GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) reporting_unit	Sep. 30, 2018 USD ($)	Mar. 31, 2019 USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Number of reporting units | reporting_unit			2
Goodwill	$ 1,719,362		$ 1,719,362		$ 1,715,485
Carrying value of intangible assets	624,799		624,799		669,118
Impairment of intangible assets	0	$ 0	$ 0	$ 35,871
Weighted average useful life of acquired intangible assets			14 years 7 months 6 days
Developed and core technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets			11 years 3 months 18 days
Customer and distributor relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets			15 years 10 months 24 days
Trademarks and trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets			8 years 7 months 6 days
Capitalized software
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life of acquired intangible assets			3 years
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	18,600		$ 18,600		18,600
Service Assurance
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	1,200,000		1,200,000		1,200,000
Security
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 555,800		$ 555,800		$ 555,100