REPORTING SEGMENT AND OTHER OPERATIONS DATA - NET FINANCIAL EARNINGS (LOSS) RECONCILIATION (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting [Abstract]
Net financial earnings	$ 138,576		$ 112,310		$ 211,020	$ 222,594
Less:
Unrealized loss (gain) on derivative instruments and related transactions	25,457		13,971		20,057	(17,532)
Tax effect	(6,049)		(3,320)		(4,767)	4,167
Effects of economic hedging related to natural gas inventory	(2,845)		(11,203)		(19,073)	12,769
Tax effect	676		2,662		4,533	(3,035)
Gain on equity method investment	0		(200)		0	(200)
Tax effect	0		50		0	50
NFE tax adjustment	525		103		47	207
NET INCOME	$ 120,812	$ 89,411	$ 110,247	$ 115,921	$ 210,223	$ 226,168