COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Lease commitments [Abstract]
Expiration of cancelable and noncancelable leases, maximum	5 years
Rent expense under operating leases	$ 4,307	$ 3,120	$ 2,765
Operating leases, future minimum payments due:
2019	3,456
2020	2,466
2021	2,099
2022	1,853
2023	1,890
Thereafter	7,890
Operating leases, total	19,654
Purchase obligations [Abstract]
Purchase Obligation Payment	1,500
Purchase obligation, due in 2019	1,500
Current portion of long-term contract liability	1,487	1,500
Contractual obligation	11,208
Defined Benefit Plan, Postretirement Obligations In Foreign Jurisdictions [Abstract]
Total period pension cost	1,236	1,176	$ 1,024
Estimated Future Benefit Payments [Abstract]
2019	372
2020	611
2021	461
2022	642
2023	554
2024 to 2028	4,237
Postretirement Benefits Plan [Member] | Japan [Member]
Defined Benefit Plan, Postretirement Obligations In Foreign Jurisdictions [Abstract]
Projected benefit obligation	6,621	6,673
Accumulated benefit obligation	$ 5,234	$ 5,253
Weighted average discount rate	0.50%	0.50%
Expected rate of compensation increase	2.50%	2.50%
Pension costs in accumulated other comprehensive income	$ 1,735	$ 1,837
Postretirement Benefits Plan [Member] | South Korea [Member]
Defined Benefit Plan, Postretirement Obligations In Foreign Jurisdictions [Abstract]
Weighted average discount rate	3.75%	4.00%
Expected rate of compensation increase	4.50%	4.50%
Pension costs in accumulated other comprehensive income	$ 133	$ 6
Defined benefit obligation	$ 1,731	$ 1,663