Long-term Debt (Tables)

12 Months Ended

Sep. 30, 2021

Debt Disclosure [Abstract]

Schedule of Composition of Long-term Debt

The composition of long-term debt as of September 30 is shown in the following tables.

	2021			2020
Spire
2.52% Senior Notes, due September 1, 2021	$	—		$	35.0
3.31% Notes Payable, due December 15, 2022		25.0			25.0
3.54% Senior Notes, due February 27, 2024		150.0			150.0
0.75% Remarketable Senior Notes, due March 1, 2026		175.0			—
3.13% Senior Notes, due September 1, 2026		130.0			130.0
3.93% Senior Notes, due March 15, 2027		100.0			100.0
4.70% Senior Notes, due August 15, 2044		250.0			250.0
Total principal of Spire Missouri long-term debt (see below)		1,348.0			1,098.0
Total principal of Spire Alabama long-term debt (see below)		625.0			475.0
Other subsidiaries' long-term debt:
4.14% First Mortgage Bonds, due September 30, 2021		—			20.0
5.00% First Mortgage Bonds, due September 30, 2031		42.0			42.0
2.95% Notes, with annual principal payments through December 2034		129.6			135.0
3.52% First Mortgage Bonds, due September 30, 2049		40.0			40.0
Total principal of long-term debt		3,014.6			2,500.0
Less: Unamortized discounts and debt issuance costs		(19.7	)		(15.9	)
Less: Current portion		(55.8	)		(60.4	)
Long-term debt, excluding current portion	$	2,939.1		$	2,423.7
Spire Missouri
First Mortgage Bonds:
3.00% Series, due March 15, 2023	$	—		$	55.0
3.40% Series, due August 15, 2023		250.0			250.0
3.40% Series, due March 15, 2028		45.0			45.0
7.00% Series, due June 1, 2029		19.3			19.3
2.84% Series, due November 15, 2029		275.0			275.0
7.90% Series, due September 15, 2030		30.0			30.0
3.68% Series, due September 15, 2032		50.0			50.0
6.00% Series, due May 1, 2034		99.3			99.3
6.15% Series, due June 1, 2036		54.5			54.5
4.63% Series, due August 15, 2043		99.9			99.9
4.23% Series, due September 15, 2047		70.0			70.0
3.30% Series, due June 1, 2051		305.0			—
4.38% Series, due September 15, 2057		50.0			50.0
Total principal of Spire Missouri long-term debt		1,348.0			1,098.0
Less: Unamortized discounts and debt issuance costs		(9.6	)		(6.0	)
Spire Missouri long-term debt	$	1,338.4		$	1,092.0
Spire Alabama
3.86% Notes, due December 22, 2021	$	50.0		$	50.0
3.21% Notes, due September 15, 2025		35.0			35.0
2.88% Notes, due December 1, 2029		100.0			100.0
2.04% Notes, due December 15, 2030		150.0			—
5.90% Notes, due January 15, 2037		45.0			45.0
4.31% Notes, due December 1, 2045		80.0			80.0
3.92% Notes, due January 15, 2048		45.0			45.0
4.64% Notes, due January 15, 2049		90.0			90.0
4.02% Notes, due January 15, 2058		30.0			30.0
Total principal of Spire Alabama long-term debt		625.0			475.0
Less: Unamortized discounts and debt issuance costs		(3.8	)		(3.2	)
Less: Current portion		(50.0	)		—
Spire Alabama long-term debt, excluding current portion	$	571.2		$	471.8

Schedule of Maturities of Long-term Debt

Maturities of long-term debt for Spire on a consolidated basis, Spire Missouri and Spire Alabama for the five fiscal years after September 30, 2021 are as follows:

	2022		2023		2024		2025		2026
Spire	$	55.8	$	281.2	$	156.6	$	42.0	$	312.5
Spire Missouri		—		250.0		—		—		—
Spire Alabama		50.0		—		—		35.0		—