Note 1 - Summary of Significant Accounting Policies (Tables)

3 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Related Party Transactions [Table Text Block]

	Three Months Ended December 31,
	2023		2022
Spire Missouri
Purchases of natural gas from Spire Marketing	$	5.0	$	28.5
Transportation services received from Spire STL Pipeline		8.2		8.1
Natural gas storage services from Spire Storage Salt Plains LLC		0.3		—
Spire Alabama
Purchases of natural gas from Spire Marketing	$	3.4	$	1.1

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

	December 31,		September 30,		December 31,
	2023		2023		2022
Spire	$	90.5	$	104.3	$	63.1
Spire Missouri		38.1		56.5		32.8
Spire Alabama		2.4		4.6		9.4

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

	Spire						Spire Missouri						Spire Alabama
Three Months Ended December 31,	2023			2022			2023			2022			2023			2022
Allowance at beginning of period	$	32.5		$	31.9		$	26.2		$	24.9		$	5.7		$	6.3
Provision for expected credit losses		4.1			4.1			3.6			3.8			0.3			0.2
Write-offs, net of recoveries		(1.2	)		(1.5	)		(0.9	)		(0.5	)		(0.3	)		(1.0	)
Allowance at end of period	$	35.4		$	34.5		$	28.9		$	28.2		$	5.7		$	5.5