Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Operating Revenues	$ 2,476.4	$ 2,593.0	$ 2,666.3
Operating Expenses:
Natural gas	905.5	1,103.3	1,260.8
Operation and maintenance	542.1	507.4	517.6
Depreciation and amortization	298.2	278.4	254.8
Taxes, other than income taxes	206.7	215.6	214.5
Total Operating Expenses	1,952.5	2,104.7	2,247.7
Operating Income	523.9	488.3	418.6
Interest Expense	204.1	201.1	185.7
Other Income, Net	11.6	22.4	23.4
Income Before Income Taxes	331.4	309.6	256.3
Income Tax Expense	59.7	58.7	38.8
Net Income	271.7	250.9	217.5
Provision for preferred dividends	14.8	14.8	14.8
Income allocated to participating securities	0.3	0.3	0.3
Net Income Available to Common Shareholders	$ 256.6	$ 235.8	$ 202.4
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	58.5	56.1	52.5
Diluted (in shares)	58.7	56.3	52.6
Basic Earnings Per Share of Common Stock (in dollars per share)	$ 4.39	$ 4.2	$ 3.86
Diluted Earnings Per Share of Common Stock (in dollars per share)	$ 4.37	$ 4.19	$ 3.85
Spire Missouri [Member]
Operating Revenues	$ 1,544.1	$ 1,737.4	$ 1,762.9
Operating Expenses:
Natural gas	669.4	886.2	943.4
Operation and maintenance	300.7	287.4	296.2
Depreciation and amortization	188.4	174.0	158.7
Taxes, other than income taxes	151.1	157.7	157.5
Total Operating Expenses	1,309.6	1,505.3	1,555.8
Operating Income	234.5	232.1	207.1
Interest Expense	100.2	106.4	97.4
Other Income, Net	7.8	8.4	19.4
Income Before Income Taxes	142.1	134.1	129.1
Income Tax Expense	13.8	15.7	11.6
Net Income	128.3	118.4	117.5
Spire Alabama Inc [Member]
Operating Revenues	545.2	578.9	571.1
Operating Expenses:
Natural gas	154.4	189.5	202.7
Operation and maintenance	137.1	135.6	136.4
Depreciation and amortization	71.0	72.8	69.3
Taxes, other than income taxes	40.2	42.7	43.0
Total Operating Expenses	402.7	440.6	451.4
Operating Income	142.5	138.3	119.7
Interest Expense	29.6	33.1	34.9
Other Income, Net	0.4	1.8	1.5
Income Before Income Taxes	113.3	107.0	86.3
Income Tax Expense	28.4	26.9	20.3
Net Income	$ 84.9	$ 80.1	$ 66.0