Goodwill, In-Process Research and Development and Other Assets - Additional Information (Detail)	3 Months Ended	9 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)
Goodwill [Line Items]
Goodwill	$ 32,594,000	$ 32,594,000	$ 32,601,000
Accumulated impairment loss, goodwill	0	0
In-process research and development	15,205,000	15,205,000	15,208,000
Accumulated impairment losses on IPR&D assets	0	0
Equity method investment	2,867,000	2,867,000
Loss pertaining to equity method investment.	100,000	100,000
Aggregate carrying amount of other investments	114,169,000	114,169,000	80,779,000
Other intangible assets and other assets	6,676,000	6,676,000	4,336,000
License Manufacturing Rghts to Technology
Goodwill [Line Items]
Other intangible assets and other assets	4,100,000	$ 4,100,000
Other Intangible Assets
Goodwill [Line Items]
Intangible asset, amortized useful life		15 years
Shockwave Medical
Goodwill [Line Items]
Investment in affiliate			25,000,000.0
Fair value of investment	73,700,000	$ 73,700,000	56,200,000
Pre-tax unrealized gain on investment	23,500,000	17,500,000
Medical Device Companies
Goodwill [Line Items]
Equity method investment	3,000,000.0	3,000,000.0
Aggregate carrying amount of other investments	16,600,000	16,600,000
ECP Entwicklungsgesellschaft mbH
Goodwill [Line Items]
In-process research and development	$ 15,200,000	$ 15,200,000	$ 15,200,000
ECP Entwicklungsgesellschaft mbH | Measurement Input, Discount Rate
Goodwill [Line Items]
Fair value inputs, discount rate	0.21	0.21