CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenue	$ 181,778	$ 132,823	$ 361,788	$ 265,291
Costs and expenses:
Cost of revenue	29,846	21,627	60,696	43,489
Research and development	22,717	19,390	43,990	36,321
Selling, general and administrative	78,895	60,080	160,034	120,677
Costs and Expenses, Total	131,458	101,097	264,720	200,487
Income from operations	50,320	31,726	97,068	64,804
Other income:
Investment income, net	1,671	781	3,222	1,416
Other (expense) income, net	(158)	(23)	30	56
Nonoperating Income (Expense), Total	1,513	758	3,252	1,472
Income before income taxes	51,833	32,484	100,320	66,276
Income tax provision (benefit)	1,706	7,981	(39,873)	4,399
Net income	$ 50,127	$ 24,503	$ 140,193	$ 61,877
Basic net income per share	$ 1.11	$ 0.56	$ 3.13	$ 1.41
Basic weighted average shares outstanding	44,961	44,141	44,754	44,018
Diluted net income per share	$ 1.09	$ 0.54	$ 3.04	$ 1.36
Diluted weighted average shares outstanding	46,153	45,698	46,164	45,655