COMMITMENTS AND CONTINGENCIES - Narrative (Details) ft² in Thousands		12 Months Ended
	Jan. 23, 2018 USD ($) ft²	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Lessee, Lease, Description [Line Items]
Rent expense		$ 10,600,000	$ 5,600,000	$ 5,100,000
Property and equipment under capital lease		3,400,000	3,500,000
Accumulated depreciation related to assets under capital lease		2,800,000	1,800,000
Headquarters Facility, San Jose, California
Lessee, Lease, Description [Line Items]
Operating lease, term of contract	132 months
Lease, area | ft²	162
Line of Credit | Standby Letters of Credit
Lessee, Lease, Description [Line Items]
Line of credit facility, maximum borrowing capacity	$ 8,100,000.0
Third-Party Customer Support Commitments
Lessee, Lease, Description [Line Items]
Other commitment		1,100,000
Third-Party Network Service Provider Commitments
Lessee, Lease, Description [Line Items]
Other commitment		1,900,000
State and Local Taxes and Surcharges
Lessee, Lease, Description [Line Items]
Accrued contingent indirect tax liabilities		8,000,000	$ 800,000
Sales Tax
Lessee, Lease, Description [Line Items]
Incremental sales tax liability		$ 7,200,000