Certain Financial Statement Information Purchased Intangibles (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Sep. 30, 2014	Mar. 31, 2014
Schedule of Purchased Intangible assets
Gross Assets	$ 493,636	$ 493,636
Accumulated Amortization and Impairments	(493,636)	(493,531)
Intangible Assets, Net (Excluding Goodwill)	0	105
Developed technology/in-process research and development [Member]
Schedule of Purchased Intangible assets
Gross Assets	425,000	425,000
Accumulated Amortization and Impairments	(425,000)	(425,000)
Intangible Assets, Net (Excluding Goodwill)	0	0
Weighted average remaining useful life	0 years	0 years
Customer relationships [Member]
Schedule of Purchased Intangible assets
Gross Assets	6,330	6,330
Accumulated Amortization and Impairments	(6,330)	(6,225)
Intangible Assets, Net (Excluding Goodwill)	0	105
Weighted average remaining useful life	0 years	4 months 24 days
Patents/core technology rights/tradename [Member]
Schedule of Purchased Intangible assets
Gross Assets	62,306	62,306
Accumulated Amortization and Impairments	(62,306)	(62,306)
Intangible Assets, Net (Excluding Goodwill)	$ 0	$ 0
Weighted average remaining useful life	0 years	0 years