Fair Value Measurements (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2018	Apr. 01, 2017	Mar. 31, 2018	Sep. 30, 2017
Financial assets:
Cash equivalents			$ 82,291	$ 49,845
Fair value			55,264	50,315
Forward contracts			827	1,163
Financial assets, fair value			138,382	101,323
Financial liabilities:
Contingent consideration related to acquisitions	$ 8,400		6,743	8,400
Forward contracts			4,837	4,347
Liabilities, Fair Value Disclosure, Recurring			11,580	12,747
Business Combination. Contingent Consideration [Roll Forward]
Beginning balance	8,400
Payment of contingent consideration	(3,800)	$ (3,100)
Ending balance	6,743
Level 1
Financial assets:
Cash equivalents			82,291	49,845
Financial assets, fair value			134,941	97,518
Level 2
Financial assets:
Forward contracts			827	1,163
Financial assets, fair value			3,441	3,805
Financial liabilities:
Forward contracts			4,837	4,347
Liabilities, Fair Value Disclosure, Recurring			4,837	4,347
Level 3
Financial liabilities:
Contingent consideration related to acquisitions	8,400	19,570	6,743	8,400
Liabilities, Fair Value Disclosure, Recurring			6,743	8,400
Business Combination. Contingent Consideration [Roll Forward]
Beginning balance	8,400	19,570
Addition to Contingent Consideration	2,100
Change in present value of contingent consideration		148
Payment of contingent consideration	(3,757)	(3,050)
Ending balance	6,743	16,668
Kepware
Financial liabilities:
Contingent consideration related to acquisitions	4,600		4,600
Business Combination. Contingent Consideration [Roll Forward]
Ending balance	4,600
Kepware | Level 3
Financial liabilities:
Contingent consideration related to acquisitions	8,400	17,070	4,643	8,400
Business Combination. Contingent Consideration [Roll Forward]
Beginning balance	8,400	17,070
Addition to Contingent Consideration	0
Change in present value of contingent consideration		148
Payment of contingent consideration	(3,757)	(1,800)
Ending balance	4,643	15,418
Other | Level 3
Financial liabilities:
Contingent consideration related to acquisitions	0		2,100	0
Business Combination. Contingent Consideration [Roll Forward]
Beginning balance	0
Addition to Contingent Consideration	2,100
Payment of contingent consideration	0
Ending balance	$ 2,100
ColdLight | Level 3
Financial liabilities:
Contingent consideration related to acquisitions		2,500
Business Combination. Contingent Consideration [Roll Forward]
Beginning balance		2,500
Change in present value of contingent consideration		0
Payment of contingent consideration		(1,250)
Ending balance		$ 1,250
Certificates of deposit
Financial assets:
Fair value			219	240
Certificates of deposit | Level 2
Financial assets:
Fair value			219	240
Corporate notes/bonds
Financial assets:
Fair value			52,650	47,673
Corporate notes/bonds | Level 1
Financial assets:
Fair value			52,650	47,673
U.S. government agency securities
Financial assets:
Fair value			2,395	2,402
U.S. government agency securities | Level 2
Financial assets:
Fair value			$ 2,395	$ 2,402