Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Operating Revenues	$ 1,128.5	$ 1,123.4	$ 1,885.1	$ 1,937.4
Operating Expenses:
Natural gas	540.8	586.5	907.8	1,005.7
Operation and maintenance	137.8	132.1	268.5	264.2
Depreciation and amortization	68.9	62.6	135.9	124.7
Taxes, other than income taxes	82.4	81.9	135.1	132.3
Total Operating Expenses	829.9	863.1	1,447.3	1,526.9
Operating Income	298.6	260.3	437.8	410.5
Interest Expense, Net	52.2	47.2	102.8	90.8
Other Income, Net	7.3	7.0	24.8	13.0
Income Before Income Taxes	253.7	220.1	359.8	332.7
Income Tax Expense	49.4	40.9	70.4	62.5
Net Income	204.3	179.2	289.4	270.2
Provision for preferred dividends	3.7	3.7	7.4	7.4
Income allocated to participating securities	0.3	0.4	0.4	0.5
Net Income Available to Common Shareholders	$ 200.3	$ 175.1	$ 281.6	$ 262.3
Weighted Average Number of Common Shares Outstanding:
Basic (in shares)	55.8	52.5	54.6	52.5
Diluted (in shares)	55.9	52.6	54.7	52.6
Basic Earnings Per Common Share (in dollars per share)	$ 3.59	$ 3.33	$ 5.16	$ 5
Diluted Earnings Per Common Share (in dollars per share)	$ 3.58	$ 3.33	$ 5.14	$ 4.99
Operating Revenues	$ 1,128.5	$ 1,123.4	$ 1,885.1	$ 1,937.4
Spire Alabama Inc [Member]
Operating Revenues	259.5	218.3	401.6	370.7
Operating Expenses:
Natural gas	85.6	61.8	141.4	131.2
Operation and maintenance	35.4	34.5	69.6	69.6
Depreciation and amortization	18.2	17.0	36.1	34.0
Taxes, other than income taxes	17.9	16.1	28.1	26.7
Total Operating Expenses	157.1	129.4	275.2	261.5
Operating Income	102.4	88.9	126.4	109.2
Interest Expense, Net	8.3	9.0	17.6	17.3
Other Income, Net	0.4	0.3	0.7	0.7
Income Before Income Taxes	94.5	80.2	109.5	92.6
Income Tax Expense	23.8	20.2	27.7	23.4
Net Income	70.7	60.0	81.8	69.2
Weighted Average Number of Common Shares Outstanding:
Operating Revenues	$ 259.5	$ 218.3	$ 401.6	$ 370.7