ACQUISITIONS & DIVESTITURES - Narrative (Details) - USD ($)					1 Months Ended				12 Months Ended
	Feb. 05, 2020	Apr. 03, 2019	Sep. 14, 2018	Jul. 12, 2017	Feb. 28, 2021	Apr. 30, 2020	Sep. 30, 2018	Jul. 31, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Business Acquisition [Line Items]
Estimated fair value of contingent purchase consideration									$ 1,748,000
Weighted average useful life of acquired intangible assets									14 years 7 months 6 days
Loss on divestiture of business									$ 0	$ 9,472,000	$ 0
Goodwill									1,725,680,000	1,715,485,000	1,712,764,000
Gigavation
Business Acquisition [Line Items]
Percentage of voting interests acquired	100.00%
Estimated purchase price	$ 8,000,000
Estimated fair value of contingent purchase consideration	800,000								700,000
Withdraw from escrow account									100,000
Goodwill	$ 3,816,000
Gigavation | Scenario, Forecast
Business Acquisition [Line Items]
Payments of contingent consideration					$ 700,000
Gigavation | Developed technology
Business Acquisition [Line Items]
Weighted average useful life of acquired intangible assets	10 years
Eastwind
Business Acquisition [Line Items]
Estimated purchase price		$ 5,154,000
Estimated fair value of contingent purchase consideration		1,000,000							1,000,000.0
Cash retention payments received		300,000
Goodwill		$ 1,003,000
Eastwind | Subsequent Event
Business Acquisition [Line Items]
Payments of contingent consideration						$ 1,000,000.0
Eastwind | Developed technology
Business Acquisition [Line Items]
Weighted average useful life of acquired intangible assets		10 years
Efflux Systems, Inc.
Business Acquisition [Line Items]
Estimated purchase price				$ 8,600,000
Estimated fair value of contingent purchase consideration											$ 500,000
Payments of contingent consideration								$ 500,000
Goodwill				$ 6,100,000
Handheld Network Test Tools Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Cash proceeds from divestiture			$ 1,300,000
Contingent consideration related to the divestiture			$ 2,300,000				$ 2,300,000			800,000
Contingent consideration measurement period			2 years				2 years
Net liabilities transferred										4,600,000
Loss on divestiture of business										9,500,000
Transaction costs										1,300,000
Incentive compensation payable										500,000
Transitional services agreement			18 months
Transitional services within other expense									$ 1,200,000	$ 2,200,000
Handheld Network Test Tools Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Maximum
Business Acquisition [Line Items]
Contingent consideration related to the divestiture			$ 4,000,000.0				$ 4,000,000.0