OTHER LONG-TERM ASSETS (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2018 USD ($) Security	Sep. 30, 2017 USD ($)	Jun. 30, 2015 USD ($)
Other long-term assets [Abstract]
Auction rate securities (ARS)	$ 3,975	$ 5,319
Long-term contract assets	1,809	2,115
Other long-term assets	2,026	2,154
Other long-term investments	1,089	929
Total	$ 8,899	$ 10,517
Number of tax exempt municipal debt securities | Security	1
Minimum maturity period of municipal debt securities	10 years
Fair value of auction rate securities	$ 3,975
Long-term contract asset face amount			$ 4,500
Amount of long-term contract paid	3,000
Long-term liability, SERP investments	$ 1,089