Goodwill, In-Process Research and Development and Other Assets - Additional Information (Detail) shares in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($)	Mar. 31, 2020 USD ($)
Goodwill [Line Items]
Goodwill	$ 78,122,000		$ 78,122,000		$ 31,969,000
Accumulated impairment loss, goodwill	0		0
In-process research and development	42,895,000		42,895,000		14,913,000
Accumulated impairment losses on IPR&D assets	0		0
License Manufacturing Rghts to Technology
Goodwill [Line Items]
Payments to third party			$ 4,100,000
Other Intangible Assets
Goodwill [Line Items]
Intangible asset, amortized useful life			15 years
Other Income (Expense)
Goodwill [Line Items]
Impairment loss in other investment	800,000		$ 800,000
Shockwave Medical
Goodwill [Line Items]
Investment in Shockwave Medical	22,494,000		$ 22,494,000		55,704,000
Cash proceeds	$ 67,900,000
Shares sold | shares	1.4		1.4
Shares held by the company | shares	0.3		0.3
Shockwave Medical | Other Income (Expense)
Goodwill [Line Items]
Realized gain on the sale of investment recorded in other income	$ 47,300,000
Unrealized gain (loss) recorded in other income	8,200,000	$ (34,500,000)	$ 26,200,000	$ (4,500,000)
ECP Entwicklungsgesellschaft mbH
Goodwill [Line Items]
In-process research and development	$ 42,900,000		$ 42,900,000		$ 14,900,000
ECP Entwicklungsgesellschaft mbH | Measurement Input, Discount Rate | Maximum
Goodwill [Line Items]
Fair value inputs, discount rate	0.21		0.21
ECP Entwicklungsgesellschaft mbH | Measurement Input, Discount Rate | Minimum [Member]
Goodwill [Line Items]
Fair value inputs, discount rate	0.15		0.15