FAIR VALUE MEASUREMENTS - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Mar. 31, 2016
ASSETS:
Cash and cash equivalents	$ 304,880	$ 210,711
Marketable securities	159,825	141,364
Derivative financial instruments	110	191
Contingently returnable consideration		16,131
Total assets	464,815	368,397
LIABILITIES:
Contingent purchase consideration	(5,449)	(7,293)
Derivative financial instruments	(213)	(158)
Total liabilities	(5,662)	(7,451)
U.S. government and municipal obligations
ASSETS:
Marketable securities	120,901	123,328
Commercial paper
ASSETS:
Marketable securities	29,469	16,172
Corporate bonds
ASSETS:
Marketable securities	7,956	1,864
Certificates of deposit
ASSETS:
Marketable securities	1,499
Level 1
ASSETS:
Cash and cash equivalents	304,880	210,711
Derivative financial instruments	0	0
Contingently returnable consideration		0
Total assets	353,464	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	40,628	41,116
Level 1 | Commercial paper
ASSETS:
Marketable securities	0	0
Level 1 | Corporate bonds
ASSETS:
Marketable securities	7,956	1,864
Level 1 | Certificates of deposit
ASSETS:
Marketable securities	0
Level 2
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	110	191
Contingently returnable consideration		0
Total assets	111,351	98,575
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments	(213)	(158)
Total liabilities	(213)	(158)
Level 2 | U.S. government and municipal obligations
ASSETS:
Marketable securities	80,273	82,212
Level 2 | Commercial paper
ASSETS:
Marketable securities	29,469	16,172
Level 2 | Corporate bonds
ASSETS:
Marketable securities	0	0
Level 2 | Certificates of deposit
ASSETS:
Marketable securities	1,499
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	(5,449)	(7,293)
Derivative financial instruments	0	0
Total liabilities	(5,449)	(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
Level 3 | Certificates of deposit
ASSETS:
Marketable securities	$ 0