SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Cash payments:
Interest paid, net of amounts capitalized	$ 22,936	$ 28,011	$ 11,651
Income taxes paid	3,749	15,577	131,128
Reconciliation of total capital expenditures incurred to total capital expenditures in the consolidated statements of cash flows
Capital expenditures incurred	408,106	241,290	1,033,241
Additions incurred in prior year but paid for in current period	9,465	25,344	123,548
Additions incurred but not paid for as of the end of the period	(20,004)	(9,465)	(25,344)
Capital expenditures per Consolidated Condensed Statements of Cash Flows	$ 397,567	$ 257,169	$ 1,131,445