CONSOLIDATED STATEMENTS OF INCOME CONSOLIDATED STATEMENTS OF INCOME (PARENTHETICAL) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	$ 33,400		$ 32,319		$ 32,215
Cost of sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	5,648	[1]	6,825	[1]	7,054	[1]
Research and Development Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	14,719		12,874		12,194
Selling General And Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	$ 17,922		$ 17,113		$ 17,530

[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.