FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)

3 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of Fair value of financial instruments

		Classification of Estimated Fair Value
Carrying Amount	Fair Value	Quoted Prices in Active Markets (Level 1)	Significant Observable Inputs (Level 2)

Spire

As of December 31, 2017
Cash and cash equivalents	$	6.7	$	6.7	$	6.7	$	—
Short-term debt	583.6		583.6		—		583.6
Long-term debt, including current portion	2,135.5		2,280.1		—		2,280.1
As of September 30, 2017
Cash and cash equivalents	$	7.4	$	7.4	$	7.4	$	—
Short-term debt	477.3		477.3		—		477.3
Long-term debt, including current portion	2,095.0		2,210.3		—		2,210.3
As of December 31, 2016
Cash and cash equivalents	$	10.6	$	10.6	$	10.6	$	—
Short-term debt	506.4		506.4		—		506.4
Long-term debt, including current portion	2,071.3		2,258.1		—		2,258.1

As of December 31, 2017
Cash and cash equivalents	$	—	$	—	$	—	$	—
Short-term debt	163.1		163.1		—		163.1
Long-term debt	277.8		303.5		—		303.5
As of September 30, 2017
Cash and cash equivalents	$	0.1	$	0.1	$	0.1	$	—
Short-term debt	169.9		169.9		—		169.9
Long-term debt	247.8		269.4		—		269.4
As of December 31, 2016
Cash and cash equivalents	$	—	$	—	$	—	$	—
Short-term debt	102.5		102.5		—		102.5
Long-term debt	247.7		269.3		—		269.3

As of December 31, 2017
Cash and cash equivalents	$	4.1	$	4.1	$	4.1	$	—
Short-term debt	275.6		275.6		—		275.6
Long-term debt, including current portion	974.1		1,068.6		—		1,068.6
As of September 30, 2017
Cash and cash equivalents	$	2.5	$	2.5	$	2.5	$	—
Short-term debt	203.0		203.0		—		203.0
Long-term debt, including current portion	973.9		1,056.9		—		1,056.9
As of December 31, 2016
Cash and cash equivalents	$	4.0	$	4.0	$	4.0	$	—
Short-term debt	312.9		312.9		—		312.9
Long-term debt	804.3		910.7		—		910.7