0 51.6 51.0 Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)* 0.1 0.1 0.1 0.1 Weighted Average Diluted Common Shares (in millions) 51.7 51.1 51.7 51.1 Diluted Earnings Per Common Share $ 3.55 $ 2.54 $ 5.20 $ 3.77 * 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 0.1 0.1 0.1 0.1

Regulatory Matters (Tables)

Regulatory Matters (Tables)	6 Months Ended
	Mar. 31, 2021
Regulated Operations [Abstract]
Schedule of Regulatory Assets and Liabilities	The following regulatory assets and regulatory liabilities were reflected in the balance sheets of the Company, Spire Missouri and Spire Alabama as of March 31, 2021, September 30, 2020, and March 31, 2020. March 31, September 30, March 31, Spire 2021 2020 2020 Regulatory Assets: Current: Pension and postretirement benefit costs $ 30.9 $ 30.6 $ 30.1 Unamortized purchased gas adjustments 0.1 5.5 10.4 Other 29.4 33.4 27.5 Total Current Regulatory Assets 60.4 69.5 68.0 Noncurrent: Pension and postretirement benefit costs 418.3 439.3 415.6 Cost of removal 430.7 395.6 154.3 Future income taxes due from customers 127.4 123.5 113.5 Energy efficiency 43.2 39.6 37.7 Unamortized purchased gas adjustments 51.5 12.1 — Other 62.5 59.3 49.6 Total Noncurrent Regulatory Assets 1,133.6 1,069.4 770.7 Total Regulatory Assets $ 1,194.0 $ 1,138.9 $ 838.7 Regulatory Liabilities: Current: Pension and postretirement benefit costs $ 5.8 $ 5.8 $ 5.8 Unamortized purchased gas adjustments 28.9 73.1 8.0 Other 21.6 34.1 18.0 Total Current Regulatory Liabilities 56.3 113.0 31.8 Noncurrent: Deferred taxes due to customers 133.2 138.8 174.2 Pension and postretirement benefit costs 170.2 157.6 152.5 Accrued cost of removal 28.7 28.6 31.7 Unamortized purchased gas adjustments 49.7 4.4 82.6 Other 41.7 14.3 31.3 Total Noncurrent Regulatory Liabilities 423.5 343.7 472.3 Total Regulatory Liabilities $ 479.8 $ 456.7 $ 504.1 March 31, September 30, March 31, Spire Missouri 2021 2020 2020 Regulatory Assets: Current: Pension and postretirement benefit costs $ 21.9 $ 21.9 $ 21.9 Other 15.6 10.2 7.5 Total Current Regulatory Assets 37.5 32.1 29.4 Noncurrent: Future income taxes due from customers 118.6 114.6 106.8 Pension and postretirement benefit costs 324.6 332.6 337.5 Energy efficiency 43.2 39.6 37.7 Unamortized purchased gas adjustments 51.5 12.1 — Cost of removal 21.3 7.1 — Other 45.1 42.7 30.1 Total Noncurrent Regulatory Assets 604.3 548.7 512.1 Total Regulatory Assets $ 641.8 $ 580.8 $ 541.5 Regulatory Liabilities: Current: Pension and postretirement benefit costs $ 3.6 $ 3.6 $ 3.6 Unamortized purchased gas adjustments 17.0 72.3 7.1 Other 17.0 27.3 13.6 Total Current Regulatory Liabilities 37.6 103.2 24.3 Noncurrent: Deferred taxes due to customers 115.8 121.4 156.8 Pension and postretirement benefit costs 151.9 140.4 130.7 Accrued cost of removal — — 4.8 Unamortized purchased gas adjustments 49.7 4.4 82.6 Other 36.1 8.6 25.5 Total Noncurrent Regulatory Liabilities 353.5 274.8 400.4 Total Regulatory Liabilities $ 391.1 $ 378.0 $ 424.7 March 31, September 30, March 31, Spire Alabama 2021 2020 2020 Regulatory Assets: Current: Pension and postretirement benefit costs $ 8.0 $ 7.7 $ 7.2 Unamortized purchased gas adjustments — 5.5 10.4 Other 3.8 7.2 5.7 Total Current Regulatory Assets 11.8 20.4 23.3 Noncurrent: Pension and postretirement benefit costs 88.5 98.2 72.6 Cost of removal 409.4 388.6 154.3 Future income taxes due from customers 2.2 2.2 — Other 1.1 0.9 3.2 Total Noncurrent Regulatory Assets 501.2 489.9 230.1 Total Regulatory Assets $ 513.0 $ 510.3 $ 253.4 Regulatory Liabilities: Current: Pension and postretirement benefit costs $ 2.2 $ 2.2 $ 2.2 Unamortized purchased gas adjustments 10.6 — — Other 1.4 1.7 0.2 Total Current Regulatory Liabilities 14.2 3.9 2.4 Noncurrent: Pension and postretirement benefit costs 14.3 14.8 17.8 Other 3.7 3.7 3.8 Total Noncurrent Regulatory Liabilities 18.0 18.5 21.6 Total Regulatory Liabilities $ 32.2 $ 22.4 $ 24.0
Schedule of Regulatory Assets Not Earning a Return	A portion of the Company’s and Spire Missouri’s regulatory assets are not earning a return, as shown in the table below: March 31, September 30, March 31, 2021 2020 2020 Spire Pension and postretirement benefit costs $ 226.3 $ 232.3 $ 226.2 Future income taxes due from customers 125.1 121.3 113.5 Other 122.9 12.9 13.7 Total Regulatory Assets Not Earning a Return $ 474.3 $ 366.5 $ 353.4 Spire Missouri Pension and postretirement benefit costs $ 226.3 $ 232.3 $ 226.2 Future income taxes due from customers 118.6 114.6 106.8 Other 122.9 12.9 13.7 Total Regulatory Assets Not Earning a Return $ 467.8 $ 359.8 $ 346.7

Financing (Tables)

Financing (Tables)	6 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of Short-term Borrowings	Information about Spire’s consolidated short-term borrowings and about Spire Missouri’s and Spire Alabama’s borrowings from Spire is presented in the following table. As of March 31, 2021, $398.1 of Spire’s short-term borrowings were used to support lending to the Utilities. Spire (Parent Only) Spire Missouri Spire Alabama Spire Credit Term CP Credit Term Spire Credit Spire Consol- Facility Loan Program Facility Loan Note Facility Note idated Six Months Ended March 31, 2021 Weighted average borrowings $ — $ 63.5 $ 606.9 $ — $ 11.0 $ 360.8 $ — $ 59.6 $ 681.4 Lowest borrowings outstanding — — 403.5 — — 277.2 — — 455.5 Highest borrowings outstanding — 150.0 775.0 — 250.0 441.9 — 152.2 850.5 Weighted average interest rate n/a 1.1 % 0.3 % n/a 0.8 % 0.3 % n/a 0.2 % 0.4 % As of March 31, 2021 Borrowings outstanding $ — $ — $ 403.5 $ — $ 250.0 $ 369.4 $ — $ — $ 653.5 Weighted average interest rate n/a n/a 0.2 % n/a 0.8 % 0.2 % n/a n/a 0.4 % As of September 30, 2020 Borrowings outstanding $ — $ 150.0 $ 498.0 $ — $ — $ 301.2 $ — $ 121.3 $ 648.0 Weighted average interest rate n/a 1.1 % 0.2 % n/a n/a 0.2 % n/a 0.2 % 0.6 % As of March 31, 2020 Borrowings outstanding $ — $ 150.0 $ 175.5 $ 185.1 $ — $ 39.6 $ 50.0 $ 33.0 $ 560.6 Weighted average interest rate n/a 2.1 % 1.8 % 1.8 % n/a 1.9 % 1.9 % 1.9 % 1.9 %
Summary Capitalized Interest	Interest expense shown on Spire’s consolidated statements of income and Spire Missouri’s statements of comprehensive income is net of the capitalized interest amounts shown in the following table. Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire $ 1.1 $ 1.4 $ 2.0 $ 3.6 Spire Missouri 0.1 0.3 0.1 0.6 Spire Alabama 0.7 0.4 1.3 1.0
Schedule of Variable Stock Purchase Contract Settlement Rates	Each stock purchase contract obligates the holder to purchase, and Spire to issue and deliver, on March 1, 2024, for a price of fifty dollars If the applicable market value * of Spire common stock is: Number of shares to be purchased per 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 trading days before settlement.

