Financial Instruments Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021	Apr. 24, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	$ 787,666	$ 772,367
Contingent consideration	24,814	24,706	$ 13,300
Cross Currency Interest Rate Contract
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative fair value	2,767	4,298
Repurchase Agreements
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	75,998	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	408,677	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	210,979	264,085
Shockwave Medical
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	61,096	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	92,012	124,297
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	195,347	45,235
Level 1 | Shockwave Medical
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities, fair value disclosure	61,096	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	92,012	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	2,767	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	75,998	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	195,347	45,235
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration	24,814	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	73,896	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	19,343
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	73,896	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	19,343
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	73,718	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	152,726	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	73,718	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	152,726	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	65,716	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	38,910	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	65,716	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	$ 38,910	$ 38,701