Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Operating activities:
Net income	$ 225,525	$ 203,009	$ 259,016
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	24,097	20,430	14,121
Bad debt (recoveries) expense	(126)	487	720
Stock-based compensation	47,006	39,781	54,494
Write-down of inventory and other	8,518	4,249	4,252
Accretion on marketable securities	1,977	(2,731)	(2,744)
Change in fair value of other investments	(50,983)	5,184	(30,161)
Deferred tax provision	29,380	32,953	(7,745)
Change in fair value of contingent consideration	2,406	(575)	(915)
Other non-cash operating activities	4,164	4,108
Changes in assets and liabilities:
Accounts receivable	(12,059)	5,551	(22,023)
Inventories	2,535	(13,237)	(37,181)
Prepaid expenses and other assets	(1,032)	(5,333)	(2,527)
Accounts payable	2,629	2,581	7,976
Accrued expenses and other liabilities	(14,632)	15,676	13,406
Deferred revenue	5,173	2,787	1,508
Net cash provided by operating activities	274,578	314,920	252,197
Investing activities:
Purchases of marketable securities	(556,199)	(611,280)	(361,602)
Proceeds from the sale and maturity of marketable securities and other	396,643	550,788	331,886
Acquisition of Breethe Inc., net of cash acquired	52,183
Purchases of other investments and intangible assets	(26,104)	(20,957)	(42,735)
Proceeds from sale of Shockwave Medical Investment	67,882
Purchases of property and equipment	(53,383)	(44,006)	(44,004)
Net cash used for investing activities	(223,344)	(125,455)	(116,455)
Financing activities:
Proceeds from the exercise of stock options	9,075	3,748	12,949
Taxes paid related to net share settlement upon vesting of stock awards	(11,311)	(41,687)	(71,776)
Repurchase of common stock	(11,310)	(84,879)
Proceeds from the issuance of stock under employee stock purchase plan	5,479	5,103	3,052
Net cash used for financing activities	(8,067)	(117,715)	(55,775)
Effect of exchange rate changes on cash	(2,798)	(430)	(1,921)
Net increase in cash and cash equivalents	40,369	71,320	78,046
Cash and cash equivalents at beginning of year	192,341	121,021	42,975
Cash and cash equivalents at end of year	232,710	192,341	121,021
Supplemental disclosure of cash flow information:
Cash paid for income taxes	48,693	9,685	5,290
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment in accounts payable and accrued expenses	1,638	2,977	$ 4,787
Right-of-use assets obtained in exchange for lease liabilities	$ 2,592	$ 15,650