Investable Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Mar. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 899,296	$ 915,660
Gross Unrealized Gains	1	37
Gross Unrealized Losses	10,301	7,906
Fair Market Value	888,996	907,791
Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	65,293	61,916
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2	3
Fair Market Value	65,291	61,913
Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	669,349	628,200
Gross Unrealized Gains	1	37
Gross Unrealized Losses	5,521	2,448
Fair Market Value	663,829	625,789
Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	164,654	225,544
Gross Unrealized Gains	0	0
Gross Unrealized Losses	4,778	5,455
Fair Market Value	159,876	220,089
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Market Value	59,296	32,955
Money Market Funds | Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	59,296	32,955
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	59,296	32,955
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Market Value	5,995	28,958
Commercial Paper | Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	5,997	28,961
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2	3
Fair Market Value	5,995	28,958
Commercial Paper | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	116,738	148,128
Gross Unrealized Gains	0	0
Gross Unrealized Losses	457	397
Fair Market Value	116,281	147,731
U.S. Treasury mutual fund securities | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	359,213	287,010
Gross Unrealized Gains	0	0
Gross Unrealized Losses	3,010	1,384
Fair Market Value	356,203	285,626
U.S. Treasury mutual fund securities | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	48,631	89,168
Gross Unrealized Gains	0	0
Gross Unrealized Losses	1,428	1,796
Fair Market Value	47,203	87,372
Government-backed securities | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	160,288	131,954
Gross Unrealized Gains	1	1
Gross Unrealized Losses	1,875	554
Fair Market Value	158,414	131,401
Government-backed securities | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	105,838	126,150
Gross Unrealized Gains	0	0
Gross Unrealized Losses	3,026	3,378
Fair Market Value	102,812	122,772
Corporate Debt Securities | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	33,110	61,108
Gross Unrealized Gains	0	36
Gross Unrealized Losses	179	113
Fair Market Value	32,931	61,031
Corporate Debt Securities | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	10,185	10,226
Gross Unrealized Gains	0	0
Gross Unrealized Losses	324	281
Fair Market Value	$ 9,861	$ 9,945