CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income	$ 49,776	$ 22,184
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31,543	33,079
Stock-based compensation	14,191	8,624
Amortization of premium on marketable securities and deferred financing costs	113	94
Deferred income taxes	(10,161)	(9,477)
Other losses on disposals of assets	51	125
Adjustment to the gain on divestiture, net of tax	948	319
Taxes paid stemming from divestiture		(91,500)
Changes in operating assets and liabilities, net of acquisitions and divestiture:
Accounts receivable	(35,033)	(12,670)
Inventories	(11,301)	(9,094)
Prepaid expenses and other assets	3,157	5,374
Accounts payable	14,136	5,807
Deferred revenue	4,659	(1,478)
Accrued warranty and retrofit costs	(261)	735
Accrued compensation and tax withholdings	(5,371)	(522)
Accrued restructuring costs	(124)	(112)
Accrued expenses and other liabilities	21,619	8,455
Net cash provided by (used in) operating activities	77,942	(40,057)
Cash flows from investing activities
Purchases of property, plant and equipment	(25,531)	(21,170)
Purchases of marketable securities	(75)	(10,843)
Sales of marketable securities	25	2,492
Maturities of marketable securities		42,226
Adjustment to proceeds from divestiture	(1,802)
Acquisitions, net of cash acquired	(15,061)	(15,743)
Issuance of a note receivable		(1,000)
Net cash used in by investing activities	(42,444)	(4,038)
Cash flows from financing activities
Proceeds from issuance of common stock	2,583	2,330
Principal payments on debt	(414)	(414)
Payments of finance leases	(638)	(639)
Common stock dividends paid	(14,856)	(14,747)
Net cash used in financing activities	(13,325)	(13,470)
Effects of exchange rate changes on cash and cash equivalents	6,051	(1,803)
Net increase (decrease) in cash, cash equivalents and restricted cash	28,224	(59,368)
Cash, cash equivalents and restricted cash, beginning of period	302,526	305,171
Cash, cash equivalents and restricted cash, end of period	330,750	245,803
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property, plant and equipment included in accounts payable	$ 3,733	$ 1,305