DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Derivative Instruments Reconciliation (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	$ 7.7	[1]	$ 6.3	[1]
Fair value of cash margin receivables offset with derivatives	3.0		1.7
Netting of assets and liabilities with the same counterparty	(7.9)		(4.7)
Derivative instrument assets	3.2		3.3
Other deferred charges	(0.4)		0
Derivative Asset	2.8		3.3
Fair value of liability derivatives presented above	12.0	[1]	10.6	[1]
Fair value of cash margin payables offset with derivatives	0		0
Other current liabilities	0		4.4
Other deferred credits	4.1		1.5
Derivative Liability, Current	4.1		5.9
Laclede Gas
Derivatives, Fair Value [Line Items]
Fair value of asset derivatives presented above	2.5		1.8
Fair value of cash margin receivables offset with derivatives	3.0		1.9
Netting of assets and liabilities with the same counterparty	(5.9)		(3.7)
Derivative instrument assets	(0.4)		0
Derivative Asset	(0.4)		0
Fair value of liability derivatives presented above	9.5		8.9
Other current liabilities	0		3.8
Other deferred credits	3.6		1.4
Derivative Liability, Current	$ 3.6		$ 5.2

[1] The fair values of Asset Derivatives and Liability Derivatives exclude the fair value of cash margin receivables or payables with counterparties subject to netting arrangements. Fair value amounts of derivative contracts (including the fair value amounts of cash margin receivables and payables) for which there is a legal right to set off are presented net on the Consolidated Balance Sheets. As such, the gross balances presented in the table above are not indicative of the Company’s net economic exposure. Refer to Note 9, Fair Value Measurements, to the Financial Statements for information on the valuation of derivative instruments.