FAIR VALUE MEASUREMENTS (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Assets:
Cash and cash equivalents	$ 48,237	$ 68,359
Short-term investments	20,925	26,829
Restricted cash	30,478	24,851
Deferred compensation	6,516	6,442
Liabilities:
Deferred compensation	5,309	4,991
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	48,237	68,359
Short-term investments	20,925	26,829
Restricted cash	30,478	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	6,516	6,442
Liabilities:
Deferred compensation	5,309	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