Note 5 - Shareholders' Equity (Tables)

12 Months Ended

Sep. 30, 2024

Notes Tables

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

	Net			Defined Benefit			Net Unrealized
	Unrealized			Pension and			Gain (Loss) on
	Gain (Loss)			Other			Available-for-
	on Cash Flow			Postretirement			Sale Debt
	Hedges			Benefit Plans			Securities			Total
Spire
Balance at September 30, 2022	$	50.4		$	(2.7	)	$	(0.5	)	$	47.2
Other comprehensive income		0.1			0.2			0.1			0.4
Balance at September 30, 2023		50.5			(2.5	)		(0.4	)		47.6
Other comprehensive income		(36.3	)		0.5			0.3			(35.5	)
Balance at September 30, 2024	$	14.2		$	(2.0	)	$	(0.1	)	$	12.1
Spire Missouri
Balance at September 30, 2022	$	—		$	(2.7	)	$	—		$	(2.7	)
Other comprehensive income		—			0.2			—			0.2
Balance at September 30, 2023		—			(2.5	)		—			(2.5	)
Other comprehensive (loss) income		—			0.5			—			0.5
Balance at September 30, 2024	$	—		$	(2.0	)	$	—		$	(2.0	)