FAIR VALUE MEASUREMENTS - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Mar. 31, 2018
ASSETS:
Cash and cash equivalents	$ 332,183	$ 369,821
Available-for-sale securities	119,935	77,941
Derivative financial instruments	16	122
Contingent consideration	2,267
Total assets	454,401	447,884
LIABILITIES:
Contingent purchase consideration	(5,017)	(5,464)
Derivative financial instruments	(220)	(40)
Total liabilities	(5,237)	(5,504)
U.S. government and municipal obligations
ASSETS:
Available-for-sale securities	62,473	42,186
Commercial paper
ASSETS:
Available-for-sale securities	54,701	33,003
Corporate bonds
ASSETS:
Available-for-sale securities	2,761	2,752
Level 1
ASSETS:
Cash and cash equivalents	332,183	369,821
Derivative financial instruments	0	0
Contingent consideration	0
Total assets	378,350	387,086
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments	0	0
Total liabilities	0	0
Level 1 \| U.S. government and municipal obligations
ASSETS:
Available-for-sale securities	43,406	14,513
Level 1 \| Commercial paper
ASSETS:
Available-for-sale securities	0	0
Level 1 \| Corporate bonds
ASSETS:
Available-for-sale securities	2,761	2,752
Level 2
ASSETS:
Derivative financial instruments	16	122
Contingent consideration	0
Total assets	73,784	60,798
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments	(220)	(40)
Total liabilities	(220)	(40)
Level 2 \| U.S. government and municipal obligations
ASSETS:
Available-for-sale securities	19,067	27,673
Level 2 \| Commercial paper
ASSETS:
Available-for-sale securities	54,701	33,003
Level 2 \| Corporate bonds
ASSETS:
Available-for-sale securities	0	0
Level 3
ASSETS:
Derivative financial instruments	0	0
Contingent consideration	2,267
Total assets	2,267	0
LIABILITIES:
Contingent purchase consideration	(5,017)	(5,464)
Derivative financial instruments	0	0
Total liabilities	(5,017)	(5,464)
Level 3 \| U.S. government and municipal obligations
ASSETS:
Available-for-sale securities	0	0
Level 3 \| Commercial paper
ASSETS:
Available-for-sale securities	0	0
Level 3 \| Corporate bonds
ASSETS:
Available-for-sale securities	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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