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Summary of Financial Instruments Measured at Fair Value on Recurring Basis	The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis are shown in the following tables, classified according to the fair value hierarchy. There were no such instruments classified as Level 3 (significant unobservable inputs) as of March 31, 2021, September 30, 2020, and March 31, 2020. Classification of Estimated Fair Value Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Spire As of March 31, 2021 Cash and cash equivalents $ 104.0 $ 104.0 $ 104.0 $ — Notes payable 653.5 653.5 — 653.5 Long-term debt, including current portion 2,803.3 3,090.9 — 3,090.9 As of September 30, 2020 Cash and cash equivalents $ 4.1 $ 4.1 $ 4.1 $ — Notes payable 648.0 648.0 — 648.0 Long-term debt, including current portion 2,484.1 2,908.6 — 2,908.6 As of March 31, 2020 Cash and cash equivalents $ 108.4 $ 108.4 $ 108.4 $ — Notes payable 560.6 560.6 — 560.6 Long-term debt, including current portion 2,490.2 2,671.0 — 2,671.0 Spire Missouri As of March 31, 2021 Notes payable $ 250.0 $ 250.0 $ — $ 250.0 Notes payable – associated companies 369.4 369.4 — 369.4 Long-term debt 1,092.4 1,254.2 — 1,254.2 As of September 30, 2020 Notes payable – $ 301.2 $ 301.2 $ — $ 301.2 Long-term debt 1,092.0 1,313.5 — 1,313.5 As of March 31, 2020 Cash and cash equivalents $ 5.1 $ 5.1 $ 5.1 $ — Notes payable 185.1 185.1 — 185.1 Notes payable – 39.6 39.6 — 39.6 Long-term debt 1,098.7 1,231.2 — 1,231.2 Spire Alabama As of March 31, 2021 Cash and cash equivalents $ 18.2 $ 18.2 $ 18.2 $ — Notes receivable – associated companies 20.0 20.0 — 20.0 Long-term debt, including current portion 621.1 682.3 — 682.3 As of September 30, 2020 Notes payable – $ 121.3 $ 121.3 $ — $ 121.3 Long-term debt, including current portion 471.8 576.9 — 576.9 As of March 31, 2020 Cash and cash equivalents $ 0.1 $ 0.1 $ 0.1 $ — Notes payable 50.0 50.0 — 50.0 Notes payable – 33.0 33.0 — 33.0 Long-term debt 471.7 535.1 — 535.1

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Mar. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	Spire Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of March 31, 2021 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 23.5 $ — $ — $ — $ 23.5 NYMEX/ICE natural gas contracts 0.4 — — (0.4 ) — Gasoline and heating oil contracts 0.3 — — (0.3 ) — Gas Marketing: NYMEX/ICE natural gas contracts — 15.1 — (12.3 ) 2.8 Natural gas commodity contracts — 9.3 — — 9.3 Other: U.S. stock/bond mutual funds 22.9 — — — 22.9 Interest rate swaps — 27.9 — — 27.9 Total $ 47.1 $ 52.3 $ — $ (13.0 ) $ 86.4 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 1.8 $ — $ — $ (1.8 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts — 4.7 — (4.7 ) — Natural gas commodity contracts — 24.5 — — 24.5 Other: Interest rate swaps — 21.4 — — 21.4 Total $ 1.8 $ 50.6 $ — $ (6.5 ) $ 45.9 Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of September 30, 2020 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 21.9 $ — $ — $ — $ 21.9 NYMEX/ICE natural gas contracts 6.3 — — (6.3 ) — Gasoline and heating oil contracts 0.3 — — (0.3 ) — Gas Marketing: NYMEX/ICE natural gas contracts — 27.7 — (25.4 ) 2.3 Natural gas commodity contracts — 14.5 0.4 — 14.9 Other: U.S. stock/bond mutual funds 18.6 — — — 18.6 Total $ 47.1 $ 42.2 $ 0.4 $ (32.0 ) $ 57.7 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 0.9 $ — $ — $ (0.9 ) $ — Gas Marketing: NYMEX/ICE natural gas contracts 0.7 21.4 — (22.1 ) — Natural gas commodity contracts — 22.3 — — 22.3 Other: Interest rate swaps — 54.2 — — 54.2 Total $ 1.6 $ 97.9 $ — $ (23.0 ) $ 76.5 As of March 31, 2020 ASSETS Gas Utility: U.S. stock/bond mutual funds $ 18.1 $ — $ — $ — $ 18.1 NYMEX/ICE natural gas contracts 0.1 — — (0.1 ) — Gas Marketing: NYMEX/ICE natural gas contracts 0.2 6.8 — (7.0 ) — Natural gas commodity contracts — 17.5 — (4.8 ) 12.7 Other: U.S. stock/bond mutual funds 17.6 — — — 17.6 Total $ 36.0 $ 24.3 $ — $ (11.9 ) $ 48.4 LIABILITIES Gas Utility: NYMEX/ICE natural gas contracts $ 12.2 $ — $ — $ (12.2 ) $ — Gasoline and heating oil contracts 0.4 — — (0.4 ) — Gas Marketing: NYMEX/ICE natural gas contracts 0.5 8.4 — (8.9 ) — Natural gas commodity contracts — 27.7 1.1 (4.8 ) 24.0 Other: Interest rate swaps — 66.9 — — 66.9 Total $ 13.1 $ 103.0 $ 1.1 $ (26.3 ) $ 90.9
Spire Missouri
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	Spire Missouri Quoted Prices in Active Markets (Level 1) Significant Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Effects of Netting and Cash Margin Receivables /Payables Total As of March 31, 2021 ASSETS U.S. stock/bond mutual funds $ 23.5 $ — $ — $ — $ 23.5 NYMEX/ICE natural gas contracts 0.4 — — (0.4 ) — Gasoline and heating oil contracts 0.3 — — (0.3 ) — Total $ 24.2 $ — $ — $ (0.7 ) $ 23.5 LIABILITIES NYMEX/ICE natural gas contracts $ 1.8 $ — $ — $ (1.8 ) $ — As of September 30, 2020 ASSETS U.S. stock/bond mutual funds $ 21.9 $ — $ — $ — $ 21.9 NYMEX/ICE natural gas contracts 6.3 — — (6.3 ) — Gasoline and heating oil contracts 0.3 — — (0.3 ) — Total $ 28.5 $ — $ — $ (6.6 ) $ 21.9 LIABILITIES NYMEX/ICE natural gas contracts $ 0.9 $ — $ — $ (0.9 ) $ — As of March 31, 2020 ASSETS U.S. stock/bond mutual funds $ 18.1 $ — $ — $ — $ 18.1 NYMEX/ICE natural gas contracts 0.1 — — (0.1 ) — Total $ 18.2 $ — $ — $ (0.1 ) $ 18.1 LIABILITIES NYMEX/ICE natural gas contracts $ 12.2 $ — $ — $ (12.2 ) $ — Gasoline and heating oil contracts 0.4 — — (0.4 ) — Total $ 12.6 $ — $ — $ (12.6 ) $ —

Pension Plans and Other Postr_2

Pension Plans and Other Postretirement Benefits (Tables)	6 Months Ended
	Mar. 31, 2021
Pension Plans
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic cost	The net periodic pension cost includes components shown in the following tables. The components other than the service costs and regulatory adjustment are presented in “Other Income (Expense), 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 (Expense), Net.” Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Service cost – benefits earned during the period $ 5.3 $ 5.6 $ 10.9 $ 11.1 Interest cost on projected benefit obligation 4.6 5.8 9.8 11.7 Expected return on plan assets (7.1 ) (9.0 ) (15.1 ) (18.2 ) Amortization of prior service credit (0.7 ) (0.6 ) (1.5 ) (1.2 ) Amortization of actuarial loss 3.8 3.9 7.8 7.6 Loss on lump-sum settlements 3.8 21.0 3.8 21.0 Subtotal 9.7 26.7 15.7 32.0 Regulatory adjustment 5.2 (11.3 ) 14.8 (1.7 ) Net pension cost $ 14.9 $ 15.4 $ 30.5 $ 30.3 Spire Missouri Service cost – benefits earned during the period $ 3.9 $ 3.9 $ 7.8 $ 7.7 Interest cost on projected benefit obligation 3.5 4.0 7.0 8.2 Expected return on plan assets (5.6 ) (6.3 ) (11.2 ) (12.9 ) Amortization of prior service (credit) cost (0.1 ) 0.1 (0.3 ) 0.1 Amortization of actuarial loss 2.8 3.1 5.7 6.0 Loss on lump-sum settlements — 21.0 — 21.0 Subtotal 4.5 25.8 9.0 30.1 Regulatory adjustment 7.5 (13.2 ) 15.1 (5.5 ) Net pension cost $ 12.0 $ 12.6 $ 24.1 $ 24.6 Spire Alabama Service cost – benefits earned during the period $ 1.4 $ 1.5 $ 2.9 $ 3.0 Interest cost on projected benefit obligation 1.2 1.3 2.4 2.5 Expected return on plan assets (1.5 ) (1.8 ) (3.1 ) (3.5 ) Amortization of prior service credit (0.6 ) (0.6 ) (1.2 ) (1.2 ) Amortization of actuarial loss 1.0 0.8 2.1 1.6 Loss on lump-sum settlements 3.8 — 3.8 — Subtotal 5.3 1.2 6.9 2.4 Regulatory adjustment (2.5 ) 1.7 (0.7 ) 3.4 Net pension cost $ 2.8 $ 2.9 $ 6.2 $ 5.8
Other Postretirement Plans
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic cost	The net periodic postretirement benefit cost includes components shown in the following tables. The components other than the service costs and regulatory adjustment are presented in “Other Income (Expense), Net” in the income statement, except in the event Spire Alabama incurs losses on lump-sum settlements. Any 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 (Expense), Net.” Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Spire Service cost – benefits earned during the period $ 1.9 $ 1.5 $ 3.7 $ 2.9 Interest cost on accumulated postretirement benefit obligation 1.6 1.5 3.0 3.1 Expected return on plan assets (4.1 ) (4.1 ) (8.1 ) (8.2 ) Amortization of prior service cost (credit) 0.2 (0.1 ) 0.5 (0.3 ) Amortization of actuarial gain (0.4 ) (0.5 ) (0.8 ) (1.0 ) Subtotal (0.8 ) (1.7 ) (1.7 ) (3.5 ) Regulatory adjustment 3.2 4.0 6.6 8.0 Net postretirement benefit cost $ 2.4 $ 2.3 $ 4.9 $ 4.5 Spire Missouri Service cost – benefits earned during the period $ 1.5 $ 1.3 $ 3.1 $ 2.6 Interest cost on accumulated postretirement benefit obligation 1.1 1.1 2.2 2.3 Expected return on plan assets (2.8 ) (2.9 ) (5.5 ) (5.7 ) Amortization of prior service cost (credit) 0.2 — 0.4 (0.1 ) Amortization of actuarial gain (0.3 ) (0.5 ) (0.7 ) (1.0 ) Subtotal (0.3 ) (1.0 ) (0.5 ) (1.9 ) Regulatory adjustment 3.7 4.5 7.5 8.9 Net postretirement benefit cost $ 3.4 $ 3.5 $ 7.0 $ 7.0 Spire Alabama Service cost – benefits earned during the period $ 0.3 $ 0.1 $ 0.5 $ 0.2 Interest cost on accumulated postretirement benefit obligation 0.4 0.4 0.7 0.7 Expected return on plan assets (1.3 ) (1.2 ) (2.5 ) (2.4 ) Amortization of prior service (credit) cost — (0.1 ) 0.1 (0.2 ) Subtotal (0.6 ) (0.8 ) (1.2 ) (1.7 ) Regulatory adjustment (0.5 ) (0.5 ) (0.9 ) (0.9 ) Net postretirement benefit income $ (1.1 ) $ (1.3 ) $ (2.1 ) $ (2.6 )

