OTHER LONG-TERM ASSETS (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($) Security	Sep. 30, 2017 USD ($)	Jun. 30, 2015 USD ($)
Other long-term assets [Abstract]
Auction rate securities (ARS)	$ 5,319	$ 5,319
Long-term contract asset	2,333	2,115
Other long-term assets	2,268	2,154
Other long-term investments	1,157	929
Total	$ 11,077	$ 10,517
Number of tax exempt municipal debt securities | Security	2
Minimum maturity period of municipal debt securities	10 years
Fair value of auction rate securities	$ 5,040
Gross unrecognized loss of ARS	279
Long-term contract asset face amount			$ 4,500
Long-term liability, SERP investments	$ 1,157