DEBT - Components of Unsecured Long-Term Debt Outstanding (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Long-term debt, gross
Face Amount	$ 550,000	$ 1,037,148
Unamortized Discount and Debt Issuance Cost	(8,031)	(11,665)
Book Value	541,969	1,025,483
Less long-term debt due within one year
Face Amount	0	(487,148)
Unamortized Discount and Debt Issuance Cost	0	3,662
Current portion of long-term debt	0	(483,486)
Long-term debt
Face Amount	550,000	550,000
Unamortized Discount and Debt Issuance Cost	(8,031)	(8,003)
Long-term debt, net	541,969	541,997
Unsecured Senior Notes Issued 2025
Long-term debt, gross
Face Amount	0	487,148
Unamortized Discount and Debt Issuance Cost	0	(3,662)
Book Value	0	483,486
Unsecured Senior Notes Issued 2031
Long-term debt, gross
Face Amount	550,000	550,000
Unamortized Discount and Debt Issuance Cost	(8,031)	(8,003)
Book Value	$ 541,969	$ 541,997