INCOME TAXES, COMPONENTS OF INCOME TAX PROVISION (BENEFIT) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Current:
Federal	$ (23,597)	$ 20,492	$ 37,904
State	(2,209)	5,473	11,096
Deferred:
Federal	70,386	56,480	24,963
State	11,441	7,375	960
Investment/production tax credits	(32,491)	(30,096)	(23,083)
Income tax provision	$ 23,530	$ 59,724	$ 51,840