Fair Value of Financial Instruments (Tables)

6 Months Ended

Mar. 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 March 31, 2019
Cash and cash equivalents	$	11.1	$	11.1	$	11.1	$	—
Notes payable		512.0		512.0		—		512.0
Long-term debt, including current portion		2,256.9		2,319.9		—		2,319.9
As of September 30, 2018
Cash and cash equivalents	$	4.4	$	4.4	$	4.4	$	—
Notes payable		553.6		553.6		—		553.6
Long-term debt, including current portion		2,075.6		2,074.0		—		2,074.0
As of March 31, 2018
Cash and cash equivalents	$	17.8	$	17.8	$	17.8	$	—
Notes payable		391.7		391.7		—		391.7
Long-term debt, including current portion		2,179.4		2,241.3		—		2,241.3
Spire Missouri
As of March 31, 2019
Cash and cash equivalents	$	6.9	$	6.9	$	6.9	$	—
Notes payable – associated companies		232.9		232.9		—		232.9
Long-term debt, including current portion		974.7		1,036.9		—		1,036.9
As of September 30, 2018
Cash and cash equivalents	$	2.0	$	2.0	$	2.0	$	—
Notes payable – associated companies		345.3		345.3		—		345.3
Long-term debt, including current portion		874.4		906.6		—		906.6
As of March 31, 2018
Cash and cash equivalents	$	10.2	$	10.2	$	10.2	$	—
Notes payable – associated companies		175.8		175.8		—		175.8
Long-term debt, including current portion		974.0		1,033.6		—		1,033.6
Spire Alabama
As of March 31, 2019
Cash and cash equivalents	$	0.1	$	0.1	$	0.1	$	—
Notes payable – associated companies		73.7		73.7		—		73.7
Long-term debt, including current portion		412.1		423.8		—		423.8
As of September 30, 2018
Notes payable – associated companies	$	142.5	$	142.5	$	—	$	142.5
Long-term debt		322.6		321.7		—		321.7
As of March 31, 2018
Notes payable – associated companies	$	82.3	$	82.3	$	—	$	82.3
Long-term debt		322.5		332.7		—		332.7