CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Net sales and contract revenues:
Net product sales and contract revenues	$ 32,375	$ 59,705	$ 61,424	$ 92,179
Net service revenues	22,403	20,932	44,457	42,101
Total net sales and contract revenues	54,778	80,637	105,881	134,280
Cost of sales and contracts:
Cost of product sales and contracts	17,309	29,775	32,530	48,565
Cost of service revenues	12,348	11,018	24,328	22,059
Total cost of sales and contracts	29,657	40,793	56,858	70,624
Gross profit	25,121	39,844	49,023	63,656
Expenses:
Selling, general and administrative expenses	8,379	10,997	17,637	20,810
Research and development costs	6,537	5,225	12,614	10,235
Total operating expenses	14,916	16,222	30,251	31,045
Operating income	10,205	23,622	18,772	32,611
Other income (expense):
Interest and investment income	143	135	309	363
Interest expense	(23)	(28)	(48)	(58)
Other, net	55	(1,082)	(27)	114
Total other income (expense)	175	(975)	234	419
Income before provision for income taxes	10,380	22,647	19,006	33,030
Provision for income taxes	3,529	7,978	6,462	11,560
Net income	$ 6,851	$ 14,669	$ 12,544	$ 21,470
Income per share - Basic (in dollars per share)	$ 0.75	$ 1.63	$ 1.37	$ 2.38
Income per share - Diluted (in dollars per share)	$ 0.74	$ 1.59	$ 1.35	$ 2.33
Weighted average shares - Basic (in shares)	9,148	9,020	9,170	9,020
Weighted average shares - Diluted (in shares)	9,232	9,221	9,285	9,219
Dividends declared per share (in dollars per share)	$ 0.30	$ 0.30	$ 0.60	$ 0.60