FAIR VALUE MEASUREMENTS - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Mar. 31, 2020
ASSETS:
Cash and cash equivalents	$ 477,755	$ 338,489
Available-for-sale securities	12,689	50,582
Derivative financial instruments	174
Total assets	490,618	389,071
LIABILITIES:
Contingent purchase consideration	(748)	(1,748)
Derivative financial instruments		(49)
Total liabilities	(748)	(1,797)
U.S. government and municipal obligations
ASSETS:
Available-for-sale securities	3,576	31,341
Commercial paper
ASSETS:
Available-for-sale securities	7,196	14,644
Corporate bonds
ASSETS:
Available-for-sale securities	1,917	4,597
Level 1
ASSETS:
Cash and cash equivalents	477,755	338,489
Derivative financial instruments	0
Total assets	482,210	374,427
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments		0
Total liabilities	0	0
Level 1 \| U.S. government and municipal obligations
ASSETS:
Available-for-sale securities	2,538	31,341
Level 1 \| Commercial paper
ASSETS:
Available-for-sale securities	0	0
Level 1 \| Corporate bonds
ASSETS:
Available-for-sale securities	1,917	4,597
Level 2
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	174
Total assets	8,408	14,644
LIABILITIES:
Contingent purchase consideration	0	0
Derivative financial instruments		(49)
Total liabilities	0	(49)
Level 2 \| U.S. government and municipal obligations
ASSETS:
Available-for-sale securities	1,038	0
Level 2 \| Commercial paper
ASSETS:
Available-for-sale securities	7,196	14,644
Level 2 \| Corporate bonds
ASSETS:
Available-for-sale securities	0	0
Level 3
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	0
Total assets	0	0
LIABILITIES:
Contingent purchase consideration	(748)	(1,748)
Derivative financial instruments		0
Total liabilities	(748)	(1,748)
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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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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