Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Millions	Mar. 31, 2024		Sep. 30, 2023		Mar. 31, 2023
ASSETS
Utility Plant	$ 8,480.3		$ 8,210.1		$ 7,892.4
Less: Accumulated depreciation and amortization	2,509.3		2,431.2		2,358.5
Net Utility Plant	5,971.0		5,778.9		5,533.9
Non-utility Property (net of accumulated depreciation and amortization of $115.9, $71.1 and $60.6 at March 31, 2024, September 30, 2023, and March 31, 2023, respectively)	886.2		628.5		520.4
Other Investments	105.3		102.6		131.3
Total Other Property and Investments	991.5		731.1		651.7
Other Property and Investments	991.5		731.1		651.7
Current Assets:
Cash and cash equivalents	25.6		5.6		6.9
Utility	398.5		192.4		453.7
Other	107.3		128.6		166.0
Allowance for credit losses	(39.1)		(32.5)		(40.6)
Delayed customer billings	54.8		22.0		85.6
Accounts receivable:
Utility	398.5		192.4		453.7
Other	107.3		128.6		166.0
Allowance for credit losses	(39.1)		(32.5)		(40.6)
Delayed customer billings	54.8		22.0		85.6
Inventories:
Natural gas	159.0		223.7		146.8
Propane gas	8.6		8.6		8.6
Materials and supplies	47.2		47.2		48.9
Regulatory assets	116.9		348.3		143.0
Prepayments	34.1		48.2		32.5
Other current assets	92.8		84.8		60.2
Total Current Assets	1,005.7		1,076.9		1,111.6
Deferred Charges and Other Assets:
Goodwill	1,171.6		1,171.6		1,171.6
Regulatory assets	1,272.7		1,249.2		1,316.7
Other	298.9		305.9		263.5
Total Deferred Charges and Other Assets	2,743.2		2,726.7		2,751.8
Total Assets	10,711.4		10,313.6		10,049.0
Capitalization:
Preferred stock ($25.00 par value per share; 10.0 million depositary shares authorized, issued and outstanding at March 31, 2024, September 30, 2023, and March 31, 2023)	242.0		242.0		242.0
Common stock (par value $1.00 per share; 70.0 million shares authorized; 57.7 million, 53.2 million, and 52.6 million shares issued and outstanding at March 31, 2024, September 30, 2023, and March 31, 2023, respectively)	57.7		53.2		52.6
Paid-in capital	1,899.7		1,616.5		1,576.5
Retained earnings	1,155.3		958.0		1,089.5
Accumulated other comprehensive income	35.6		47.6		25.9
Total Shareholders' Equity	3,390.3		2,917.3		2,986.5
Temporary equity	10.3		16.5		18.8
Long-term debt (less current portion)	3,421.4		3,554.0		3,702.5
Total Capitalization	6,822.0		6,487.8		6,707.8
Current Liabilities:
Current portion of long-term debt	307.0		156.6		256.6
Notes payable	786.0		955.5		561.0
Accounts payable	193.4		253.1		232.3
Advance customer billings	6.1		20.9		6.8
Wages and compensation accrued	40.2		47.0		38.6
Customer deposits	29.4		27.7		28.3
Taxes accrued	82.6		104.1		79.9
Regulatory liabilities	25.1		7.3		5.3
Other current liabilities	180.5		183.2		198.1
Total Current Liabilities	1,650.3		1,755.4		1,406.9
Deferred Credits and Other Liabilities:
Deferred income taxes	816.6		743.7		737.9
Pension and postretirement benefit costs	130.0		137.3		158.6
Asset retirement obligations	589.7		577.4		531.5
Regulatory liabilities	557.7		472.4		360.3
Other noncurrent liabilities	145.1		139.6		146.0
Total Deferred Credits and Other Liabilities	2,239.1		2,070.4		1,934.3
Commitments and Contingencies (Note 11)
Total Capitalization and Liabilities	10,711.4		10,313.6		10,049.0
Spire Missouri [Member]
ASSETS
Utility Plant	5,193.5		4,964.9		4,731.2
Less: Accumulated depreciation and amortization	1,088.1		1,043.2		1,027.1
Net Utility Plant	4,105.4		3,921.7		3,704.1
Total Other Property and Investments	67.8		65.7		66.7
Other Property and Investments	67.8		65.7		66.7
Current Assets:
Cash and cash equivalents	0.0		0.8		0.0
Other	23.8		21.1		32.5
Allowance for credit losses	(32.0)		(26.2)		(34.5)
Delayed customer billings	53.6		17.9		84.5
Accounts receivable:
Other	23.8		21.1		32.5
Allowance for credit losses	(32.0)		(26.2)		(34.5)
Delayed customer billings	53.6		17.9		84.5
Inventories:
Natural gas	101.9		132.8		86.7
Propane gas	8.6		8.6		8.6
Materials and supplies	24.0		24.2		24.4
Regulatory assets	89.2		293.1		62.7
Prepayments	17.0		26.7		18.5
Total Current Assets	595.8		642.9		649.2
Deferred Charges and Other Assets:
