FAIR VALUE MEASUREMENTS - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Mar. 31, 2016
ASSETS:
Cash and cash equivalents	$ 195,423	$ 210,711
Marketable securities	107,972	141,364
Derivative financial instruments	63	191
Contingently returnable consideration	11,643	16,131
Total assets	315,101	368,397
LIABILITIES:
Contingent purchase consideration	(9,282)	(7,293)
Derivative financial instruments	(175)	(158)
Total liabilities	(9,457)	(7,451)
U.S. government and municipal obligations
ASSETS:
Marketable securities	86,907	123,328
Commercial paper
ASSETS:
Marketable securities	21,065	16,172
Corporate bonds
ASSETS:
Marketable securities		1,864
Level 1
ASSETS:
Cash and cash equivalents	195,423	210,711
Derivative financial instruments	0	0
Contingently returnable consideration	0
Total assets	214,505	253,691
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments	0	0
Total liabilities	0	0
Level 1 | U.S. government and municipal obligations
ASSETS:
Marketable securities	19,082	41,116
Level 1 | Commercial paper
ASSETS:
Marketable securities	0	0
Level 1 | Corporate bonds
ASSETS:
Marketable securities		1,864
Level 2
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	63	191
Contingently returnable consideration	0
Total assets	88,953	98,575
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments	(175)	(158)
Total liabilities	(175)	(158)
Level 2 | U.S. government and municipal obligations
ASSETS:
Marketable securities	67,825	82,212
Level 2 | Commercial paper
ASSETS:
Marketable securities	21,065	16,172
Level 2 | Corporate bonds
ASSETS:
Marketable securities		0
Level 3
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	0	0
Contingently returnable consideration	11,643	16,131
Total assets	11,643	16,131
LIABILITIES:
Contingent purchase consideration	(9,282)	(7,293)
Derivative financial instruments	0	0
Total liabilities	(9,282)	(7,293)
Level 3 | U.S. government and municipal obligations
ASSETS:
Marketable securities	0	0
Level 3 | Commercial paper
ASSETS:
Marketable securities	$ 0	0
Level 3 | Corporate bonds
ASSETS:
Marketable securities		$ 0