FAIR VALUE MEASUREMENTS - Schedule of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021
ASSETS:
Cash and cash equivalents	$ 468,470	$ 467,176
Available-for-sale securities	7,347	9,277
Derivative financial instruments	9	57
Total assets	475,826	476,510
LIABILITIES:
Derivative financial instruments	(32)	(191)
Total liabilities	(32)	(191)
U.S. government and municipal obligations
ASSETS:
Available-for-sale securities		3,578
Commercial paper
ASSETS:
Available-for-sale securities	7,347	5,699
Level 1
ASSETS:
Cash and cash equivalents	468,470	467,176
Derivative financial instruments	0	0
Total assets	468,470	469,715
LIABILITIES:
Derivative financial instruments	0	0
Total liabilities	0	0
Level 1 | U.S. government and municipal obligations
ASSETS:
Available-for-sale securities		2,539
Level 1 | Commercial paper
ASSETS:
Available-for-sale securities	0	0
Level 2
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	9	57
Total assets	7,356	6,795
LIABILITIES:
Derivative financial instruments	(32)	(191)
Total liabilities	(32)	(191)
Level 2 | U.S. government and municipal obligations
ASSETS:
Available-for-sale securities		1,039
Level 2 | Commercial paper
ASSETS:
Available-for-sale securities	7,347	5,699
Level 3
ASSETS:
Cash and cash equivalents	0	0
Derivative financial instruments	0	0
Total assets	0	0
LIABILITIES:
Derivative financial instruments	0	0
Total liabilities	0	0
Level 3 | U.S. government and municipal obligations
ASSETS:
Available-for-sale securities		0
Level 3 | Commercial paper
ASSETS:
Available-for-sale securities	$ 0	$ 0