Document And Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2022	Nov. 11, 2022	Mar. 31, 2022
Document Information [Line Items]
Entity Central Index Key	0001126956
Entity Registrant Name	Spire Inc.
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2022
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	1-16681
Entity Address, Address Line One	700 Market Street
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63101
City Area Code	314
Local Phone Number	342-0500
Entity Incorporation, State or Country Code	MO
Entity Tax Identification Number	74-2976504
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
ICFR Auditor Attestation Flag	true
Entity Common Stock, Shares Outstanding		52,499,844
Entity Public Float			$ 3,627,663,025
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 Shell Company	false
Auditor Name	Deloitte & Touche LLP
Auditor Location	St. Louis, Missouri
Auditor Firm ID	34
Spire Missouri [Member]
Document Information [Line Items]
Entity Central Index Key	0001126956
Entity Registrant Name	Spire Missouri Inc.
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2022
Entity File Number	1-1822
Entity Address, Address Line One	700 Market Street
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63101
City Area Code	314
Local Phone Number	342-0500
Entity Incorporation, State or Country Code	MO
Entity Tax Identification Number	43-0368139
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
ICFR Auditor Attestation Flag	false
Entity Common Stock, Shares Outstanding		25,325
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 Shell Company	false
Auditor Name	Deloitte & Touche LLP
Auditor Location	St. Louis, Missouri
Auditor Firm ID	34
Spire Alabama Inc [Member]
Document Information [Line Items]
Entity Central Index Key	0001126956
Entity Registrant Name	Spire Alabama Inc.
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2022
Entity File Number	2-38960
Entity Address, Address Line One	605 Richard Arrington Blvd N
Entity Address, City or Town	Birmingham
Entity Address, State or Province	AL
Entity Address, Postal Zip Code	35203
City Area Code	205
Local Phone Number	326-8100
Entity Incorporation, State or Country Code	AL
Entity Tax Identification Number	63-0022000
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
ICFR Auditor Attestation Flag	false
Entity Common Stock, Shares Outstanding		1,972,052
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 Shell Company	false
Auditor Name	Deloitte & Touche LLP
Auditor Location	St. Louis, Missouri
Auditor Firm ID	34
Depositary Shares [Member]
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/1,000th interest in a share of 5.90% Series A Cumulative Redeemable Perpetual
Trading Symbol	SR.PRA
Security Exchange Name	NYSE
Common Stock [Member]
Document Information [Line Items]
Title of 12(b) Security	Common Stock $1.00 par value
Trading Symbol	SR
Security Exchange Name	NYSE