Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 79,850	$ 488,227
Adjustment for (income) loss from discontinued operations	371	10,782
Income (loss) from continuing operations	80,221	499,009
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	284,620	288,942
Amortization of debt discount and debt issuance costs	752	531
(Recovery of) bad debt	(75)
Provision for bad debt		429
Stock-based compensation	16,589	15,546
Loss on investment securities	36,957
Gain on sale of assets	(17,090)	(10,820)
Deferred income tax (benefit) expense	8,827	(506,373)
Other	(3,209)	5,701
Change in assets and liabilities increasing (decreasing) cash:
Accounts receivable	13,642	(61,791)
Inventories of materials and supplies	(3,268)	(5,973)
Prepaid expenses and other	3,960	6,992
Other noncurrent assets	(4,602)	(4,993)
Accounts payable	(2,639)	(13,119)
Accrued liabilities	(456)	12,918
Deferred income tax liability	160	(5,980)
Other noncurrent liabilities	(5,326)	(13,272)
Net cash provided by operating activities from continuing operations	409,063	207,747
Net cash used in operating activities from discontinued operations	(45)	(96)
Net cash provided by operating activities	409,018	207,651
Cash flows from investing activities:
Capital expenditures	(329,980)	(191,202)
Purchase of short-term investments	(42,406)	(36,784)
Payment for acquisition of business, net of cash acquired	(2,781)	(47,886)
Proceeds from sale of short-term investments	58,015	32,020
Proceeds from asset sales	24,559	17,826
Net cash used in investing activities	(292,593)	(226,026)
Cash flows from financing activities:
Dividends paid	(156,580)	(153,433)
Debt issuance costs paid	(3,912)
Proceeds from stock option exercises	2,257	1,645
Payments for employee taxes on net settlement of equity awards	(6,268)	(5,791)
Payment of contingent consideration from acquisition of business		(4,500)
Net cash used in financing activities	(164,503)	(162,079)
Net decrease in cash and cash equivalents and restricted cash	(48,078)	(180,454)
Cash and cash equivalents and restricted cash, beginning of period	326,185	560,509
Cash and cash equivalents and restricted cash, end of period	278,107	380,055
Cash paid during the period:
Interest paid	13,234	11,796
Income tax paid, net	9,127	3,278
Changes in accounts payable and accrued liabilities related to purchases of property, plant and equipment	$ 12,734	$ 237