FAIR VALUE MEASUREMENTS (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
Assets:
Cash and cash equivalents	$ 49,587	$ 68,359
Short-term investments	23,101	26,829
Restricted cash	27,776	24,851
Deferred compensation	6,641	6,442
Liabilities:
Deferred compensation	5,322	4,991
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	49,587	68,359
Short-term investments	23,101	26,829
Restricted cash	27,776	24,851
Deferred compensation	0	0
Liabilities:
Deferred compensation	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Short-term investments	0
Restricted cash	0
Deferred compensation	6,641	6,442
Liabilities:
Deferred compensation	5,322	4,991
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Short-term investments	0
Restricted cash	0
Deferred compensation	0	0
Liabilities:
Deferred compensation	$ 0	$ 0