CONDENSED STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Spire Missouri	Spire Alabama	Common Stock	Common Stock Spire Missouri	Common Stock Spire Alabama	Paid-in Capital	Paid-in Capital Spire Missouri	Paid-in Capital Spire Alabama	Retained Earnings	Retained Earnings Spire Missouri	Retained Earnings Spire Alabama	AOCI	[1]	AOCI Spire Missouri	[1]
BALANCE at Sep. 30, 2018	$ 2,255.4	$ 1,259.9	$ 808.7	$ 50.7	$ 0.1		$ 1,482.7	$ 760.3	$ 390.9	$ 715.6	$ 501.1	$ 417.8	$ 6.4		$ (1.6)
BALANCE (in shares) at Sep. 30, 2018				50,671,903	24,577	1,972,052
Stockholders' Equity Rollforward
Net Income	67.3	51.2	10.3							67.3	51.2	10.3
Stock-based compensation costs	2.0	1.2					2.0	1.2
Dividends declared on common stock	(30.0)	(9.8)	(8.5)							(30.0)	(9.8)	(8.5)
Other comprehensive income/loss, net of tax	(8.2)												(8.2)
BALANCE at Dec. 31, 2018	2,284.6	1,302.5	810.5	$ 50.7	$ 0.1		1,482.8	761.5	390.9	752.9	542.5	419.6	(1.8)		(1.6)
BALANCE (in shares) at Dec. 31, 2018				50,724,168	24,577	1,972,052
BALANCE at Sep. 30, 2019	2,543.0	1,339.3	830.0	$ 51.0	$ 0.1		1,505.8	765.0	370.9	775.5	576.6	459.1	(31.3)		(2.4)
BALANCE (in shares) at Sep. 30, 2019				50,973,515	24,577	1,972,052
Stockholders' Equity Rollforward
Net Income	67.0	48.0	13.2							67.0	48.0	13.2
Stock-based compensation costs	1.6						1.6
Dividends declared on common stock	(31.9)	(11.3)	(6.0)							(31.9)	(11.3)	(6.0)
Other comprehensive income/loss, net of tax	14.4	0.1											14.4		0.1
BALANCE at Dec. 31, 2019	$ 2,586.0	$ 1,376.1	$ 837.2	$ 51.1	$ 0.1		$ 1,506.7	$ 765.0	$ 370.9	$ 803.1	$ 613.3	$ 466.3	$ (16.9)		$ (2.3)
BALANCE (in shares) at Dec. 31, 2019				51,063,460	24,577	1,972,052

[1] Accumulated other comprehensive income (loss)