SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) (USD $)	0 Months Ended	9 Months Ended	12 Months Ended		0 Months Ended
	Jun. 01, 2010	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 02, 2014 Laclede Group Inc Alagasco	Sep. 02, 2014 Laclede Group Inc Alagasco
Business Acquisition [Line Items]
Consideration transferred					$ 1,600,000,000
Long-term debt assumed in a business combination						250,000,000
Composite depreciation rate (percent)	3.10%
Refundable gas costs		13,400,000
Gas imbalances		0	0
Taxes on revenues		$ 20,600,000	$ 25,900,000	$ 21,500,000