Acquisitions (Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	Mar. 26, 2021	Dec. 13, 2019	Jun. 30, 2021	Sep. 30, 2020
Business Acquisition [Line Items]
Goodwill			$ 221,331	$ 210,135
Opengear
Business Acquisition [Line Items]
Cash		$ 148,058
Contingent consideration		5,100
Total consideration transferred		153,158
Fair value of net tangible assets acquired		18,096
Deferred tax liability on identifiable intangible assets		(27,126)
Goodwill		57,088
Total assets acquired and liabilities assumed		153,158
Haxiot
Business Acquisition [Line Items]
Cash	$ 7,146
Contingent consideration	5,900
Total consideration transferred	13,046
Fair value of net tangible assets acquired	124
Deferred tax liability on identifiable intangible assets	(1,145)
Goodwill	8,617
Total assets acquired and liabilities assumed	13,046
Customer Relationships | Opengear
Business Acquisition [Line Items]
Identifiable intangible assets		79,000
Customer Relationships | Haxiot
Business Acquisition [Line Items]
Identifiable intangible assets	3,900
Purchased and Core Technology | Opengear
Business Acquisition [Line Items]
Identifiable intangible assets		18,100
Purchased and Core Technology | Haxiot
Business Acquisition [Line Items]
Identifiable intangible assets	1,050
Trademarks | Opengear
Business Acquisition [Line Items]
Identifiable intangible assets		$ 8,000
Trademarks | Haxiot
Business Acquisition [Line Items]
Identifiable intangible assets	$ 500