CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net sales and contract revenues:
Net product sales and contract revenues	$ 22,208	$ 25,084	$ 43,488	$ 50,793
Net service revenues	21,608	21,169	43,412	42,804
Total net sales and contract revenues	43,816	46,253	86,900	93,597
Cost of sales and contracts:
Cost of product sales and contracts	14,341	15,493	26,894	30,617
Cost of service revenues	10,269	9,763	21,653	20,510
Total cost of sales and contracts	24,610	25,256	48,547	51,127
Gross profit	19,206	20,997	38,353	42,470
Expenses:
Selling, general and administrative expenses	6,913	4,895	14,322	12,893
Research and development costs	5,172	6,505	9,586	13,620
Total operating expenses	12,085	11,400	23,908	26,513
Operating income	7,121	9,597	14,445	15,957
Other income (expense):
Interest and investment income	75	175	169	382
Interest expense	(14)	(19)	(29)	(39)
Other, net	(56)	(58)	(143)	(238)
Total other income (expense)	5	98	(3)	105
Income before provision for income taxes	7,126	9,695	14,442	16,062
Provision for income taxes	2,387	3,296	4,838	5,461
Net income	4,739	6,399	9,604	10,601
Other comprehensive income:
Unrealized gain on available for sale securities (net of tax)	60	40	34	4
Comprehensive income	$ 4,799	$ 6,439	$ 9,638	$ 10,605
Income per share - Basic (in dollars per share)	$ 0.61	$ 0.77	$ 1.23	$ 1.23
Income per share - Diluted (in dollars per share)	$ 0.60	$ 0.76	$ 1.22	$ 1.22
Weighted average shares - Basic (in shares)	7,820	8,364	7,831	8,609
Weighted average shares - Diluted (in shares)	7,851	8,418	7,866	8,662
Dividends declared per share (in dollars per share)	$ 0.50	$ 0.50	$ 1.00	$ 1.00