REPORTING SEGMENT AND OTHER OPERATIONS DATA - NET FINANCIAL EARNINGS (LOSS) RECONCILIATION (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting [Abstract]
Net financial earnings	$ 178,296		$ 138,576		$ 307,190	$ 211,020
Less:
Unrealized (gain) loss on derivative instruments and related transactions	(27,206)		25,457		(20,838)	20,057
Tax effect	6,466		(6,049)		4,953	(4,767)
Effects of economic hedging related to natural gas inventory	(6,650)		(2,845)		(16,177)	(19,073)
Tax effect	1,580		676		3,844	4,533
NFE tax adjustment	(181)		525		(198)	47
NET INCOME	$ 204,287	$ 131,319	$ 120,812	$ 89,411	$ 335,606	$ 210,223