CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Revenue:
Product sales	$ 189,476	$ 205,027	$ 194,996
Contract services	74,622	54,371	56,707
Total revenue	264,098	259,398	251,703
Cost of sales:
Product sales	105,987	118,834	119,137
Contract services	46,008	36,296	38,953
Total cost of sales	151,995	155,130	158,090
Gross margin:
Product sales	83,489	86,193	75,859
Contract services	28,614	18,075	17,754
Total gross margin	112,103	104,268	93,613
Selling, general and administrative	60,077	55,763	55,679
Research and development	42,291	46,491	25,515
Income from operations	9,735	2,014	12,419
Other income (expense):
Interest income, net	1,032	882	855
Other (expense) income, net	(2,699)	(1,003)	1,622
Income before income taxes	8,068	1,893	14,896
(Benefit) provision for income taxes	(898)	(1,002)	1,178
Net Income	$ 8,966	$ 2,895	$ 13,718
Earnings per share data:
Basic (in dollars per share)	$ 0.39	$ 0.13	$ 0.61
Diluted (in dollars per share)	$ 0.39	$ 0.13	$ 0.60
Weighted average shares outstanding:
Basic (in shares)	22,936,413	22,868,733	22,354,444
Diluted (in shares)	23,153,493	23,145,997	22,719,218