SHAREHOLDERS' EQUITY (Tables)

12 Months Ended

Sep. 30, 2018

Stockholders' Equity Note [Abstract]

Schedule of accumulated other comprehensive income (loss)

The components of AOCI, net of income taxes, recognized in the balance sheets at September 30 were as follows:

	Net Unrealized Gains (Losses) on Cash Flow Hedges			Defined Benefit Pension and Other Postretirement Benefit Plans			Net Unrealized Losses on Available-for-Sale Debt Securities			Total
Spire
Balance at September 30, 2016	$	(2.3	)	$	(1.8	)	$	(0.1	)	$	(4.2	)
Other comprehensive income (loss)	7.2			0.3			(0.1		)	7.4
Balance at September 30, 2017	4.9			(1.5		)	(0.2		)	3.2
Other comprehensive income	2.0			0.3			0.2			2.5
Reclassification of certain income tax effects	1.0			(0.3		)	—			0.7
Balance at September 30, 2018	$	7.9		$	(1.5	)	$	—		$	6.4
Spire Missouri
Balance at September 30, 2016	$	0.1		$	(1.8	)	$	(0.1	)	$	(1.8	)
Other comprehensive income (loss)	—			0.2			(0.1		)	0.1
Balance at September 30, 2017	0.1			(1.6		)	(0.2		)	(1.7		)
Other comprehensive (loss) income	(0.1		)	0.3			0.2			0.4
Reclassification of certain income tax effects	—			(0.3		)	—			(0.3		)
Balance at September 30, 2018	$	—		$	(1.6	)	$	—		$	(1.6	)