CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010
Net sales and contract revenues:
Net product sales and contract revenues	$ 34,997	$ 54,743	$ 96,421	$ 146,922
Net service revenues	22,910	21,845	67,367	63,946
Total net sales and contract revenues	57,907	76,588	163,788	210,868
Cost of sales and contracts:
Cost of product sales and contracts	20,530	30,340	53,060	78,905
Cost of service revenues	10,932	11,544	35,260	33,603
Total cost of sales and contracts	31,462	41,884	88,320	112,508
Gross profit	26,445	34,704	75,468	98,360
Expenses:
Selling, general and administrative expenses	9,091	10,774	26,728	31,584
Research and development costs	6,113	6,568	18,727	16,803
Total operating expenses	15,204	17,342	45,455	48,387
Operating income	11,241	17,362	30,013	49,973
Other income (expense):
Interest and investment income	158	152	467	515
Interest expense	(22)	(27)	(70)	(85)
Other, net	40	(151)	13	(37)
Total other income (expense)	176	(26)	410	393
Income before provision for income taxes	11,417	17,336	30,423	50,366
Provision for income taxes	3,882	5,554	10,344	17,114
Net income	$ 7,535	$ 11,782	$ 20,079	$ 33,252
Income per share - Basic (in dollars per share)	$ 0.84	$ 1.31	$ 2.21	$ 3.69
Income per share - Diluted (in dollars per share)	$ 0.84	$ 1.28	$ 2.18	$ 3.60
Weighted average shares - Basic (in shares)	8,924	9,023	9,088	9,022
Weighted average shares - Diluted (in shares)	9,009	9,236	9,193	9,225
Dividends declared per share (in dollars per share)	$ 0.50	$ 0.30	$ 1.10	$ 0.90