Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 39,081	$ 46,218
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	42,827	44,575
Amortization	1,250	2,504
Provision for doubtful accounts	757	0
Deferred income tax benefit	(714)	(3,380)
Share-based compensation expense	2,371	4,024
Asset impairment	64,724	60,777
Loss on sale of assets	77	9,806
Changes in assets and liabilities:
Accounts receivable	60,883	27,965
Income tax receivable	(829)	(717)
Inventories of materials and supplies	11,023	(6,771)
Prepaid expenses, deferred costs and other current assets	7,462	5,095
Deferred costs and other assets	(1,050)	62
Accounts payable	(17,615)	(14,248)
Accrued liabilities	8,570	14,866
Income tax payable	(642)	(1,333)
Deferred credits and other liabilities	1,973	5,263
Net cash provided by operating activities	220,148	194,706
Cash flows from investing activities:
Capital expenditures	(131,547)	(149,042)
Proceeds from sale of assets	0	1,348
Net cash used in investing activities	(131,547)	(147,694)
Cash flows from financing activities:
Proceeds from borrowing of long-term debt	45,000	0
Principal repayments on long-term debt	(115,000)	0
Repayments on short-term debt, net	0	(5,931)
Dividends paid	(16,316)	0
Proceeds (payments) related to exercise of stock options	(599)	784
Debt issuance costs paid	0	(142)
Net cash used by financing activities	(86,915)	(5,289)
Net increase in cash and cash equivalents	1,686	41,723
Cash and cash equivalents, at beginning of period	113,983	80,080
Cash and cash equivalents, at end of period	115,669	121,803
Non-cash activities:
Increase (decrease) in accounts payable and accrued liabilities related to capital expenditures	10,530	(4,525)
Dividends payable	$ 4,858	$ 0