GOODWILL AND INTANGIBLE ASSETS - Narrative (Details)	3 Months Ended
	Jun. 30, 2016 USD ($) Segment	Jun. 30, 2015 USD ($)	Mar. 31, 2016 USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Number of operating segments | Segment	5
Goodwill	$ 1,710,286,000		$ 1,709,369,000
Carrying value of intangible assets	1,023,968,000		1,054,040,000
Amortization expenses	$ 17,572,000	$ 809,000
Weighted average useful life of acquired intangible assets	14 years 7 months
Acquired software and core technology | Included as cost of product revenue
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses	$ 10,700,000	758,000
Other acquired intangible assets | Included as operating expense
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses	$ 17,600,000	847,000
Developed and core technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets	11 years 6 months
Customer and distributor relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets	16 years 1 month
Trademarks and trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets	8 years 6 months
Leasehold interest
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets	5 years 7 months 6 days
Backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets	2 years
Backlog | Product revenue
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expenses	$ 2,900,000	$ 0
Capitalized Software
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets	4 years
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 18,600,000		18,600,000
Legacy NetScout
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	197,800,000		198,100,000
Arbor Networks
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	534,900,000		534,800,000
Service assurance for service provider
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	795,500,000		794,400,000
Network visibility
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	57,000,000		57,000,000
Service assurance for enterprise
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 125,100,000		$ 125,100,000