FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2020	Sep. 30, 2019
Assets:
Cash and cash equivalents	$ 354,708	$ 188,495
Other long-term investments	1,147	980
Total assets	355,855	189,475
Liabilities:
Derivative financial instruments	41,692	24,244
Total liabilities	41,692	24,244
Level 1
Assets:
Cash and cash equivalents	354,708	188,495
Other long-term investments	1,147	980
Total assets	355,855	189,475
Liabilities:
Derivative financial instruments	0	0
Total liabilities	0	0
Level 2
Assets:
Cash and cash equivalents	0	0
Other long-term investments	0	0
Total assets	0	0
Liabilities:
Derivative financial instruments	41,692	24,244
Total liabilities	41,692	24,244
Level 3
Assets:
Cash and cash equivalents	0	0
Other long-term investments	0	0
Total assets	0	0
Liabilities:
Derivative financial instruments	0	0
Total liabilities	$ 0	$ 0