FAIR VALUE MEASUREMENTS - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Mar. 31, 2015
ASSETS:
Cash and cash equivalents	$ 230,521	$ 104,893
Marketable securities	145,712	159,964
Derivative financial instruments	9	15
Contingently returnable consideration	16,687
Total assets	392,930	264,872
LIABILITIES:
Contingent purchase consideration	(7,234)	(4,484)
Derivative financial instruments	(467)	(1,664)
Total liabilities	(7,701)	(6,148)
U.S. government and municipal obligations
ASSETS:
Marketable securities	128,858	145,345
Commercial paper
ASSETS:
Marketable securities	12,970	5,095
Corporate bonds
ASSETS:
Marketable securities	3,885	9,524
Level 1
ASSETS:
Cash and cash equivalents	230,521	104,893
Derivative financial instruments	0	0
Contingently returnable consideration	0
Total assets	273,446	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	39,040	46,564
Level 1 | Commercial paper
ASSETS:
Marketable securities	0	0
Level 1 | Corporate bonds
ASSETS:
Marketable securities	3,885	9,524
Level 2
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	9	15
Contingently returnable consideration	0
Total assets	102,797	103,891
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments	(467)	(1,664)
Total liabilities	(467)	(1,664)
Level 2 | U.S. government and municipal obligations
ASSETS:
Marketable securities	89,818	98,781
Level 2 | Commercial paper
ASSETS:
Marketable securities	12,970	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	16,687
Total assets	16,687	0
LIABILITIES:
Contingent purchase consideration	(7,234)	(4,484)
Derivative financial instruments	0	0
Total liabilities	(7,234)	(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