Consolidated Statements Of Operations (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Consolidated Statements Of Operations [Abstract]
Net revenues	$ 230,887	$ 247,710	$ 205,598
Cost of revenues	98,804	95,282	92,931
Gross profit	132,083	152,428	112,667
Operating expenses:
Research and development	175,656	108,732	88,096
Selling, general and administrative	45,794	49,173	45,901
Amortization of purchased intangible assets	3,202	5,285	4,020
Restructuring charges, net	875	532	746
Total operating expenses	225,527	163,722	138,763
Operating loss	(93,444)	(11,294)	(26,096)
Interest income (expense), net and other-than-temporary impairment	4,247	9,890	3,440
Other income (expense), net	7,437	797	(1,551)
Loss from continuing operations before income taxes	(81,760)	(607)	(24,207)
Income tax expense (benefit)	928	399	(10,610)
Loss from continuing operations	(82,688)	(1,006)	(13,597)
Income from discontinued operations, net of taxes			6,112
Net loss	$ (82,688)	$ (1,006)	$ (7,485)
Basic and diluted net income (loss) per share:
Net loss per share from continuing operations	$ (1.33)	$ (0.02)	$ (0.21)
Net income per share from discontinued operations			$ 0.10
Net loss per share	$ (1.33)	$ (0.02)	$ (0.11)
Shares used in calculating basic and diluted net income (loss) per share	62,245	65,160	66,006