Information by Operating Segm_2

Information by Operating Segment (Tables)	6 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Schedule of Operating Segment Information	Gas Utility Gas Marketing Other Eliminations Consolidated Three Months Ended March 31, 2021 Operating Revenues: Revenues from external customers $ 1,053.0 $ 47.4 $ 4.5 $ — $ 1,104.9 Intersegment revenues 0.1 (14.0 ) 11.1 2.8 — Total Operating Revenues 1,053.1 33.4 15.6 2.8 1,104.9 Operating Expenses: Natural gas 619.2 (6.2 ) 0.1 6.0 619.1 Operation and maintenance 104.0 7.1 11.1 (3.2 ) 119.0 Depreciation and amortization 49.5 0.3 1.7 — 51.5 Taxes, other than income taxes 56.4 0.5 1.0 — 57.9 Total Operating Expenses 829.1 1.7 13.9 2.8 847.5 Operating Income $ 224.0 $ 31.7 $ 1.7 $ — $ 257.4 Net Economic Earnings (Loss) $ 159.7 $ 39.8 $ (3.9 ) $ — $ 195.6 Gas Utility Gas Marketing Other Eliminations Consolidated Three Months Ended March 31, 2020 Operating Revenues: Revenues from external customers $ 679.1 $ 33.3 $ 3.1 $ — $ 715.5 Intersegment revenues (0.1 ) — 11.6 (11.5 ) — Total Operating Revenues 679.0 33.3 14.7 (11.5 ) 715.5 Operating Expenses: Natural gas 271.6 33.6 0.1 (8.2 ) 297.1 Operation and maintenance 95.8 3.6 9.6 (3.3 ) 105.7 Depreciation and amortization 47.0 0.1 2.1 — 49.2 Taxes, other than income taxes 51.7 0.4 0.9 — 53.0 Total Operating Expenses 466.1 37.7 12.7 (11.5 ) 505.0 Operating Income $ 212.9 $ (4.4 ) $ 2.0 $ — $ 210.5 Net Economic Earnings (Loss) $ 144.3 $ 5.1 $ (5.4 ) $ — $ 144.0 Gas Utility Gas Marketing Other Eliminations Consolidated Six Months Ended March 31, 2021 Operating Revenues: Revenues from external customers $ 1,550.2 $ 58.1 $ 9.2 $ — $ 1,617.5 Intersegment revenues 1.1 0.1 23.1 (24.3 ) — Total Operating Revenues 1,551.3 58.2 32.3 (24.3 ) 1,617.5 Operating Expenses: Natural gas 823.5 (5.5 ) 0.1 (17.8 ) 800.3 Operation and maintenance 207.0 10.4 19.7 (6.5 ) 230.6 Depreciation and amortization 98.1 0.6 3.6 — 102.3 Taxes, other than income taxes 91.9 0.7 1.4 — 94.0 Total Operating Expenses 1,220.5 6.2 24.8 (24.3 ) 1,227.2 Operating Income $ 330.8 $ 52.0 $ 7.5 $ — $ 390.3 Net Economic Earnings (Loss) $ 236.1 $ 43.1 $ (6.7 ) $ — $ 272.5 Gas Utility Gas Marketing Other Eliminations Consolidated Six Months Ended March 31, 2020 Operating Revenues: Revenues from external customers $ 1,209.7 $ 65.6 $ 7.1 $ — $ 1,282.4 Intersegment revenues — — 18.7 (18.7 ) — Total Operating Revenues 1,209.7 65.6 25.8 (18.7 ) 1,282.4 Operating Expenses: Natural gas 513.1 58.1 0.2 (12.4 ) 559.0 Operation and maintenance 204.4 6.7 17.5 (6.3 ) 222.3 Depreciation and amortization 93.4 0.1 3.2 — 96.7 Taxes, other than income taxes 89.6 0.7 1.3 — 91.6 Total Operating Expenses 900.5 65.6 22.2 (18.7 ) 969.6 Operating Income $ 309.2 $ — $ 3.6 $ — $ 312.8 Net Economic Earnings (Loss) $ 213.4 $ 11.2 $ (8.8 ) $ — $ 215.8 March 31, September 30, March 31, 2021 2020 2020 Total Assets: Gas Utility $ 7,265.0 $ 6,716.2 $ 6,311.6 Gas Marketing 341.0 182.7 159.3 Other 2,513.7 2,443.5 2,214.7 Eliminations (1,182.9 ) (1,101.2 ) (667.6 ) Total Assets $ 8,936.8 $ 8,241.2 $ 8,018.0
Schedule of Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income	The following table reconciles the Company’s net economic earnings to net income. For information about the Missouri regulatory adjustment for $9.0 of pension costs in fiscal 2021 and the provision for ISRS rulings in fiscal 2020, see Note 4 , Regulatory Matters. Three Months Ended March 31, Six Months Ended March 31, 2021 2020 2021 2020 Net Income $ 187.4 $ 133.6 $ 276.3 $ 200.6 Adjustments, pre-tax: Missouri regulatory adjustment (9.0 ) — (9.0 ) — Provision for ISRS rulings — 2.2 — 4.8 Fair value and timing adjustments 20.1 11.6 4.1 15.3 Income tax effect of adjustments (2.9 ) (3.4 ) 1.1 (4.9 ) Net Economic Earnings $ 195.6 $ 144.0 $ 272.5 $ 215.8

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	6 Months Ended
	Mar. 31, 2021USD ($)reporting_unit	Mar. 31, 2021USD ($)operating-segment
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of reportable segments	2	2
Accounting Standards Update 2016-13
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Credit loss allowances for available-for-sale securities recognized at adoption of ASU	$ 0	$ 0
Change in accounting principle, accounting standards update, adopted	true	true
Change in accounting principle, accounting standards update, adoption date	Dec. 31, 2020	Dec. 31, 2020
Change in accounting principle, accounting standards update, material effect	true	true
Accounting Standards Update 2016-13 | Spire Missouri
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Credit loss allowances for available-for-sale securities recognized at adoption of ASU	$ 0	$ 0
Change in accounting principle, accounting standards update, adopted	true	true
Change in accounting principle, accounting standards update, adoption date	Dec. 31, 2020	Dec. 31, 2020
Change in accounting principle, accounting standards update, material effect	true	true
Accounting Standards Update 2016-13 | Spire Alabama
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Credit loss allowances for available-for-sale securities recognized at adoption of ASU	$ 0	$ 0
Change in accounting principle, accounting standards update, adopted	true	true
Change in accounting principle, accounting standards update, adoption date	Dec. 31, 2020	Dec. 31, 2020
Change in accounting principle, accounting standards update, material effect	true	true

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Inter-Company Transactions (Details) - Affiliated Entity - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Spire Marketing Inc | Spire Missouri | Regulated Operation
Related Party Transaction [Line Items]
Purchases of natural gas from related party	$ 57.6	$ 13.3	$ 68.3	$ 32.8
Sales of natural gas to Spire Marketing Inc.			1.1
Spire Marketing Inc | Spire Alabama | Regulated Operation
Related Party Transaction [Line Items]
Purchases of natural gas from related party	5.8	1	10.6	4.3
Sales of natural gas to Spire Marketing Inc.	0.1		0.1
Spire STL Pipeline LLC | Spire Missouri | Unregulated Operation
Related Party Transaction [Line Items]
Transportation services received	7.9	7.9	16	11.8
Spire NGL Inc. | Spire Missouri | Unregulated Operation
Related Party Transaction [Line Items]
Transportation services received	$ 0.2	$ 0.2	$ 0.5	$ 0.5

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Accrued Capital Expenditures (Details) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Schedule Of Accrued Capital Expenditures Excluded From Statement Of Cash Flow [Line Items]
Accruals for capital expenditures	$ 36.1	$ 51.4	$ 67.6
Spire Missouri
Schedule Of Accrued Capital Expenditures Excluded From Statement Of Cash Flow [Line Items]
Accruals for capital expenditures	21.8	21.5	34.3
Spire Alabama
Schedule Of Accrued Capital Expenditures Excluded From Statement Of Cash Flow [Line Items]
Accruals for capital expenditures	$ 4.7	$ 17.6	$ 17

