Quarterly Financial Information (unaudited) - Operating Results (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended											12 Months Ended
	Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012		Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Schedule of Quarterly Information [Line Items]
Net revenues	$ 56,326,000	[1],[2]	$ 51,698,000	[3]	$ 46,324,000	$ 41,294,000	$ 48,767,000	[1],[4]	$ 56,347,000	$ 64,929,000	$ 60,844,000	$ 195,642,000	$ 230,887,000	$ 247,710,000
Cost of revenues	21,174,000	[1],[2]	22,958,000	[3]	20,561,000	18,355,000	20,974,000	[1],[4]	23,795,000	27,704,000	26,331,000	83,048,000	98,804,000	95,282,000
Gross profit	35,152,000	[1],[2]	28,740,000	[3]	25,763,000	22,939,000	27,793,000	[1],[4]	32,552,000	37,225,000	34,513,000	112,594,000	132,083,000	152,428,000
Total operating expenses	49,116,000	[1],[2]	101,942,000	[3]	48,515,000	47,891,000	102,941,000	[1],[4]	40,337,000	39,313,000	42,936,000	247,464,000	225,527,000	163,722,000
Operating loss	(13,964,000)	[1],[2]	(73,202,000)	[3]	(22,752,000)	(24,952,000)	(75,148,000)	[1],[4]	(7,785,000)	(2,088,000)	(8,423,000)	(134,870,000)	(93,444,000)	(11,294,000)
Interest income (expense), net	(4,654,000)	[1],[2]	2,258,000	[3]	835,000	1,762,000	7,897,000	[1],[4]	914,000	1,517,000	1,356,000	2,595,000	4,247,000	9,890,000
Loss before income taxes	(18,618,000)	[1],[2]	(70,944,000)	[3]	(21,917,000)	(23,190,000)	(67,251,000)	[1],[4]	(6,871,000)	(571,000)	(7,067,000)	(134,669,000)	(81,760,000)	(607,000)
Income tax expense	(1,012,000)	[1],[2]	618,000	[3]	(360,000)	200,000	331,000	[1],[4]	206,000	581,000	(190,000)	(554,000)	928,000	399,000
Net loss	(17,606,000)	[1],[2]	(71,562,000)	[3]	(21,557,000)	(23,390,000)	(67,582,000)	[1],[4]	(7,077,000)	(1,152,000)	(6,877,000)	(134,115,000)	(82,688,000)	(1,006,000)
Basic and diluted net loss per share (USD per share)	$ (0.26)	[1],[2]	$ (1.08)	[3]	$ (0.33)	$ (0.37)	$ (1.10)	[1],[4]	$ (0.12)	$ (0.02)	$ (0.11)	$ (2.06)	$ (1.33)	$ (0.02)
Shares used in calculating basic and diluted net loss per share	67,566	[1],[2]	66,113	[3]	64,947	62,409	61,587	[1],[4]	60,990	62,526	63,878	65,258	62,245	65,160
Research and development	9,600,000		51,900,000				60,400,000					187,419,000	175,656,000	108,732,000
Restructuring charges			6,200,000									6,435,000	875,000	532,000
Veloce Technologies Inc [Member]
Schedule of Quarterly Information [Line Items]
Research and development													60,400,000
Gain on sale of investments							8.1
Immaterial R&D expense error													$ 8,000,000

[1] During fiscal 2012, one significant product development milestone relating to the Veloce project was considered probable of achievement and accordingly $60.4 million was recognized as research and development expense (see further discussion in Note 4 to the Notes to Consolidated Financial Statements relating to Veloce). However, approximately $8.0 million of the R&D expense was incorrectly recognized as this expense amount related to Unallocated Veloce Units that had not yet been distributed as of March 31, 2012. R&D expenses were also recognized during the first three quarters of fiscal 2013 in connection with further progress made in connection with the performance milestones relating to Veloce. However, the R&D expenses recognized during the first three quarters of fiscal 2013 also incorrectly included immaterial amounts related to the Unallocated Veloce Units. During the fourth quarter of fiscal 2013, the Company corrected the error impacting fiscal 2012 and the first three quarters of fiscal 2013. The correction of the errors resulted in a reduction of R&D expenses recognized by $10.4 million during the fourth quarter of fiscal 2013.

[2] The consolidated operating results for the fourth quarter of fiscal 2013 included a charge of $9.6 million related to the Veloce consideration.

[3] The consolidated operating results for the third quarter of fiscal 2013 included a charge of $51.9 million related to the Veloce consideration and a charge of $6.2 million related to restructuring charges.

[4] The consolidated operating results for the fourth quarter of fiscal 2012 included a charge of $60.4 million related to the Veloce initial consideration and a gain of $8.1 related to the sale of a strategic investment.