DEBT - Unsecured Long-Term Debt Outstanding (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Long-term debt
Face Amount	$ 550,000	$ 550,000
Unamortized Discount and Debt Issuance Cost	(4,708)	(4,856)
Long-term debt, net	545,292	545,144
Unsecured Senior Notes due September 29, 2031
Long-term debt, gross
Face Amount	550,000	550,000
Unamortized Discount and Debt Issuance Cost	(4,708)	(4,856)
Book Value	$ 545,292	$ 545,144