CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income	$ 26,028	$ 13,057
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15,746	16,477
Stock-based compensation	6,710	4,410
Amortization of premium on marketable securities and deferred financing costs	56	67
Deferred income taxes	(4,960)	(8,183)
Other losses on disposals of assets	1	126
Adjustment to the gain on divestiture, net of tax	948	319
Changes in operating assets and liabilities, net of acquisitions and divestiture:
Accounts receivable	(4,504)	1,503
Inventories	(6,307)	(4,335)
Prepaid expenses and other assets	28,945	6,120
Accounts payable	5,727	5,255
Deferred revenue	3,186	(720)
Accrued warranty and retrofit costs	(185)	221
Accrued compensation and tax withholdings	(12,307)	(5,755)
Accrued restructuring costs	(75)	(203)
Accrued expenses and other liabilities	(15,279)	(2,616)
Net cash provided by operating activities	43,730	25,743
Cash flows from investing activities
Purchases of property, plant and equipment	(15,227)	(9,614)
Purchases of marketable securities	(4)	(10,742)
Maturities of marketable securities		33,584
Acquisitions, net of cash acquired	(15,061)
Net cash (used in) provided by investing activities	(30,292)	13,228
Cash flows from financing activities
Principal payments on debt	(414)	(414)
Payments of finance leases	(319)	(319)
Common stock dividends paid	(7,424)	(7,369)
Net cash used in financing activities	(8,157)	(8,102)
Effects of exchange rate changes on cash and cash equivalents	11,250	2,808
Net increase in cash, cash equivalents and restricted cash	16,531	33,677
Cash, cash equivalents and restricted cash, beginning of period	302,526	305,171
Cash, cash equivalents and restricted cash, end of period	319,057	338,848
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property, plant and equipment included in accounts payable	$ 2,112	$ 2,622