Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 204,974	$ 181,778	$ 412,640	$ 361,788
Costs and expenses:
Cost of revenue	34,867	29,846	71,940	60,696
Research and development	23,969	22,717	47,759	43,990
Selling, general and administrative	85,956	78,895	172,034	160,034
Costs and Expenses, Total	144,792	131,458	291,733	264,720
Income from operations	60,182	50,320	120,907	97,068
Other (expenses) income:
Investment income, net	2,932	1,671	5,981	3,222
Other (expense) income, net	(45,756)	(158)	(6,392)	30
Nonoperating Income (Expense), Total	(42,824)	1,513	(411)	3,252
Income before income taxes	17,358	51,833	120,496	100,320
Income tax provision (benefit)	4,287	1,706	18,502	(39,873)
Net income	$ 13,071	$ 50,127	$ 101,994	$ 140,193
Basic net income per share	$ 0.29	$ 1.11	$ 2.25	$ 3.13
Basic weighted average shares outstanding	45,319	44,961	45,267	44,754
Diluted net income per share	$ 0.28	$ 1.09	$ 2.22	$ 3.04
Diluted weighted average shares outstanding	45,912	46,153	46,031	46,164