Goodwill and Other Identifiable Intangible Assets, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018		Sep. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 122,878		$ 122,878			$ 122,910
Accumulated amortization	(88,071)		(88,071)			(83,590)
Net	34,807		34,807			39,320	[1]
Amortization expense			4,609	$ 4,287	[1]
Purchased and Core Technology
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	58,011		58,011			58,102
Accumulated amortization	(49,938)		(49,938)			(48,693)
Net	8,073		8,073			9,409
License Agreements
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	102		102			102
Accumulated amortization	(60)		(60)			(46)
Net	42		42			56
Patents and Trademarks
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	15,835		15,835			15,701
Accumulated amortization	(12,777)		(12,777)			(12,242)
Net	3,058		3,058			3,459
Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	46,530		46,530			46,605
Accumulated amortization	(23,226)		(23,226)			(21,049)
Net	23,304		23,304			25,556
Non-compete Agreements
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	600		600			600
Accumulated amortization	(270)		(270)			(210)
Net	330		330			390
Order backlog
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,800		1,800			1,800
Accumulated amortization	(1,800)		(1,800)			(1,350)
Net	0		0			$ 450
Cost of Sales and General and Administrative Expense
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 2,100	$ 2,600	$ 4,600	$ 4,300

[1] Prior period information has been restated for the adoption of ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606),” which we adopted on October 1, 2018.