Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Operating Revenues	$ 1,051.3	$ 1,128.5	$ 1,720.4	$ 1,885.1
Operating Expenses:
Natural gas	454.9	540.8	724.9	907.8
Operation and maintenance	139.4	137.8	268.7	268.5
Depreciation and amortization	73.7	68.9	146.0	135.9
Taxes, other than income taxes	76.9	82.4	125.6	135.1
Total Operating Expenses	744.9	829.9	1,265.2	1,447.3
Operating Income	306.4	298.6	455.2	437.8
Interest Expense, Net	47.4	52.2	95.4	102.8
Other Income (Expense), Net	3.0	7.3	3.6	24.8
Income Before Income Taxes	262.0	253.7	363.4	359.8
Income Tax Expense	52.7	49.4	72.8	70.4
Net Income (Loss)	209.3	204.3	290.6	289.4
Provision for preferred dividends	3.7	3.7	7.4	7.4
Income allocated to participating securities	0.3	0.3	0.4	0.4
Net Income Available to Common Shareholders	$ 205.3	$ 200.3	$ 282.8	$ 281.6
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	58.3	55.8	58.0	54.6
Diluted (in shares)	58.5	55.9	58.2	54.7
Basic Earnings Per Common Share (in dollars per share)	$ 3.52	$ 3.59	$ 4.88	$ 5.16
Diluted Earnings Per Common Share (in dollars per share)	$ 3.51	$ 3.58	$ 4.86	$ 5.14
Spire Alabama Inc [Member]
Operating Revenues	$ 252.4	$ 259.5	$ 372.8	$ 401.6
Operating Expenses:
Natural gas	79.6	85.6	112.3	141.4
Operation and maintenance	37.6	35.4	69.5	69.6
Depreciation and amortization	17.9	18.2	35.7	36.1
Taxes, other than income taxes	16.7	17.9	25.3	28.1
Total Operating Expenses	151.8	157.1	242.8	275.2
Operating Income	100.6	102.4	130.0	126.4
Interest Expense, Net	7.4	8.3	15.2	17.6
Other Income (Expense), Net	0.3	0.4	(0.4)	0.7
Income Before Income Taxes	93.5	94.5	114.4	109.5
Income Tax Expense	23.5	23.8	28.7	27.7
Net Income (Loss)	$ 70.0	$ 70.7	$ 85.7	$ 81.8