PENSION PLANS AND OTHER POSTRETIREMENT BENEFITS Part 1 (Details) (USD $)	6 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2014 Pension Plans [Member]	Mar. 31, 2013 Pension Plans [Member]	Mar. 31, 2014 Pension Plans [Member]	Mar. 31, 2013 Pension Plans [Member]	Mar. 31, 2014 Postretirement Benefit [Member]	Mar. 31, 2013 Postretirement Benefit [Member]	Mar. 31, 2014 Postretirement Benefit [Member]	Mar. 31, 2013 Postretirement Benefit [Member]	Dec. 31, 2010 Laclede Gas [Member]	Feb. 20, 2010 Missouri Gas Energy (MGE) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Extent of Lump-sum payments recognized, percentage	100.00%
Anticipated Contributions To Postretirement Plans Qualified Trusts	$ 14,400,000
Contributions to pension plans for qualified trust	9,600,000
Contributions to pension plans for non-qualified plans	200,000
Anticipated Contributions To Pension Plans Non Qualified Trusts	200,000
Rate Recovery Of Benefit Costs										15,500,000	10,000,000
Service cost - benefits earned during the period		2,428,000	2,311,000	4,856,000	4,622,000	2,804,000	2,534,000	5,608,000	5,067,000
Interest cost		6,010,000	4,066,000	12,020,000	8,132,000	2,170,000	1,279,000	4,339,000	2,558,000
Expected return on plan assets		(6,645,000)	(4,741,000)	(13,290,000)	(9,482,000)	(1,709,000)	(1,081,000)	(3,418,000)	(2,162,000)
Amortization of transition obligation						0	23,000	0	46,000
Amortization of prior service cost (credit)		125,000	136,000	249,000	272,000	(1,000)	1,000	(2,000)	2,000
Amortization of actuarial loss		1,772,000	2,839,000	3,544,000	5,678,000	1,505,000	1,325,000	3,010,000	2,650,000
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements				(1,319,000)	0
Sub-total		5,009,000	4,611,000	8,698,000	9,222,000	4,769,000	4,081,000	9,537,000	8,161,000
Regulatory adjustment		1,571,000	(433,000)	4,461,000	(867,000)	(2,388,000)	(1,699,000)	(4,775,000)	(3,398,000)
Net benefit cost		6,580,000	4,178,000	13,159,000	8,355,000	2,381,000	2,382,000	4,762,000	4,763,000
Anticipated Contributions To Pension Plans Qualified Trusts	14,400,000
Anticipated payment directly to participants in postretirement plan	300,000
Lump-sum payments recognized as settlements	$ 10,900,000