Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (191,434)	$ (389,935)
Adjustment for (income) loss from discontinued operations	(9,786)	196
Loss from continuing operations	(201,220)	(389,739)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	213,278	262,137
Asset impairment charge	54,284	563,234
Amortization of debt discount and debt issuance costs	920	900
Provision for credit loss	(227)	1,779
Provision for obsolete inventory	423	684
Stock-based compensation	14,277	20,952
(Gain) loss on investment securities	(5,444)	9,592
(Gain) loss on sale of assets	6,179	(14,589)
Gain on sale of subsidiary	0	(14,963)
Deferred income tax benefit	(46,068)	(106,878)
Other	3,646	(3,779)
Change in assets and liabilities:
Accounts receivable	(8,498)	(37,717)
Inventories of materials and supplies	7,159	(2,064)
Prepaid expenses and other	(7,951)	(15,962)
Other noncurrent assets	(3,696)	10,107
Accounts payable	25,277	21,764
Accrued liabilities	(451)	(68,146)
Other noncurrent liabilities	6,939	(4,642)
Net cash provided by operating activities from continuing operations	58,827	232,670
Net cash used in operating activities from discontinued operations	(25)	(28)
Net cash provided by operating activities	58,802	232,642
Cash flows from investing activities:
Capital expenditures	(30,745)	(94,312)
Purchase of investments	(106,731)	(36,336)
Proceeds from sale of investments	63,742	43,894
Proceeds from sale of subsidiary	0	15,056
Proceeds from asset sales	13,419	24,799
Other	0	(51)
Net cash used in investing activities	(60,315)	(46,950)
Cash flows from financing activities:
Dividends paid	(54,230)	(155,890)
Proceeds from stock option exercises	0	4,100
Payments for employee taxes on net settlement of equity awards	(2,119)	(3,455)
Payment of contingent consideration from acquisition of business	(250)	(4,250)
Share repurchases	0	(28,504)
Other	0	(445)
Net cash used in financing activities	(56,599)	(188,444)
Net decrease in cash and cash equivalents and restricted cash	(58,112)	(2,752)
Cash and cash equivalents and restricted cash, beginning of period	536,747	382,971
Cash and cash equivalents and restricted cash, end of period	478,635	380,219
Cash paid during the period:
Interest paid	11,473	11,440
Income tax paid (received), net	(31,965)	43,509
Payments for operating leases	8,970	9,626
Non-cash operating and investing activities:
Changes in accounts payable and accrued liabilities related to purchases of property, plant and equipment	(1,296)	189
Changes in accounts receivable, property, plant and equipment and other noncurrent assets related to the sale of equipment	9,290	0
Cumulative effect adjustment for adoption of ASU No. 2016-13	$ (1,251)	$ 0