GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) $ in Thousands		9 Months Ended	12 Months Ended
	Jun. 30, 2016 reporting_unit	Mar. 31, 2017 USD ($) reporting_unit	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Number of reporting units | reporting_unit	5	2
Goodwill		$ 1,718,162	$ 1,718,162	$ 1,709,369	$ 197,445
Carrying value of intangible assets		931,269	931,269	1,054,040
Amortization expenses			$ 126,089	84,421	$ 7,142
Weighted average useful life of acquired intangible assets			14 years 7 months 2 days
Technology license
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired			$ 1,000	$ 3,700
Weighted average useful life of acquired intangible assets			3 years	4 years
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 18 days
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
Backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets			2 years
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	$ 18,600	$ 18,600
Service Assurance reporting unit
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill		1,200,000	1,200,000	1,200,000
Security reporting unit
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 548,500	$ 548,500	$ 547,400