Certain Financial Statement Information - Schedule of Interest income (expense), net and other-than-temporary impairment (Details) (USD $) In Thousands, 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 Interest Income, Net
Interest income												$ 2,347	$ 3,601	$ 6,163
Net realized gain on short-term investments												1,391	646	3,727
Impairments of short-term investments and marketable securities												(1,143)	0	0
Interest income, net	$ (4,654)	[1],[2]	$ 2,258	[3]	$ 835	$ 1,762	$ 7,897	[1],[4]	$ 914	$ 1,517	$ 1,356	$ 2,595	$ 4,247	$ 9,890

[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.