Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income (loss)	$ (70,431)	$ 30,605
Adjustment for (income) loss from discontinued operations	(7,493)	124
Income (loss) from continuing operations	(77,924)	30,729
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	106,861	130,131
Amortization of debt discount and debt issuance costs	460	444
Provision for credit loss	(465)	(2,069)
Provision for obsolete inventory	216	693
Stock-based compensation	7,451	10,201
Gain on investment securities	(2,924)	(2,821)
Gain on sale of assets	(12,336)	(4,279)
Gain on sale of subsidiary	0	(14,963)
Deferred income tax benefit	(15,016)	(7,966)
Other	1,458	(139)
Change in assets and liabilities:
Accounts receivable	(32,586)	(3,269)
Inventories of materials and supplies	4,612	272
Prepaid expenses and other	(5,935)	(19,699)
Other noncurrent assets	1,629	6,367
Accounts payable	9,738	(1,580)
Accrued liabilities	(6,674)	(8,093)
Other noncurrent liabilities	1,834	(2,178)
Net cash provided by (used in) operating activities from continuing operations	(19,601)	111,781
Net cash used in operating activities from discontinued operations	(3)	0
Net cash provided by (used in) operating activities	(19,604)	111,781
Cash flows from investing activities:
Capital expenditures	(13,985)	(46,021)
Purchase of investments	(95,151)	(28,948)
Proceeds from sale of investments	37,097	25,000
Proceeds from sale of subsidiary	0	15,056
Proceeds from asset sales	6,836	11,878
Net cash used in investing activities	(65,203)	(23,035)
Cash flows from financing activities:
Dividends paid	(26,918)	(77,602)
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)	0
Other	0	(445)
Net cash used in financing activities	(29,287)	(77,402)
Net increase (decrease) in cash and cash equivalents and restricted cash	(114,094)	11,344
Cash and cash equivalents and restricted cash, beginning of period	536,747	382,971
Cash and cash equivalents and restricted cash, end of period	422,653	394,315
Cash paid during the period:
Interest paid	77	46
Income tax paid (received), net	(190)	934
Payments for operating leases	3,986	4,877
Non-cash operating and investing activities:
Changes in accounts payable and accrued liabilities related to purchases of property, plant and equipment	(369)	(1,339)
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