FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Sep. 30, 2017

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Fair value of financial instruments

The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for the Company are as follows:

					Classification of Estimated Fair Value
	Carrying Amount		Fair Value		Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)
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 September 30, 2016
Cash and cash equivalents	$	5.2	$	5.2	$	5.2	$	—
Short-term debt	398.7		398.7		—		398.7
Long-term debt, including current portion	2,070.7		2,257.1		—		2,257.1

Spire Missouri

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Fair value of financial instruments

The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for Spire Missouri are as follows:

					Classification of Estimated Fair Value
	Carrying Amount		Fair Value		Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)
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 September 30, 2016
Cash and cash equivalents	$	2.1	$	2.1	$	2.1	$	—
Short-term debt	243.7		243.7		—		243.7
Long-term debt	804.1		900.4		—		900.4

Spire Alabama

Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]

Fair value of financial instruments

The carrying amounts and estimated fair values of financial instruments not measured at fair value on a recurring basis for Spire Alabama are as follows:

					Classification of Estimated Fair Value
	Carrying Amount		Fair Value		Quoted Prices in Active Markets (Level 1)		Significant Observable Inputs (Level 2)
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 September 30, 2016
Short-term debt	$	82.0	$	82.0	$	—	$	82.0
Long-term debt, including current portion	247.6		275.5		—		275.5