SHORT-TERM INVESTMENTS (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 452,869	$ 448,941
Gross Unrealized Gain	259	226
Gross Unrealized Loss	(179)	(235)
Fair Value	452,949	448,932
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Rolling Maturity [Abstract]
Amortized cost, Due in 1 year or less	358,780
Amortized cost, Due in 1-2 years	94,085
Total amortized cost	452,865
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Fair value, Due in 1 year or less	358,881
Fair value, Due in 1-2 years	94,068
Total fair value	452,949
Bank time deposits
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	200,945	175,745
Gross Unrealized Gain	0	0
Gross Unrealized Loss	0	0
Fair Value	200,945	175,745
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	230,070	243,140
Gross Unrealized Gain	110	98
Gross Unrealized Loss	(165)	(219)
Fair Value	230,015	243,019
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	17,517	25,938
Gross Unrealized Gain	2	5
Gross Unrealized Loss	0	(7)
Fair Value	17,519	25,936
Mutual funds
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,337	4,118
Gross Unrealized Gain	147	123
Gross Unrealized Loss	(14)	(9)
Fair Value	$ 4,470	$ 4,232