Fair Value of Financial Instruments (Tables)

3 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Financial Instruments Measured at Fair Value on Recurring Basis

					Classification of Estimated Fair Value
	Carrying Amount		Fair Value		Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)
Spire
As of December 31, 2019
Cash and cash equivalents	$	21.5	$	21.5	$	21.5	$	—
Notes payable		518.9		518.9		—		518.9
Long-term debt, including current portion		2,529.7		2,765.9		—		2,765.9
As of September 30, 2019
Cash and cash equivalents	$	5.8	$	5.8	$	5.8	$	—
Notes payable		743.2		743.2		—		743.2
Long-term debt, including current portion		2,122.6		2,373.4		—		2,373.4
As of December 31, 2018
Cash and cash equivalents	$	8.4	$	8.4	$	8.4	$	—
Notes payable		626.1		626.1		—		626.1
Long-term debt, including current portion		2,167.0		2,133.9		—		2,133.9
Spire Missouri
As of December 31, 2019
Cash and cash equivalents	$	9.3	$	9.3	$	9.3	$	—
Notes payable – associated companies		288.1		288.1		—		288.1
Long-term debt		1,098.6		1,234.9		—		1,234.9
As of September 30, 2019
Cash and cash equivalents	$	2.6	$	2.6	$	2.6	$	—
Notes payable – associated companies		386.4		386.4		—		386.4
Long-term debt		925.0		1,065.2		—		1,065.2
As of December 31, 2018
Cash and cash equivalents	$	4.9	$	4.9	$	4.9	$	—
Notes payable – associated companies		308.0		308.0		—		308.0
Long-term debt, including current portion		974.5		997.3		—		997.3
Spire Alabama
As of December 31, 2019
Notes payable – associated companies	$	67.1	$	67.1	$	—	$	67.1
Long-term debt, including current portion		511.7		572.8		—		572.8
As of September 30, 2019
Notes payable – associated companies	$	128.7	$	128.7	$	—	$	128.7
Long-term debt, including current portion		412.2		474.8		—		474.8
As of December 31, 2018
Notes payable – associated companies	$	164.2	$	164.2	$	—	$	164.2
Long-term debt		322.6		311.3		—		311.3