REPORTING SEGMENT AND OTHER OPERATIONS DATA - NET FINANCIAL EARNINGS LOSS RECONCILIATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting [Abstract]
Net financial earnings	$ 261,827	$ 240,321	$ 207,712
Less:
Unrealized (gain) loss on derivative instruments and related transactions	(38,081)	(59,906)	54,203
Tax effect	9,050	14,248	(12,887)
Effects of economic hedging related to natural gas inventory	34,699	19,939	(42,405)
Tax effect	(8,246)	(4,738)	10,078
(Gain on) impairment of equity method investment	(300)	(5,521)	92,000
Tax effect	(19)	1,377	(11,167)
NET INCOME	$ 264,724	$ 274,922	$ 117,890