CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net income	$ 64,853	$ 437,416	$ 116,464
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	65,496	54,454	37,429
Allowance for Loan and Lease Losses, Write-offs		285
Stock-based compensation	16,317	20,113	19,822
Amortization of premium on marketable securities and deferred financing costs	233	1,121	710
Earnings of equity method investments		(6,188)	(6,788)
Loss recovery on insurance claim			(1,103)
Deferred income taxes	(5,407)	(15,161)	(45,217)
Loss on extinguishment of debt		14,339
Other losses on disposals of assets	226	209	(758)
Loss (gain) on sale of divestiture, net of tax	319	(408,575)
Contingent transaction fees paid stemming from divestiture		(13,388)
Taxes paid stemming from divestiture	(91,500)
Changes in operating assets and liabilities, net of acquisitions and divestiture:
Accounts receivable	(18,755)	(11,445)	(28,463)
Inventories	(13,144)	(2,933)	(24,365)
Prepaid expenses and other assets	25,642	(16,009)	(3,676)
Accounts payable	792	4,695	5,457
Deferred revenue	(139)	4,213	2,791
Accrued warranty and retrofit costs	760	1,109	(157)
Accrued compensation and tax withholdings	11,097	(6,453)	5,978
Accrued restructuring costs	(865)	399	(1,080)
Proceeds from recovery on insurance claim		1,082
Accrued expenses and other liabilities	(18,059)	31,615	(3,080)
Net cash provided by operating activities	37,866	90,898	73,964
Cash flows from investing activities
Purchases of property, plant and equipment	(39,924)	(23,861)	(12,787)
Purchases of marketable securities	(10,894)	(35,225)	(69,692)
Sales of marketable securities	2,492	48,903	1,584
Maturities of marketable securities	42,328	2,557	17,482
Acquisitions, net of cash acquired	(15,744)	(442,704)	(85,755)
Issuance of a note receivable	(1,000)
Proceeds from sales of property, plant and equipment			200
Proceeds from other investments			500
Proceeds from divestiture		661,642
Net cash (used in) provided by investing activities	(22,742)	211,312	(148,468)
Cash flows from financing activities
Proceeds from term loans, net of discount		686,386	197,554
Proceeds from issuance of common stock	4,595	3,422	2,826
Payments of financing costs		(687)	(318)
Principal payments on debt	(828)	(850,190)	(1,500)
Payments of finance leases	(1,277)	(1,197)
Common stock dividends paid	(29,513)	(28,895)	(28,285)
Net cash (used in) provided by financing activities	(27,023)	(191,161)	170,277
Effects of exchange rate changes on cash and cash equivalents	9,254	(3,586)	313
Net (decrease) increase in cash, cash equivalents and restricted cash	(2,645)	107,463	96,086
Cash, cash equivalents and restricted cash, beginning of period	305,171	197,708	101,622
Cash, cash equivalents and restricted cash, end of period	302,526	305,171	197,708
Supplemental disclosures:
Cash paid for interest	2,159	20,799	6,537
Cash paid for income taxes, net	$ 102,010	$ 16,990	$ 21,051