Revenue Recognition - Schedule of Disaggregated Revenue by Major Business Line (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Disaggregation Of Revenue [Line Items]
Total revenue	$ 241,246	$ 231,663	$ 209,764	$ 164,850	$ 206,658	$ 221,584	$ 204,974	$ 207,666	$ 847,522	$ 840,883	$ 769,432
U S [Member]
Disaggregation Of Revenue [Line Items]
Total revenue									691,579	705,409	665,082
Europe [Member]
Disaggregation Of Revenue [Line Items]
Total revenue									105,320	94,266	57,460
Japan [Member]
Disaggregation Of Revenue [Line Items]
Total revenue									42,868	35,215	17,502
Other international [Member]
Disaggregation Of Revenue [Line Items]
Total revenue									7,755	5,993	29,388
Impella Product
Disaggregation Of Revenue [Line Items]
Total revenue									806,322	806,824	741,699
Service and Other
Disaggregation Of Revenue [Line Items]
Total revenue									$ 41,200	$ 34,059	$ 27,733