FAIR VALUE MEASUREMENTS (Details) (Recurring basis, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Level 1
Financial Assets
Total cash equivalents and short-term investments	$ 16,549	$ 20,018
Level 1 | U.S. Treasury bills
Financial Assets
Total cash equivalents and short-term investments		20,018
Level 1 | Money market funds
Financial Assets
Total cash equivalents and short-term investments	16,549
Level 2
Financial Assets
Total cash equivalents and short-term investments	108,546	164,514
Level 2 | Corporate debentures/bonds
Financial Assets
Total cash equivalents and short-term investments	75,572	78,169
Level 2 | Commercial paper
Financial Assets
Total cash equivalents and short-term investments	28,974	40,334
Level 2 | Government agency bonds
Financial Assets
Total cash equivalents and short-term investments		26,582
Level 2 | Money market funds
Financial Assets
Total cash equivalents and short-term investments		13,698
Level 2 | Certificates of deposit
Financial Assets
Total cash equivalents and short-term investments	4,000	5,731
Total fair value
Financial Assets
Total cash equivalents and short-term investments	$ 125,095	$ 184,532