INCOME TAXES, INCOME TAX RECONCILIATION (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Income Tax Disclosure [Abstract]
Federal statutory rate	35.00%
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory income tax expense	$ 52,661	$ 35,213	$ 48,638
State income taxes	5,168	5,434	3,435
Depreciation and cost of removal	(5,769)	(3,999)	(2,558)
Investment tax credits	(18,749)	(34,397)	(13,150)
Basis adjustment of solar assets due to ITC	3,225	5,974	2,266
Other	(961)	(496)	(966)
Income tax provision	$ 35,575	$ 7,729	$ 37,665
Effective income tax rate	23.60%	7.70%	27.10%