BACKGROUND AND BASIS OF PRESENTATION (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($)	Sep. 30, 2018 USD ($) Segment	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
BACKGROUND AND BASIS OF PRESENTATION [Abstract]
Number of reportable segments | Segment		1
Immaterial Error Correction		The results of operations for the quarter ended December 31, 2017 and year ended September 30, 2018 include a correction to prior period amounts, which we determined to be immaterial to the prior periods to which they relate and to our fiscal 2018 results. The adjustments, relating primarily to accumulated earnings taxes of a foreign operation, increased the income tax expense for the first quarter of fiscal 2018 by $2,071.
Transition tax for accumulated foreign earnings, Income tax expense | $	$ 2,071	$ 11,340	$ 0	$ 0