Revenue Recognition - Schedule of Categorizes Revenue by Major Business Line (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Table]
Total revenue	$ 221,584	$ 200,563	$ 634,225	$ 562,351
U.S.
Disaggregation Of Revenue [Table]
Total revenue	185,569	172,548	533,070	488,386
International
Disaggregation Of Revenue [Table]
Total revenue	36,015	28,015	101,155	73,965
Impella Product
Disaggregation Of Revenue [Table]
Total revenue	212,626	193,253	609,430	542,198
Service and Other
Disaggregation Of Revenue [Table]
Total revenue	$ 8,958	$ 7,310	$ 24,795	$ 20,153