SHORT-TERM INVESTMENTS (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Sep. 30, 2015	Mar. 31, 2015
Short-term investments:
Cost or Amortized Cost	$ 353,031	$ 186,954
Gross Unrealized Gains	19	39
Gross Unrealized Losses	(89)	(64)
Fair Value	352,961	186,929
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Rolling Maturity
Due in 1 year or less	340,073
Due in 1-2 years	12,958
Total amortized cost	353,031
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity
Due in 1 year or less	340,009
Due in 1-2 years	12,952
Total fair value	352,961
Bank time deposits
Short-term investments:
Cost or Amortized Cost	248,590	87,500
Fair Value	248,590	87,500
Corporate bonds
Short-term investments:
Cost or Amortized Cost	104,441	99,454
Gross Unrealized Gains	19	39
Gross Unrealized Losses	(89)	(64)
Fair Value	$ 104,371	$ 99,429