Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Net revenues	$ 159,287	$ 165,011	$ 216,150
Cost of revenues	69,739	69,297	85,189
Gross profit	89,548	95,714	130,961
Operating expenses:
Research and development	91,518	107,220	146,579
Selling, general and administrative	33,507	33,643	38,927
Gain on sale of TPack	0	0	(19,699)
Gain on sale of building	0	0	(25,815)
Amortization of purchased intangible assets	0	104	316
Restructuring	25	5,421	1,134
Total operating expenses	125,050	146,388	141,442
Operating loss	(35,502)	(50,674)	(10,481)
Realized gain on short-term investments and interest income, net	2,238	2,764	5,052
Other income (expense), net	69	(3,056)	354
Loss before income taxes	(33,195)	(50,966)	(5,075)
Income tax expense (benefit)	(624)	1,092	619
Net loss	$ (32,571)	$ (52,058)	$ (5,694)
Basic and diluted net loss per share (in dollars per share)	$ (0.39)	$ (0.66)	$ (0.08)
Shares used in calculating basic and diluted net loss per share	82,668	78,814	72,897