CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Net revenues	$ 762,226	$ 713,368	$ 683,602
Cost of revenues	359,045	329,017	321,846
Gross profit	403,181	384,351	361,756
Operating expenses:
Research, development and engineering	80,373	69,664	63,183
Selling, general and administrative	182,445	173,334	163,389
Gain from litigation settlement	0	0	(5,100)
Restructuring and other related charges	2,266	0	(428)
Total operating expenses	265,084	242,998	221,044
Operating income	138,097	141,353	140,712
Interest and other income (expense), net	328	1,249	(56)
Income before income taxes	138,425	142,602	140,656
Income tax expense	32,023	33,566	31,413
Net income	$ 106,402	$ 109,036	$ 109,243
Earnings Per Share, Basic [Abstract]
Continuing operations	$ 2.55	$ 2.48	$ 2.29
Net income	$ 2.55	$ 2.48	$ 2.29
Earnings Per Share, Diluted [Abstract]
Continuing operations	$ 2.49	$ 2.41	$ 2.21
Net Income	$ 2.49	$ 2.41	$ 2.21
Shares used in basic per share calculations	41,748	44,023	47,713
Shares used in diluted per share calculations	42,738	45,265	49,344
Cash dividends declared per common share	$ 0.40	$ 0.2	$ 0.2