SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Part 1 (Details) (USD $)	3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2012
Related Party Transaction [Line Items]
Outstanding borrowings from Laclede Group under a revolving credit note	$ 50,766,000	$ 62,822,000	$ 37,125,000
Interest rate on the borrowings	0.30%	0.30%	0.20%
REVENUE RECOGNITION [Abstract]
Amounts of accrued unbilled revenues	39,600,000	38,300,000	11,600,000
GROSS RECEIPT TAXES [Abstract]
Gross receipts taxes recorded in utility operating revenues	10,300,000	10,200,000
STOCK-BASED COMPENSATION [Abstract]
Total equity compensation cost	532,000	567,000
Compensation cost capitalized	(183,000)	(138,000)
Compensation cost recognized in net income	349,000	429,000
Income tax benefit recognized in net income	(135,000)	(165,000)
Compensation cost recognized in net income, net of income tax	214,000	264,000
Total unrecognized compensation cost	6,500,000
Weighted average period allocation (in years)	2 years 6 months
Laclede Energy Resources, Inc. [Member]
Related Party Transaction [Line Items]
Description of transaction	sales of natural gas	sales of natural gas
Purchases from related parties	7,600,000	6,600,000
Revenue from related Parties	700,000
Laclede Pipeline Company [Member]
Related Party Transaction [Line Items]
Description of transaction	transportation services	transportation services
Purchases from related parties	$ 300,000	$ 300,000