FAIR VALUE MEASUREMENTS - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Mar. 31, 2015
ASSETS:
Cash and cash equivalents	$ 215,539	$ 104,893
Marketable securities	135,846	159,964
Derivative financial instruments	34	15
Contingently returnable consideration	19,125
Total assets	370,544	264,872
LIABILITIES:
Contingent purchase consideration	(4,560)	(4,484)
Derivative financial instruments	(416)	(1,664)
Total liabilities	(4,976)	(6,148)
U.S. government and municipal obligations
ASSETS:
Marketable securities	126,240	145,345
Commercial paper
ASSETS:
Marketable securities	2,990	5,095
Corporate bonds
ASSETS:
Marketable securities	6,616	9,524
Level 1
ASSETS:
Cash and cash equivalents	215,539	104,893
Derivative financial instruments	0	0
Contingently returnable consideration	0
Total assets	256,239	160,981
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	34,084	46,564
Level 1 | Commercial paper
ASSETS:
Marketable securities	0	0
Level 1 | Corporate bonds
ASSETS:
Marketable securities	6,616	9,524
Level 2
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	34	15
Contingently returnable consideration	0
Total assets	95,180	103,891
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments	(416)	(1,664)
Total liabilities	(416)	(1,664)
Level 2 | U.S. government and municipal obligations
ASSETS:
Marketable securities	92,156	98,781
Level 2 | Commercial paper
ASSETS:
Marketable securities	2,990	5,095
Level 2 | Corporate bonds
ASSETS:
Marketable securities	0	0
Level 3
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	0	0
Contingently returnable consideration	19,125
Total assets	19,125	0
LIABILITIES:
Contingent purchase consideration	(4,560)	(4,484)
Derivative financial instruments	0	0
Total liabilities	(4,560)	(4,484)
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	$ 0