Note 1 - Summary of Significant Accounting Policies (Tables)

3 Months Ended

Dec. 31, 2022

Notes Tables

Schedule of Related Party Transactions [Table Text Block]

	Three Months Ended December 31,
	2022		2021
Spire Missouri
Purchases of natural gas from Spire Marketing Inc.	$	28.5	$	18.2
Transportation services received from Spire STL Pipeline LLC		8.1		8.1
Spire Alabama
Purchases of natural gas from Spire Marketing Inc.	$	1.1	$	—

Schedule Of Capital Expenditure Excluded From Statement Of Cash Flow [Table Text Block]

	December 31,		September 30,		December 31,
	2022		2022		2021
Spire	$	63.1	$	77.8	$	33.5
Spire Missouri		32.8		45.6		27.2
Spire Alabama		9.4		19.2		1.2

Accounts Receivable, Allowance for Credit Loss [Table Text Block]

	Spire						Spire Missouri						Spire Alabama
Three Months Ended December 31,	2022			2021			2022			2021			2022			2021
Allowance at beginning of period	$	31.9		$	30.3		$	24.9		$	22.6		$	6.3		$	6.6
Provision for expected credit losses		4.1			1.5			3.8			2.1			0.2			(0.5	)
Write-offs, net of recoveries		(1.5	)		(0.4	)		(0.5	)		(0.9	)		(1.0	)		0.6
Allowance at end of period	$	34.5		$	31.4		$	28.2		$	23.8		$	5.5		$	6.7