FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Assets:
Cash and cash equivalents	$ 340,702	$ 188,495
Other long-term investments	1,036	980
Total assets	341,738	189,475
Liabilities:
Derivative financial instruments	41,452	24,244
Total liabilities	41,452	24,244
Level 1
Assets:
Cash and cash equivalents	340,702	188,495
Other long-term investments	1,036	980
Total assets	341,738	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	41,452	24,244
Total liabilities	41,452	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