Summary of Unaudited Quarterly Results of Operations (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Mar. 31, 2021		Dec. 31, 2020	[1]	Sep. 30, 2020	[1]	Jun. 30, 2020	[1]	Mar. 31, 2020	[1]	Dec. 31, 2019	[1]	Sep. 30, 2019	[1]	Jun. 30, 2019	[1]	Mar. 31, 2021		Mar. 31, 2020		Mar. 31, 2019
Schedule Of Quarterly Financial Data [Line Items]
Income tax provision	$ 16,638	[1]	$ 18,867		$ 10,702		$ 16,488		$ 7,515		$ 27,799		$ 4,287		$ 14,215		$ 62,695	[1]	$ 53,816	[1]	$ 4,344
Vested Restricted Stock Units or Stock Options
Schedule Of Quarterly Financial Data [Line Items]
Income tax provision																	12,100		14,800
Shockwave Medical, Inc.
Schedule Of Quarterly Financial Data [Line Items]
Investments																					$ 25,000
Fair value of investment	$ 38,700																38,700
Shockwave Medical, Inc. | Other Expense
Schedule Of Quarterly Financial Data [Line Items]
Gain (loss) recorded in other income (expense)																	$ 50,800
Shockwave Medical, Inc. | Other Income (Expense)
Schedule Of Quarterly Financial Data [Line Items]
Gain (loss) recorded in other income (expense)																			$ 500

[1] The income tax provision for the years ended March 31, 2021 and 2020 included excess tax benefits of $12.1 million and $14.8 million, respectively. These recognized excess tax benefits resulted from restricted stock units that vested or stock options that were exercised during the years ended March 31, 2021 and 2020.