SHAREHOLDERS' EQUITY - Summary of the Changes in Accumulated Other Comprehensive Loss, Net of Tax, by Component (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2022	Mar. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,776,591	$ 2,912,618	$ 3,224,918	$ 3,318,514	$ 2,912,618	$ 3,318,514
Other comprehensive income	394	394	457	457	788	914
Ending balance	2,734,410	2,776,591	$ 3,083,696	$ 3,224,918	2,734,410	$ 3,083,696
Defined Benefit Pension Plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(19,850)	(20,244)			(20,244)
Amounts reclassified from accumulated other comprehensive loss	394				788
Other comprehensive income	394				788
Ending balance	$ (19,456)	$ (19,850)			$ (19,456)