Financial Instruments Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	$ 722,349	$ 772,367
Contingent consideration	25,577	24,706
Cross Currency Interest Rate Contract
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative fair value	5,559	4,298
Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	47,000	33,000
Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	347,577	350,985
Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	281,776	264,085
Shockwave Medical
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	56,303	38,655
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	45,996
Commercial Paper | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	44,981	45,235
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure		124,297
Level 1 | Shockwave Medical
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	56,303	38,655
Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	45,996
Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure		124,297
Level 2 | Cross Currency Interest Rate Contract
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative fair value	5,559	4,298
Level 2 | Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	47,000	33,000
Level 2 | Commercial Paper | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	44,981	45,235
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	25,577	24,706
U.S. Treasury mutual fund securities | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	110,829	72,249
U.S. Treasury mutual fund securities | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	20,393
U.S. Treasury mutual fund securities | Level 2 | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	110,829	72,249
U.S. Treasury mutual fund securities | Level 2 | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	20,393
Government-backed securities | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	89,964	128,669
Government-backed securities | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	224,754	225,384
Government-backed securities | Level 2 | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	89,964	128,669
Government-backed securities | Level 2 | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	224,754	225,384
Corporate Debt Securities | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	101,803	104,832
Corporate Debt Securities | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	36,629	38,701
Corporate Debt Securities | Level 2 | Short-term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	101,803	104,832
Corporate Debt Securities | Level 2 | Long Term Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	$ 36,629	$ 38,701