Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Mar. 31, 2019		Mar. 31, 2018		Mar. 31, 2017
Income Statement [Abstract]
Revenue	$ 769,432		$ 593,749		$ 445,304
Costs and expenses:
Cost of revenue	129,567		98,581		70,627
Research and development	93,503		75,297		66,386
Selling, general and administrative	321,550		262,734		218,153
Costs and Expenses, Total	544,620		436,612		355,166
Income from operations	224,812		157,137		90,138
Other income:
Investment income, net	8,166		3,688		1,554
Other income (expense), net	30,382		(388)		(349)
Nonoperating Income (Expense), Total	38,548	[1]	3,300		1,205
Income before income taxes	263,360		160,437		91,343
Income tax provision	4,344	[2]	48,267	[2],[3]	39,227
Net income	$ 259,016		$ 112,170		$ 52,116
Basic net income per share	$ 5.77		$ 2.54		$ 1.21
Basic weighted average shares outstanding	44,911		44,153		43,238
Diluted net income per share	$ 5.61		$ 2.45		$ 1.17
Diluted weighted average shares outstanding	46,151		45,849		44,658

[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, 2019 was $56.2 million and the Company recognized a gain of $31.2 million in Other income.

[2] On December 22, 2017, the Tax Cuts and Jobs Act, or Tax Reform Act, was enacted into law. This new law, among other items, reduces the U.S. federal statutory corporate income tax rate from 35% to 21% effective January 1, 2018. During the year ended March 31, 2018, the Company recorded tax expense adjustments for $21.4 million related to the revaluation of its deferred taxes due to a reduction of the U.S. federal statutory corporate income tax rate.

[3] In the first quarter of fiscal 2018, the Company adopted ASU 2016-09, which requires that all excess tax benefits and tax deficiencies related share-based compensation arrangements be recognized as income tax benefit or expense, instead of in stockholders’ equity as previous guidance required. The income tax provision for the years ended March 31, 2019 and 2018 included excess tax benefits of $69.3 million and $31.0 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, 2019 and 2018.