CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) (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
Net revenues	$ 179,280	$ 176,948	$ 360,645	$ 352,548
Cost of revenues	82,052	77,982	165,721	159,524
Gross profit	97,228	98,966	194,924	193,024
Operating expenses:
Research, development and engineering	19,581	17,651	39,277	34,557
Selling, general and administrative	43,130	44,418	89,034	86,534
Total operating expenses	62,711	62,069	128,311	121,091
Operating income	34,517	36,897	66,613	71,933
Interest and other income (expense), net	275	(58)	287	583
Income before income taxes	34,792	36,839	66,900	72,516
Income tax expense	8,868	9,318	17,413	18,264
Net income	$ 25,924	$ 27,521	$ 49,487	$ 54,252
Earnings per common share:
Basic	$ 0.62	$ 0.62	$ 1.19	$ 1.19
Diluted	$ 0.61	$ 0.60	$ 1.16	$ 1.16
Shares used in computing basic earnings per common share	41,482	44,556	41,571	45,664
Shares used in computing diluted earnings per common share	42,403	45,717	42,521	46,950
Cash dividends declared per common share	$ 0.10	$ 0.05	$ 0.20	$ 0.10