Note 9 - Fair Value Measurements (Details Textual) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Spire Alabama Inc [Member] \| Gasoline Derivative Program [Member]
Derivative Assets (Liabilities), at Fair Value, Net, Total	$ 0	$ 0

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=126966630&loc=d3e41228-113958

Name:	us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant