Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Mar. 31, 2020		Mar. 31, 2019		Mar. 31, 2018
Income Statement [Abstract]
Revenue	$ 840,883		$ 769,432		$ 593,749
Costs and expenses:
Cost of revenue	151,305		129,567		98,581
Research and development	98,759		93,503		75,297
Selling, general and administrative	341,600		321,550		262,734
Costs and Expenses, Total	591,664		544,620		436,612
Income from operations	249,219		224,812		157,137
Other income:
Investment income, net	12,167		8,166		3,688
Other (expense) income, net	(4,561)		30,382		(388)
Nonoperating Income (Expense), Total	7,606	[1]	38,548	[1]	3,300
Income before income taxes	256,825		263,360		160,437
Income tax provision	53,816	[2]	4,344	[2]	48,267
Net income	$ 203,009		$ 259,016		$ 112,170
Basic net income per share	$ 4.49		$ 5.77		$ 2.54
Basic weighted average shares outstanding	45,179		44,911		44,153
Diluted net income per share	$ 4.43		$ 5.61		$ 2.45
Diluted weighted average shares outstanding	45,816		46,151		45,849

[1]   (1) In fiscal 2019, the Company invested $25.0 million in medical device company Shockwave Medical. The fair value of this investment as of March 31, 2020 was $55.7 million and the Company recognized a pre-tax loss of $0.5 million for the year ended March 31, 2020 and a pre-tax gain of $32.0 million for the year ended March 31, 2019 in other (expense) income, net.

[2]   (2) The income tax provision for the years ended March 31, 2020 and 2019 included excess tax benefits of $14.8 million and $69.3 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, 2020 and 2019.