STOCKHOLDERS' EQUITY (Tables)

12 Months Ended

Sep. 30, 2017

Stockholders' Equity Note [Abstract]

Schedule of accumulated other comprehensive income (loss)

The components of accumulated other comprehensive income (loss), 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 Securities			Total
Spire
Balance at September 30, 2015	$	(0.4	)	$	(1.5	)	$	(0.1	)	$	(2.0	)
Other comprehensive loss	(1.9		)	(0.3		)	—			(2.2		)
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
Spire Missouri
Balance at September 30, 2015	(0.2		)	(1.5		)	—			$	(1.7	)
Other comprehensive income (loss)	0.3			(0.3		)	(0.1		)	(0.1		)
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	)