CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities
Net income (loss)	$ 116,464	$ 62,612	$ (69,476)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	37,429	28,149	28,046
Gain on settlement of equity method investment		(1,847)
Impairment of other assets			807
Stock-based compensation	19,822	17,278	11,737
Amortization of premium on marketable securities and deferred financing costs	710	252	339
Earnings of equity method investments	(6,788)	(9,381)	(2,380)
Loss recovery on insurance claim	(1,103)
Deferred income tax benefit	(45,217)	517	70,273
Pension settlement		(259)
Other gains on disposals of assets	(758)	(406)	(41)
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(28,463)	(11,178)	(1,796)
Inventories	(24,365)	(12,792)	8,565
Prepaid expenses and other current assets	(3,676)	(5,829)	(428)
Accounts payable	5,457	7,846	(5,143)
Deferred revenue	2,791	8,049	(3,290)
Accrued warranty and retrofit costs	(157)	1,602	290
Accrued compensation and tax withholdings	5,978	5,565	(3,234)
Accrued restructuring costs	(1,080)	(4,241)	3,860
Accrued pension costs		(32)	(811)
Accrued expenses and other current liabilities	(3,080)	10,319	2,229
Net cash provided by operating activities	73,964	96,224	39,547
Cash flows from investing activities
Purchases of property, plant and equipment	(12,787)	(12,677)	(12,848)
Purchases of technology intangibles		(240)
Purchases of marketable securities	(69,692)		(12,901)
Sales of marketable securities	1,584	3,590	139,388
Maturities of marketable securities	17,482
Disbursement for a loan receivable			(1,821)
Acquisitions, net of cash acquired	(85,755)	(44,791)	(125,248)
Proceeds from other investments	500
Purchases of other investments		(170)	(250)
Proceeds from sales of property, plant and equipment	200	100	2,806
Net cash used in investing activities	(148,468)	(54,188)	(10,874)
Cash flows from financing activities
Proceeds from term loan	197,554		366
Proceeds from issuance of common stock	2,826	2,040	1,888
Payment of deferred financing costs	(318)	(28)	(708)
Repayment of term loan	(1,500)
Common stock dividends paid	(28,285)	(27,932)	(27,503)
Net cash provided by (used in) financing activities	170,277	(25,920)	(25,957)
Effects of exchange rate changes on cash and cash equivalents	313	420	1,648
Net increase in cash and cash equivalents	96,086	16,536	4,364
Cash and cash equivalents, beginning of period	101,622	85,086	80,722
Cash and cash equivalents, end of period	197,708	101,622	85,086
Supplemental disclosures:
Cash paid for interest	6,537	200	114
Cash paid for income taxes, net	$ 21,051	8,142	$ 4,930
Supplemental disclosure of non-cash investing and financing activities:
Deferred financing costs included in accounts payable		423
Fair value of non-cash consideration for the acquisition of Cool Lab, LLC		$ 10,348