Notes Payable and Credit Agreements (Tables)

12 Months Ended

Sep. 30, 2020

Short Term Borrowings [Abstract]

Schedule of Spire Missouri and Alabama Short-term Borrowings

Information about Spire’s consolidated short-term borrowings and about Spire Missouri’s and Spire Alabama’s borrowings from Spire is presented in the following table. As of September 30, 2020, $449.8 of Spire’s short-term borrowings were used to support lending to the Utilities.

	Spire (Parent Only)									Spire Missouri						Spire Alabama						Spire
	Credit			Term			CP			Credit			Spire			Credit			Spire			Consol-
	Facility			Loan			Program			Facility			Note			Facility			Note			idated
Year Ended September 30, 2020
Weighted average borrowings	$	0.1		$	77.5		$	476.1		$	17.9		$	242.0		$	4.6		$	89.0		$	576.2
Lowest borrowings outstanding		—			—			73.5			—			16.0			—			18.5			432.6
Highest borrowings outstanding		23.1			150.0			856.6			185.1			429.5			50.0			161.3			856.6
Weighted average interest rate		1.9	%		1.6	%		1.7	%		1.9	%		1.5	%		1.9	%		1.4	%		1.7	%
As of September 30, 2020
Borrowings outstanding	$	—		$	150.0		$	498.0		$	—		$	301.2		$	—		$	121.3		$	648.0
Weighted average interest rate	n/a				1.1	%		0.2	%	n/a				0.2	%	n/a				0.2	%		0.6	%
As of September 30, 2019
Borrowings outstanding	$	—		$	—		$	743.2		$	—		$	386.4		$	—		$	128.7		$	743.2
Weighted average interest rate	n/a			n/a				2.3	%	n/a				2.3	%	n/a				2.3	%		2.3	%