CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Net revenues	$ 215,805	$ 193,980	$ 432,467	$ 396,798
Cost of revenues	97,978	94,366	199,930	191,552
Gross profit	117,827	99,614	232,537	205,246
Operating expenses:
Research, development, and engineering	23,769	20,447	46,289	41,310
Selling, general, and administrative	60,350	48,507	116,779	96,604
Gain from litigation settlements	(4,150)	0	(6,150)	0
Restructuring and other related charges	0	(176)	0	547
Total operating expenses	79,969	68,778	156,918	138,461
Operating income	37,858	30,836	75,619	66,785
Interest and other income (expense), net	(685)	359	335	(127)
Income before income taxes	37,173	31,195	75,954	66,658
Income tax expense	9,752	8,057	19,861	16,567
Net income	$ 27,421	$ 23,138	$ 56,093	$ 50,091
Earnings per common share:
Basic	$ 0.66	$ 0.54	$ 1.35	$ 1.17
Diluted	$ 0.65	$ 0.53	$ 1.32	$ 1.15
Shares used in computing basic earnings per common share	41,765	42,810	41,692	42,751
Shares used in computing diluted earnings per common share	42,505	43,597	42,560	43,667
Cash dividends declared per common share	$ 0.15	$ 0.10	$ 0.30	$ 0.20