INCOME TAXES Income Tax Reconciliation (Details) (USD $)	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Income Tax Examination [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate	35.00%
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Statutory income tax expense	$ 35,213,000	$ 48,638,000	$ 63,753,000
State income taxes	5,434,000	3,435,000	4,626,000
Depreciation and cost of removal	(3,999,000)	(2,558,000)	(1,986,000)
Investment tax credits	(34,397,000)	(13,150,000)	(769,000)
Basis adjustment of solar assets due to ITC	5,974,000	2,266,000	91,000
Other	(496,000)	(966,000)	(1,023,000)
Income tax provision (benefit)	7,729,000	37,665,000	64,692,000
Effective income tax rate	7.70%	27.10%	35.50%
Income Tax Reconciliation, Tax Credits, Investment	27,100,000	9,600,000
Current
Federal	14,983,000	14,566,000	(7,343,000)
State	4,025,000	6,618,000	(981,000)
Deferred
Federal	18,757,000	30,932,000	65,258,000
State	4,361,000	(1,301,000)	8,527,000
Investment tax credits	(34,397,000)	(13,150,000)	(769,000)
Income tax provision (benefit)	$ 7,729,000	$ 37,665,000	$ 64,692,000