BUSINESS SEGMENT AND OTHER OPERATIONS DATA - NET FINANCIAL EARNINGS LOSS RECONCILIATION (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting [Abstract]
Net financial earnings	$ 77,880	$ 99,143	$ 127,512	$ 154,253
Less:
Unrealized loss (gain) on derivative instruments and related transactions	3,170	68,474	2,035	(20,198)
Effects of economic hedging related to natural gas inventory	(1,054)	(23,450)	2,759	(32,215)
Tax adjustments	2,436	(6,784)	743	22,443
NET INCOME	$ 73,328	$ 60,903	$ 121,975	$ 184,223