FINANCIAL INFORMATION BY INDUSTRY SEGMENT, GEOGRAPHIC AREA AND PRODUCT LINE, Long-Lived Assets by Major Customers (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 19,610	$ 21,408	$ 26,268
South Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	16,857	16,915	11,135
Taiwan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 13,592	$ 15,119	$ 17,949