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2021
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	$ 28.9	$ 24.9
Provision for expected credit losses	6.6	10.7
Write-offs, net of recoveries	(1.1)	(1.2)
Allowance at end of period	34.4	34.4
Spire Missouri
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	21.4	18.1
Provision for expected credit losses	5.7	9
Write-offs, net of recoveries	(0.5)	(0.5)
Allowance at end of period	26.6	26.6
Spire Alabama
Accounts Notes And Loans Receivable [Line Items]
Allowance at beginning of period	6.2	5.5
Provision for expected credit losses	0.6	1.3
Write-offs, net of recoveries	(0.3)	(0.3)
Allowance at end of period	$ 6.5	$ 6.5

Revenue - Schedule of Revenue D

Revenue - Schedule of Revenue Disaggregated by Source and Customer Type (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Disaggregation Of Revenue [Line Items]
Total operating revenues	$ 1,104.9	$ 715.5	$ 1,617.5	$ 1,282.4
Intersegment Eliminations
Disaggregation Of Revenue [Line Items]
Total operating revenues	2.8	(11.5)	(24.3)	(18.7)
Gas Utility | Operating Segments
Disaggregation Of Revenue [Line Items]
Total operating revenues	1,053.1	679	1,551.3	1,209.7
Gas Marketing | Operating Segments
Disaggregation Of Revenue [Line Items]
Total operating revenues	33.4	33.3	58.2	65.6
Spire
Disaggregation Of Revenue [Line Items]
Total operating revenues	1,104.9	715.5	1,617.5	1,282.4
Spire | Operating Segments
Disaggregation Of Revenue [Line Items]
Total operating revenues	1,102.1	727	1,641.8	1,301.1
Spire | Intersegment Eliminations
Disaggregation Of Revenue [Line Items]
Total operating revenues	2.8	(11.5)	(24.3)	(18.7)
Spire | Gas Utility | Operating Segments
Disaggregation Of Revenue [Line Items]
Total operating revenues	1,059.7	673.7	1,556.3	1,207.4
Changes in accrued revenue under alternative revenue programs	(6.6)	5.3	(5)	2.3
Total operating revenues	1,053.1	679	1,551.3	1,209.7
Spire | Gas Utility | Operating Segments | Residential
Disaggregation Of Revenue [Line Items]
Total operating revenues	537.6	471.9	887.5	840.3
Spire | Gas Utility | Operating Segments | Commercial & Industrial
Disaggregation Of Revenue [Line Items]
Total operating revenues	369.2	156.8	472.2	279.3
Spire | Gas Utility | Operating Segments | Transportation
Disaggregation Of Revenue [Line Items]
Total operating revenues	34.2	32.5	66.4	63.5
Spire | Gas Utility | Operating Segments | Off-system & Other Incentive
Disaggregation Of Revenue [Line Items]
Total operating revenues	130.6	9.3	139.9	18.7
Spire | Gas Utility | Operating Segments | Other Customer Revenue
Disaggregation Of Revenue [Line Items]
Total operating revenues	(11.9)	3.2	(9.7)	5.6
Spire | Gas Marketing | Operating Segments
Disaggregation Of Revenue [Line Items]
Total operating revenues	33.4	33.3	58.2	65.6
Spire | Other | Operating Segments
Disaggregation Of Revenue [Line Items]
Total operating revenues	$ 15.6	$ 14.7	$ 32.3	$ 25.8

Revenue - Schedule of Operating

Revenue - Schedule of Operating Revenue Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Disaggregation Of Revenue [Line Items]
Total operating revenues	$ 1,104.9	$ 715.5	$ 1,617.5	$ 1,282.4
Spire Missouri
Disaggregation Of Revenue [Line Items]
Total operating revenues	790.3	450.2	1,142.5	825.8
Changes in accrued revenue under alternative revenue programs	0.6	7.3	3.9	5.7
Total operating revenues	790.9	457.5	1,146.4	831.5
Spire Missouri | Residential
Disaggregation Of Revenue [Line Items]
Total operating revenues	365.4	331.1	628.4	607
Spire Missouri | Commercial & Industrial
Disaggregation Of Revenue [Line Items]
Total operating revenues	304	99.2	373.9	180
Spire Missouri | Transportation
Disaggregation Of Revenue [Line Items]
Total operating revenues	9.9	9.7	18.9	18.7
Spire Missouri | Off-system & Other Incentive
Disaggregation Of Revenue [Line Items]
Total operating revenues	128.5	9.3	135.9	18.7
Spire Missouri | Other Customer Revenue
Disaggregation Of Revenue [Line Items]
Total operating revenues	(17.5)	0.9	(14.6)	1.4
Spire Alabama
Disaggregation Of Revenue [Line Items]
Total operating revenues	225.5	188.3	339.6	315.1
Changes in accrued revenue under alternative revenue programs	(2.9)	(2.8)	(3.4)	(3.4)
Total operating revenues	222.6	185.5	336.2	311.7
Spire Alabama | Residential
Disaggregation Of Revenue [Line Items]
Total operating revenues	144.8	120.5	214	194.8
Spire Alabama | Commercial & Industrial
Disaggregation Of Revenue [Line Items]
Total operating revenues	53.2	46.2	77.5	77.5
Spire Alabama | Transportation
Disaggregation Of Revenue [Line Items]
Total operating revenues	21.7	19.9	42.2	39.5
Spire Alabama | Off-system & Other Incentive
Disaggregation Of Revenue [Line Items]
Total operating revenues	1.9		3.9
Spire Alabama | Other Customer Revenue
Disaggregation Of Revenue [Line Items]
Total operating revenues	$ 3.9	$ 1.7	$ 2	$ 3.3

Revenue - Additional Informatio

Revenue - Additional Information (Details) $ in Millions	Feb. 28, 2021USD ($)
Spire Missouri
Disaggregation Of Revenue [Line Items]
Regulatory liability with a reduction in revenue	$ 25

Revenue - Schedule of Gross Rec

Revenue - Schedule of Gross Receipts Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Scheduleof Gross Receipts Taxes [Line Items]
Gross receipts taxes recorded in regulated gas distribution operating revenues	$ 42.2	$ 37.9	$ 63.9	$ 62.5
Spire Missouri
Scheduleof Gross Receipts Taxes [Line Items]
Gross receipts taxes recorded in regulated gas distribution operating revenues	28.6	26.2	43.8	43.4
Spire Alabama
Scheduleof Gross Receipts Taxes [Line Items]
Gross receipts taxes recorded in regulated gas distribution operating revenues	$ 11.8	$ 9.9	$ 17.1	$ 16.1

Earnings Per Common Share - Sch

Earnings Per Common Share - Schedule of Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Basic Earnings Per Common Share:
Net Income	$ 187.4	$ 133.6	$ 276.3	$ 200.6
Less: Provision for preferred dividends	3.7	3.7	7.4	7.4
Income allocated to participating securities	0.3	0.2	0.4	0.3
Net Income Available to Common Shareholders	$ 183.4	$ 129.7	$ 268.5	$ 192.9
Weighted Average Common Shares Outstanding (in millions)	51.6	51	51.6	51
Basic Earnings Per Common Share	$ 3.56	$ 2.55	$ 5.21	$ 3.78
Diluted Earnings Per Common Share:
Net Income	$ 187.4	$ 133.6	$ 276.3	$ 200.6
Less: Provision for preferred dividends	3.7	3.7	7.4	7.4
Income allocated to participating securities	0.3	0.2	0.4	0.3
Income Available to Common Shareholders	$ 183.4	$ 129.7	$ 268.5	$ 192.9
Weighted Average Common Shares Outstanding (in millions)	51.6	51	51.6	51
Dilutive Effect of Restricted Stock and Restricted Stock Units (in millions)	0.1	0.1	0.1	0.1
Weighted Average Diluted Common Shares (in millions)	51.7	51.1	51.7	51.1
Diluted Earnings Per Common Share	$ 3.55	$ 2.54	$ 5.20	$ 3.77

Earnings Per Common Share - S_2

Earnings Per Common Share - Schedule of Basic and Diluted Earnings Per Common Share (Parenthetical) (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Restricted Stock and Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding common shares excluded from calculation of diluted EPS (in shares)	0.1	0.1	0.1	0.1

