INCOME TAXES, COMPONENTS OF INCOME TAX PROVISION (BENEFIT) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Current
Federal	$ 20,492	$ 37,904	$ 12,248
State	5,473	11,096	1,763
Deferred
Federal	56,480	24,963	34,127
State	7,375	960	6,186
Investment/production tax credits	(30,096)	(23,083)	(18,749)
Income tax provision	$ 59,724	$ 51,840	$ 35,575