Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2024		Mar. 31, 2023		Mar. 31, 2024		Mar. 31, 2023
Net Income	$ 204.3		$ 179.2		$ 289.4		$ 270.2
Other Comprehensive Income (Loss), Before Tax:
Net hedging gain (loss) arising during the period	9.1		(6.8)		(6.3)		(9.8)
Amounts reclassified into regulatory liabilities	0.0		(17.5)		0.0		(17.5)
Amounts reclassified into net income	(0.6)		(0.5)		(9.6)		(0.8)
Net gain (loss) on cash flow hedging derivative instruments	8.5		(24.8)		(15.9)		(28.1)
Net gain on defined benefit pension and other postretirement plans	0.0		0.1		0.1		0.2
Net unrealized gain on available for sale securities	0.0		0.0		0.1		0.0
Other Comprehensive Income (Loss), Before Tax	8.5		(24.7)		(15.7)		(27.9)
Income Tax Expense (Benefit) Related to Items of Other Comprehensive Income (Loss)	2.0		(5.8)		(3.7)		(6.6)
Other Comprehensive Income (Loss), Net of Tax	6.5		(18.9)		(12.0)		(21.3)
Comprehensive Income	210.8		160.3		277.4		248.9
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
Other Comprehensive Income, Net of Tax	6.5		(18.9)		(12.0)		(21.3)
Comprehensive Income	210.8		160.3		277.4		248.9
Spire Missouri [Member]
Net Income	105.2	[1]	112.1		162.2		159.4
Other Comprehensive Income (Loss), Before Tax:
Other Comprehensive Income (Loss), Net of Tax	0.0		0.1	[1]	0.1	[1]	0.2
Comprehensive Income	105.2		112.2		162.3		159.6
Operating Revenues	766.5		791.0		1,301.9		1,332.2
Operating Expenses:
Natural gas	443.7		465.7		736.3		782.4
Operation and maintenance	78.6		77.4		153.5		154.5
Depreciation and amortization	43.1		39.2		85.2		77.8
Taxes, other than income taxes	59.8		61.2		98.3		97.6
Total Operating Expenses	625.2		643.5		1,073.3		1,112.3
Operating Income	141.3		147.5		228.6		219.9
Interest Expense, Net	27.7		24.6		55.6		46.6
Other Income, Net	5.7		5.9		12.9		10.9
Income Before Income Taxes	119.3		128.8		185.9		184.2
Income Tax Expense	14.1		16.7		23.7		24.8
Net Income	105.2	[1]	112.1		162.2		159.4
Other Comprehensive Income, Net of Tax	0.0		0.1	[1]	0.1	[1]	0.2
Comprehensive Income	$ 105.2		$ 112.2		$ 162.3		$ 159.6

[1] Accumulated other comprehensive income (loss)