Regulatory Matters - Schedule o

Regulatory Matters - Schedule of Regulatory Assets and Liabilities, Reflected in Balance Sheets (Details) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	$ 60.4	$ 69.5	$ 68
Regulatory assets, non current	1,133.6	1,069.4	770.7
Total Regulatory Assets	1,194	1,138.9	838.7
Regulatory liabilities, current	56.3	113	31.8
Regulatory liabilities, non current	423.5	343.7	472.3
Total Regulatory Liabilities	479.8	456.7	504.1
Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	37.5	32.1	29.4
Regulatory assets, non current	604.3	548.7	512.1
Total Regulatory Assets	641.8	580.8	541.5
Regulatory liabilities, current	37.6	103.2	24.3
Regulatory liabilities, non current	353.5	274.8	400.4
Total Regulatory Liabilities	391.1	378	424.7
Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	11.8	20.4	23.3
Regulatory assets, non current	501.2	489.9	230.1
Total Regulatory Assets	513	510.3	253.4
Regulatory liabilities, current	14.2	3.9	2.4
Regulatory liabilities, non current	18	18.5	21.6
Total Regulatory Liabilities	32.2	22.4	24
Pension and Other Postretirement Benefits
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	30.9	30.6	30.1
Regulatory assets, non current	418.3	439.3	415.6
Pension and Other Postretirement Benefits | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	21.9	21.9	21.9
Regulatory assets, non current	324.6	332.6	337.5
Pension and Other Postretirement Benefits | Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	8	7.7	7.2
Regulatory assets, non current	88.5	98.2	72.6
Unamortized Purchased Gas Adjustments
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	0.1	5.5	10.4
Regulatory assets, non current	51.5	12.1	0
Unamortized Purchased Gas Adjustments | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	51.5	12.1	0
Unamortized Purchased Gas Adjustments | Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current		5.5	10.4
Other
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	29.4	33.4	27.5
Regulatory assets, non current	62.5	59.3	49.6
Other | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	15.6	10.2	7.5
Regulatory assets, non current	45.1	42.7	30.1
Other | Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, current	3.8	7.2	5.7
Regulatory assets, non current	1.1	0.9	3.2
Future Income Taxes Due from Customers
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	127.4	123.5	113.5
Future Income Taxes Due from Customers | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	118.6	114.6	106.8
Future Income Taxes Due from Customers | Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	2.2	2.2	0
Accrued Cost of Removal
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	430.7	395.6	154.3
Accrued Cost of Removal | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	21.3	7.1	0
Accrued Cost of Removal | Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	409.4	388.6	154.3
Energy Efficiency
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	43.2	39.6	37.7
Energy Efficiency | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory assets, non current	43.2	39.6	37.7
Pension and Other Postretirement Benefits
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	5.8	5.8	5.8
Regulatory liabilities, non current	170.2	157.6	152.5
Pension and Other Postretirement Benefits | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	3.6	3.6	3.6
Regulatory liabilities, non current	151.9	140.4	130.7
Pension and Other Postretirement Benefits | Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	2.2	2.2	2.2
Regulatory liabilities, non current	14.3	14.8	17.8
Unamortized Purchased Gas Adjustments
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	28.9	73.1	8
Regulatory liabilities, non current	49.7	4.4	82.6
Unamortized Purchased Gas Adjustments | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	17	72.3	7.1
Regulatory liabilities, non current	49.7	4.4	82.6
Unamortized Purchased Gas Adjustments | Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	10.6	0	0
Other
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	21.6	34.1	18
Regulatory liabilities, non current	41.7	14.3	31.3
Other | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	17	27.3	13.6
Regulatory liabilities, non current	36.1	8.6	25.5
Other | Spire Alabama
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, current	1.4	1.7	0.2
Regulatory liabilities, non current	3.7	3.7	3.8
Deferred Taxes Due to Customers
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, non current	133.2	138.8	174.2
Deferred Taxes Due to Customers | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, non current	115.8	121.4	156.8
Accrued Cost of Removal
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, non current	28.7	28.6	31.7
Accrued Cost of Removal | Spire Missouri
Regulatory Asset And Liabilities [Line Items]
Regulatory liabilities, non current	$ 0	$ 0	$ 4.8

Regulatory Matters - Schedule_2

Regulatory Matters - Schedule of Regulatory Assets Not Earning a Return (Details) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	$ 474.3	$ 366.5	$ 353.4
Pension and Other Postretirement Benefits
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	226.3	232.3	226.2
Future Income Taxes Due from Customers
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	125.1	121.3	113.5
Other
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	122.9	12.9	13.7
Spire Missouri
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	467.8	359.8	346.7
Spire Missouri | Pension and Other Postretirement Benefits
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	226.3	232.3	226.2
Spire Missouri | Future Income Taxes Due from Customers
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	118.6	114.6	106.8
Spire Missouri | Other
Regulatory Assets [Line Items]
Total Regulatory Assets Not Earning a Return	$ 122.9	$ 12.9	$ 13.7

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Details) - USD ($) $ in Millions	Dec. 11, 2020	Apr. 25, 2018	Feb. 28, 2021	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020	Feb. 09, 2021
Public Utilities, General Disclosures [Line Items]
Remaining recovery period for certain regulatory assets for which no return on investment during recovery period is provided (in years)						20 years
Remaining recovery period for regulatory assets for which no return on investment during recovery period is provided (in years)						15 years
Regulatory assets, current				$ 60.4	$ 68	$ 60.4	$ 68	$ 69.5
Natural gas			$ 195.8	619.1	297.1	800.3	559
Spire Missouri
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current				37.5	29.4	37.5	29.4	32.1
Natural gas				537.4	$ 223.6	699	409.4
Incremental gross revenue			100
Regulatory liability with a reduction in revenue			$ 25
Approved percentage of excess natural gas supply and capacity retain			25.00%
Approved percentage of excess natural gas supply and capacity to customers			75.00%
Change in net deferred gas costs and average inventory costs				110
MoPSC
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease) amount	$ 64.2							2,780
Requested rate increase	$ 111.5
Common equity ratio	54.25%
Requested return rate on equity	9.95%
Infrastructure System Replacement Surcharge | MoPSC
Public Utilities, General Disclosures [Line Items]
Accrued pension assets added to prepaid pension asset									$ 9
Requested rate increase	$ 47.3
Infrastructure System Replacement Surcharge | MoPSC | Spire Missouri
Public Utilities, General Disclosures [Line Items]
Provision for regulatory liability							4.2
Provision for interest							0.6
After-tax impact on loss contingency provision reducing net income							$ 3.7
Accounting Authority Order | MoPSC
Public Utilities, General Disclosures [Line Items]
Regulatory assets, current				$ 3.4		$ 3.4		$ 3.8
Pension Cost | Infrastructure System Replacement Surcharge | MoPSC
Public Utilities, General Disclosures [Line Items]
Regulatory assets recovery		$ (28.8)

Financing - Additional Informat

Financing - Additional Information (Details)	Mar. 23, 2021USD ($)	Dec. 15, 2020USD ($)	Mar. 26, 2020USD ($)bank	Feb. 28, 2021USD ($)$ / sharesshares	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)shares	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)shares	Dec. 14, 2016bank
Debt Instrument And Equity Units [Line Items]
Long-term Debt					$ 975,000,000		$ 975,000,000
Common stock issued						$ 9,500,000		$ 9,500,000
Common Stock $1.00 par value
Debt Instrument And Equity Units [Line Items]
Common stock issued (in shares) | shares						112,758		112,758
Common stock issued						$ 100,000		$ 100,000
Liabilities | Lender Concentration Risk
Debt Instrument And Equity Units [Line Items]
Line of credit facility, number of banks in agreement | bank									11
Spire
Debt Instrument And Equity Units [Line Items]
Term loan bear interest rate per annum							0.40%
Short-term borrowings used to support lending to Utilities					398,100,000		$ 398,100,000
Present value of stock purchase contract payment recorded as liability					35,000,000
Spire | Common Stock $1.00 par value
Debt Instrument And Equity Units [Line Items]
Price divided by applicable market value to determine number of shares per stock purchase contract | $ / shares				$ 50
Spire | 2021 Series A 0.75% Remarketable Senior Notes
Debt Instrument And Equity Units [Line Items]
Stated interest rate				0.75%
Debt instrument, maturity date				Mar. 1, 2026
Debt instrument, payment terms				The Company will make 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%.
Common stock issued (in shares) | shares				3,500,000
Common stock issued				$ 175,000,000
Net proceeds after underwriting fees and other issuance costs				$ 169,300,000
Units price | $ / shares				$ 50
Percentage of undivided beneficial ownership interest				5.00%
Principal amount				$ 1,000
Stock purchase contracts rate				6.75%
Spire | 2021 Series A 0.75% Remarketable Senior Notes | Stock Purchase Contract
Debt Instrument And Equity Units [Line Items]
Units price | $ / shares				$ 50
Spire | Term Loan
Debt Instrument And Equity Units [Line Items]
Line of credit facility, number of banks in agreement | bank			2
Long-term Debt			$ 150,000,000
Team loan interest rate description							The term loan bore interest at the LIBOR Rate (as defined in the loan agreement) plus 0.85% per annum.
Term loan bear interest rate per annum							1.10%
Spire | Term Loan | LIBOR
Debt Instrument And Equity Units [Line Items]
Term loan bear interest rate per annum			0.85%
Spire | Senior Notes | 2021 Series A 0.75% Remarketable Senior Notes
Debt Instrument And Equity Units [Line Items]
Debt amount				$ 175,000,000
Stated interest rate				0.75%
Spire | Maximum | Common Stock $1.00 par value
Debt Instrument And Equity Units [Line Items]
Number of shares to be purchased per stock purchase contract, settlement rate | shares				0.7783
Spire | Minimum | Common Stock $1.00 par value
Debt Instrument And Equity Units [Line Items]
Number of shares to be purchased per stock purchase contract, settlement rate | shares				0.6354
Spire Missouri | Term Loan
Debt Instrument And Equity Units [Line Items]
Term loan bear interest rate per annum							0.80%
Spire Alabama | Senior Notes | Private Placement | Series 2020 Senior Notes due 2030
Debt Instrument And Equity Units [Line Items]
Long-term debt		$ 150,000,000
Stated interest rate		2.04%
Debt instrument, maturity date		Dec. 15, 2030
Debt instrument, payment terms							Interest is payable semi-annually.
Revolving Credit Facility Borrowings
Debt Instrument And Equity Units [Line Items]
Line of credit facility borrowing capacity					$ 975,000,000		$ 975,000,000
Minimum required ratio of earnings before interest, taxes, depreciation, and amortization (EBITDA) times interest expense as required by the line of credit covenant					70.00%		70.00%
Revolving Credit Facility Borrowings | Maximum
Debt Instrument And Equity Units [Line Items]
Debt to total capitalization ratio					0.60		0.60
Revolving Credit Facility Borrowings | Spire
Debt Instrument And Equity Units [Line Items]
Line of credit facility borrowing capacity					$ 300,000,000		$ 300,000,000
Revolving Credit Facility Borrowings | Spire Missouri
Debt Instrument And Equity Units [Line Items]
Line of credit facility borrowing capacity					475,000,000		475,000,000
Revolving Credit Facility Borrowings | Spire Alabama
Debt Instrument And Equity Units [Line Items]
Line of credit facility borrowing capacity					200,000,000		200,000,000
Commercial Paper Notes
Debt Instrument And Equity Units [Line Items]
Debt amount					$ 975,000,000		$ 975,000,000
Debt term							365 days
Commercial Paper Notes | Spire
Debt Instrument And Equity Units [Line Items]
Term loan bear interest rate per annum							0.30%
Unsecured Term Loan | Spire Missouri
Debt Instrument And Equity Units [Line Items]
Debt amount	$ 250,000,000
Debt term	364 days
Prepayment penalty	$ 0
Unsecured Term Loan | Spire Missouri | LIBOR
Debt Instrument And Equity Units [Line Items]
Interest rate	0.65%

