Share-Based Compensation (Details) (USD $)	3 Months Ended				6 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Stock-based compensation expense [Line Items]
Allocated Share-based Compensation Expense	$ 13,440,000		$ 13,411,000		$ 25,341,000		$ 24,665,000
Inventory [Member]
Stock-based compensation expense [Line Items]
Amount of share-based compensation expense capitalized to inventory	1,600,000		2,400,000		3,300,000		3,800,000
Cost of Sales [Member]
Stock-based compensation expense [Line Items]
Allocated Share-based Compensation Expense	2,640,000	[1]	1,864,000	[1]	4,695,000	[1]	3,833,000	[1]
Research and development [Member]
Stock-based compensation expense [Line Items]
Allocated Share-based Compensation Expense	7,261,000		6,931,000		13,570,000		12,621,000
Selling, General and Administrative Expenses [Member]
Stock-based compensation expense [Line Items]
Allocated Share-based Compensation Expense	5,372,000		6,205,000		10,329,000		11,202,000
Pre-tax effect of share based compensation [Member]
Stock-based compensation expense [Line Items]
Allocated Share-based Compensation Expense	15,273,000		15,000,000		28,594,000		27,656,000
Income tax benefit [Member]
Stock-based compensation expense [Line Items]
Allocated Share-based Compensation Expense	$ 1,833,000		$ 1,589,000		$ 3,253,000		$ 2,991,000

[1] During the three and six months ended September 30, 2014, $1.6 million and $3.3 million, respectively, of share-based compensation expense was capitalized to inventory and $2.6 million and $4.7 million, respectively, of previously capitalized share-based compensation expenses in inventory was sold. During the three and six months ended September 30, 2013, $2.4 million and $3.8 million, respectively, of share-based compensation expense was capitalized to inventory and $1.9 million and $3.8 million, respectively, of previously capitalized share-based compensation expense in inventory was sold.