CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 9,671	$ 39,081
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	41,808	42,827
Amortization	922	1,250
Provision for doubtful accounts	2,369	757
Deferred income tax benefit	(185)	(714)
Share-based compensation expense	3,655	2,371
Asset impairment	0	64,724
(Gain) loss on sale of assets	(67)	77
Changes in assets and liabilities:
Accounts receivable	15,258	60,883
Income tax receivable	(376)	(829)
Inventories of materials and supplies	(537)	11,023
Prepaid expenses, deferred costs and other current assets	2,759	7,462
Deferred costs and other assets	(496)	(1,050)
Accounts payable	(1,396)	(17,615)
Accrued liabilities	9,191	8,570
Income tax payable	19	(642)
Deferred credits and other liabilities	902	1,973
Net cash provided by operating activities	83,497	220,148
Cash flows from investing activities:
Capital expenditures	(138,814)	(131,547)
Net cash used in investing activities	(138,814)	(131,547)
Cash flows from financing activities:
Proceeds from issuance of long-term debt	125,000	45,000
Principal payments on long-term debt	(55,000)	(115,000)
Dividends paid	0	(16,316)
Payments related to exercise of stock options	0	(599)
Net cash provided by (used in) or financing activities	70,000	(86,915)
Net increase in cash and cash equivalents	14,683	1,686
Cash and cash equivalents, at beginning of period	145,427	113,983
Cash and cash equivalents, at end of period	160,110	115,669
Non-cash activities:
Decrease (increase) in accounts payable related to capital expenditures	(1,613)	10,530
Dividends payable	$ 0	$ 4,858