Financing -Schedule of Short-te

Financing -Schedule of Short-term Borrowings (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020
Spire Alabama | Spire Note
Short-term Debt [Line Items]
Weighted average borrowings	$ 59.6
Highest borrowings outstanding	$ 152.2
Weighted average interest rate	0.20%
Borrowings outstanding		$ 121.3	$ 33
Weighted average interest rate		0.20%	1.90%
Spire Alabama | Revolving Credit Facility Borrowings
Short-term Debt [Line Items]
Borrowings outstanding			$ 50
Weighted average interest rate			1.90%
Spire Missouri | Term Loan
Short-term Debt [Line Items]
Weighted average borrowings	$ 11
Highest borrowings outstanding	$ 250
Weighted average interest rate	0.80%
Borrowings outstanding	$ 250
Weighted average interest rate	0.80%
Spire Missouri | Spire Note
Short-term Debt [Line Items]
Weighted average borrowings	$ 360.8
Lowest borrowings outstanding	277.2
Highest borrowings outstanding	$ 441.9
Weighted average interest rate	0.30%
Borrowings outstanding	$ 369.4	$ 301.2	$ 39.6
Weighted average interest rate	0.20%	0.20%	1.90%
Spire Missouri | Revolving Credit Facility Borrowings
Short-term Debt [Line Items]
Borrowings outstanding			$ 185.1
Weighted average interest rate			1.80%
Spire
Short-term Debt [Line Items]
Weighted average borrowings	$ 681.4
Lowest borrowings outstanding	455.5
Highest borrowings outstanding	$ 850.5
Weighted average interest rate	0.40%
Borrowings outstanding	$ 653.5	$ 648	$ 560.6
Weighted average interest rate	0.40%	0.60%	1.90%
Spire | Term Loan
Short-term Debt [Line Items]
Weighted average borrowings	$ 63.5
Highest borrowings outstanding	$ 150
Weighted average interest rate	1.10%
Borrowings outstanding		$ 150	$ 150
Weighted average interest rate		1.10%	2.10%
Spire | Commercial Paper Notes
Short-term Debt [Line Items]
Weighted average borrowings	$ 606.9
Lowest borrowings outstanding	403.5
Highest borrowings outstanding	$ 775
Weighted average interest rate	0.30%
Borrowings outstanding	$ 403.5	$ 498	$ 175.5
Weighted average interest rate	0.20%	0.20%	1.80%

Financing - Summary of Net of C

Financing - Summary of Net of Capitalized Interest (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Spire Missouri
Debt Instrument [Line Items]
Interest expense, net	$ 0.1	$ 0.3	$ 0.1	$ 0.6
Spire Alabama
Debt Instrument [Line Items]
Interest expense, net	0.7	0.4	1.3	1
Spire
Debt Instrument [Line Items]
Interest expense, net	$ 1.1	$ 1.4	$ 2	$ 3.6

Financing - Schedule of Variabl

Financing - Schedule of Variable Stock Purchase Contract Settlement Rates (Details) - Spire - Common Stock $1.00 par value	Feb. 28, 2021$ / sharesshares
Equity Units [Line Items]
Price divided by applicable market value to determine number of shares per stock purchase contract	$ 50
Maximum
Equity Units [Line Items]
Applicable market value per share	78.6906
Applicable market value per share, reference price	$ 64.24
Number of shares to be purchased per stock purchase contract, settlement rate | shares	0.7783
Minimum
Equity Units [Line Items]
Applicable market value per share, threshold appreciation price	$ 78.6906
Applicable market value per share	$ 64.24
Number of shares to be purchased per stock purchase contract, settlement rate | shares	0.6354

Financing - Schedule of Varia_2

Financing - Schedule of Variable Stock Purchase Contract Settlement Rates (Parenthetical) (Details)	1 Months Ended
	Feb. 28, 2021Day
Spire | 2021 Series A 0.75% Remarketable Senior Notes
Equity Units [Line Items]
Trading days before settlement	20

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020
Quoted Prices in Active Markets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 104	$ 4.1	$ 108.4
Quoted Prices in Active Markets (Level 1) | Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents			5.1
Quoted Prices in Active Markets (Level 1) | Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	18.2		0.1
Significant Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable	653.5	648	560.6
Long-term debt, including current portion	3,090.9	2,908.6	2,671
Significant Observable Inputs (Level 2) | Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable	250		185.1
Notes payable – associated companies	369.4	301.2	39.6
Long-term debt, including current portion	1,254.2	1,313.5	1,231.2
Significant Observable Inputs (Level 2) | Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable			50
Notes payable – associated companies		121.3	33
Notes receivable, associated companies	20
Long-term debt, including current portion	682.3	576.9	535.1
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	104	4.1	108.4
Notes payable	653.5	648	560.6
Long-term debt, including current portion	2,803.3	2,484.1	2,490.2
Carrying Amount | Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents			5.1
Notes payable	250		185.1
Notes payable – associated companies	369.4	301.2	39.6
Long-term debt, including current portion	1,092.4	1,092	1,098.7
Carrying Amount | Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	18.2		0.1
Notes payable			50
Notes payable – associated companies		121.3	33
Notes receivable, associated companies	20
Long-term debt, including current portion	621.1	471.8	471.7
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	104	4.1	108.4
Notes payable	653.5	648	560.6
Long-term debt, including current portion	3,090.9	2,908.6	2,671
Fair Value | Spire Missouri
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents			5.1
Notes payable	250		185.1
Notes payable – associated companies	369.4	301.2	39.6
Long-term debt, including current portion	1,254.2	1,313.5	1,231.2
Fair Value | Spire Alabama
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	18.2		0.1
Notes payable			50
Notes payable – associated companies		121.3	33
Notes receivable, associated companies	20
Long-term debt, including current portion	$ 682.3	$ 576.9	$ 535.1

