REPORTING SEGMENT AND OTHER OPERATIONS DATA - NET FINANCIAL EARNINGS (LOSS) RECONCILIATION (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting [Abstract]
Net financial (loss) earnings	$ 40,405	$ 54,093
Less:
Unrealized gain on derivative instruments and related transactions	(41,766)	(10,932)
Tax effect	9,931	2,583
Effects of economic hedging related to natural gas inventory	(8,887)	(21,611)
Tax effect	2,112	5,136
NFE tax adjustment	(10,346)	(7,331)
NET INCOME	$ 89,361	$ 86,248