CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011	Nov. 30, 2010
CONSOLIDATED STATEMENTS OF OPERATIONS [Abstract]
Sales and revenues	$ 106,161	$ 107,025	$ 322,237	$ 308,268
Costs of goods sold	52,998	51,270	152,945	142,061
Gross profit on sales and revenues	53,163	55,755	169,292	166,207
Operating expenses:
Research and development	27,296	28,893	74,455	72,475
Selling, general and administrative	25,807	33,026	65,271	74,425
Restructuring charges	7	146	706	1,014
Impairment loss on equity investment	0	3,208	0	3,208
Gain on equity investment	0	(249)	0	(249)
Revaluation of contingent consideration	(1,110)	(1,083)	(1,491)	(626)
Income (loss) from operations	1,163	(8,186)	30,351	15,960
Interest income	64	241	251	559
Interest expense	(33)	(20)	(109)	(114)
Other expense, net	(469)	(139)	(425)	(475)
Income (loss) before income taxes	725	(8,104)	30,068	15,930
Provision for (benefit from) income taxes	4,002	(3,530)	15,276	6,975
Net (loss) income	$ (3,277)	$ (4,574)	$ 14,792	$ 8,955
Net (loss) income per share:
Basic (in dollars per share)	$ (0.15)	$ (0.20)	$ 0.65	$ 0.40
Diluted (in dollars per share)	$ (0.15)	$ (0.20)	$ 0.63	$ 0.39
Weighted average common shares outstanding:
Basic (in shares)	22,486	22,679	22,847	22,586
Diluted (in shares)	22,486	22,679	23,324	22,969