Equity Incentive Plans, Stock Compensation Expensed (Details) (USD $)	12 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2010
Stock-based compensation expense [Line Items]
Allocated share based compensation expense	$ 33,400,000		$ 32,319,000		$ 32,215,000
Inventory [Member]
Stock-based compensation expense [Line Items]
Amount of share-based compensation expense capitalized to inventory	6,800,000		7,100,000		7,000,000
Cost of sales [Member]
Stock-based compensation expense [Line Items]
Allocated share based compensation expense	5,648,000	[1]	6,825,000	[1]	7,054,000	[1]
Research and development [Member]
Stock-based compensation expense [Line Items]
Allocated share based compensation expense	14,719,000		12,874,000		12,194,000
Selling, general and administrative [Member]
Stock-based compensation expense [Line Items]
Allocated share based compensation expense	17,922,000		17,113,000		17,530,000
Pre-tax effect of share based compensation [Member]
Stock-based compensation expense [Line Items]
Allocated share based compensation expense	38,289,000		36,812,000		36,778,000
Income tax benefit [Member]
Stock-based compensation expense [Line Items]
Allocated share based compensation expense	$ 4,889,000		$ 4,493,000		$ 4,563,000

[1] During the year ended March 31, 2012, $6.8 million of share-based compensation expense was capitalized to inventory, and $5.6 million of previously capitalized share-based compensation expenses in inventory was sold. During the year ended March 31, 2011, $7.1 million of share-based compensation expense was capitalized to inventory, and $6.8 million of previously capitalized share-based compensation expense in inventory was sold. During the year ended March 31, 2010, $7.0 million of share-based compensation expense was capitalized to inventory, and $7.1 million of previously capitalized share-based compensation expense in inventory was sold.