SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, PROPERTY PLANT AND EQUIPMENT (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Public Utility, Property, Plant and Equipment [Line Items]
Composite rate of depreciation	2.43%	2.38%	2.39%
Property, Plant and Equipment, Gross	$ 2,055,155	$ 1,906,536
Accumulated depreciation	(412,039)	(421,659)
Property, plant and equipment, net	1,643,116	1,484,877
Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution facilities	1,421,885	1,352,101
Transmission facilities	273,853	248,774
Storage facilities	41,687	41,663
Unregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Solar facilities	232,409	181,123
All other property	$ 85,321	$ 82,875
Minimum [Member] | All other property [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Minimum [Member] | Distribution Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	38 years
Minimum [Member] | Transmission Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	35 years
Minimum [Member] | Storage Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	34 years
Minimum [Member] | Solar Property [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	20 years
Maximum [Member] | All other property [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	35 years
Maximum [Member] | Distribution Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	74 years
Maximum [Member] | Transmission Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	56 years
Maximum [Member] | Storage Facilities [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	47 years
Maximum [Member] | Solar Property [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Estimated useful lives	25 years