Goodwill and Other Identifiable Intangible Assets, Net (Additional Information) (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)
Goodwill [Line Items]
Number of Reportable Segments | segment	2
Goodwill	$ 221,331	$ 210,135
Market Capitalization	686,300
Enterprise Routers
Goodwill [Line Items]
Goodwill	32,700
Console Servers
Goodwill [Line Items]
Goodwill	60,200
OEM Solutions
Goodwill [Line Items]
Goodwill	63,400
Infrastructure Mgmt.
Goodwill [Line Items]
Goodwill	15,400
IoT Solutions Segment
Goodwill [Line Items]
Goodwill	49,500
IoT Products & Services Segment
Goodwill [Line Items]
Goodwill	170,710	160,365
IoT Solutions Segment
Goodwill [Line Items]
Goodwill	$ 50,621	$ 49,770
Control Premium | Minimum
Goodwill [Line Items]
Goodwill Valuation Implied Control Premium	(4.50%)
Control Premium | Maximum
Goodwill [Line Items]
Goodwill Valuation Implied Control Premium	5.40%