CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Net revenues	$ 713,368	$ 683,602	$ 613,837
Cost of revenues	329,017	321,846	312,767
Gross profit	384,351	361,756	301,070
Operating expenses:
Research, development and engineering	69,664	63,183	57,784
Selling, general and administrative	173,334	163,389	143,784
Gain from litigation settlement	0	(5,100)	0
Restructuring and other related charges	0	(428)	1,867
Total operating expenses	242,998	221,044	203,435
Operating income	141,353	140,712	97,635
Interest and other income (expense), net	1,249	(56)	3,105
Income from continuing operations before income taxes	142,602	140,656	100,740
Income tax expense from continuing operations	33,566	31,413	24,287
Income from continuing operations, net of tax	109,036	109,243	76,453
Loss from operations of discontinued AEG segment (including loss on sale)	0	0	(30,468)
Income tax benefit on discontinued operations	0	0	(11,393)
Loss from discontinued operations, net of tax	0	0	(19,075)
Net income	$ 109,036	$ 109,243	$ 57,378
Earnings Per Share, Basic [Abstract]
Continuing operations	$ 2.48	$ 2.29	$ 1.58
Discontinued operations	$ 0.00	$ 0.00	$ (0.39)
Net income	$ 2.48	$ 2.29	$ 1.18
Earnings Per Share, Diluted [Abstract]
Continuing operations	$ 2.41	$ 2.21	$ 1.55
Discontinued operations	$ 0.00	$ 0.00	$ (0.39)
Net Income	$ 2.41	$ 2.21	$ 1.16
Shares used in basic per share calculations	44,023	47,713	48,504
Shares used in diluted per share calculations	45,265	49,344	49,331
Cash dividends declared per common share	$ 0.20	$ 0.20	$ 0.20