SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)		1 Months Ended				6 Months Ended		12 Months Ended			36 Months Ended
	Sep. 14, 2018 USD ($)	Feb. 28, 2021 USD ($)	Nov. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jul. 31, 2018 USD ($)	Mar. 31, 2020 USD ($) reporting_unit	Sep. 30, 2019 reporting_unit	Mar. 31, 2020 USD ($) company segment	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 30, 2020 company	Feb. 05, 2020 USD ($)	Apr. 03, 2019 USD ($)	Jan. 16, 2018 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments | segment								1
Unrecognized accounts receivable and deferred revenue						$ 11,100,000		$ 11,100,000	$ 23,300,000
Number of reporting units | reporting_unit						1	2
Number of companies acquired | company								2			3
Number of businesses divested | company											1
Fair value of contingent consideration									762,000
Fair value of contingent liability						$ 1,748,000		$ 1,748,000
Amortization included as cost of product								500,000	1,100,000	$ 1,000,000.0
Capitalized software development costs						0		0	100,000
Foreign currency losses								700,000	2,000,000.0	4,100,000
Advertising expense								8,300,000	9,400,000	6,500,000
Senior secured revolving credit facility | Line of credit
Summary Of Significant Accounting Policies [Line Items]
Credit facility						1,000,000,000.0		1,000,000,000.0						$ 1,000,000,000.0
Current borrowing capacity						285,000,000		$ 285,000,000
Computer equipment and internal use software
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life								3 years
Gigavation
Summary Of Significant Accounting Policies [Line Items]
Fair value of contingent liability						700,000		$ 700,000				$ 800,000
Gigavation | Scenario, Forecast
Summary Of Significant Accounting Policies [Line Items]
Payments of contingent consideration		$ 700,000
Eastwind
Summary Of Significant Accounting Policies [Line Items]
Fair value of contingent liability						1,000,000.0		$ 1,000,000.0					$ 1,000,000
Efflux Systems, Inc.
Summary Of Significant Accounting Policies [Line Items]
Fair value of contingent liability										500,000
Payments of contingent consideration					$ 500,000
Simena LLC
Summary Of Significant Accounting Policies [Line Items]
Fair value of contingent liability										$ 4,900,000
Payments of contingent consideration			$ 5,000,000.0
Maximum | Computer equipment and internal use software
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life								5 years
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Handheld Network Test Tools Business
Summary Of Significant Accounting Policies [Line Items]
Contingent consideration related to the divestiture	$ 2,300,000			$ 2,300,000					800,000
Contingent consideration measurement period	2 years			2 years
Fair value of contingent consideration						$ 0		$ 0	$ 800,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Maximum | Handheld Network Test Tools Business
Summary Of Significant Accounting Policies [Line Items]
Contingent consideration related to the divestiture	$ 4,000,000.0			$ 4,000,000.0