SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, PUBLIC UTILITIES (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Public Utility, Property, Plant and Equipment [Line Items]
Composite rate of depreciation	2.38%	2.39%	2.24%
Property, Plant and Equipment, Gross	$ 1,906,536	$ 1,706,164
Accumulated depreciation	(421,659)	(410,237)
Property, plant and equipment, net	1,484,877	1,295,927
Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution facilities	1,352,101	1,304,182
Transmission facilities	248,774	200,051
Storage facilities	41,663	42,364
Unregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Solar facilities	181,123	78,322
All other property	$ 82,875	$ 81,245
All other property [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives, Minimum, Years	5
Estimated Useful Lives, Maximum, Years	35
Distribution Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives, Minimum, Years	38
Estimated Useful Lives, Maximum, Years	74
Transmission Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives, Minimum, Years	35
Estimated Useful Lives, Maximum, Years	56
Storage Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives, Minimum, Years	34
Estimated Useful Lives, Maximum, Years	47
Solar Property [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated Useful Lives, Minimum, Years	20
Estimated Useful Lives, Maximum, Years	25