Certain Financial Statement Information (Details 5) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Sep. 30, 2012	Mar. 31, 2012
Schedule of Purchased Intangible assets
Gross	$ 517,336	$ 517,336
Accumulated Amortization and Impairments	(503,312)	(500,702)
Net	14,024	16,634
Developed technology/in-process research and development [Member]
Schedule of Purchased Intangible assets
Gross	441,300	441,300
Accumulated Amortization and Impairments	(430,413)	(429,054)
Net	10,887	12,246
Weighted average remaining useful life (In years)	4 years	4 years 7 months 6 days
Customer relationships [Member]
Schedule of Purchased Intangible assets
Gross	12,830	12,830
Accumulated Amortization and Impairments	(9,982)	(8,881)
Net	2,848	3,949
Weighted average remaining useful life (In years)	2 years 9 months 18 days	2 years 10 months 24 days
Patents/core technology rights/tradename [Member]
Schedule of Purchased Intangible assets
Gross	63,206	63,206
Accumulated Amortization and Impairments	(62,917)	(62,767)
Net	$ 289	$ 439
Weighted average remaining useful life (In years)	1 year	1 year 6 months