Revenue (Tables)

12 Months Ended

Sep. 30, 2025

Revenue from Contract with Customer [Abstract]

Schedule of Revenue Disaggregated by Source and Customer Type

	2025			2024			2023
Spire
Gas Utility:
Residential	$	1,462.6		$	1,617.4		$	1,648.5
Commercial & industrial		501.3			581.0			606.0
Transportation		133.6			130.0			121.6
Off-system & other incentive		65.3			37.0			30.0
Other customer revenue		24.4			21.2			16.1
Total revenue from contracts with customers		2,187.2			2,386.6			2,422.2
Changes in accrued revenue under alternative revenue programs		20.3			51.3			34.7
Total Gas Utility operating revenues		2,207.5			2,437.9			2,456.9
Gas Marketing		157.2			99.2			179.1
Midstream		155.5			100.7			66.1
Other		20.6			17.6			16.7
Total before eliminations		2,540.8			2,655.4			2,718.8
Intercompany eliminations		(64.4	)		(62.4	)		(52.5	)
Total Operating Revenues	$	2,476.4		$	2,593.0		$	2,666.3
Spire Missouri
Residential	$	1,092.1		$	1,217.7		$	1,261.3
Commercial & industrial		326.0			390.9			411.9
Transportation		35.9			34.1			33.2
Off-system & other incentive		51.9			28.8			20.1
Other customer revenue		14.0			14.9			12.5
Total revenue from contracts with customers		1,519.9			1,686.4			1,739.0
Changes in accrued revenue under alternative revenue programs		24.2			51.0			23.9
Total Operating Revenues	$	1,544.1		$	1,737.4		$	1,762.9
Spire Alabama
Residential	$	307.5		$	336.4		$	322.9
Commercial & industrial		134.5			149.5			150.4
Transportation		87.3			85.1			77.6
Off-system & other incentive		13.4			8.1			9.9
Other customer revenue		6.3			(0.4	)		3.6
Total revenue from contracts with customers		549.0			578.7			564.4
Changes in accrued revenue under alternative revenue programs		(3.8	)		0.2			6.7
Total Operating Revenues	$	545.2		$	578.9		$	571.1

Schedule of Gross Receipts Taxes Associated Revenues

	2025		2024		2023
Spire	$	115.7	$	128.2	$	131.8
Spire Missouri		82.9		93.1		96.7
Spire Alabama		27.9		30.1		29.9