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020
ASSETS
Effects of netting and cash margin receivables/payables	$ (13)	$ (32)	$ (11.9)
Derivative asset after the effects of netting	86.4	57.7	48.4
LIABILITIES
Effects of netting and cash margin receivables/payables	(6.5)	(23)	(26.3)
Derivative liability after the effects of netting	45.9	76.5	90.9
Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	(0.7)	(6.6)	(0.1)
Derivative asset after the effects of netting	23.5	21.9	18.1
LIABILITIES
Effects of netting and cash margin receivables/payables			(12.6)
Derivative liability after the effects of netting			0
U.S. stock/bond mutual funds | Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	0	0	0
Derivative asset after the effects of netting	23.5	21.9	18.1
NYMEX/ICE natural gas contracts | Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	(0.4)	(6.3)	(0.1)
Derivative asset after the effects of netting	0	0	0
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.8)	(0.9)	(12.2)
Derivative liability after the effects of netting	0	0	0
Gasoline and heating oil contracts | Spire Missouri
ASSETS
Effects of netting and cash margin receivables/payables	(0.3)	(0.3)
Derivative asset after the effects of netting	0	0
LIABILITIES
Effects of netting and cash margin receivables/payables			(0.4)
Derivative liability after the effects of netting			0
Other | U.S. stock/bond mutual funds
ASSETS
Effects of netting and cash margin receivables/payables	0	0	0
Derivative asset after the effects of netting	22.9	18.6	17.6
Other | Interest Rate Swap
ASSETS
Effects of netting and cash margin receivables/payables	0
Derivative asset after the effects of netting	27.9
LIABILITIES
Effects of netting and cash margin receivables/payables	0	0	0
Derivative liability after the effects of netting	21.4	54.2	66.9
Gas Utility | Operating Segments | U.S. stock/bond mutual funds
ASSETS
Effects of netting and cash margin receivables/payables	0	0	0
Derivative asset after the effects of netting	23.5	21.9	18.1
Gas Utility | Operating Segments | NYMEX/ICE natural gas contracts
ASSETS
Effects of netting and cash margin receivables/payables	(0.4)	(6.3)	(0.1)
Derivative asset after the effects of netting	0	0	0
LIABILITIES
Effects of netting and cash margin receivables/payables	(1.8)	(0.9)	(12.2)
Derivative liability after the effects of netting	0	0	0
Gas Utility | Operating Segments | Gasoline and heating oil contracts
ASSETS
Effects of netting and cash margin receivables/payables	(0.3)	(0.3)
Derivative asset after the effects of netting	0	0
LIABILITIES
Effects of netting and cash margin receivables/payables			(0.4)
Derivative liability after the effects of netting			0
Gas Marketing | Operating Segments | NYMEX/ICE natural gas contracts
ASSETS
Effects of netting and cash margin receivables/payables	(12.3)	(25.4)	(7)
Derivative asset after the effects of netting	2.8	2.3	0
LIABILITIES
Effects of netting and cash margin receivables/payables	(4.7)	(22.1)	(8.9)
Derivative liability after the effects of netting	0	0	0
Gas Marketing | Operating Segments | Natural gas commodity contracts
ASSETS
Effects of netting and cash margin receivables/payables	0	0	(4.8)
Derivative asset after the effects of netting	9.3	14.9	12.7
LIABILITIES
Effects of netting and cash margin receivables/payables	0	0	(4.8)
Derivative liability after the effects of netting	24.5	22.3	24
Quoted Prices in Active Markets (Level 1)
ASSETS
Derivative asset before effects of netting	47.1	47.1	36
LIABILITIES
Derivative liability before effects of netting	1.8	1.6	13.1
Quoted Prices in Active Markets (Level 1) | Spire Missouri
ASSETS
Derivative asset before effects of netting	24.2	28.5	18.2
LIABILITIES
Derivative liability before effects of netting			12.6
Quoted Prices in Active Markets (Level 1) | U.S. stock/bond mutual funds | Spire Missouri
ASSETS
Derivative asset before effects of netting	23.5	21.9	18.1
Quoted Prices in Active Markets (Level 1) | NYMEX/ICE natural gas contracts | Spire Missouri
ASSETS
Derivative asset before effects of netting	0.4	6.3	0.1
LIABILITIES
Derivative liability before effects of netting	1.8	0.9	12.2
Quoted Prices in Active Markets (Level 1) | Gasoline and heating oil contracts | Spire Missouri
ASSETS
Derivative asset before effects of netting	0.3	0.3
LIABILITIES
Derivative liability before effects of netting			0.4
Quoted Prices in Active Markets (Level 1) | Other | U.S. stock/bond mutual funds
ASSETS
Derivative asset before effects of netting	22.9	18.6	17.6
Quoted Prices in Active Markets (Level 1) | Other | Interest Rate Swap
ASSETS
Derivative asset before effects of netting	0
LIABILITIES
Derivative liability before effects of netting	0	0	0
Quoted Prices in Active Markets (Level 1) | Gas Utility | Operating Segments | U.S. stock/bond mutual funds
ASSETS
Derivative asset before effects of netting	23.5	21.9	18.1
Quoted Prices in Active Markets (Level 1) | Gas Utility | Operating Segments | NYMEX/ICE natural gas contracts
ASSETS
Derivative asset before effects of netting	0.4	6.3	0.1
LIABILITIES
Derivative liability before effects of netting	1.8	0.9	12.2
Quoted Prices in Active Markets (Level 1) | Gas Utility | Operating Segments | Gasoline and heating oil contracts
ASSETS
Derivative asset before effects of netting	0.3	0.3
LIABILITIES
Derivative liability before effects of netting			0.4
Quoted Prices in Active Markets (Level 1) | Gas Marketing | Operating Segments | NYMEX/ICE natural gas contracts
ASSETS
Derivative asset before effects of netting	0	0	0.2
LIABILITIES
Derivative liability before effects of netting	0	0.7	0.5
Quoted Prices in Active Markets (Level 1) | Gas Marketing | Operating Segments | Natural gas commodity contracts
ASSETS
Derivative asset before effects of netting	0	0	0
LIABILITIES
Derivative liability before effects of netting	0	0	0
Significant Observable Inputs (Level 2)
ASSETS
Derivative asset before effects of netting	52.3	42.2	24.3
LIABILITIES
Derivative liability before effects of netting	50.6	97.9	103
Significant Observable Inputs (Level 2) | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0	0
LIABILITIES
Derivative liability before effects of netting			0
Significant Observable Inputs (Level 2) | U.S. stock/bond mutual funds | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0	0
Significant Observable Inputs (Level 2) | NYMEX/ICE natural gas contracts | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0	0
LIABILITIES
Derivative liability before effects of netting	0	0	0
Significant Observable Inputs (Level 2) | Gasoline and heating oil contracts | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting			0
Significant Observable Inputs (Level 2) | Other | U.S. stock/bond mutual funds
ASSETS
Derivative asset before effects of netting	0	0	0
Significant Observable Inputs (Level 2) | Other | Interest Rate Swap
ASSETS
Derivative asset before effects of netting	27.9
LIABILITIES
Derivative liability before effects of netting	21.4	54.2	66.9
Significant Observable Inputs (Level 2) | Gas Utility | Operating Segments | U.S. stock/bond mutual funds
ASSETS
Derivative asset before effects of netting	0	0	0
Significant Observable Inputs (Level 2) | Gas Utility | Operating Segments | NYMEX/ICE natural gas contracts
ASSETS
Derivative asset before effects of netting	0	0	0
LIABILITIES
Derivative liability before effects of netting	0	0	0
Significant Observable Inputs (Level 2) | Gas Utility | Operating Segments | Gasoline and heating oil contracts
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting			0
Significant Observable Inputs (Level 2) | Gas Marketing | Operating Segments | NYMEX/ICE natural gas contracts
ASSETS
Derivative asset before effects of netting	15.1	27.7	6.8
LIABILITIES
Derivative liability before effects of netting	4.7	21.4	8.4
Significant Observable Inputs (Level 2) | Gas Marketing | Operating Segments | Natural gas commodity contracts
ASSETS
Derivative asset before effects of netting	9.3	14.5	17.5
LIABILITIES
Derivative liability before effects of netting	24.5	22.3	27.7
Significant Unobservable Inputs (Level 3)
ASSETS
Derivative asset before effects of netting	0	0.4	0
LIABILITIES
Derivative liability before effects of netting	0	0	1.1
Significant Unobservable Inputs (Level 3) | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0	0
LIABILITIES
Derivative liability before effects of netting			0
Significant Unobservable Inputs (Level 3) | U.S. stock/bond mutual funds | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0	0
Significant Unobservable Inputs (Level 3) | NYMEX/ICE natural gas contracts | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0	0
LIABILITIES
Derivative liability before effects of netting	0	0	0
Significant Unobservable Inputs (Level 3) | Gasoline and heating oil contracts | Spire Missouri
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting			0
Significant Unobservable Inputs (Level 3) | Other | U.S. stock/bond mutual funds
ASSETS
Derivative asset before effects of netting	0	0	0
Significant Unobservable Inputs (Level 3) | Other | Interest Rate Swap
ASSETS
Derivative asset before effects of netting	0
LIABILITIES
Derivative liability before effects of netting	0	0	0
Significant Unobservable Inputs (Level 3) | Gas Utility | Operating Segments | U.S. stock/bond mutual funds
ASSETS
Derivative asset before effects of netting	0	0	0
Significant Unobservable Inputs (Level 3) | Gas Utility | Operating Segments | NYMEX/ICE natural gas contracts
ASSETS
Derivative asset before effects of netting	0	0	0
LIABILITIES
Derivative liability before effects of netting	0	0	0
Significant Unobservable Inputs (Level 3) | Gas Utility | Operating Segments | Gasoline and heating oil contracts
ASSETS
Derivative asset before effects of netting	0	0
LIABILITIES
Derivative liability before effects of netting			0
Significant Unobservable Inputs (Level 3) | Gas Marketing | Operating Segments | NYMEX/ICE natural gas contracts
ASSETS
Derivative asset before effects of netting	0	0	0
LIABILITIES
Derivative liability before effects of netting	0	0	0
Significant Unobservable Inputs (Level 3) | Gas Marketing | Operating Segments | Natural gas commodity contracts
ASSETS
Derivative asset before effects of netting	0	0.4	0
LIABILITIES
Derivative liability before effects of netting	$ 0	$ 0	$ 1.1

