INCOME TAXES - Effective tax rate (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Effective income tax rates as compared to the U.S. Federal income tax rate
Income tax (benefit) provision	$ 1,352	$ (500,641)
Effective income tax rate (as a percent)	13.90%	(50064100.00%)
U.S. Federal income tax rate (as a percent)	21.00%	24.53%
Unrecognized tax benefit	$ 1,700
Income tax expense (benefit) related to new tax act		$ 500,400