Summary of Significant Accounting Policies (Tables)

6 Months Ended

Mar. 31, 2022

Accounting Policies [Abstract]

Schedule of Inter-Company Transactions

Spire Missouri’s and Spire Alabama’s other transactions with affiliates are presented below

	Three Months Ended March 31,				Six Months Ended March 31,
	2022		2021		2022		2021
Spire Missouri
Purchases of natural gas from Spire Marketing Inc.	$	17.9	$	57.6	$	36.1	$	68.3
Transportation services received from Spire STL Pipeline LLC		7.8		7.9		15.9		16.0
Sales of natural gas to Spire Marketing Inc.		—		—		—		1.1
Transportation services received from Spire NGL Inc.		—		0.2		—		0.5
Spire Alabama
Purchases of natural gas from Spire Marketing Inc.	$	—	$	5.8	$	—	$	10.6
Sales of natural gas to Spire Marketing Inc.		—		0.1		—		0.1

Schedule of Capital Expenditures Excluded from Statement of Cash Flow

Accrued capital expenditures, shown in the following table, are excluded from capital expenditures in the statements of cash flows until paid.

	March 31,		September 30,		March 31,
	2022		2021		2021
Spire	$	38.8	$	59.5	$	36.1
Spire Missouri		28.7		37.1		21.8
Spire Alabama		5.0		13.6		4.7

Schedule of Allowance for Credit Losses

	Spire						Spire Missouri						Spire Alabama
Three Months Ended March 31,	2022			2021			2022			2021			2022			2021
Allowance at beginning of period	$	31.4		$	28.9		$	23.8		$	21.4		$	6.7		$	6.2
Provision for expected credit losses		5.2			6.6			4.7			5.7			0.5			0.6
Write-offs, net of recoveries		(1.5	)		(1.1	)		(1.5	)		(0.5	)		(0.1	)		(0.3	)
Allowance at end of period	$	35.1		$	34.4		$	27.0		$	26.6		$	7.1		$	6.5
Six Months Ended March 31,	2022			2021			2022			2021			2022			2021
Allowance at beginning of period	$	30.3		$	24.9		$	22.6		$	18.1		$	6.6		$	5.5
Provision for expected credit losses		6.7			10.7			6.8			9.0			—			1.3
Write-offs, net of recoveries		(1.9	)		(1.2	)		(2.4	)		(0.5	)		0.5			(0.3	)
Allowance at end of period	$	35.1		$	34.4		$	27.0		$	26.6		$	7.1		$	6.5