Pension Plans and Other Postr_3

Pension Plans and Other Postretirement Benefits - Schedule of Net Periodic Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	$ 5.3	$ 5.6	$ 10.9	$ 11.1
Interest cost on projected benefit obligation	4.6	5.8	9.8	11.7
Expected return on plan assets	(7.1)	(9)	(15.1)	(18.2)
Amortization of prior service cost (credit)	(0.7)	(0.6)	(1.5)	(1.2)
Amortization of actuarial (gain) loss	3.8	3.9	7.8	7.6
Loss on lump-sum settlements	3.8	21	3.8	21
Subtotal	9.7	26.7	15.7	32
Regulatory adjustment	5.2	(11.3)	14.8	(1.7)
Net pension cost	14.9	15.4	30.5	30.3
Other Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	1.9	1.5	3.7	2.9
Interest cost on projected benefit obligation	1.6	1.5	3	3.1
Expected return on plan assets	(4.1)	(4.1)	(8.1)	(8.2)
Amortization of prior service cost (credit)	0.2	(0.1)	0.5	(0.3)
Amortization of actuarial (gain) loss	(0.4)	(0.5)	(0.8)	(1)
Subtotal	(0.8)	(1.7)	(1.7)	(3.5)
Regulatory adjustment	3.2	4	6.6	8
Net pension cost	2.4	2.3	4.9	4.5
Spire Missouri | Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	3.9	3.9	7.8	7.7
Interest cost on projected benefit obligation	3.5	4	7	8.2
Expected return on plan assets	(5.6)	(6.3)	(11.2)	(12.9)
Amortization of prior service cost (credit)	(0.1)	0.1	(0.3)	0.1
Amortization of actuarial (gain) loss	2.8	3.1	5.7	6
Loss on lump-sum settlements		21		21
Subtotal	4.5	25.8	9	30.1
Regulatory adjustment	7.5	(13.2)	15.1	(5.5)
Net pension cost	12	12.6	24.1	24.6
Spire Missouri | Other Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	1.5	1.3	3.1	2.6
Interest cost on projected benefit obligation	1.1	1.1	2.2	2.3
Expected return on plan assets	(2.8)	(2.9)	(5.5)	(5.7)
Amortization of prior service cost (credit)	0.2		0.4	(0.1)
Amortization of actuarial (gain) loss	(0.3)	(0.5)	(0.7)	(1)
Subtotal	(0.3)	(1)	(0.5)	(1.9)
Regulatory adjustment	3.7	4.5	7.5	8.9
Net pension cost	3.4	3.5	7	7
Spire Alabama | Pension Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	1.4	1.5	2.9	3
Interest cost on projected benefit obligation	1.2	1.3	2.4	2.5
Expected return on plan assets	(1.5)	(1.8)	(3.1)	(3.5)
Amortization of prior service cost (credit)	(0.6)	(0.6)	(1.2)	(1.2)
Amortization of actuarial (gain) loss	1	0.8	2.1	1.6
Loss on lump-sum settlements	3.8		3.8
Subtotal	5.3	1.2	6.9	2.4
Regulatory adjustment	(2.5)	1.7	(0.7)	3.4
Net pension cost	2.8	2.9	6.2	5.8
Spire Alabama | Other Postretirement Plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost – benefits earned during the period	0.3	0.1	0.5	0.2
Interest cost on projected benefit obligation	0.4	0.4	0.7	0.7
Expected return on plan assets	(1.3)	(1.2)	(2.5)	(2.4)
Amortization of prior service cost (credit)		(0.1)	0.1	(0.2)
Subtotal	(0.6)	(0.8)	(1.2)	(1.7)
Regulatory adjustment	(0.5)	(0.5)	(0.9)	(0.9)
Net pension cost	$ (1.1)	$ (1.3)	$ (2.1)	$ (2.6)

Pension Plans and Other Postr_4

Pension Plans and Other Postretirement Benefits - Additional Information (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2021USD ($)plan	Mar. 31, 2020USD ($)plan	Mar. 31, 2021USD ($)plan	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Medical insurance available until age is reached after early retirement			65 years
Other Postretirement Benefits Plan
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions			$ 4,500,000
Other Postretirement Benefits Plan | Spire Alabama
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of Plans | plan	1		1
Settlement benefits paid	$ 12,900,000		$ 0
Settlement loss	$ 3,800,000
Discount rates				2.95%	3.20%
Settlement losses amortized over remaining actuarial life			11 years 4 months 24 days
Anticipated contributions to pension plans for qualified trust			$ 6,600,000
Other Postretirement Benefits Plan | Spire Missouri
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of Plans | plan		2
Settlement benefits paid		$ 59,100,000
Settlement loss		$ 21,000,000
Discount rates				2.85%	3.20%
Anticipated contributions to pension plans for qualified trust			13,700,000
Other Postretirement Benefits Plan | Spire Missouri | Qualified Plan
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions			28,300,000
Other Postretirement Benefits Plan | Spire Missouri | Nonqualified Plan
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions			0
Other Postretirement Benefits Plan | Spire Alabama
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions			0
Anticipated contributions to pension plans for qualified trust			0
Other Postretirement Benefits Plan | Spire Missouri
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions			0
Anticipated contributions to pension plans for qualified trust			$ 0

Information by Operating Segm_3

Information by Operating Segment - Additional Information (Details) - 6 months ended Mar. 31, 2021	reporting_unit	operating-segment
Segment Reporting [Abstract]
Number of reportable segments	2	2

Information by Operating Segm_4

Information by Operating Segment - Schedule of Operating Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Operating Segment Information [Abstract]
Revenues from external customers	$ 1,104.9	$ 715.5	$ 1,617.5	$ 1,282.4
Total operating revenues	1,104.9	715.5	1,617.5	1,282.4
Operating Expenses:
Natural gas	619.1	297.1	800.3	559
Operation and maintenance	119	105.7	230.6	222.3
Depreciation and amortization	51.5	49.2	102.3	96.7
Taxes, other than income taxes	57.9	53	94	91.6
Total Operating Expenses	847.5	505	1,227.2	969.6
Net Economic Earnings (Loss)	195.6	144	272.5	215.8
Operating Income	257.4	210.5	390.3	312.8
Total Assets	8,936.8	8,018	8,936.8	8,018	$ 8,241.2
Eliminations
Operating Segment Information [Abstract]
Total operating revenues	2.8	(11.5)	(24.3)	(18.7)
Operating Expenses:
Natural gas	6	(8.2)	(17.8)	(12.4)
Operation and maintenance	(3.2)	(3.3)	(6.5)	(6.3)
Depreciation and amortization	0	0	0	0
Taxes, other than income taxes	0	0	0	0
Total Operating Expenses	2.8	(11.5)	(24.3)	(18.7)
Net Economic Earnings (Loss)	0	0	0	0
Operating Income	0	0	0	0
Total Assets	(1,182.9)	(667.6)	(1,182.9)	(667.6)	(1,101.2)
Other
Operating Segment Information [Abstract]
Revenues from external customers	4.5	3.1	9.2	7.1
Intersegment revenues	11.1	11.6	23.1	18.7
Total operating revenues	15.6	14.7	32.3	25.8
Operating Expenses:
Natural gas	0.1	0.1	0.1	0.2
Operation and maintenance	11.1	9.6	19.7	17.5
Depreciation and amortization	1.7	2.1	3.6	3.2
Taxes, other than income taxes	1	0.9	1.4	1.3
Total Operating Expenses	13.9	12.7	24.8	22.2
Net Economic Earnings (Loss)	(3.9)	(5.4)	(6.7)	(8.8)
Operating Income	1.7	2	7.5	3.6
Total Assets	2,513.7	2,214.7	2,513.7	2,214.7	2,443.5
Gas Utility
Operating Segment Information [Abstract]
Revenues from external customers	1,053	679.1	1,550.2	1,209.7
Intersegment revenues	0.1	(0.1)	1.1	0
Gas Utility | Operating Segments
Operating Segment Information [Abstract]
Total operating revenues	1,053.1	679	1,551.3	1,209.7
Operating Expenses:
Natural gas	619.2	271.6	823.5	513.1
Operation and maintenance	104	95.8	207	204.4
Depreciation and amortization	49.5	47	98.1	93.4
Taxes, other than income taxes	56.4	51.7	91.9	89.6
Total Operating Expenses	829.1	466.1	1,220.5	900.5
Net Economic Earnings (Loss)	159.7	144.3	236.1	213.4
Operating Income	224	212.9	330.8	309.2
Total Assets	7,265	6,311.6	7,265	6,311.6	6,716.2
Gas Marketing
Operating Segment Information [Abstract]
Revenues from external customers	47.4	33.3	58.1	65.6
Intersegment revenues	(14)	0	0.1	0
Gas Marketing | Operating Segments
Operating Segment Information [Abstract]
Total operating revenues	33.4	33.3	58.2	65.6
Operating Expenses:
Natural gas	(6.2)	33.6	(5.5)	58.1
Operation and maintenance	7.1	3.6	10.4	6.7
Depreciation and amortization	0.3	0.1	0.6	0.1
Taxes, other than income taxes	0.5	0.4	0.7	0.7
Total Operating Expenses	1.7	37.7	6.2	65.6
Net Economic Earnings (Loss)	39.8	5.1	43.1	11.2
Operating Income	31.7	(4.4)	52	0
Total Assets	$ 341	$ 159.3	$ 341	$ 159.3	$ 182.7

Information by Operating Segm_5

Information by Operating Segment - Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting [Abstract]
Net Income	$ 187.4	$ 133.6	$ 276.3	$ 200.6
Missouri regulatory adjustment	(9)	0	(9)	0
Provision for ISRS rulings	0	2.2	0	4.8
Fair value and timing adjustments	20.1	11.6	4.1	15.3
Income tax effect of adjustments	(2.9)	(3.4)	1.1	(4.9)
Net Economic Earnings (Loss)	$ 195.6	$ 144	$ 272.5	$ 215.8

Commitments and Contingencies -

Commitments and Contingencies - Additional Information - Commitments (Details) $ in Millions	6 Months Ended
	Mar. 31, 2021USD ($)
Long-term Purchase Commitment [Line Items]
Minimum total payments required for natural gas contracts	$ 1,632.2
Spire Missouri
Long-term Purchase Commitment [Line Items]
Minimum total payments required for natural gas contracts	1,264.6
Spire Alabama
Long-term Purchase Commitment [Line Items]
Minimum total payments required for natural gas contracts	$ 244.7

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information - Contingencies (Details)	Mar. 31, 2021site
Spire Missouri East
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP) sites in Missouri	3
Number of sites enrolled in Brownfields/Voluntary clean up program	2
Spire Missouri West | Previous Ownership
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP)	6
Spire Alabama
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP)	9
Number of former manufactured gas distribution	5
Spire Alabama | Current Ownership
Site Contingency [Line Items]
Number of former manufactured gas plant (MGP)	4
Number of former manufactured gas distribution	1