Statement of Earnings (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income Statement [Abstract]
Net revenues	$ 68,461	$ 99,004	$ 149,318	$ 200,782
Cost of goods sold	47,943	67,526	101,611	134,269
Gross profit	20,518	31,478	47,707	66,513
Operating expenses:
Research, development and engineering	6,752	6,504	13,401	13,437
Selling, general and administrative	9,905	10,186	21,092	21,315
Amortization of acquisition-related intangible assets	484	603	1,124	1,245
Total operating expenses	17,141	17,293	35,617	35,997
Operating income	3,377	14,185	12,090	30,516
Other income (expense):
Interest income	84	92	168	161
Interest expense	(234)	(293)	(491)	(577)
Other income, net	206	1,661	907	1,267
Income before income tax provision	3,433	15,645	12,674	31,367
Provision for income tax	(1,076)	(4,698)	(4,310)	(10,444)
Net income	$ 2,357	$ 10,947	$ 8,364	$ 20,923
Net income per share:
Basic	$ 0.08	$ 0.35	$ 0.27	$ 0.67
Diluted	$ 0.07	$ 0.34	$ 0.26	$ 0.64
Weighted average shares used in per share calculation:
Basic	31,310	31,383	31,331	31,445
Diluted	31,975	32,545	32,192	32,669