Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2023		Sep. 30, 2022		Sep. 30, 2021
Operating Revenues	$ 2,666.3		$ 2,198.5		$ 2,235.5
Operating Expenses:
Natural gas	1,260.8		923.9		946.3
Operation and maintenance	517.6		449.6		465.8
Depreciation and amortization	254.8		237.3		213.1
Taxes, other than income taxes	214.5		179.5		160.1
Total Operating Expenses	2,247.7		1,790.3		1,785.3
Operating Income	418.6		408.2		450.2
Interest Expense	185.7		119.8		106.6
Other Income (Expense), Net	23.4		(8.7)		(3.4)
Income Before Income Taxes	256.3		279.7		340.2
Income Tax Expense	38.8		58.9		68.5
Net Income	217.5		220.8		271.7
Provision for preferred dividends	14.8		14.8		14.8
Income allocated to participating securities	0.3		0.3		0.4
Net Income Available to Common Shareholders	202.4		205.7		256.5
Other Comprehensive Income (Loss), Net of Tax	0.4		43.6		44.8
Comprehensive Income	217.9		264.4		316.5
Operating Revenues	$ 2,666.3		$ 2,198.5		$ 2,235.5
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	52.5		52.0		51.6
Diluted (in shares)	52.6		52.1		51.7
Basic Earnings Per Share of Common Stock (in dollars per share)	$ 3.86		$ 3.96		$ 4.97
Diluted Earnings Per Share of Common Stock (in dollars per share)	$ 3.85		$ 3.95		$ 4.96
Operating Revenues	$ 2,666.3		$ 2,198.5		$ 2,235.5
Spire Missouri [Member]
Operating Revenues	1,762.9		1,321.0		1,516.6
Operating Expenses:
Natural gas	943.4		587.0		786.8
Operation and maintenance	296.2		255.7		261.1
Depreciation and amortization	158.7		145.3		129.2
Taxes, other than income taxes	157.5		129.0		110.9
Total Operating Expenses	1,555.8		1,117.0		1,288.0
Operating Income	207.1		204.0		228.6
Interest Expense	97.4		60.9		50.3
Other Income (Expense), Net	19.4		(6.9)		(8.9)
Income Before Income Taxes	129.1		136.2		169.4
Income Tax Expense	11.6		21.3		25.3
Net Income	117.5		114.9		144.1	[1]
Other Comprehensive Income (Loss), Net of Tax	0.2	[1]	1.5	[1]	(1.3)
Comprehensive Income	117.7		116.4		142.8
Operating Revenues	1,762.9		1,321.0		1,516.6
Weighted Average Number of Common Shares Outstanding:
Operating Revenues	1,762.9		1,321.0		1,516.6
Spire Alabama Inc [Member]
Operating Revenues	571.1		509.1		494.0
Operating Expenses:
Natural gas	202.7		161.5		145.3
Operation and maintenance	136.4		130.1		132.5
Depreciation and amortization	69.3		66.8		62.1
Taxes, other than income taxes	43.0		38.1		37.1
Total Operating Expenses	451.4		396.5		377.0
Operating Income	119.7		112.6		117.0
Interest Expense	34.9		21.3		20.2
Other Income (Expense), Net	1.5		0.4		2.0
Income Before Income Taxes	86.3		91.7		98.8
Income Tax Expense	20.3		23.2		25.0
Net Income	66.0		68.5		73.8
Operating Revenues	571.1		509.1		494.0
Weighted Average Number of Common Shares Outstanding:
Operating Revenues	$ 571.1		$ 509.1		$ 494.0

[1] Accumulated other comprehensive income (loss)