CONSOLIDATED STATEMENTS OF INCOME CONSOLIDATED STATEMENTS OF INCOME (PARENTHETICAL) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share based compensation expense	$ 47,956		$ 48,065		$ 48,977
Cost of sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share based compensation expense	9,010	[1]	7,340	[1]	8,234	[1]
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share based compensation expense	28,164		24,554		22,178
Selling General And Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Allocated share based compensation expense	$ 21,422		$ 21,893		$ 27,603

[1] During the year ended March 31, 2015, $6.8 million of share-based compensation expense was capitalized to inventory, and $9.0 million of previously capitalized share-based compensation expense in inventory was sold. During the year ended March 31, 2014, $7.4 million of share-based compensation expense was capitalized to inventory, and $7.3 million of previously capitalized share-based compensation expense in inventory was sold. During the year ended March 31, 2013, $5.9 million of share-based compensation expense was capitalized to inventory, and $8.2 million of previously capitalized share-based compensation expense in inventory was sold.