Acquisitions (Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	Dec. 13, 2019	Jun. 30, 2020	Sep. 30, 2019
Business Acquisition [Line Items]
Goodwill		$ 206,693	$ 153,422
Opengear
Business Acquisition [Line Items]
Cash	$ 148,058
Contingent consideration	5,100
Total consideration transferred	153,158
Fair value of net tangible assets acquired	20,086
Deferred tax liability on identifiable intangible assets	(25,634)
Goodwill	53,606
Total assets acquired and liabilities assumed	153,158
Customer Relationships | Opengear
Business Acquisition [Line Items]
Identifiable intangible assets	79,000
Purchased and Core Technology | Opengear
Business Acquisition [Line Items]
Identifiable intangible assets	18,100
Trademarks | Opengear
Business Acquisition [Line Items]
Identifiable intangible assets	$ 8,000