Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
OPERATING ACTIVITIES:
Net income	$ 422,225	$ 708,719	$ 736,639
Adjustment for (income) loss from discontinued operations	47	47	(15,186)
Income (loss) from continuing operations	422,272	708,766	721,453
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	606,992	523,549	455,623
Asset impairment charge	39,242
Amortization of debt issuance costs	749	400	409
Provision for (recovery of) bad debt	6,034	(200)	3,875
Stock-based compensation	25,195	26,703	23,271
Pension settlement charges	2,873	1,376
Gain on sale of investment securities		(45,234)	(162,121)
Income from asset sales	(11,716)	(19,585)	(18,923)
Deferred income tax expense	131,580	27,124	29,557
Other	(368)	2	2,490
Change in assets and liabilities:
Accounts receivable	249,873	(83,594)	(4,806)
Inventories	(22,488)	(17,375)	(12,289)
Prepaid expenses and other	(13,812)	(6,687)	5,321
Accounts payable	(34,150)	(21,082)	(52,076)
Accrued liabilities	(22,901)	35,845	24,259
Deferred income taxes	598	(784)	(1,673)
Other noncurrent liabilities	38,818	(10,650)	(17,371)
Net cash provided by operating activities from continuing operations	1,418,791	1,118,574	996,999
Net cash provided by (used in) operating activities from discontinued operations	(47)	(47)	186
Net cash provided by operating activities	1,418,744	1,118,527	997,185
INVESTING ACTIVITIES:
Capital expenditures	(1,133,482)	(952,892)	(809,066)
Purchase of short-term investments	(45,607)
Proceeds from asset sales	22,501	30,770	28,026
Proceeds from sale of investments		49,205	232,221
Net cash used in investing activities from continuing operations	(1,156,588)	(872,917)	(548,819)
Net cash provided by investing activities from discontinued operations			15,000
Net cash provided by (used in) investing activities	(1,156,588)	(872,917)	(533,819)
FINANCING ACTIVITIES:
Payments on long-term debt	(40,000)	(115,000)	(40,000)
Proceeds from senior notes, net of discount	497,125
Debt issuance costs	(5,474)
Proceeds on short-term debt	1,002
Payments on short-term debt	(1,002)
Repurchase of common stock	(59,654)
Dividends paid	(298,367)	(264,386)	(93,053)
Exercise of stock options, net of tax withholding	2,650	23,250	13,317
Tax withholdings related to net share settlements of restricted stock	(5,140)	(3,049)	(1,677)
Excess tax benefit from stock-based compensation	3,772	26,616	9,820
Net cash provided by (used in) financing activities	94,912	(332,569)	(111,593)
Net increase (decrease) in cash and cash equivalents	357,068	(86,959)	351,773
Cash and cash equivalents, beginning of period	360,909	447,868	96,095
Cash and cash equivalents, end of period	$ 717,977	$ 360,909	$ 447,868