FAIR VALUE MEASUREMENTS (Details) (Recurring basis, USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013
Level 1
Financial Assets
Total cash equivalents and short-term investments	$ 57,115	$ 16,549
Level 1 | Money market funds
Financial Assets
Total cash equivalents and short-term investments	57,115	16,549
Level 2
Financial Assets
Total cash equivalents and short-term investments	68,501	108,546
Level 2 | Corporate debentures/bonds
Financial Assets
Total cash equivalents and short-term investments	42,184	75,572
Level 2 | Government agency bonds
Financial Assets
Total cash equivalents and short-term investments	18,321
Level 2 | Commercial paper
Financial Assets
Total cash equivalents and short-term investments	3,996	28,974
Level 2 | Certificates of deposit
Financial Assets
Total cash equivalents and short-term investments	4,000	4,000
Total fair value
Financial Assets
Total cash equivalents and short-term investments	$ 125,616	$ 125,095