Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
OPERATING ACTIVITIES:
Net income (loss)	$ (128,212)	$ (56,828)	$ 420,427
Adjustment for loss from discontinued operations	349	3,838	47
Income (loss) from continuing operations	(127,863)	(52,990)	420,474
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	585,543	598,587	608,039
Asset impairment charge		6,250	39,242
Amortization of debt discount and debt issuance costs	1,055	1,168	749
Provision for bad debt	2,016		6,034
(Recovery of) bad debt		(2,013)
Stock-based compensation	26,183	24,383	25,195
Pension settlement charge	1,640	4,964	2,873
Loss on investment securities		25,989
Income from asset sales	(20,627)	(9,896)	(11,834)
Deferred income tax (benefit) expense	(24,111)	60,088	131,431
Other	543	151	(368)
Change in assets and liabilities:
Accounts receivable	(97,114)	72,792	259,024
Inventories	(10,607)	1,944	(23,052)
Prepaid expenses and other	31,434	(2,460)	(4,457)
Accounts payable	39,412	(10,907)	(38,983)
Accrued liabilities	(36,120)	49,562	(24,756)
Deferred income taxes	(942)	2,769	688
Other noncurrent liabilities	(13,075)	(16,831)	38,322
Net cash provided by operating activities from continuing operations	357,367	753,550	1,428,621
Net cash provided by (used in) operating activities from discontinued operations	(150)	47	(47)
Net cash provided by operating activities	357,217	753,597	1,428,574
INVESTING ACTIVITIES:
Capital expenditures	(397,567)	(257,169)	(1,131,445)
Purchase of short-term investments	(69,866)	(57,276)	(45,607)
Payment for acquisition of business, net of cash acquired	(70,416)
Proceeds from sale of short-term investments	69,449	58,381
Proceeds from asset sales	23,412	21,845	22,643
Net cash used in investing activities	(444,988)	(234,219)	(1,154,409)
FINANCING ACTIVITIES:
Payments on long-term debt		(40,000)	(40,000)
Proceeds from senior notes, net of discount			497,125
Debt issuance costs		(1,111)	(5,474)
Proceeds on short-term debt			1,002
Payments on short-term debt			(1,002)
Repurchase of common stock			(59,654)
Dividends paid	(305,515)	(300,152)	(298,367)
Exercise of stock options, net of tax withholding	10,534	1,040	2,650
Tax withholdings related to net share settlements of restricted stock	(5,848)	(3,912)	(5,140)
Excess tax benefit from stock-based compensation	4,414	934	3,772
Net cash provided by (used in) financing activities	(296,415)	(343,201)	94,912
Net increase (decrease) in cash and cash equivalents	(384,186)	176,177	369,077
Cash and cash equivalents, beginning of period	905,561	729,384	360,307
Cash and cash equivalents, end of period	$ 521,375	$ 905,561	$ 729,384