FAIR VALUE MEASUREMENTS - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Mar. 31, 2016
ASSETS:
Cash and cash equivalents	$ 244,833	$ 210,711
Marketable securities	132,076	141,364
Derivative financial instruments	9	191
Contingently returnable consideration		16,131
Total assets	376,918	368,397
LIABILITIES:
Contingent purchase consideration	(5,410)	(7,293)
Derivative financial instruments	(391)	(158)
Total liabilities	(5,801)	(7,451)
U.S. government and municipal obligations
ASSETS:
Marketable securities	106,240	123,328
Commercial paper
ASSETS:
Marketable securities	21,153	16,172
Corporate bonds
ASSETS:
Marketable securities	4,683	1,864
Level 1
ASSETS:
Cash and cash equivalents	244,833	210,711
Derivative financial instruments	0	0
Contingently returnable consideration		0
Total assets	284,900	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	35,384	41,116
Level 1 | Commercial paper
ASSETS:
Marketable securities	0	0
Level 1 | Corporate bonds
ASSETS:
Marketable securities	4,683	1,864
Level 2
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	9	191
Contingently returnable consideration		0
Total assets	92,018	98,575
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments	(391)	(158)
Total liabilities	(391)	(158)
Level 2 | U.S. government and municipal obligations
ASSETS:
Marketable securities	70,856	82,212
Level 2 | Commercial paper
ASSETS:
Marketable securities	21,153	16,172
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		16,131
Total assets	0	16,131
LIABILITIES:
Contingent purchase consideration	(5,410)	(7,293)
Derivative financial instruments	0	0
Total liabilities	(5,410)	(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	$ 0