Fair Value Measurements (Details) - USD ($)		1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 05, 2015	Apr. 30, 2020	Mar. 31, 2021	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Jul. 06, 2021	Mar. 26, 2021	Dec. 13, 2019	Jan. 22, 2018	Nov. 01, 2016
Estimate of Fair Value Measurement | Contingent consideration on acquired business | Fair Value, Measurements, Recurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration fair value					$ 6,200,000	$ 4,228,000
Estimate of Fair Value Measurement | Bluenica Corporation | Contingent consideration on acquired business | Fair Value, Measurements, Recurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration fair value	$ 10,400,000
Estimate of Fair Value Measurement | FreshTemp | Contingent consideration on acquired business | Fair Value, Measurements, Recurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration fair value																$ 1,300,000
Estimate of Fair Value Measurement | TempAlert | Contingent consideration on acquired business | Fair Value, Measurements, Recurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration fair value																$ 0
Estimate of Fair Value Measurement | Accelerated Concepts | Contingent consideration on acquired business | Fair Value, Measurements, Recurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration fair value															$ 2,300,000
Change in fair value of contingent consideration					5,772,000	(128,000)		$ 1,190,000
Goodwill					225,522,000	210,135,000		153,422,000
Fair Value, Inputs, Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration fair value					6,200,000	4,228,000		5,407,000
Contingent consideration on acquired business | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent consideration fair value					6,200,000	4,228,000
Bluenica Corporation
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Business Combination, Contingent Liability, Payout Period	4 years
Bluenica Corporation | Contingent consideration on acquired business
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Change in fair value of contingent consideration						$ 2,900,000		2,200,000		$ 0	$ 500,000
FreshTemp | Contingent consideration on acquired business
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Change in fair value of contingent consideration								200,000
TempAlert | Contingent consideration on acquired business
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Change in fair value of contingent consideration							$ 0		$ 0
Accelerated Concepts | Contingent consideration on acquired business
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Change in fair value of contingent consideration		$ 2,400,000						$ 3,500,000
Opengear
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Goodwill														$ 57,088,000
Opengear | Contingent consideration on acquired business
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Change in fair value of contingent consideration			$ 10,000,000	$ 900,000
Haxiot
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Goodwill													$ 8,605,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability													$ 5,900,000
Ctek
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Goodwill												$ 4,867,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contingent Liability					$ 300,000							$ 300,000