Fair Value Measurements - Debt Securities, Available-for-sale (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Mar. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 535,202	$ 573,567
Unrealized Gains	298	1,859
Unrealized Losses	(1,548)	(172)
Total	533,952	575,254
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	93,800	48,100
Unrealized Gains	3	18
Unrealized Losses	(83)	(19)
Total	93,720	48,099
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	32,067	11,676
Unrealized Gains	2	5
Unrealized Losses	(20)	0
Total	32,049	11,681
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	89,381	39,620
Unrealized Gains	14	261
Unrealized Losses	(531)	(8)
Total	88,864	39,873
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	319,954	474,171
Unrealized Gains	279	1,575
Unrealized Losses	(914)	(145)
Total	$ 319,319	$ 475,601

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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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Amortized cost 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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