Goodwill	210.2		210.2		210.2
Regulatory assets	630.5		617.6		722.0
Other	145.2		147.4		107.2
Total Deferred Charges and Other Assets	985.9		975.2		1,039.4
Total Assets	5,754.9		5,605.5		5,459.4
Capitalization:
Retained earnings	1,154.6		992.4		1,061.3
Accumulated other comprehensive income	(2.4)		(2.5)		(2.5)
Total Shareholders' Equity	2,007.1	[1]	1,844.8	[1]	1,875.0
Long-term debt (less current portion)	1,486.2		1,785.4		1,784.5
Total Capitalization	3,493.3		3,630.2		3,659.5
Paid-in capital and common stock	854.9		854.9		816.2
Current Liabilities:
Current portion of long-term debt	300.0		0.0		250.0
Advance customer billings	0.0		11.0		0.0
Wages and compensation accrued	19.9		23.6		20.4
Customer deposits	5.9		5.8		6.0
Taxes accrued	47.0		60.3		47.2
Other current liabilities	44.6		48.7		52.5
Total Current Liabilities	949.5		786.3		726.9
Deferred Credits and Other Liabilities:
Deferred income taxes	563.9		531.8		533.3
Pension and postretirement benefit costs	100.5		103.3		99.8
Asset retirement obligations	113.4		111.1		112.8
Regulatory liabilities	475.3		389.4		276.9
Other noncurrent liabilities	59.0		53.4		50.2
Total Deferred Credits and Other Liabilities	1,312.1		1,189.0		1,073.0
Total Capitalization and Liabilities	5,754.9		5,605.5		5,459.4
Spire Missouri [Member] | Nonrelated Party [Member]
Current Assets:
Utility	307.6		142.6		362.0
Accounts receivable:
Utility	307.6		142.6		362.0
Current Liabilities:
Notes payable	200.0		0.0		200.0
Accounts payable	78.7		85.8		78.8
Spire Missouri [Member] | Related Party [Member]
Current Assets:
Utility	2.1		1.3		3.8
Accounts receivable:
Utility	2.1		1.3		3.8
Current Liabilities:
Notes payable	243.9		540.6		60.7
Accounts payable	9.5		10.5		11.3
Spire Alabama Inc [Member]
ASSETS
Utility Plant	2,900.7		2,862.6		2,781.4
Less: Accumulated depreciation and amortization	1,307.4		1,273.0		1,208.7
Net Utility Plant	1,593.3		1,589.6		1,572.7
Current Assets:
Cash and cash equivalents	1.8		1.2		1.0
Other	6.8		6.6		5.3
Allowance for credit losses	(6.2)		(5.7)		(5.3)
Delayed customer billings	1.0		3.6		1.0
Accounts receivable:
Other	6.8		6.6		5.3
Allowance for credit losses	(6.2)		(5.7)		(5.3)
Delayed customer billings	1.0		3.6		1.0
Inventories:
Natural gas	34.1		52.4		41.4
Materials and supplies	19.2		19.1		20.5
Regulatory assets	14.9		41.6		64.8
Prepayments	3.3		6.4		3.8
Total Current Assets	148.9		168.6		208.7
Deferred Charges and Other Assets:
Regulatory assets	619.1		606.9		568.3
Other	84.2		84.2		81.9
Total Deferred Charges and Other Assets	703.3		691.1		650.2
Total Assets	2,445.5		2,449.3		2,431.6
Capitalization:
Retained earnings	687.5		642.1		645.3
Total Shareholders' Equity	966.9		928.0		935.2
Long-term debt (less current portion)	746.1		745.9		745.7
Total Capitalization	1,713.0		1,673.9		1,680.9
Paid-in capital and common stock	279.4		285.9		289.9
Current Liabilities:
Advance customer billings	4.7		8.1		5.3
Wages and compensation accrued	5.6		6.6		5.4
Customer deposits	20.5		19.3		19.6
Taxes accrued	28.8		34.5		26.4
Regulatory liabilities	18.7		0.0		0.0
Other current liabilities	14.1		14.7		15.7
Total Current Liabilities	163.6		240.3		230.5
Deferred Credits and Other Liabilities:
Deferred income taxes	36.8		9.1		12.3
Pension and postretirement benefit costs	22.5		27.2		52.8
Asset retirement obligations	460.6		451.0		406.9
Regulatory liabilities	20.1		21.2		21.5
Other noncurrent liabilities	28.9		26.6		26.7
Total Deferred Credits and Other Liabilities	568.9		535.1		520.2
Total Capitalization and Liabilities	2,445.5		2,449.3		2,431.6
Spire Alabama Inc [Member] | Nonrelated Party [Member]
Current Assets:
Utility	74.0		42.2		75.4
Accounts receivable:
Utility	74.0		42.2		75.4
Current Liabilities:
Accounts payable	28.4		28.4		29.8
Spire Alabama Inc [Member] | Related Party [Member]
Current Assets:
Utility	0.0		1.2		0.8
Accounts receivable:
Utility	0.0		1.2		0.8
Current Liabilities:
Notes payable	37.4		124.1		121.3
Accounts payable	$ 5.4		$ 4.6		$ 7.0

[1] Accumulated other comprehensive income (loss)